const std = @import("std");

pub fn main() !void {
    const stdout = std.io.getStdOut().writer();
    try stdout.print("Hello, {s}!\n", .{"world"});
}

$ zig build-exe hello.zig

$ ./hello
Hello, world!

const print = @import("std").debug.print;

pub fn main() void {
    print("Hello, world!\n", .{});
}

$ zig build-exe hello_again.zig

$ ./hello_again
Hello, world!

const print = @import("std").debug.print;

pub fn main() void {
    // Comments in Zig start with "//" and end at the next LF byte (end of line).
    // The line below is a comment and won't be executed.

    //print("Hello?", .{});

    print("Hello, world!\n", .{}); // another comment
}

$ zig build-exe comments.zig

$ ./comments
Hello, world!

/// A structure for storing a timestamp, with nanosecond precision (this is a
/// multiline doc comment).
const Timestamp = struct {
    /// The number of seconds since the epoch (this is also a doc comment).
    seconds: i64,  // signed so we can represent pre-1970 (not a doc comment)
    /// The number of nanoseconds past the second (doc comment again).
    nanos: u32,

    /// Returns a `Timestamp` struct representing the Unix epoch; that is, the
    /// moment of 1970 Jan 1 00:00:00 UTC (this is a doc comment too).
    pub fn unixEpoch() Timestamp {
        return Timestamp{
            .seconds = 0,
            .nanos = 0,
        };
    }
};

//! This module provides functions for retrieving the current date and
//! time with varying degrees of precision and accuracy. It does not
//! depend on libc, but will use functions from it if available.

// Top-level declarations are order-independent:
const print = std.debug.print;
const std = @import("std");
const os = std.os;
const assert = std.debug.assert;

pub fn main() void {
    // integers
    const one_plus_one: i32 = 1 + 1;
    print("1 + 1 = {}\n", .{one_plus_one});

    // floats
    const seven_div_three: f32 = 7.0 / 3.0;
    print("7.0 / 3.0 = {}\n", .{seven_div_three});

    // boolean
    print("{}\n{}\n{}\n", .{
        true and false,
        true or false,
        !true,
    });

    // optional
    var optional_value: ?[]const u8 = null;
    assert(optional_value == null);

    print("\noptional 1\ntype: {s}\nvalue: {s}\n", .{
        @typeName(@TypeOf(optional_value)),
        optional_value,
    });

    optional_value = "hi";
    assert(optional_value != null);

    print("\noptional 2\ntype: {s}\nvalue: {s}\n", .{
        @typeName(@TypeOf(optional_value)),
        optional_value,
    });

    // error union
    var number_or_error: anyerror!i32 = error.ArgNotFound;

    print("\nerror union 1\ntype: {s}\nvalue: {}\n", .{
        @typeName(@TypeOf(number_or_error)),
        number_or_error,
    });

    number_or_error = 1234;

    print("\nerror union 2\ntype: {s}\nvalue: {}\n", .{
        @typeName(@TypeOf(number_or_error)),
        number_or_error,
    });
}

$ zig build-exe values.zig

$ ./values
1 + 1 = 2
7.0 / 3.0 = 2.33333325e+00
false
true
false

optional 1
type: ?[]const u8
value: null

optional 2
type: ?[]const u8
value: hi

error union 1
type: anyerror!i32
value: error.ArgNotFound

error union 2
type: anyerror!i32
value: 1234

const print = @import("std").debug.print;
const mem = @import("std").mem; // will be used to compare bytes

pub fn main() void {
    const bytes = "hello";
    print("{s}\n", .{@typeName(@TypeOf(bytes))});       // *const [5:0]u8
    print("{d}\n", .{bytes.len});                       // 5
    print("{c}\n", .{bytes[1]});                        // 'e'
    print("{d}\n", .{bytes[5]});                        // 0
    print("{}\n", .{'e' == '\x65'});                    // true
    print("{d}\n", .{'\u{1f4a9}'});                     // 128169
    print("{d}\n", .{'💯'});                            // 128175
    print("{}\n", .{mem.eql(u8, "hello", "h\x65llo")}); // true
    print("0x{x}\n", .{"\xff"[0]}); // non-UTF-8 strings are possible with \xNN notation.
    print("{u}\n", .{'⚡'});
}

$ zig build-exe string_literals.zig

$ ./string_literals
*const [5:0]u8
5
e
0
true
128169
128175
true
0xff
⚡

const hello_world_in_c =
    \\#include <stdio.h>
    \\
    \\int main(int argc, char **argv) {
    \\    printf("hello world\n");
    \\    return 0;
    \\}
;

const x = 1234;

fn foo() void {
    // It works at file scope as well as inside functions.
    const y = 5678;

    // Once assigned, an identifier cannot be changed.
    y += 1;
}

pub fn main() void {
    foo();
}

$ zig build-exe constant_identifier_cannot_change.zig
./docgen_tmp/constant_identifier_cannot_change.zig:8:7: error: cannot assign to constant
    y += 1;
      ^

const print = @import("std").debug.print;

pub fn main() void {
    var y: i32 = 5678;

    y += 1;

    print("{d}", .{y});
}

$ zig build-exe mutable_var.zig

$ ./mutable_var
5679

pub fn main() void {
    var x: i32;

    x = 1;
}

$ zig build-exe var_must_be_initialized.zig
docgen_tmp/var_must_be_initialized.zig:2:5: error: variables must be initialized
    var x: i32;
    ^

const print = @import("std").debug.print;

pub fn main() void {
    var x: i32 = undefined;
    x = 1;
    print("{d}", .{x});
}

$ zig build-exe assign_undefined.zig

$ ./assign_undefined
1

const std = @import("std");

test "expect addOne adds one to 41" {

    // The Standard Library contains useful functions to help create tests.
    // `expect` is a function that verifies its argument is true.
    // It will return an error if its argument is false to indicate a failure.
    // `try` is used to return an error to the test runner to notify it that the test failed.
    try std.testing.expect(addOne(41) == 42);
}

/// The function `addOne` adds one to the number given as its argument.
fn addOne(number: i32) i32 {
    return number + 1;
}

$ zig test introducing_zig_test.zig
1/1 test "expect addOne adds one to 41"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

// Imported source file tests will run when referenced from a top-level test declaration.
// The next line alone does not cause "introducing_zig_test.zig" tests to run.
const imported_file = @import("introducing_zig_test.zig");

test {
    // To run nested container tests, either, call `refAllDecls` which will
    // reference all declarations located in the given argument.
    // `@This()` is a builtin function that returns the innermost container it is called from.
    // In this example, the innermost container is this file (implicitly a struct).
    std.testing.refAllDecls(@This());

    // or, reference each container individually from a top-level test declaration.
    // The `_ = C;` syntax is a no-op reference to the identifier `C`.
    _ = S;
    _ = U;
    _ = @import("introducing_zig_test.zig");
}

const S = struct {
    test "S demo test" {
        try expect(true);
    }

    const SE = enum {
        V,

        // This test won't run because its container (SE) is not referenced.
        test "This Test Won't Run" {
            try expect(false);
        }
    };
};

const U = union { // U is referenced by the file's top-level test declaration
    s: US,        // and US is referenced here; therefore, "U.Us demo test" will run

    const US = struct {
        test "U.US demo test" {
            // This test is a top-level test declaration for the struct.
            // The struct is nested (declared) inside of a union.
            try expect(true);
        }
    };

    test "U demo test" {
        try expect(true);
    }
};

$ zig test testdecl_container_top_level.zig
1/5 test ""... OK
2/5 S.test "S demo test"... OK
3/5 U.test "U demo test"... OK
4/5 introducing_zig_test.test "expect addOne adds one to 41"... OK
5/5 US.test "U.US demo test"... OK
All 5 tests passed.

const std = @import("std");

test "expect this to fail" {
    try std.testing.expect(false);
}

test "expect this to succeed" {
    try std.testing.expect(true);
}

$ zig test test.zig
1/2 test "expect this to fail"... test "expect this to fail"... FAIL (TestUnexpectedResult)
FAIL (TestUnexpectedResult)
/home/andy/Downloads/zig/lib/std/testing.zig:303:14: 0x20801b in std.testing.expect (test)
    if (!ok) return error.TestUnexpectedResult;
             ^
/home/andy/Downloads/zig/docgen_tmp/test.zig:4:5: 0x207a51 in test "expect this to fail" (test)
    try std.testing.expect(false);
    ^
2/2 test "expect this to succeed"... OK
1 passed; 0 skipped; 1 failed.
error: the following test command failed with exit code 1:
docgen_tmp/zig-cache/o/8e4964e05ddaf866e77360a551b3c05b/test /home/andy/Downloads/zig/build-release/zig

test "this will be skipped" {
    return error.SkipZigTest;
}

$ zig test test.zig
1/1 test "this will be skipped"... test "this will be skipped"... SKIP
SKIP
0 passed; 1 skipped; 0 failed.

const std = @import("std");

test "async skip test" {
    var frame = async func();
    const result = await frame;
    try std.testing.expect(result == 1);
}

fn func() i32 {
    suspend {
        resume @frame();
    }
    return 1;
}

$ zig test async_skip.zig
1/1 test "async skip test"... test "async skip test"... SKIP (async test)
SKIP (async test)
0 passed; 1 skipped; 0 failed.

const std = @import("std");

test "detect leak" {
    var list = std.ArrayList(u21).init(std.testing.allocator);
    // missing `defer list.deinit();`
    try list.append('☔');

    try std.testing.expect(list.items.len == 1);
}

$ zig test test.zig
1/1 test "detect leak"... OK
[gpa] (err): memory address 0x7fc140eb0000 leaked:
/home/andy/Downloads/zig/lib/std/array_list.zig:325:69: 0x20d9d9 in std.array_list.ArrayListAligned(u21,null).ensureTotalCapacityPrecise (test)
                const new_memory = try self.allocator.reallocAtLeast(self.allocatedSlice(), new_capacity);
                                                                    ^
/home/andy/Downloads/zig/lib/std/array_list.zig:310:55: 0x20d7de in std.array_list.ArrayListAligned(u21,null).ensureTotalCapacity (test)
                return self.ensureTotalCapacityPrecise(better_capacity);
                                                      ^
/home/andy/Downloads/zig/lib/std/array_list.zig:349:41: 0x20d758 in std.array_list.ArrayListAligned(u21,null).addOne (test)
            try self.ensureTotalCapacity(newlen);
                                        ^
/home/andy/Downloads/zig/lib/std/array_list.zig:161:49: 0x209d54 in std.array_list.ArrayListAligned(u21,null).append (test)
            const new_item_ptr = try self.addOne();
                                                ^
/home/andy/Downloads/zig/docgen_tmp/test.zig:6:20: 0x209730 in test "detect leak" (test)
    try list.append('☔');
                   ^
/home/andy/Downloads/zig/lib/std/special/test_runner.zig:80:28: 0x23bd83 in std.special.main (test)
        } else test_fn.func();
                           ^
/home/andy/Downloads/zig/lib/std/start.zig:543:22: 0x233cac in std.start.callMain (test)
            root.main();
                     ^
/home/andy/Downloads/zig/lib/std/start.zig:495:12: 0x20e7ce in std.start.callMainWithArgs (test)
    return @call(.{ .modifier = .always_inline }, callMain, .{});
           ^


All 1 tests passed.
1 errors were logged.
1 tests leaked memory.
error: the following test command failed with exit code 1:
docgen_tmp/zig-cache/o/8e4964e05ddaf866e77360a551b3c05b/test /home/andy/Downloads/zig/build-release/zig

const std = @import("std");
const builtin = @import("builtin");
const expect = std.testing.expect;

test "builtin.is_test" {
    try expect(isATest());
}

fn isATest() bool {
    return builtin.is_test;
}

$ zig test detect_test.zig
1/1 test "builtin.is_test"... OK
All 1 tests passed.

const std = @import("std");

test "expectEqual demo" {
    const expected: i32 = 42;
    const actual = 42;

    // The first argument to `expectEqual` is the known, expected, result.
    // The second argument is the result of some expression.
    // The actual's type is casted to the type of expected.
    try std.testing.expectEqual(expected, actual);
}

test "expectError demo" {
    const expected_error = error.DemoError;
    const actual_error_union: anyerror!void = error.DemoError;

    // `expectError` will fail when the actual error is different than
    // the expected error.
    try std.testing.expectError(expected_error, actual_error_union);
}

$ zig test testing_functions.zig
1/2 test "expectEqual demo"... OK
2/2 test "expectError demo"... OK
All 2 tests passed.

var y: i32 = add(10, x);
const x: i32 = add(12, 34);

test "container level variables" {
    try expect(x == 46);
    try expect(y == 56);
}

fn add(a: i32, b: i32) i32 {
    return a + b;
}

const std = @import("std");
const expect = std.testing.expect;

$ zig test container_level_variables.zig
1/1 test "container level variables"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "namespaced container level variable" {
    try expect(foo() == 1235);
    try expect(foo() == 1236);
}

const S = struct {
    var x: i32 = 1234;
};

fn foo() i32 {
    S.x += 1;
    return S.x;
}

$ zig test namespaced_container_level_variable.zig
1/1 test "namespaced container level variable"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "static local variable" {
    try expect(foo() == 1235);
    try expect(foo() == 1236);
}

fn foo() i32 {
    const S = struct {
        var x: i32 = 1234;
    };
    S.x += 1;
    return S.x;
}

$ zig test static_local_variable.zig
1/1 test "static local variable"... OK
All 1 tests passed.

const std = @import("std");
const assert = std.debug.assert;

threadlocal var x: i32 = 1234;

test "thread local storage" {
    const thread1 = try std.Thread.spawn(.{}, testTls, .{});
    const thread2 = try std.Thread.spawn(.{}, testTls, .{});
    testTls();
    thread1.join();
    thread2.join();
}

fn testTls() void {
    assert(x == 1234);
    x += 1;
    assert(x == 1235);
}

$ zig test tls.zig
1/1 test "thread local storage"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "comptime vars" {
    var x: i32 = 1;
    comptime var y: i32 = 1;

    x += 1;
    y += 1;

    try expect(x == 2);
    try expect(y == 2);

    if (y != 2) {
        // This compile error never triggers because y is a comptime variable,
        // and so `y != 2` is a comptime value, and this if is statically evaluated.
        @compileError("wrong y value");
    }
}

$ zig test comptime_vars.zig
1/1 test "comptime vars"... OK
All 1 tests passed.

const decimal_int = 98222;
const hex_int = 0xff;
const another_hex_int = 0xFF;
const octal_int = 0o755;
const binary_int = 0b11110000;

// underscores may be placed between two digits as a visual separator
const one_billion = 1_000_000_000;
const binary_mask = 0b1_1111_1111;
const permissions = 0o7_5_5;
const big_address = 0xFF80_0000_0000_0000;

fn divide(a: i32, b: i32) i32 {
    return a / b;
}

const floating_point = 123.0E+77;
const another_float = 123.0;
const yet_another = 123.0e+77;

const hex_floating_point = 0x103.70p-5;
const another_hex_float = 0x103.70;
const yet_another_hex_float = 0x103.70P-5;

// underscores may be placed between two digits as a visual separator
const lightspeed = 299_792_458.000_000;
const nanosecond = 0.000_000_001;
const more_hex = 0x1234_5678.9ABC_CDEFp-10;

const std = @import("std");

const inf = std.math.inf(f32);
const negative_inf = -std.math.inf(f64);
const nan = std.math.nan(f128);

const std = @import("std");
const big = @as(f64, 1 << 40);

export fn foo_strict(x: f64) f64 {
    return x + big - big;
}

export fn foo_optimized(x: f64) f64 {
    @setFloatMode(.Optimized);
    return x + big - big;
}

$ zig build-obj foo.zig -O ReleaseFast

const print = @import("std").debug.print;

extern fn foo_strict(x: f64) f64;
extern fn foo_optimized(x: f64) f64;

pub fn main() void {
    const x = 0.001;
    print("optimized = {}\n", .{foo_optimized(x)});
    print("strict = {}\n", .{foo_strict(x)});
}

$ zig build-exe float_mode.zig foo.o

$ ./float_mode
optimized = 1.0e-03
strict = 9.765625e-04

const expect = @import("std").testing.expect;
const assert = @import("std").debug.assert;
const mem = @import("std").mem;

// array literal
const message = [_]u8{ 'h', 'e', 'l', 'l', 'o' };

// get the size of an array
comptime {
    assert(message.len == 5);
}

// A string literal is a single-item pointer to an array literal.
const same_message = "hello";

comptime {
    assert(mem.eql(u8, &message, same_message));
}

test "iterate over an array" {
    var sum: usize = 0;
    for (message) |byte| {
        sum += byte;
    }
    try expect(sum == 'h' + 'e' + 'l' * 2 + 'o');
}

// modifiable array
var some_integers: [100]i32 = undefined;

test "modify an array" {
    for (some_integers) |*item, i| {
        item.* = @intCast(i32, i);
    }
    try expect(some_integers[10] == 10);
    try expect(some_integers[99] == 99);
}

// array concatenation works if the values are known
// at compile time
const part_one = [_]i32{ 1, 2, 3, 4 };
const part_two = [_]i32{ 5, 6, 7, 8 };
const all_of_it = part_one ++ part_two;
comptime {
    assert(mem.eql(i32, &all_of_it, &[_]i32{ 1, 2, 3, 4, 5, 6, 7, 8 }));
}

// remember that string literals are arrays
const hello = "hello";
const world = "world";
const hello_world = hello ++ " " ++ world;
comptime {
    assert(mem.eql(u8, hello_world, "hello world"));
}

// ** does repeating patterns
const pattern = "ab" ** 3;
comptime {
    assert(mem.eql(u8, pattern, "ababab"));
}

// initialize an array to zero
const all_zero = [_]u16{0} ** 10;

comptime {
    assert(all_zero.len == 10);
    assert(all_zero[5] == 0);
}

// use compile-time code to initialize an array
var fancy_array = init: {
    var initial_value: [10]Point = undefined;
    for (initial_value) |*pt, i| {
        pt.* = Point{
            .x = @intCast(i32, i),
            .y = @intCast(i32, i) * 2,
        };
    }
    break :init initial_value;
};
const Point = struct {
    x: i32,
    y: i32,
};

test "compile-time array initialization" {
    try expect(fancy_array[4].x == 4);
    try expect(fancy_array[4].y == 8);
}

// call a function to initialize an array
var more_points = [_]Point{makePoint(3)} ** 10;
fn makePoint(x: i32) Point {
    return Point{
        .x = x,
        .y = x * 2,
    };
}
test "array initialization with function calls" {
    try expect(more_points[4].x == 3);
    try expect(more_points[4].y == 6);
    try expect(more_points.len == 10);
}

$ zig test arrays.zig
1/4 test "iterate over an array"... OK
2/4 test "modify an array"... OK
3/4 test "compile-time array initialization"... OK
4/4 test "array initialization with function calls"... OK
All 4 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "anonymous list literal syntax" {
    var array: [4]u8 = .{11, 22, 33, 44};
    try expect(array[0] == 11);
    try expect(array[1] == 22);
    try expect(array[2] == 33);
    try expect(array[3] == 44);
}

$ zig test anon_list.zig
1/1 test "anonymous list literal syntax"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "fully anonymous list literal" {
    try dump(.{ @as(u32, 1234), @as(f64, 12.34), true, "hi"});
}

fn dump(args: anytype) !void {
    try expect(args.@"0" == 1234);
    try expect(args.@"1" == 12.34);
    try expect(args.@"2");
    try expect(args.@"3"[0] == 'h');
    try expect(args.@"3"[1] == 'i');
}

$ zig test infer_list_literal.zig
1/1 test "fully anonymous list literal"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

const mat4x4 = [4][4]f32{
    [_]f32{ 1.0, 0.0, 0.0, 0.0 },
    [_]f32{ 0.0, 1.0, 0.0, 1.0 },
    [_]f32{ 0.0, 0.0, 1.0, 0.0 },
    [_]f32{ 0.0, 0.0, 0.0, 1.0 },
};
test "multidimensional arrays" {
    // Access the 2D array by indexing the outer array, and then the inner array.
    try expect(mat4x4[1][1] == 1.0);

    // Here we iterate with for loops.
    for (mat4x4) |row, row_index| {
        for (row) |cell, column_index| {
            if (row_index == column_index) {
                try expect(cell == 1.0);
            }
        }
    }
}

$ zig test multidimensional.zig
1/1 test "multidimensional arrays"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "null terminated array" {
    const array = [_:0]u8 {1, 2, 3, 4};

    try expect(@TypeOf(array) == [4:0]u8);
    try expect(array.len == 4);
    try expect(array[4] == 0);
}

$ zig test null_terminated_array.zig
1/1 test "null terminated array"... OK
All 1 tests passed.

const std = @import("std");
const Vector = std.meta.Vector;
const expectEqual = std.testing.expectEqual;

test "Basic vector usage" {
    // Vectors have a compile-time known length and base type,
    // and can be assigned to using array literal syntax
    const a: Vector(4, i32) = [_]i32{ 1, 2, 3, 4 };
    const b: Vector(4, i32) = [_]i32{ 5, 6, 7, 8 };

    // Math operations take place element-wise
    const c = a + b;

    // Individual vector elements can be accessed using array indexing syntax.
    try expectEqual(6, c[0]);
    try expectEqual(8, c[1]);
    try expectEqual(10, c[2]);
    try expectEqual(12, c[3]);
}

test "Conversion between vectors, arrays, and slices" {
    // Vectors and fixed-length arrays can be automatically assigned back and forth
    var arr1: [4]f32 = [_]f32{ 1.1, 3.2, 4.5, 5.6 };
    var vec: Vector(4, f32) = arr1;
    var arr2: [4]f32 = vec;
    try expectEqual(arr1, arr2);

    // You can also assign from a slice with comptime-known length to a vector using .*
    const vec2: Vector(2, f32) = arr1[1..3].*;

    var slice: []const f32 = &arr1;
    var offset: u32 = 1;
    // To extract a comptime-known length from a runtime-known offset,
    // first extract a new slice from the starting offset, then an array of
    // comptime known length
    const vec3: Vector(2, f32) = slice[offset..][0..2].*;
    try expectEqual(slice[offset], vec2[0]);
    try expectEqual(slice[offset + 1], vec2[1]);
    try expectEqual(vec2, vec3);
}

$ zig test vector_example.zig
1/2 test "Basic vector usage"... OK
2/2 test "Conversion between vectors, arrays, and slices"... OK
All 2 tests passed.

const expect = @import("std").testing.expect;

test "address of syntax" {
    // Get the address of a variable:
    const x: i32 = 1234;
    const x_ptr = &x;

    // Dereference a pointer:
    try expect(x_ptr.* == 1234);

    // When you get the address of a const variable, you get a const single-item pointer.
    try expect(@TypeOf(x_ptr) == *const i32);

    // If you want to mutate the value, you'd need an address of a mutable variable:
    var y: i32 = 5678;
    const y_ptr = &y;
    try expect(@TypeOf(y_ptr) == *i32);
    y_ptr.* += 1;
    try expect(y_ptr.* == 5679);
}

test "pointer array access" {
    // Taking an address of an individual element gives a
    // single-item pointer. This kind of pointer
    // does not support pointer arithmetic.
    var array = [_]u8{ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
    const ptr = &array[2];
    try expect(@TypeOf(ptr) == *u8);

    try expect(array[2] == 3);
    ptr.* += 1;
    try expect(array[2] == 4);
}

$ zig test single_item_pointer_test.zig
1/2 test "address of syntax"... OK
2/2 test "pointer array access"... OK
All 2 tests passed.

const expect = @import("std").testing.expect;

test "pointer slicing" {
    var array = [_]u8{ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
    const slice = array[2..4];
    try expect(slice.len == 2);

    try expect(array[3] == 4);
    slice[1] += 1;
    try expect(array[3] == 5);
}

$ zig test slice_bounds.zig
1/1 test "pointer slicing"... OK
All 1 tests passed.

const expect = @import("std").testing.expect;

test "comptime pointers" {
    comptime {
        var x: i32 = 1;
        const ptr = &x;
        ptr.* += 1;
        x += 1;
        try expect(ptr.* == 3);
    }
}

$ zig test comptime_pointers.zig
1/1 test "comptime pointers"... OK
All 1 tests passed.

const expect = @import("std").testing.expect;

test "@ptrToInt and @intToPtr" {
    const ptr = @intToPtr(*i32, 0xdeadbee0);
    const addr = @ptrToInt(ptr);
    try expect(@TypeOf(addr) == usize);
    try expect(addr == 0xdeadbee0);
}

$ zig test integer_pointer_conversion.zig
1/1 test "@ptrToInt and @intToPtr"... OK
All 1 tests passed.

const expect = @import("std").testing.expect;

test "comptime @intToPtr" {
    comptime {
        // Zig is able to do this at compile-time, as long as
        // ptr is never dereferenced.
        const ptr = @intToPtr(*i32, 0xdeadbee0);
        const addr = @ptrToInt(ptr);
        try expect(@TypeOf(addr) == usize);
        try expect(addr == 0xdeadbee0);
    }
}

$ zig test comptime_pointer_conversion.zig
1/1 test "comptime @intToPtr"... OK
All 1 tests passed.

const expect = @import("std").testing.expect;

test "volatile" {
    const mmio_ptr = @intToPtr(*volatile u8, 0x12345678);
    try expect(@TypeOf(mmio_ptr) == *volatile u8);
}

$ zig test volatile.zig
1/1 test "volatile"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "pointer casting" {
    const bytes align(@alignOf(u32)) = [_]u8{ 0x12, 0x12, 0x12, 0x12 };
    const u32_ptr = @ptrCast(*const u32, &bytes);
    try expect(u32_ptr.* == 0x12121212);

    // Even this example is contrived - there are better ways to do the above than
    // pointer casting. For example, using a slice narrowing cast:
    const u32_value = std.mem.bytesAsSlice(u32, bytes[0..])[0];
    try expect(u32_value == 0x12121212);

    // And even another way, the most straightforward way to do it:
    try expect(@bitCast(u32, bytes) == 0x12121212);
}

test "pointer child type" {
    // pointer types have a `child` field which tells you the type they point to.
    try expect(@typeInfo(*u32).Pointer.child == u32);
}

$ zig test pointer_casting.zig
1/2 test "pointer casting"... OK
2/2 test "pointer child type"... OK
All 2 tests passed.

const std = @import("std");
const builtin = @import("builtin");
const expect = std.testing.expect;

test "variable alignment" {
    var x: i32 = 1234;
    const align_of_i32 = @alignOf(@TypeOf(x));
    try expect(@TypeOf(&x) == *i32);
    try expect(*i32 == *align(align_of_i32) i32);
    if (builtin.target.cpu.arch == .x86_64) {
        try expect(@typeInfo(*i32).Pointer.alignment == 4);
    }
}

$ zig test variable_alignment.zig
1/1 test "variable alignment"... OK
All 1 tests passed.

const expect = @import("std").testing.expect;

var foo: u8 align(4) = 100;

test "global variable alignment" {
    try expect(@typeInfo(@TypeOf(&foo)).Pointer.alignment == 4);
    try expect(@TypeOf(&foo) == *align(4) u8);
    const as_pointer_to_array: *[1]u8 = &foo;
    const as_slice: []u8 = as_pointer_to_array;
    try expect(@TypeOf(as_slice) == []align(4) u8);
}

fn derp() align(@sizeOf(usize) * 2) i32 { return 1234; }
fn noop1() align(1) void {}
fn noop4() align(4) void {}

test "function alignment" {
    try expect(derp() == 1234);
    try expect(@TypeOf(noop1) == fn() align(1) void);
    try expect(@TypeOf(noop4) == fn() align(4) void);
    noop1();
    noop4();
}

$ zig test variable_func_alignment.zig
1/2 test "global variable alignment"... OK
2/2 test "function alignment"... OK
All 2 tests passed.

const std = @import("std");

test "pointer alignment safety" {
    var array align(4) = [_]u32{ 0x11111111, 0x11111111 };
    const bytes = std.mem.sliceAsBytes(array[0..]);
    try std.testing.expect(foo(bytes) == 0x11111111);
}
fn foo(bytes: []u8) u32 {
    const slice4 = bytes[1..5];
    const int_slice = std.mem.bytesAsSlice(u32, @alignCast(4, slice4));
    return int_slice[0];
}

$ zig test test.zig
1/1 test "pointer alignment safety"... thread 792246 panic: incorrect alignment
/home/andy/Downloads/zig/docgen_tmp/test.zig:10:63: 0x2080ec in foo (test)
    const int_slice = std.mem.bytesAsSlice(u32, @alignCast(4, slice4));
                                                              ^
/home/andy/Downloads/zig/docgen_tmp/test.zig:6:31: 0x207a69 in test "pointer alignment safety" (test)
    try std.testing.expect(foo(bytes) == 0x11111111);
                              ^
/home/andy/Downloads/zig/lib/std/special/test_runner.zig:80:28: 0x22f6d3 in std.special.main (test)
        } else test_fn.func();
                           ^
/home/andy/Downloads/zig/lib/std/start.zig:543:22: 0x2280cc in std.start.callMain (test)
            root.main();
                     ^
/home/andy/Downloads/zig/lib/std/start.zig:495:12: 0x20953e in std.start.callMainWithArgs (test)
    return @call(.{ .modifier = .always_inline }, callMain, .{});
           ^
/home/andy/Downloads/zig/lib/std/start.zig:409:17: 0x208546 in std.start.posixCallMainAndExit (test)
    std.os.exit(@call(.{ .modifier = .always_inline }, callMainWithArgs, .{ argc, argv, envp }));
                ^
/home/andy/Downloads/zig/lib/std/start.zig:322:5: 0x208352 in std.start._start (test)
    @call(.{ .modifier = .never_inline }, posixCallMainAndExit, .{});
    ^
error: the following test command crashed:
docgen_tmp/zig-cache/o/8e4964e05ddaf866e77360a551b3c05b/test /home/andy/Downloads/zig/build-release/zig

const std = @import("std");
const expect = std.testing.expect;

test "allowzero" {
    var zero: usize = 0;
    var ptr = @intToPtr(*allowzero i32, zero);
    try expect(@ptrToInt(ptr) == 0);
}

$ zig test allowzero.zig
1/1 test "allowzero"... OK
All 1 tests passed.

const std = @import("std");

// This is also available as `std.c.printf`.
pub extern "c" fn printf(format: [*:0]const u8, ...) c_int;

pub fn main() anyerror!void {
    _ = printf("Hello, world!\n"); // OK

    const msg = "Hello, world!\n";
    const non_null_terminated_msg: [msg.len]u8 = msg.*;
    _ = printf(&non_null_terminated_msg);
}

$ zig build-exe test.zig -lc
./docgen_tmp/test.zig:11:17: error: expected type '[*:0]const u8', found '*const [14]u8'
    _ = printf(&non_null_terminated_msg);
                ^
./docgen_tmp/test.zig:11:17: note: destination pointer requires a terminating '0' sentinel
    _ = printf(&non_null_terminated_msg);
                ^

const expect = @import("std").testing.expect;

test "basic slices" {
    var array = [_]i32{ 1, 2, 3, 4 };
    // A slice is a pointer and a length. The difference between an array and
    // a slice is that the array's length is part of the type and known at
    // compile-time, whereas the slice's length is known at runtime.
    // Both can be accessed with the `len` field.
    var known_at_runtime_zero: usize = 0;
    const slice = array[known_at_runtime_zero..array.len];
    try expect(&slice[0] == &array[0]);
    try expect(slice.len == array.len);

    // Using the address-of operator on a slice gives a single-item pointer,
    // while using the `ptr` field gives a many-item pointer.
    try expect(@TypeOf(slice.ptr) == [*]i32);
    try expect(@TypeOf(&slice[0]) == *i32);
    try expect(@ptrToInt(slice.ptr) == @ptrToInt(&slice[0]));

    // Slices have array bounds checking. If you try to access something out
    // of bounds, you'll get a safety check failure:
    slice[10] += 1;

    // Note that `slice.ptr` does not invoke safety checking, while `&slice[0]`
    // asserts that the slice has len >= 1.
}

$ zig test test.zig
1/1 test "basic slices"... thread 792342 panic: index out of bounds
/home/andy/Downloads/zig/docgen_tmp/test.zig:22:10: 0x207c83 in test "basic slices" (test)
    slice[10] += 1;
         ^
/home/andy/Downloads/zig/lib/std/special/test_runner.zig:80:28: 0x22f6d3 in std.special.main (test)
        } else test_fn.func();
                           ^
/home/andy/Downloads/zig/lib/std/start.zig:543:22: 0x2280cc in std.start.callMain (test)
            root.main();
                     ^
/home/andy/Downloads/zig/lib/std/start.zig:495:12: 0x20953e in std.start.callMainWithArgs (test)
    return @call(.{ .modifier = .always_inline }, callMain, .{});
           ^
/home/andy/Downloads/zig/lib/std/start.zig:409:17: 0x2085d6 in std.start.posixCallMainAndExit (test)
    std.os.exit(@call(.{ .modifier = .always_inline }, callMainWithArgs, .{ argc, argv, envp }));
                ^
/home/andy/Downloads/zig/lib/std/start.zig:322:5: 0x2083e2 in std.start._start (test)
    @call(.{ .modifier = .never_inline }, posixCallMainAndExit, .{});
    ^
error: the following test command crashed:
docgen_tmp/zig-cache/o/8e4964e05ddaf866e77360a551b3c05b/test /home/andy/Downloads/zig/build-release/zig

const std = @import("std");
const expect = std.testing.expect;
const mem = std.mem;
const fmt = std.fmt;

test "using slices for strings" {
    // Zig has no concept of strings. String literals are const pointers
    // to null-terminated arrays of u8, and by convention parameters
    // that are "strings" are expected to be UTF-8 encoded slices of u8.
    // Here we coerce *const [5:0]u8 and *const [6:0]u8 to []const u8
    const hello: []const u8 = "hello";
    const world: []const u8 = "世界";

    var all_together: [100]u8 = undefined;
    // You can use slice syntax on an array to convert an array into a slice.
    const all_together_slice = all_together[0..];
    // String concatenation example.
    const hello_world = try fmt.bufPrint(all_together_slice, "{s} {s}", .{ hello, world });

    // Generally, you can use UTF-8 and not worry about whether something is a
    // string. If you don't need to deal with individual characters, no need
    // to decode.
    try expect(mem.eql(u8, hello_world, "hello 世界"));
}

test "slice pointer" {
    var array: [10]u8 = undefined;
    const ptr = &array;

    // You can use slicing syntax to convert a pointer into a slice:
    const slice = ptr[0..5];
    slice[2] = 3;
    try expect(slice[2] == 3);
    // The slice is mutable because we sliced a mutable pointer.
    // Furthermore, it is actually a pointer to an array, since the start
    // and end indexes were both comptime-known.
    try expect(@TypeOf(slice) == *[5]u8);

    // You can also slice a slice:
    const slice2 = slice[2..3];
    try expect(slice2.len == 1);
    try expect(slice2[0] == 3);
}

$ zig test slices.zig
1/2 test "using slices for strings"... OK
2/2 test "slice pointer"... OK
All 2 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "null terminated slice" {
    const slice: [:0]const u8 = "hello";

    try expect(slice.len == 5);
    try expect(slice[5] == 0);
}

$ zig test null_terminated_slice.zig
1/1 test "null terminated slice"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "null terminated slicing" {
    var array = [_]u8{ 3, 2, 1, 0, 3, 2, 1, 0 };
    var runtime_length: usize = 3;
    const slice = array[0..runtime_length :0];

    try expect(@TypeOf(slice) == [:0]u8);
    try expect(slice.len == 3);
}

$ zig test null_terminated_slicing.zig
1/1 test "null terminated slicing"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "sentinel mismatch" {
    var array = [_]u8{ 3, 2, 1, 0 };
    
    // Creating a sentinel-terminated slice from the array with a length of 2 
    // will result in the value `1` occupying the sentinel element position. 
    // This does not match the indicated sentinel value of `0` and will lead 
    // to a runtime panic.
    var runtime_length: usize = 2;
    const slice = array[0..runtime_length :0];

    _ = slice;
}

$ zig test test.zig
1/1 test "sentinel mismatch"... thread 792492 panic: sentinel mismatch
/home/andy/Downloads/zig/docgen_tmp/test.zig:12:24: 0x207a3a in test "sentinel mismatch" (test)
    const slice = array[0..runtime_length :0];
                       ^
/home/andy/Downloads/zig/lib/std/special/test_runner.zig:80:28: 0x22f463 in std.special.main (test)
        } else test_fn.func();
                           ^
/home/andy/Downloads/zig/lib/std/start.zig:543:22: 0x227e5c in std.start.callMain (test)
            root.main();
                     ^
/home/andy/Downloads/zig/lib/std/start.zig:495:12: 0x20927e in std.start.callMainWithArgs (test)
    return @call(.{ .modifier = .always_inline }, callMain, .{});
           ^
/home/andy/Downloads/zig/lib/std/start.zig:409:17: 0x208316 in std.start.posixCallMainAndExit (test)
    std.os.exit(@call(.{ .modifier = .always_inline }, callMainWithArgs, .{ argc, argv, envp }));
                ^
/home/andy/Downloads/zig/lib/std/start.zig:322:5: 0x208122 in std.start._start (test)
    @call(.{ .modifier = .never_inline }, posixCallMainAndExit, .{});
    ^
error: the following test command crashed:
docgen_tmp/zig-cache/o/8e4964e05ddaf866e77360a551b3c05b/test /home/andy/Downloads/zig/build-release/zig

// Declare a struct.
// Zig gives no guarantees about the order of fields and the size of
// the struct but the fields are guaranteed to be ABI-aligned.
const Point = struct {
    x: f32,
    y: f32,
};

// Maybe we want to pass it to OpenGL so we want to be particular about
// how the bytes are arranged.
const Point2 = packed struct {
    x: f32,
    y: f32,
};


// Declare an instance of a struct.
const p = Point {
    .x = 0.12,
    .y = 0.34,
};

// Maybe we're not ready to fill out some of the fields.
var p2 = Point {
    .x = 0.12,
    .y = undefined,
};

// Structs can have methods
// Struct methods are not special, they are only namespaced
// functions that you can call with dot syntax.
const Vec3 = struct {
    x: f32,
    y: f32,
    z: f32,

    pub fn init(x: f32, y: f32, z: f32) Vec3 {
        return Vec3 {
            .x = x,
            .y = y,
            .z = z,
        };
    }

    pub fn dot(self: Vec3, other: Vec3) f32 {
        return self.x * other.x + self.y * other.y + self.z * other.z;
    }
};

const expect = @import("std").testing.expect;
test "dot product" {
    const v1 = Vec3.init(1.0, 0.0, 0.0);
    const v2 = Vec3.init(0.0, 1.0, 0.0);
    try expect(v1.dot(v2) == 0.0);

    // Other than being available to call with dot syntax, struct methods are
    // not special. You can reference them as any other declaration inside
    // the struct:
    try expect(Vec3.dot(v1, v2) == 0.0);
}

// Structs can have declarations.
// Structs can have 0 fields.
const Empty = struct {
    pub const PI = 3.14;
};
test "struct namespaced variable" {
    try expect(Empty.PI == 3.14);
    try expect(@sizeOf(Empty) == 0);

    // you can still instantiate an empty struct
    const does_nothing = Empty {};

    _ = does_nothing;
}

// struct field order is determined by the compiler for optimal performance.
// however, you can still calculate a struct base pointer given a field pointer:
fn setYBasedOnX(x: *f32, y: f32) void {
    const point = @fieldParentPtr(Point, "x", x);
    point.y = y;
}
test "field parent pointer" {
    var point = Point {
        .x = 0.1234,
        .y = 0.5678,
    };
    setYBasedOnX(&point.x, 0.9);
    try expect(point.y == 0.9);
}

// You can return a struct from a function. This is how we do generics
// in Zig:
fn LinkedList(comptime T: type) type {
    return struct {
        pub const Node = struct {
            prev: ?*Node,
            next: ?*Node,
            data: T,
        };

        first: ?*Node,
        last:  ?*Node,
        len:   usize,
    };
}

test "linked list" {
    // Functions called at compile-time are memoized. This means you can
    // do this:
    try expect(LinkedList(i32) == LinkedList(i32));

    var list = LinkedList(i32) {
        .first = null,
        .last = null,
        .len = 0,
    };
    try expect(list.len == 0);

    // Since types are first class values you can instantiate the type
    // by assigning it to a variable:
    const ListOfInts = LinkedList(i32);
    try expect(ListOfInts == LinkedList(i32));

    var node = ListOfInts.Node {
        .prev = null,
        .next = null,
        .data = 1234,
    };
    var list2 = LinkedList(i32) {
        .first = &node,
        .last = &node,
        .len = 1,
    };
    try expect(list2.first.?.data == 1234);
}

$ zig test structs.zig
1/4 test "dot product"... OK
2/4 test "struct namespaced variable"... OK
3/4 test "field parent pointer"... OK
4/4 test "linked list"... OK
All 4 tests passed.

const Foo = struct {
    a: i32 = 1234,
    b: i32,
};

test "default struct initialization fields" {
    const x = Foo{
        .b = 5,
    };
    if (x.a + x.b != 1239) {
        @compileError("it's even comptime known!");
    }
}

$ zig test default_field_values.zig
1/1 test "default struct initialization fields"... OK
All 1 tests passed.

const std = @import("std");
const native_endian = @import("builtin").target.cpu.arch.endian();
const expect = std.testing.expect;

const Full = packed struct {
    number: u16,
};
const Divided = packed struct {
    half1: u8,
    quarter3: u4,
    quarter4: u4,
};

test "@bitCast between packed structs" {
    try doTheTest();
    comptime try doTheTest();
}

fn doTheTest() !void {
    try expect(@sizeOf(Full) == 2);
    try expect(@sizeOf(Divided) == 2);
    var full = Full{ .number = 0x1234 };
    var divided = @bitCast(Divided, full);
    switch (native_endian) {
        .Big => {
            try expect(divided.half1 == 0x12);
            try expect(divided.quarter3 == 0x3);
            try expect(divided.quarter4 == 0x4);
        },
        .Little => {
            try expect(divided.half1 == 0x34);
            try expect(divided.quarter3 == 0x2);
            try expect(divided.quarter4 == 0x1);
        },
    }
}

$ zig test packed_structs.zig
1/1 test "@bitCast between packed structs"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

const BitField = packed struct {
    a: u3,
    b: u3,
    c: u2,
};

var foo = BitField{
    .a = 1,
    .b = 2,
    .c = 3,
};

test "pointer to non-byte-aligned field" {
    const ptr = &foo.b;
    try expect(ptr.* == 2);
}

$ zig test pointer_to_non-byte_aligned_field.zig
1/1 test "pointer to non-byte-aligned field"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

const BitField = packed struct {
    a: u3,
    b: u3,
    c: u2,
};

var bit_field = BitField{
    .a = 1,
    .b = 2,
    .c = 3,
};

test "pointer to non-bit-aligned field" {
    try expect(bar(&bit_field.b) == 2);
}

fn bar(x: *const u3) u3 {
    return x.*;
}

$ zig test test.zig
./docgen_tmp/test.zig:17:30: error: expected type '*const u3', found '*align(:3:1) u3'
    try expect(bar(&bit_field.b) == 2);
                             ^

const std = @import("std");
const expect = std.testing.expect;

const BitField = packed struct {
    a: u3,
    b: u3,
    c: u2,
};

var bit_field = BitField{
    .a = 1,
    .b = 2,
    .c = 3,
};

test "pointer to non-bit-aligned field" {
    try expect(@ptrToInt(&bit_field.a) == @ptrToInt(&bit_field.b));
    try expect(@ptrToInt(&bit_field.a) == @ptrToInt(&bit_field.c));
}

$ zig test pointer_to_non-bit_aligned_field.zig
1/1 test "pointer to non-bit-aligned field"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

const BitField = packed struct {
    a: u3,
    b: u3,
    c: u2,
};

test "pointer to non-bit-aligned field" {
    comptime {
        try expect(@bitOffsetOf(BitField, "a") == 0);
        try expect(@bitOffsetOf(BitField, "b") == 3);
        try expect(@bitOffsetOf(BitField, "c") == 6);

        try expect(@offsetOf(BitField, "a") == 0);
        try expect(@offsetOf(BitField, "b") == 0);
        try expect(@offsetOf(BitField, "c") == 0);
    }
}

$ zig test test_bitOffsetOf_offsetOf.zig
1/1 test "pointer to non-bit-aligned field"... OK
All 1 tests passed.

const S = packed struct {
    a: u32,
    b: u32,
};
test "overaligned pointer to packed struct" {
    var foo: S align(4) = undefined;
    const ptr: *align(4) S = &foo;
    const ptr_to_b: *u32 = &ptr.b;
    _ = ptr_to_b;
}

$ zig test test.zig
./docgen_tmp/test.zig:8:32: error: expected type '*u32', found '*align(1) u32'
    const ptr_to_b: *u32 = &ptr.b;
                               ^

const std = @import("std");
const expectEqual = std.testing.expectEqual;

test "aligned struct fields" {
    const S = struct {
        a: u32 align(2),
        b: u32 align(64),
    };
    var foo = S{ .a = 1, .b = 2 };

    try expectEqual(64, @alignOf(S));
    try expectEqual(*align(2) u32, @TypeOf(&foo.a));
    try expectEqual(*align(64) u32, @TypeOf(&foo.b));
}

$ zig test test_aligned_struct_fields.zig
1/1 test "aligned struct fields"... OK
All 1 tests passed.

const std = @import("std");

pub fn main() void {
    const Foo = struct {};
    std.debug.print("variable: {s}\n", .{@typeName(Foo)});
    std.debug.print("anonymous: {s}\n", .{@typeName(struct {})});
    std.debug.print("function: {s}\n", .{@typeName(List(i32))});
}

fn List(comptime T: type) type {
    return struct {
        x: T,
    };
}

$ zig build-exe struct_name.zig

$ ./struct_name
variable: Foo
anonymous: struct:6:53
function: List(i32)

const std = @import("std");
const expect = std.testing.expect;

const Point = struct {x: i32, y: i32};

test "anonymous struct literal" {
    var pt: Point = .{
        .x = 13,
        .y = 67,
    };
    try expect(pt.x == 13);
    try expect(pt.y == 67);
}

$ zig test struct_result.zig
1/1 test "anonymous struct literal"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "fully anonymous struct" {
    try dump(.{
        .int = @as(u32, 1234),
        .float = @as(f64, 12.34),
        .b = true,
        .s = "hi",
    });
}

fn dump(args: anytype) !void {
    try expect(args.int == 1234);
    try expect(args.float == 12.34);
    try expect(args.b);
    try expect(args.s[0] == 'h');
    try expect(args.s[1] == 'i');
}

$ zig test struct_anon.zig
1/1 test "fully anonymous struct"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "tuple" {
    const values = .{
        @as(u32, 1234),
        @as(f64, 12.34),
        true,
        "hi",
    } ++ .{false} ** 2;
    try expect(values[0] == 1234);
    try expect(values[4] == false);
    inline for (values) |v, i| {
        if (i != 2) continue;
        try expect(v);
    }
    try expect(values.len == 6);
    try expect(values.@"3"[0] == 'h');
}

$ zig test tuple.zig
1/1 test "tuple"... OK
All 1 tests passed.

const expect = @import("std").testing.expect;
const mem = @import("std").mem;

// Declare an enum.
const Type = enum {
    ok,
    not_ok,
};

// Declare a specific instance of the enum variant.
const c = Type.ok;

// If you want access to the ordinal value of an enum, you
// can specify the tag type.
const Value = enum(u2) {
    zero,
    one,
    two,
};

// Now you can cast between u2 and Value.
// The ordinal value starts from 0, counting up for each member.
test "enum ordinal value" {
    try expect(@enumToInt(Value.zero) == 0);
    try expect(@enumToInt(Value.one) == 1);
    try expect(@enumToInt(Value.two) == 2);
}

// You can override the ordinal value for an enum.
const Value2 = enum(u32) {
    hundred = 100,
    thousand = 1000,
    million = 1000000,
};
test "set enum ordinal value" {
    try expect(@enumToInt(Value2.hundred) == 100);
    try expect(@enumToInt(Value2.thousand) == 1000);
    try expect(@enumToInt(Value2.million) == 1000000);
}

// Enums can have methods, the same as structs and unions.
// Enum methods are not special, they are only namespaced
// functions that you can call with dot syntax.
const Suit = enum {
    clubs,
    spades,
    diamonds,
    hearts,

    pub fn isClubs(self: Suit) bool {
        return self == Suit.clubs;
    }
};
test "enum method" {
    const p = Suit.spades;
    try expect(!p.isClubs());
}

// An enum variant of different types can be switched upon.
const Foo = enum {
    string,
    number,
    none,
};
test "enum variant switch" {
    const p = Foo.number;
    const what_is_it = switch (p) {
        Foo.string => "this is a string",
        Foo.number => "this is a number",
        Foo.none => "this is a none",
    };
    try expect(mem.eql(u8, what_is_it, "this is a number"));
}

// @typeInfo can be used to access the integer tag type of an enum.
const Small = enum {
    one,
    two,
    three,
    four,
};
test "std.meta.Tag" {
    try expect(@typeInfo(Small).Enum.tag_type == u2);
}

// @typeInfo tells us the field count and the fields names:
test "@typeInfo" {
    try expect(@typeInfo(Small).Enum.fields.len == 4);
    try expect(mem.eql(u8, @typeInfo(Small).Enum.fields[1].name, "two"));
}

// @tagName gives a [:0]const u8 representation of an enum value:
test "@tagName" {
    try expect(mem.eql(u8, @tagName(Small.three), "three"));
}

$ zig test enums.zig
1/7 test "enum ordinal value"... OK
2/7 test "set enum ordinal value"... OK
3/7 test "enum method"... OK
4/7 test "enum variant switch"... OK
5/7 test "std.meta.Tag"... OK
6/7 test "@typeInfo"... OK
7/7 test "@tagName"... OK
All 7 tests passed.

const Foo = enum { a, b, c };
export fn entry(foo: Foo) void { _ = foo; }

$ zig build-obj test.zig
./docgen_tmp/test.zig:2:22: error: parameter of type 'Foo' not allowed in function with calling convention 'C'
export fn entry(foo: Foo) void { _ = foo; }
                     ^

const Foo = enum(c_int) { a, b, c };
export fn entry(foo: Foo) void { _ = foo; }

$ zig build-obj test.zig

const std = @import("std");
const expect = std.testing.expect;

const Color = enum {
    auto,
    off,
    on,
};

test "enum literals" {
    const color1: Color = .auto;
    const color2 = Color.auto;
    try expect(color1 == color2);
}

test "switch using enum literals" {
    const color = Color.on;
    const result = switch (color) {
        .auto => false,
        .on => true,
        .off => false,
    };
    try expect(result);
}

$ zig test test_enum_literals.zig
1/2 test "enum literals"... OK
2/2 test "switch using enum literals"... OK
All 2 tests passed.

const std = @import("std");
const expect = std.testing.expect;

const Number = enum(u8) {
    one,
    two,
    three,
    _,
};

test "switch on non-exhaustive enum" {
    const number = Number.one;
    const result = switch (number) {
        .one => true,
        .two,
        .three => false,
        _ => false,
    };
    try expect(result);
    const is_one = switch (number) {
        .one => true,
        else => false,
    };
    try expect(is_one);
}

$ zig test test_switch_non-exhaustive.zig
1/1 test "switch on non-exhaustive enum"... OK
All 1 tests passed.

const Payload = union {
    int: i64,
    float: f64,
    boolean: bool,
};
test "simple union" {
    var payload = Payload{ .int = 1234 };
    payload.float = 12.34;
}

$ zig test test.zig
1/1 test "simple union"... thread 793111 panic: access of inactive union field
/home/andy/Downloads/zig/docgen_tmp/test.zig:8:12: 0x207a4b in test "simple union" (test)
    payload.float = 12.34;
           ^
/home/andy/Downloads/zig/lib/std/special/test_runner.zig:80:28: 0x22f453 in std.special.main (test)
        } else test_fn.func();
                           ^
/home/andy/Downloads/zig/lib/std/start.zig:543:22: 0x227e4c in std.start.callMain (test)
            root.main();
                     ^
/home/andy/Downloads/zig/lib/std/start.zig:495:12: 0x20926e in std.start.callMainWithArgs (test)
    return @call(.{ .modifier = .always_inline }, callMain, .{});
           ^
/home/andy/Downloads/zig/lib/std/start.zig:409:17: 0x208306 in std.start.posixCallMainAndExit (test)
    std.os.exit(@call(.{ .modifier = .always_inline }, callMainWithArgs, .{ argc, argv, envp }));
                ^
/home/andy/Downloads/zig/lib/std/start.zig:322:5: 0x208112 in std.start._start (test)
    @call(.{ .modifier = .never_inline }, posixCallMainAndExit, .{});
    ^
error: the following test command crashed:
docgen_tmp/zig-cache/o/8e4964e05ddaf866e77360a551b3c05b/test /home/andy/Downloads/zig/build-release/zig

const std = @import("std");
const expect = std.testing.expect;

const Payload = union {
    int: i64,
    float: f64,
    boolean: bool,
};
test "simple union" {
    var payload = Payload{ .int = 1234 };
    try expect(payload.int == 1234);
    payload = Payload{ .float = 12.34 };
    try expect(payload.float == 12.34);
}

$ zig test test_simple_union.zig
1/1 test "simple union"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

const ComplexTypeTag = enum {
    ok,
    not_ok,
};
const ComplexType = union(ComplexTypeTag) {
    ok: u8,
    not_ok: void,
};

test "switch on tagged union" {
    const c = ComplexType{ .ok = 42 };
    try expect(@as(ComplexTypeTag, c) == ComplexTypeTag.ok);

    switch (c) {
        ComplexTypeTag.ok => |value| try expect(value == 42),
        ComplexTypeTag.not_ok => unreachable,
    }
}

test "get tag type" {
    try expect(std.meta.Tag(ComplexType) == ComplexTypeTag);
}

test "coerce to enum" {
    const c1 = ComplexType{ .ok = 42 };
    const c2 = ComplexType.not_ok;

    try expect(c1 == .ok);
    try expect(c2 == .not_ok);
}

$ zig test test_switch_tagged_union.zig
1/3 test "switch on tagged union"... OK
2/3 test "get tag type"... OK
3/3 test "coerce to enum"... OK
All 3 tests passed.

const std = @import("std");
const expect = std.testing.expect;

const ComplexTypeTag = enum {
    ok,
    not_ok,
};
const ComplexType = union(ComplexTypeTag) {
    ok: u8,
    not_ok: void,
};

test "modify tagged union in switch" {
    var c = ComplexType{ .ok = 42 };
    try expect(@as(ComplexTypeTag, c) == ComplexTypeTag.ok);

    switch (c) {
        ComplexTypeTag.ok => |*value| value.* += 1,
        ComplexTypeTag.not_ok => unreachable,
    }

    try expect(c.ok == 43);
}

$ zig test test_switch_modify_tagged_union.zig
1/1 test "modify tagged union in switch"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

const Variant = union(enum) {
    int: i32,
    boolean: bool,

    // void can be omitted when inferring enum tag type.
    none,

    fn truthy(self: Variant) bool {
        return switch (self) {
            Variant.int => |x_int| x_int != 0,
            Variant.boolean => |x_bool| x_bool,
            Variant.none => false,
        };
    }
};

test "union method" {
    var v1 = Variant{ .int = 1 };
    var v2 = Variant{ .boolean = false };

    try expect(v1.truthy());
    try expect(!v2.truthy());
}

$ zig test test_union_method.zig
1/1 test "union method"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

const Small2 = union(enum) {
    a: i32,
    b: bool,
    c: u8,
};
test "@tagName" {
    try expect(std.mem.eql(u8, @tagName(Small2.a), "a"));
}

$ zig test test_tagName.zig
1/1 test "@tagName"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

const Number = union {
    int: i32,
    float: f64,
};

test "anonymous union literal syntax" {
    var i: Number = .{.int = 42};
    var f = makeNumber();
    try expect(i.int == 42);
    try expect(f.float == 12.34);
}

fn makeNumber() Number {
    return .{.float = 12.34};
}

$ zig test anon_union.zig
1/1 test "anonymous union literal syntax"... OK
All 1 tests passed.

const Derp = opaque {};
const Wat = opaque {};

extern fn bar(d: *Derp) void;
fn foo(w: *Wat) callconv(.C) void {
    bar(w);
}

test "call foo" {
    foo(undefined);
}

$ zig test test.zig
./docgen_tmp/test.zig:6:9: error: expected type '*Derp', found '*Wat'
    bar(w);
        ^
./docgen_tmp/test.zig:6:9: note: pointer type child 'Wat' cannot cast into pointer type child 'Derp'
    bar(w);
        ^

test "access variable after block scope" {
    {
        var x: i32 = 1;
        _ = x;
    }
    x += 1;
}

$ zig test test.zig
docgen_tmp/test.zig:6:5: error: use of undeclared identifier 'x'
    x += 1;
    ^

const std = @import("std");
const expect = std.testing.expect;

test "labeled break from labeled block expression" {
    var y: i32 = 123;

    const x = blk: {
        y += 1;
        break :blk y;
    };
    try expect(x == 124);
    try expect(y == 124);
}

$ zig test test_labeled_break.zig
1/1 test "labeled break from labeled block expression"... OK
All 1 tests passed.

const pi = 3.14;

test "inside test block" {
    // Let's even go inside another block
    {
        var pi: i32 = 1234;
    }
}

$ zig test test.zig
docgen_tmp/test.zig:6:13: error: local shadows declaration of 'pi'
        var pi: i32 = 1234;
            ^
docgen_tmp/test.zig:1:1: note: declared here
const pi = 3.14;
^

test "separate scopes" {
    {
        const pi = 3.14;
        _ = pi;
    }
    {
        var pi: bool = true;
        _ = pi;
    }
}

$ zig test test_scopes.zig
1/1 test "separate scopes"... OK
All 1 tests passed.

const std = @import("std");
const builtin = @import("builtin");
const expect = std.testing.expect;

test "switch simple" {
    const a: u64 = 10;
    const zz: u64 = 103;

    // All branches of a switch expression must be able to be coerced to a
    // common type.
    //
    // Branches cannot fallthrough. If fallthrough behavior is desired, combine
    // the cases and use an if.
    const b = switch (a) {
        // Multiple cases can be combined via a ','
        1, 2, 3 => 0,

        // Ranges can be specified using the ... syntax. These are inclusive
        // both ends.
        5...100 => 1,

        // Branches can be arbitrarily complex.
        101 => blk: {
            const c: u64 = 5;
            break :blk c * 2 + 1;
        },

        // Switching on arbitrary expressions is allowed as long as the
        // expression is known at compile-time.
        zz => zz,
        blk: {
            const d: u32 = 5;
            const e: u32 = 100;
            break :blk d + e;
        } => 107,

        // The else branch catches everything not already captured.
        // Else branches are mandatory unless the entire range of values
        // is handled.
        else => 9,
    };

    try expect(b == 1);
}

// Switch expressions can be used outside a function:
const os_msg = switch (builtin.target.os.tag) {
    .linux => "we found a linux user",
    else => "not a linux user",
};

// Inside a function, switch statements implicitly are compile-time
// evaluated if the target expression is compile-time known.
test "switch inside function" {
    switch (builtin.target.os.tag) {
        .fuchsia => {
            // On an OS other than fuchsia, block is not even analyzed,
            // so this compile error is not triggered.
            // On fuchsia this compile error would be triggered.
            @compileError("fuchsia not supported");
        },
        else => {},
    }
}

$ zig test switch.zig
1/2 test "switch simple"... OK
2/2 test "switch inside function"... OK
All 2 tests passed.

const expect = @import("std").testing.expect;

test "switch on tagged union" {
    const Point = struct {
        x: u8,
        y: u8,
    };
    const Item = union(enum) {
        a: u32,
        c: Point,
        d,
        e: u32,
    };

    var a = Item{ .c = Point{ .x = 1, .y = 2 } };

    // Switching on more complex enums is allowed.
    const b = switch (a) {
        // A capture group is allowed on a match, and will return the enum
        // value matched. If the payload types of both cases are the same
        // they can be put into the same switch prong.
        Item.a, Item.e => |item| item,

        // A reference to the matched value can be obtained using `*` syntax.
        Item.c => |*item| blk: {
            item.*.x += 1;
            break :blk 6;
        },

        // No else is required if the types cases was exhaustively handled
        Item.d => 8,
    };

    try expect(b == 6);
    try expect(a.c.x == 2);
}

$ zig test test_switch_tagged_union.zig
1/1 test "switch on tagged union"... OK
All 1 tests passed.

const Color = enum {
    auto,
    off,
    on,
};

test "exhaustive switching" {
    const color = Color.off;
    switch (color) {
        Color.auto => {},
        Color.on => {},
    }
}

$ zig test test.zig
./docgen_tmp/test.zig:9:5: error: enumeration value 'Color.off' not handled in switch
    switch (color) {
    ^
./docgen_tmp/test.zig:7:29: note: referenced here
test "exhaustive switching" {
                            ^

const std = @import("std");
const expect = std.testing.expect;

const Color = enum {
    auto,
    off,
    on,
};

test "enum literals with switch" {
    const color = Color.off;
    const result = switch (color) {
        .auto => false,
        .on => false,
        .off => true,
    };
    try expect(result);
}

$ zig test test_exhaustive_switch.zig
1/1 test "enum literals with switch"... OK
All 1 tests passed.

const expect = @import("std").testing.expect;

test "while basic" {
    var i: usize = 0;
    while (i < 10) {
        i += 1;
    }
    try expect(i == 10);
}

$ zig test while.zig
1/1 test "while basic"... OK
All 1 tests passed.

const expect = @import("std").testing.expect;

test "while break" {
    var i: usize = 0;
    while (true) {
        if (i == 10)
            break;
        i += 1;
    }
    try expect(i == 10);
}

$ zig test while.zig
1/1 test "while break"... OK
All 1 tests passed.

const expect = @import("std").testing.expect;

test "while continue" {
    var i: usize = 0;
    while (true) {
        i += 1;
        if (i < 10)
            continue;
        break;
    }
    try expect(i == 10);
}

$ zig test while.zig
1/1 test "while continue"... OK
All 1 tests passed.

const expect = @import("std").testing.expect;

test "while loop continue expression" {
    var i: usize = 0;
    while (i < 10) : (i += 1) {}
    try expect(i == 10);
}

test "while loop continue expression, more complicated" {
    var i: usize = 1;
    var j: usize = 1;
    while (i * j < 2000) : ({ i *= 2; j *= 3; }) {
        const my_ij = i * j;
        try expect(my_ij < 2000);
    }
}

$ zig test while.zig
1/2 test "while loop continue expression"... OK
2/2 test "while loop continue expression, more complicated"... OK
All 2 tests passed.

const expect = @import("std").testing.expect;

test "while else" {
    try expect(rangeHasNumber(0, 10, 5));
    try expect(!rangeHasNumber(0, 10, 15));
}

fn rangeHasNumber(begin: usize, end: usize, number: usize) bool {
    var i = begin;
    return while (i < end) : (i += 1) {
        if (i == number) {
            break true;
        }
    } else false;
}

$ zig test while.zig
1/1 test "while else"... OK
All 1 tests passed.

test "nested break" {
    outer: while (true) {
        while (true) {
            break :outer;
        }
    }
}

test "nested continue" {
    var i: usize = 0;
    outer: while (i < 10) : (i += 1) {
        while (true) {
            continue :outer;
        }
    }
}

$ zig test test_nested_break.zig
1/2 test "nested break"... OK
2/2 test "nested continue"... OK
All 2 tests passed.

const expect = @import("std").testing.expect;

test "while null capture" {
    var sum1: u32 = 0;
    numbers_left = 3;
    while (eventuallyNullSequence()) |value| {
        sum1 += value;
    }
    try expect(sum1 == 3);

    var sum2: u32 = 0;
    numbers_left = 3;
    while (eventuallyNullSequence()) |value| {
        sum2 += value;
    } else {
        try expect(sum2 == 3);
    }
}

var numbers_left: u32 = undefined;
fn eventuallyNullSequence() ?u32 {
    return if (numbers_left == 0) null else blk: {
        numbers_left -= 1;
        break :blk numbers_left;
    };
}

$ zig test while.zig
1/1 test "while null capture"... OK
All 1 tests passed.

const expect = @import("std").testing.expect;

test "while error union capture" {
    var sum1: u32 = 0;
    numbers_left = 3;
    while (eventuallyErrorSequence()) |value| {
        sum1 += value;
    } else |err| {
        try expect(err == error.ReachedZero);
    }
}

var numbers_left: u32 = undefined;

fn eventuallyErrorSequence() anyerror!u32 {
    return if (numbers_left == 0) error.ReachedZero else blk: {
        numbers_left -= 1;
        break :blk numbers_left;
    };
}

$ zig test while.zig
1/1 test "while error union capture"... OK
All 1 tests passed.

const expect = @import("std").testing.expect;

test "inline while loop" {
    comptime var i = 0;
    var sum: usize = 0;
    inline while (i < 3) : (i += 1) {
        const T = switch (i) {
            0 => f32,
            1 => i8,
            2 => bool,
            else => unreachable,
        };
        sum += typeNameLength(T);
    }
    try expect(sum == 9);
}

fn typeNameLength(comptime T: type) usize {
    return @typeName(T).len;
}

$ zig test test_inline_while.zig
1/1 test "inline while loop"... OK
All 1 tests passed.

const expect = @import("std").testing.expect;

test "for basics" {
    const items = [_]i32 { 4, 5, 3, 4, 0 };
    var sum: i32 = 0;

    // For loops iterate over slices and arrays.
    for (items) |value| {
        // Break and continue are supported.
        if (value == 0) {
            continue;
        }
        sum += value;
    }
    try expect(sum == 16);

    // To iterate over a portion of a slice, reslice.
    for (items[0..1]) |value| {
        sum += value;
    }
    try expect(sum == 20);

    // To access the index of iteration, specify a second capture value.
    // This is zero-indexed.
    var sum2: i32 = 0;
    for (items) |_, i| {
        try expect(@TypeOf(i) == usize);
        sum2 += @intCast(i32, i);
    }
    try expect(sum2 == 10);
}

test "for reference" {
    var items = [_]i32 { 3, 4, 2 };

    // Iterate over the slice by reference by
    // specifying that the capture value is a pointer.
    for (items) |*value| {
        value.* += 1;
    }

    try expect(items[0] == 4);
    try expect(items[1] == 5);
    try expect(items[2] == 3);
}

test "for else" {
    // For allows an else attached to it, the same as a while loop.
    var items = [_]?i32 { 3, 4, null, 5 };

    // For loops can also be used as expressions.
    // Similar to while loops, when you break from a for loop, the else branch is not evaluated.
    var sum: i32 = 0;
    const result = for (items) |value| {
        if (value != null) {
            sum += value.?;
        }
    } else blk: {
        try expect(sum == 12);
        break :blk sum;
    };
    try expect(result == 12);
}

$ zig test for.zig
1/3 test "for basics"... OK
2/3 test "for reference"... OK
3/3 test "for else"... OK
All 3 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "nested break" {
    var count: usize = 0;
    outer: for ([_]i32{ 1, 2, 3, 4, 5 }) |_| {
        for ([_]i32{ 1, 2, 3, 4, 5 }) |_| {
            count += 1;
            break :outer;
        }
    }
    try expect(count == 1);
}

test "nested continue" {
    var count: usize = 0;
    outer: for ([_]i32{ 1, 2, 3, 4, 5, 6, 7, 8 }) |_| {
        for ([_]i32{ 1, 2, 3, 4, 5 }) |_| {
            count += 1;
            continue :outer;
        }
    }

    try expect(count == 8);
}

$ zig test test_nested_break.zig
1/2 test "nested break"... OK
2/2 test "nested continue"... OK
All 2 tests passed.

const expect = @import("std").testing.expect;

test "inline for loop" {
    const nums = [_]i32{2, 4, 6};
    var sum: usize = 0;
    inline for (nums) |i| {
        const T = switch (i) {
            2 => f32,
            4 => i8,
            6 => bool,
            else => unreachable,
        };
        sum += typeNameLength(T);
    }
    try expect(sum == 9);
}

fn typeNameLength(comptime T: type) usize {
    return @typeName(T).len;
}

$ zig test test_inline_loop.zig
1/1 test "inline for loop"... OK
All 1 tests passed.

// If expressions have three uses, corresponding to the three types:
// * bool
// * ?T
// * anyerror!T

const expect = @import("std").testing.expect;

test "if expression" {
    // If expressions are used instead of a ternary expression.
    const a: u32 = 5;
    const b: u32 = 4;
    const result = if (a != b) 47 else 3089;
    try expect(result == 47);
}

test "if boolean" {
    // If expressions test boolean conditions.
    const a: u32 = 5;
    const b: u32 = 4;
    if (a != b) {
        try expect(true);
    } else if (a == 9) {
        unreachable;
    } else {
        unreachable;
    }
}

test "if optional" {
    // If expressions test for null.

    const a: ?u32 = 0;
    if (a) |value| {
        try expect(value == 0);
    } else {
        unreachable;
    }

    const b: ?u32 = null;
    if (b) |_| {
        unreachable;
    } else {
        try expect(true);
    }

    // The else is not required.
    if (a) |value| {
        try expect(value == 0);
    }

    // To test against null only, use the binary equality operator.
    if (b == null) {
        try expect(true);
    }

    // Access the value by reference using a pointer capture.
    var c: ?u32 = 3;
    if (c) |*value| {
        value.* = 2;
    }

    if (c) |value| {
        try expect(value == 2);
    } else {
        unreachable;
    }
}

test "if error union" {
    // If expressions test for errors.
    // Note the |err| capture on the else.

    const a: anyerror!u32 = 0;
    if (a) |value| {
        try expect(value == 0);
    } else |err| {
        _ = err;
        unreachable;
    }

    const b: anyerror!u32 = error.BadValue;
    if (b) |value| {
        _ = value;
        unreachable;
    } else |err| {
        try expect(err == error.BadValue);
    }

    // The else and |err| capture is strictly required.
    if (a) |value| {
        try expect(value == 0);
    } else |_| {}

    // To check only the error value, use an empty block expression.
    if (b) |_| {} else |err| {
        try expect(err == error.BadValue);
    }

    // Access the value by reference using a pointer capture.
    var c: anyerror!u32 = 3;
    if (c) |*value| {
        value.* = 9;
    } else |_| {
        unreachable;
    }

    if (c) |value| {
        try expect(value == 9);
    } else |_| {
        unreachable;
    }
}

test "if error union with optional" {
    // If expressions test for errors before unwrapping optionals.
    // The |optional_value| capture's type is ?u32.

    const a: anyerror!?u32 = 0;
    if (a) |optional_value| {
        try expect(optional_value.? == 0);
    } else |err| {
        _ = err;
        unreachable;
    }

    const b: anyerror!?u32 = null;
    if (b) |optional_value| {
        try expect(optional_value == null);
    } else |_| {
        unreachable;
    }

    const c: anyerror!?u32 = error.BadValue;
    if (c) |optional_value| {
        _ = optional_value;
        unreachable;
    } else |err| {
        try expect(err == error.BadValue);
    }

    // Access the value by reference by using a pointer capture each time.
    var d: anyerror!?u32 = 3;
    if (d) |*optional_value| {
        if (optional_value.*) |*value| {
            value.* = 9;
        }
    } else |_| {
        unreachable;
    }

    if (d) |optional_value| {
        try expect(optional_value.? == 9);
    } else |_| {
        unreachable;
    }
}

$ zig test if.zig
1/5 test "if expression"... OK
2/5 test "if boolean"... OK
3/5 test "if optional"... OK
4/5 test "if error union"... OK
5/5 test "if error union with optional"... OK
All 5 tests passed.

const std = @import("std");
const expect = std.testing.expect;
const print = std.debug.print;

// defer will execute an expression at the end of the current scope.
fn deferExample() !usize {
    var a: usize = 1;

    {
        defer a = 2;
        a = 1;
    }
    try expect(a == 2);

    a = 5;
    return a;
}

test "defer basics" {
    try expect((try deferExample()) == 5);
}

// If multiple defer statements are specified, they will be executed in
// the reverse order they were run.
fn deferUnwindExample() void {
    print("\n", .{});

    defer {
        print("1 ", .{});
    }
    defer {
        print("2 ", .{});
    }
    if (false) {
        // defers are not run if they are never executed.
        defer {
            print("3 ", .{});
        }
    }
}

test "defer unwinding" {
    deferUnwindExample();
}

// The errdefer keyword is similar to defer, but will only execute if the
// scope returns with an error.
//
// This is especially useful in allowing a function to clean up properly
// on error, and replaces goto error handling tactics as seen in c.
fn deferErrorExample(is_error: bool) !void {
    print("\nstart of function\n", .{});

    // This will always be executed on exit
    defer {
        print("end of function\n", .{});
    }

    errdefer {
        print("encountered an error!\n", .{});
    }

    if (is_error) {
        return error.DeferError;
    }
}

test "errdefer unwinding" {
    deferErrorExample(false) catch {};
    deferErrorExample(true) catch {};
}

$ zig test defer.zig
1/3 test "defer basics"... OK
2/3 test "defer unwinding"...
2 1 OK
3/3 test "errdefer unwinding"...
start of function
end of function

start of function
encountered an error!
end of function
OK
All 3 tests passed.

// unreachable is used to assert that control flow will never happen upon a
// particular location:
test "basic math" {
    const x = 1;
    const y = 2;
    if (x + y != 3) {
        unreachable;
    }
}

$ zig test test_unreachable.zig
1/1 test "basic math"... OK
All 1 tests passed.

// This is how std.debug.assert is implemented
fn assert(ok: bool) void {
    if (!ok) unreachable; // assertion failure
}

// This test will fail because we hit unreachable.
test "this will fail" {
    assert(false);
}

$ zig test test.zig
1/1 test "this will fail"... thread 794145 panic: reached unreachable code
/home/andy/Downloads/zig/docgen_tmp/test.zig:3:14: 0x207f3b in assert (test)
    if (!ok) unreachable; // assertion failure
             ^
/home/andy/Downloads/zig/docgen_tmp/test.zig:8:11: 0x2079ce in test "this will fail" (test)
    assert(false);
          ^
/home/andy/Downloads/zig/lib/std/special/test_runner.zig:80:28: 0x22f423 in std.special.main (test)
        } else test_fn.func();
                           ^
/home/andy/Downloads/zig/lib/std/start.zig:543:22: 0x227e1c in std.start.callMain (test)
            root.main();
                     ^
/home/andy/Downloads/zig/lib/std/start.zig:495:12: 0x20923e in std.start.callMainWithArgs (test)
    return @call(.{ .modifier = .always_inline }, callMain, .{});
           ^
/home/andy/Downloads/zig/lib/std/start.zig:409:17: 0x2082d6 in std.start.posixCallMainAndExit (test)
    std.os.exit(@call(.{ .modifier = .always_inline }, callMainWithArgs, .{ argc, argv, envp }));
                ^
/home/andy/Downloads/zig/lib/std/start.zig:322:5: 0x2080e2 in std.start._start (test)
    @call(.{ .modifier = .never_inline }, posixCallMainAndExit, .{});
    ^
error: the following test command crashed:
docgen_tmp/zig-cache/o/8e4964e05ddaf866e77360a551b3c05b/test /home/andy/Downloads/zig/build-release/zig

const assert = @import("std").debug.assert;

test "type of unreachable" {
    comptime {
        // The type of unreachable is noreturn.

        // However this assertion will still fail to compile because
        // unreachable expressions are compile errors.

        assert(@TypeOf(unreachable) == noreturn);
    }
}

$ zig test test.zig
docgen_tmp/test.zig:10:16: error: unreachable code
        assert(@TypeOf(unreachable) == noreturn);
               ^
docgen_tmp/test.zig:10:24: note: control flow is diverted here
        assert(@TypeOf(unreachable) == noreturn);
                       ^

fn foo(condition: bool, b: u32) void {
    const a = if (condition) b else return;
    _ = a;
    @panic("do something with a");
}
test "noreturn" {
    foo(false, 1);
}

$ zig test test_noreturn.zig
1/1 test "noreturn"... OK
All 1 tests passed.

const std = @import("std");
const builtin = @import("builtin");
const native_arch = builtin.cpu.arch;
const expect = std.testing.expect;

const WINAPI: std.builtin.CallingConvention = if (native_arch == .i386) .Stdcall else .C;
extern "kernel32" fn ExitProcess(exit_code: c_uint) callconv(WINAPI) noreturn;

test "foo" {
    const value = bar() catch ExitProcess(1);
    try expect(value == 1234);
}

fn bar() anyerror!u32 {
    return 1234;
}

$ zig test noreturn_from_exit.zig -target x86_64-windows --test-no-exec

const std = @import("std");
const builtin = @import("builtin");
const native_arch = builtin.cpu.arch;
const expect = std.testing.expect;

// Functions are declared like this
fn add(a: i8, b: i8) i8 {
    if (a == 0) {
        return b;
    }

    return a + b;
}

// The export specifier makes a function externally visible in the generated
// object file, and makes it use the C ABI.
export fn sub(a: i8, b: i8) i8 { return a - b; }

// The extern specifier is used to declare a function that will be resolved
// at link time, when linking statically, or at runtime, when linking
// dynamically.
// The callconv specifier changes the calling convention of the function.
const WINAPI: std.builtin.CallingConvention = if (native_arch == .i386) .Stdcall else .C;
extern "kernel32" fn ExitProcess(exit_code: u32) callconv(WINAPI) noreturn;
extern "c" fn atan2(a: f64, b: f64) f64;

// The @setCold builtin tells the optimizer that a function is rarely called.
fn abort() noreturn {
    @setCold(true);
    while (true) {}
}

// The naked calling convention makes a function not have any function prologue or epilogue.
// This can be useful when integrating with assembly.
fn _start() callconv(.Naked) noreturn {
    abort();
}

// The inline calling convention forces a function to be inlined at all call sites.
// If the function cannot be inlined, it is a compile-time error.
fn shiftLeftOne(a: u32) callconv(.Inline) u32 {
    return a << 1;
}

// The pub specifier allows the function to be visible when importing.
// Another file can use @import and call sub2
pub fn sub2(a: i8, b: i8) i8 { return a - b; }

// Functions can be used as values and are equivalent to pointers.
const call2_op = fn (a: i8, b: i8) i8;
fn do_op(fn_call: call2_op, op1: i8, op2: i8) i8 {
    return fn_call(op1, op2);
}

test "function" {
    try expect(do_op(add, 5, 6) == 11);
    try expect(do_op(sub2, 5, 6) == -1);
}

$ zig test functions.zig
1/1 test "function"... OK
All 1 tests passed.

const assert = @import("std").debug.assert;

comptime {
    assert(@TypeOf(foo) == fn()void);
    assert(@sizeOf(fn()void) == @sizeOf(?fn()void));
}

fn foo() void { }

$ zig build-obj test.zig

const Point = struct {
    x: i32,
    y: i32,
};

fn foo(point: Point) i32 {
    // Here, `point` could be a reference, or a copy. The function body
    // can ignore the difference and treat it as a value. Be very careful
    // taking the address of the parameter - it should be treated as if
    // the address will become invalid when the function returns.
    return point.x + point.y;
}

const expect = @import("std").testing.expect;

test "pass struct to function" {
    try expect(foo(Point{ .x = 1, .y = 2 }) == 3);
}

$ zig test pass_by_reference_or_value.zig
1/1 test "pass struct to function"... OK
All 1 tests passed.

const expect = @import("std").testing.expect;

fn addFortyTwo(x: anytype) @TypeOf(x) {
    return x + 42;
}

test "fn type inference" {
    try expect(addFortyTwo(1) == 43);
    try expect(@TypeOf(addFortyTwo(1)) == comptime_int);
    var y: i64 = 2;
    try expect(addFortyTwo(y) == 44);
    try expect(@TypeOf(addFortyTwo(y)) == i64);
}

$ zig test test_fn_type_inference.zig
1/1 test "fn type inference"... OK
All 1 tests passed.

const expect = @import("std").testing.expect;

test "fn reflection" {
    try expect(@typeInfo(@TypeOf(expect)).Fn.args[0].arg_type.? == bool);
    try expect(@typeInfo(@TypeOf(expect)).Fn.is_var_args == false);
}

$ zig test test_fn_reflection.zig
1/1 test "fn reflection"... OK
All 1 tests passed.

const std = @import("std");

const FileOpenError = error {
    AccessDenied,
    OutOfMemory,
    FileNotFound,
};

const AllocationError = error {
    OutOfMemory,
};

test "coerce subset to superset" {
    const err = foo(AllocationError.OutOfMemory);
    try std.testing.expect(err == FileOpenError.OutOfMemory);
}

fn foo(err: AllocationError) FileOpenError {
    return err;
}

$ zig test coercing_subset_to_superset.zig
1/1 test "coerce subset to superset"... OK
All 1 tests passed.

const FileOpenError = error {
    AccessDenied,
    OutOfMemory,
    FileNotFound,
};

const AllocationError = error {
    OutOfMemory,
};

test "coerce superset to subset" {
    foo(FileOpenError.OutOfMemory) catch {};
}

fn foo(err: FileOpenError) AllocationError {
    return err;
}

$ zig test test.zig
./docgen_tmp/test.zig:16:12: error: expected type 'AllocationError', found 'FileOpenError'
    return err;
           ^
./docgen_tmp/test.zig:2:5: note: 'error.AccessDenied' not a member of destination error set
    AccessDenied,
    ^
./docgen_tmp/test.zig:4:5: note: 'error.FileNotFound' not a member of destination error set
    FileNotFound,
    ^

const err = error.FileNotFound;

const err = (error {FileNotFound}).FileNotFound;

const std = @import("std");
const maxInt = std.math.maxInt;

pub fn parseU64(buf: []const u8, radix: u8) !u64 {
    var x: u64 = 0;

    for (buf) |c| {
        const digit = charToDigit(c);

        if (digit >= radix) {
            return error.InvalidChar;
        }

        // x *= radix
        if (@mulWithOverflow(u64, x, radix, &x)) {
            return error.Overflow;
        }

        // x += digit
        if (@addWithOverflow(u64, x, digit, &x)) {
            return error.Overflow;
        }
    }

    return x;
}

fn charToDigit(c: u8) u8 {
    return switch (c) {
        '0' ... '9' => c - '0',
        'A' ... 'Z' => c - 'A' + 10,
        'a' ... 'z' => c - 'a' + 10,
        else => maxInt(u8),
    };
}

test "parse u64" {
    const result = try parseU64("1234", 10);
    try std.testing.expect(result == 1234);
}

$ zig test error_union_parsing_u64.zig
1/1 test "parse u64"... OK
All 1 tests passed.

const parseU64 = @import("error_union_parsing_u64.zig").parseU64;

fn doAThing(str: []u8) void {
    const number = parseU64(str, 10) catch 13;
    _ = number; // ...
}

const parseU64 = @import("error_union_parsing_u64.zig").parseU64;

fn doAThing(str: []u8) !void {
    const number = parseU64(str, 10) catch |err| return err;
    _ = number; // ...
}

const parseU64 = @import("error_union_parsing_u64.zig").parseU64;

fn doAThing(str: []u8) !void {
    const number = try parseU64(str, 10);
    _ = number; // ...
}

fn doAThing(str: []u8) void {
    if (parseU64(str, 10)) |number| {
        doSomethingWithNumber(number);
    } else |err| switch (err) {
        error.Overflow => {
            // handle overflow...
        },
        // we promise that InvalidChar won't happen (or crash in debug mode if it does)
        error.InvalidChar => unreachable,
    }
}

fn createFoo(param: i32) !Foo {
    const foo = try tryToAllocateFoo();
    // now we have allocated foo. we need to free it if the function fails.
    // but we want to return it if the function succeeds.
    errdefer deallocateFoo(foo);

    const tmp_buf = allocateTmpBuffer() orelse return error.OutOfMemory;
    // tmp_buf is truly a temporary resource, and we for sure want to clean it up
    // before this block leaves scope
    defer deallocateTmpBuffer(tmp_buf);

    if (param > 1337) return error.InvalidParam;

    // here the errdefer will not run since we're returning success from the function.
    // but the defer will run!
    return foo;
}

const expect = @import("std").testing.expect;

test "error union" {
    var foo: anyerror!i32 = undefined;

    // Coerce from child type of an error union:
    foo = 1234;

    // Coerce from an error set:
    foo = error.SomeError;

    // Use compile-time reflection to access the payload type of an error union:
    comptime try expect(@typeInfo(@TypeOf(foo)).ErrorUnion.payload == i32);

    // Use compile-time reflection to access the error set type of an error union:
    comptime try expect(@typeInfo(@TypeOf(foo)).ErrorUnion.error_set == anyerror);
}

$ zig test test_error_union.zig
1/1 test "error union"... OK
All 1 tests passed.

const A = error{
    NotDir,

    /// A doc comment
    PathNotFound,
};
const B = error{
    OutOfMemory,

    /// B doc comment
    PathNotFound,
};

const C = A || B;

fn foo() C!void {
    return error.NotDir;
}

test "merge error sets" {
    if (foo()) {
        @panic("unexpected");
    } else |err| switch (err) {
        error.OutOfMemory => @panic("unexpected"),
        error.PathNotFound => @panic("unexpected"),
        error.NotDir => {},
    }
}

$ zig test test_merging_error_sets.zig
1/1 test "merge error sets"... OK
All 1 tests passed.

// With an inferred error set
pub fn add_inferred(comptime T: type, a: T, b: T) !T {
    var answer: T = undefined;
    return if (@addWithOverflow(T, a, b, &answer)) error.Overflow else answer;
}

// With an explicit error set
pub fn add_explicit(comptime T: type, a: T, b: T) Error!T {
    var answer: T = undefined;
    return if (@addWithOverflow(T, a, b, &answer)) error.Overflow else answer;
}

const Error = error {
    Overflow,
};

const std = @import("std");

test "inferred error set" {
    if (add_inferred(u8, 255, 1)) |_| unreachable else |err| switch (err) {
        error.Overflow => {}, // ok
    }
}

$ zig test inferred_error_sets.zig
1/1 test "inferred error set"... OK
All 1 tests passed.

pub fn main() !void {
    try foo(12);
}

fn foo(x: i32) !void {
    if (x >= 5) {
        try bar();
    } else {
        try bang2();
    }
}

fn bar() !void {
    if (baz()) {
        try quux();
    } else |err| switch (err) {
        error.FileNotFound => try hello(),
        else => try another(),
    }
}

fn baz() !void {
    try bang1();
}

fn quux() !void {
    try bang2();
}

fn hello() !void {
    try bang2();
}

fn another() !void {
    try bang1();
}

fn bang1() !void {
    return error.FileNotFound;
}

fn bang2() !void {
    return error.PermissionDenied;
}

$ zig build-exe test.zig

$ ./test
error: PermissionDenied
/home/andy/Downloads/zig/docgen_tmp/test.zig:39:5: 0x234a02 in bang1 (test)
    return error.FileNotFound;
    ^
/home/andy/Downloads/zig/docgen_tmp/test.zig:23:5: 0x2348df in baz (test)
    try bang1();
    ^
/home/andy/Downloads/zig/docgen_tmp/test.zig:43:5: 0x2348a2 in bang2 (test)
    return error.PermissionDenied;
    ^
/home/andy/Downloads/zig/docgen_tmp/test.zig:31:5: 0x2349cf in hello (test)
    try bang2();
    ^
/home/andy/Downloads/zig/docgen_tmp/test.zig:17:31: 0x23486e in bar (test)
        error.FileNotFound => try hello(),
                              ^
/home/andy/Downloads/zig/docgen_tmp/test.zig:7:9: 0x23475c in foo (test)
        try bar();
        ^
/home/andy/Downloads/zig/docgen_tmp/test.zig:2:5: 0x22d054 in main (test)
    try foo(12);
    ^

pub fn main() void {
    foo(12);
}

fn foo(x: i32) void {
    if (x >= 5) {
        bar();
    } else {
        bang2();
    }
}

fn bar() void {
    if (baz()) {
        quux();
    } else {
        hello();
    }
}

fn baz() bool {
    return bang1();
}

fn quux() void {
    bang2();
}

fn hello() void {
    bang2();
}

fn bang1() bool {
    return false;
}

fn bang2() void {
    @panic("PermissionDenied");
}

$ zig build-exe test.zig

$ ./test
thread 794855 panic: PermissionDenied
/home/andy/Downloads/zig/docgen_tmp/test.zig:38:5: 0x235876 in bang2 (test)
    @panic("PermissionDenied");
    ^
/home/andy/Downloads/zig/docgen_tmp/test.zig:30:10: 0x235fc8 in hello (test)
    bang2();
         ^
/home/andy/Downloads/zig/docgen_tmp/test.zig:17:14: 0x23585a in bar (test)
        hello();
             ^
/home/andy/Downloads/zig/docgen_tmp/test.zig:7:12: 0x2344d5 in foo (test)
        bar();
           ^
/home/andy/Downloads/zig/docgen_tmp/test.zig:2:8: 0x22ce3d in main (test)
    foo(12);
       ^
/home/andy/Downloads/zig/lib/std/start.zig:543:22: 0x225bcc in std.start.callMain (test)
            root.main();
                     ^
/home/andy/Downloads/zig/lib/std/start.zig:495:12: 0x206fce in std.start.callMainWithArgs (test)
    return @call(.{ .modifier = .always_inline }, callMain, .{});
           ^
/home/andy/Downloads/zig/lib/std/start.zig:409:17: 0x206066 in std.start.posixCallMainAndExit (test)
    std.os.exit(@call(.{ .modifier = .always_inline }, callMainWithArgs, .{ argc, argv, envp }));
                ^
/home/andy/Downloads/zig/lib/std/start.zig:322:5: 0x205e72 in std.start._start (test)
    @call(.{ .modifier = .never_inline }, posixCallMainAndExit, .{});
    ^
(process terminated by signal)

pub const StackTrace = struct {
    index: usize,
    instruction_addresses: [N]usize,
};

// marked as "no-inline" in LLVM IR
fn __zig_return_error(stack_trace: *StackTrace) void {
    stack_trace.instruction_addresses[stack_trace.index] = @returnAddress();
    stack_trace.index = (stack_trace.index + 1) % N;
}

// normal integer
const normal_int: i32 = 1234;

// optional integer
const optional_int: ?i32 = 5678;

// malloc prototype included for reference
void *malloc(size_t size);

struct Foo *do_a_thing(void) {
    char *ptr = malloc(1234);
    if (!ptr) return NULL;
    // ...
}

// malloc prototype included for reference
extern fn malloc(size: size_t) ?*u8;

fn doAThing() ?*Foo {
    const ptr = malloc(1234) orelse return null;
    _ = ptr; // ...
}

void do_a_thing(struct Foo *foo) {
    // do some stuff

    if (foo) {
        do_something_with_foo(foo);
    }

    // do some stuff
}

const Foo = struct{};
fn doSomethingWithFoo(foo: *Foo) void { _ = foo; }

fn doAThing(optional_foo: ?*Foo) void {
    // do some stuff

    if (optional_foo) |foo| {
      doSomethingWithFoo(foo);
    }

    // do some stuff
}

const expect = @import("std").testing.expect;

test "optional type" {
    // Declare an optional and coerce from null:
    var foo: ?i32 = null;

    // Coerce from child type of an optional
    foo = 1234;

    // Use compile-time reflection to access the child type of the optional:
    comptime try expect(@typeInfo(@TypeOf(foo)).Optional.child == i32);
}

$ zig test test_optional_type.zig
1/1 test "optional type"... OK
All 1 tests passed.

const optional_value: ?i32 = null;

const expect = @import("std").testing.expect;

test "optional pointers" {
    // Pointers cannot be null. If you want a null pointer, use the optional
    // prefix `?` to make the pointer type optional.
    var ptr: ?*i32 = null;

    var x: i32 = 1;
    ptr = &x;

    try expect(ptr.?.* == 1);

    // Optional pointers are the same size as normal pointers, because pointer
    // value 0 is used as the null value.
    try expect(@sizeOf(?*i32) == @sizeOf(*i32));
}

$ zig test test_optional_pointer.zig
1/1 test "optional pointers"... OK
All 1 tests passed.

test "type coercion - variable declaration" {
    var a: u8 = 1;
    var b: u16 = a;
    _ = b;
}

test "type coercion - function call" {
    var a: u8 = 1;
    foo(a);
}

fn foo(b: u16) void {
    _ = b;
}

test "type coercion - @as builtin" {
    var a: u8 = 1;
    var b = @as(u16, a);
    _ = b;
}

$ zig test type_coercion.zig
1/3 test "type coercion - variable declaration"... OK
2/3 test "type coercion - function call"... OK
3/3 test "type coercion - @as builtin"... OK
All 3 tests passed.

test "type coercion - const qualification" {
    var a: i32 = 1;
    var b: *i32 = &a;
    foo(b);
}

fn foo(_: *const i32) void {}

$ zig test no_op_casts.zig
1/1 test "type coercion - const qualification"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;
const mem = std.mem;

test "cast *[1][*]const u8 to [*]const ?[*]const u8" {
    const window_name = [1][*]const u8{"window name"};
    const x: [*]const ?[*]const u8 = &window_name;
    try expect(mem.eql(u8, std.mem.sliceTo(@ptrCast([*:0]const u8, x[0].?), 0), "window name"));
}

$ zig test pointer_coerce_const_optional.zig
1/1 test "cast *[1][*]const u8 to [*]const ?[*]const u8"... OK
All 1 tests passed.

const std = @import("std");
const builtin = @import("builtin");
const expect = std.testing.expect;
const mem = std.mem;

test "integer widening" {
    var a: u8 = 250;
    var b: u16 = a;
    var c: u32 = b;
    var d: u64 = c;
    var e: u64 = d;
    var f: u128 = e;
    try expect(f == a);
}

test "implicit unsigned integer to signed integer" {
    var a: u8 = 250;
    var b: i16 = a;
    try expect(b == 250);
}

test "float widening" {
    // Note: there is an open issue preventing this from working on aarch64:
    // https://github.com/ziglang/zig/issues/3282
    if (builtin.target.cpu.arch == .aarch64) return error.SkipZigTest;

    var a: f16 = 12.34;
    var b: f32 = a;
    var c: f64 = b;
    var d: f128 = c;
    try expect(d == a);
}

$ zig test test_integer_widening.zig
1/3 test "integer widening"... OK
2/3 test "implicit unsigned integer to signed integer"... OK
3/3 test "float widening"... OK
All 3 tests passed.

// Compile time coercion of float to int
test "implicit cast to comptime_int" {
    var f: f32 = 54.0 / 5;
    _ = f;
}

$ zig test test.zig
./docgen_tmp/test.zig:3:18: error: float value 54.000000 cannot be coerced to type 'comptime_int'
    var f: f32 = 54.0 / 5;
                 ^
./docgen_tmp/test.zig:3:23: note: referenced here
    var f: f32 = 54.0 / 5;
                      ^

const std = @import("std");
const expect = std.testing.expect;

// You can assign constant pointers to arrays to a slice with
// const modifier on the element type. Useful in particular for
// String literals.
test "*const [N]T to []const T" {
    var x1: []const u8 = "hello";
    var x2: []const u8 = &[5]u8{ 'h', 'e', 'l', 'l', 111 };
    try expect(std.mem.eql(u8, x1, x2));

    var y: []const f32 = &[2]f32{ 1.2, 3.4 };
    try expect(y[0] == 1.2);
}

// Likewise, it works when the destination type is an error union.
test "*const [N]T to E![]const T" {
    var x1: anyerror![]const u8 = "hello";
    var x2: anyerror![]const u8 = &[5]u8{ 'h', 'e', 'l', 'l', 111 };
    try expect(std.mem.eql(u8, try x1, try x2));

    var y: anyerror![]const f32 = &[2]f32{ 1.2, 3.4 };
    try expect((try y)[0] == 1.2);
}

// Likewise, it works when the destination type is an optional.
test "*const [N]T to ?[]const T" {
    var x1: ?[]const u8 = "hello";
    var x2: ?[]const u8 = &[5]u8{ 'h', 'e', 'l', 'l', 111 };
    try expect(std.mem.eql(u8, x1.?, x2.?));

    var y: ?[]const f32 = &[2]f32{ 1.2, 3.4 };
    try expect(y.?[0] == 1.2);
}

// In this cast, the array length becomes the slice length.
test "*[N]T to []T" {
    var buf: [5]u8 = "hello".*;
    const x: []u8 = &buf;
    try expect(std.mem.eql(u8, x, "hello"));

    const buf2 = [2]f32{ 1.2, 3.4 };
    const x2: []const f32 = &buf2;
    try expect(std.mem.eql(f32, x2, &[2]f32{ 1.2, 3.4 }));
}

// Single-item pointers to arrays can be coerced to many-item pointers.
test "*[N]T to [*]T" {
    var buf: [5]u8 = "hello".*;
    const x: [*]u8 = &buf;
    try expect(x[4] == 'o');
    // x[5] would be an uncaught out of bounds pointer dereference!
}

// Likewise, it works when the destination type is an optional.
test "*[N]T to ?[*]T" {
    var buf: [5]u8 = "hello".*;
    const x: ?[*]u8 = &buf;
    try expect(x.?[4] == 'o');
}

// Single-item pointers can be cast to len-1 single-item arrays.
test "*T to *[1]T" {
    var x: i32 = 1234;
    const y: *[1]i32 = &x;
    const z: [*]i32 = y;
    try expect(z[0] == 1234);
}

$ zig test coerce__slices_arrays_and_ptrs.zig
1/7 test "*const [N]T to []const T"... OK
2/7 test "*const [N]T to E![]const T"... OK
3/7 test "*const [N]T to ?[]const T"... OK
4/7 test "*[N]T to []T"... OK
5/7 test "*[N]T to [*]T"... OK
6/7 test "*[N]T to ?[*]T"... OK
7/7 test "*T to *[1]T"... OK
All 7 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "coerce to optionals" {
    const x: ?i32 = 1234;
    const y: ?i32 = null;

    try expect(x.? == 1234);
    try expect(y == null);
}

$ zig test test_coerce_optionals.zig
1/1 test "coerce to optionals"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "coerce to optionals wrapped in error union" {
    const x: anyerror!?i32 = 1234;
    const y: anyerror!?i32 = null;

    try expect((try x).? == 1234);
    try expect((try y) == null);
}

$ zig test test_coerce_optional_wrapped_error_union.zig
1/1 test "coerce to optionals wrapped in error union"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "coercion to error unions" {
    const x: anyerror!i32 = 1234;
    const y: anyerror!i32 = error.Failure;

    try expect((try x) == 1234);
    try std.testing.expectError(error.Failure, y);
}

$ zig test test_coerce_to_error_union.zig
1/1 test "coercion to error unions"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "coercing large integer type to smaller one when value is comptime known to fit" {
    const x: u64 = 255;
    const y: u8 = x;
    try expect(y == 255);
}

$ zig test test_coerce_large_to_small.zig
1/1 test "coercing large integer type to smaller one when value is comptime known to fit"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

const E = enum {
    one,
    two,
    three,
};

const U = union(E) {
    one: i32,
    two: f32,
    three,
};

test "coercion between unions and enums" {
    var u = U{ .two = 12.34 };
    var e: E = u;
    try expect(e == E.two);

    const three = E.three;
    var another_u: U = three;
    try expect(another_u == E.three);
}

$ zig test test_coerce_unions_enums.zig
1/1 test "coercion between unions and enums"... OK
All 1 tests passed.

test "coercion of zero bit types" {
    var x: void = {};
    var y: *void = x;
    _ = y;
}

$ zig test coerce_zero_bit_types.zig
1/1 test "coercion of zero bit types"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;
const mem = std.mem;

test "peer resolve int widening" {
    var a: i8 = 12;
    var b: i16 = 34;
    var c = a + b;
    try expect(c == 46);
    try expect(@TypeOf(c) == i16);
}

test "peer resolve arrays of different size to const slice" {
    try expect(mem.eql(u8, boolToStr(true), "true"));
    try expect(mem.eql(u8, boolToStr(false), "false"));
    comptime try expect(mem.eql(u8, boolToStr(true), "true"));
    comptime try expect(mem.eql(u8, boolToStr(false), "false"));
}
fn boolToStr(b: bool) []const u8 {
    return if (b) "true" else "false";
}

test "peer resolve array and const slice" {
    try testPeerResolveArrayConstSlice(true);
    comptime try testPeerResolveArrayConstSlice(true);
}
fn testPeerResolveArrayConstSlice(b: bool) !void {
    const value1 = if (b) "aoeu" else @as([]const u8, "zz");
    const value2 = if (b) @as([]const u8, "zz") else "aoeu";
    try expect(mem.eql(u8, value1, "aoeu"));
    try expect(mem.eql(u8, value2, "zz"));
}

test "peer type resolution: ?T and T" {
    try expect(peerTypeTAndOptionalT(true, false).? == 0);
    try expect(peerTypeTAndOptionalT(false, false).? == 3);
    comptime {
        try expect(peerTypeTAndOptionalT(true, false).? == 0);
        try expect(peerTypeTAndOptionalT(false, false).? == 3);
    }
}
fn peerTypeTAndOptionalT(c: bool, b: bool) ?usize {
    if (c) {
        return if (b) null else @as(usize, 0);
    }

    return @as(usize, 3);
}

test "peer type resolution: *[0]u8 and []const u8" {
    try expect(peerTypeEmptyArrayAndSlice(true, "hi").len == 0);
    try expect(peerTypeEmptyArrayAndSlice(false, "hi").len == 1);
    comptime {
        try expect(peerTypeEmptyArrayAndSlice(true, "hi").len == 0);
        try expect(peerTypeEmptyArrayAndSlice(false, "hi").len == 1);
    }
}
fn peerTypeEmptyArrayAndSlice(a: bool, slice: []const u8) []const u8 {
    if (a) {
        return &[_]u8{};
    }

    return slice[0..1];
}
test "peer type resolution: *[0]u8, []const u8, and anyerror![]u8" {
    {
        var data = "hi".*;
        const slice = data[0..];
        try expect((try peerTypeEmptyArrayAndSliceAndError(true, slice)).len == 0);
        try expect((try peerTypeEmptyArrayAndSliceAndError(false, slice)).len == 1);
    }
    comptime {
        var data = "hi".*;
        const slice = data[0..];
        try expect((try peerTypeEmptyArrayAndSliceAndError(true, slice)).len == 0);
        try expect((try peerTypeEmptyArrayAndSliceAndError(false, slice)).len == 1);
    }
}
fn peerTypeEmptyArrayAndSliceAndError(a: bool, slice: []u8) anyerror![]u8 {
    if (a) {
        return &[_]u8{};
    }

    return slice[0..1];
}

test "peer type resolution: *const T and ?*T" {
    const a = @intToPtr(*const usize, 0x123456780);
    const b = @intToPtr(?*usize, 0x123456780);
    try expect(a == b);
    try expect(b == a);
}

$ zig test peer_type_resolution.zig
1/7 test "peer resolve int widening"... OK
2/7 test "peer resolve arrays of different size to const slice"... OK
3/7 test "peer resolve array and const slice"... OK
4/7 test "peer type resolution: ?T and T"... OK
5/7 test "peer type resolution: *[0]u8 and []const u8"... OK
6/7 test "peer type resolution: *[0]u8, []const u8, and anyerror![]u8"... OK
7/7 test "peer type resolution: *const T and ?*T"... OK
All 7 tests passed.

export fn entry() void {
    var x: void = {};
    var y: void = {};
    x = y;
}

const std = @import("std");
const expect = std.testing.expect;

test "turn HashMap into a set with void" {
    var map = std.AutoHashMap(i32, void).init(std.testing.allocator);
    defer map.deinit();

    try map.put(1, {});
    try map.put(2, {});

    try expect(map.contains(2));
    try expect(!map.contains(3));

    _ = map.remove(2);
    try expect(!map.contains(2));
}

$ zig test void_in_hashmap.zig
1/1 test "turn HashMap into a set with void"... OK
All 1 tests passed.

test "ignoring expression value" {
    foo();
}

fn foo() i32 {
    return 1234;
}

$ zig test test.zig
./docgen_tmp/test.zig:2:8: error: expression value is ignored
    foo();
       ^
./docgen_tmp/test.zig:1:34: note: referenced here
test "ignoring expression value" {
                                 ^

test "void is ignored" {
    returnsVoid();
}

test "explicitly ignoring expression value" {
    _ = foo();
}

fn returnsVoid() void {}

fn foo() i32 {
    return 1234;
}

$ zig test void_ignored.zig
1/2 test "void is ignored"... OK
2/2 test "explicitly ignoring expression value"... OK
All 2 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "pointer to empty struct" {
    const Empty = struct {};
    var a = Empty{};
    var b = Empty{};
    var ptr_a = &a;
    var ptr_b = &b;
    comptime try expect(ptr_a == ptr_b);
}

$ zig test pointers_to_zero_bits.zig
1/1 test "pointer to empty struct"... OK
All 1 tests passed.

const Empty = struct {};

test "@ptrToInt for pointer to zero bit type" {
    var a = Empty{};
    _ = @ptrToInt(&a);
}

test "@intToPtr for pointer to zero bit type" {
    _ = @intToPtr(*Empty, 0x1);
}

$ zig test test.zig
./docgen_tmp/test.zig:4:5: error: pointer to size 0 type has no address
    var a = Empty{};
    ^
./docgen_tmp/test.zig:5:9: note: referenced here
    _ = @ptrToInt(&a);
        ^
./docgen_tmp/test.zig:9:19: error: type '*Empty' has 0 bits and cannot store information
    _ = @intToPtr(*Empty, 0x1);
                  ^
./docgen_tmp/test.zig:9:9: note: referenced here
    _ = @intToPtr(*Empty, 0x1);
        ^

test "using std namespace" {
    const S = struct {
        usingnamespace @import("std");
    };
    try S.testing.expect(true);
}

$ zig test usingnamespace.zig
1/1 test "using std namespace"... OK
All 1 tests passed.

pub usingnamespace @cImport({
    @cInclude("epoxy/gl.h");
    @cInclude("GLFW/glfw3.h");
    @cDefine("STBI_ONLY_PNG", "");
    @cDefine("STBI_NO_STDIO", "");
    @cInclude("stb_image.h");
});

fn max(comptime T: type, a: T, b: T) T {
    return if (a > b) a else b;
}
fn gimmeTheBiggerFloat(a: f32, b: f32) f32 {
    return max(f32, a, b);
}
fn gimmeTheBiggerInteger(a: u64, b: u64) u64 {
    return max(u64, a, b);
}

fn max(comptime T: type, a: T, b: T) T {
    return if (a > b) a else b;
}
test "try to pass a runtime type" {
    foo(false);
}
fn foo(condition: bool) void {
    const result = max(
        if (condition) f32 else u64,
        1234,
        5678);
    _ = result;
}

$ zig test test.zig
./docgen_tmp/test.zig:9:9: error: values of type 'type' must be comptime known
        if (condition) f32 else u64,
        ^

fn max(comptime T: type, a: T, b: T) T {
    return if (a > b) a else b;
}
test "try to compare bools" {
    _ = max(bool, true, false);
}

$ zig test test.zig
./docgen_tmp/test.zig:2:18: error: operator not allowed for type 'bool'
    return if (a > b) a else b;
                 ^
./docgen_tmp/test.zig:5:12: note: called from here
    _ = max(bool, true, false);
           ^
./docgen_tmp/test.zig:4:29: note: called from here
test "try to compare bools" {
                            ^

fn max(comptime T: type, a: T, b: T) T {
    if (T == bool) {
        return a or b;
    } else if (a > b) {
        return a;
    } else {
        return b;
    }
}
test "try to compare bools" {
    try @import("std").testing.expect(max(bool, false, true) == true);
}

$ zig test comptime_max_with_bool.zig
1/1 test "try to compare bools"... OK
All 1 tests passed.

fn max(a: bool, b: bool) bool {
    return a or b;
}

const expect = @import("std").testing.expect;

const CmdFn = struct {
    name: []const u8,
    func: fn(i32) i32,
};

const cmd_fns = [_]CmdFn{
    CmdFn {.name = "one", .func = one},
    CmdFn {.name = "two", .func = two},
    CmdFn {.name = "three", .func = three},
};
fn one(value: i32) i32 { return value + 1; }
fn two(value: i32) i32 { return value + 2; }
fn three(value: i32) i32 { return value + 3; }

fn performFn(comptime prefix_char: u8, start_value: i32) i32 {
    var result: i32 = start_value;
    comptime var i = 0;
    inline while (i < cmd_fns.len) : (i += 1) {
        if (cmd_fns[i].name[0] == prefix_char) {
            result = cmd_fns[i].func(result);
        }
    }
    return result;
}

test "perform fn" {
    try expect(performFn('t', 1) == 6);
    try expect(performFn('o', 0) == 1);
    try expect(performFn('w', 99) == 99);
}

$ zig test comptime_vars.zig
1/1 test "perform fn"... OK
All 1 tests passed.

// From the line:
// expect(performFn('t', 1) == 6);
fn performFn(start_value: i32) i32 {
    var result: i32 = start_value;
    result = two(result);
    result = three(result);
    return result;
}

// From the line:
// expect(performFn('o', 0) == 1);
fn performFn(start_value: i32) i32 {
    var result: i32 = start_value;
    result = one(result);
    return result;
}

// From the line:
// expect(performFn('w', 99) == 99);
fn performFn(start_value: i32) i32 {
    var result: i32 = start_value;
    return result;
}

extern fn exit() noreturn;

test "foo" {
    comptime {
        exit();
    }
}

$ zig test test.zig
./docgen_tmp/test.zig:5:9: error: unable to evaluate constant expression
        exit();
        ^
./docgen_tmp/test.zig:5:13: note: referenced here
        exit();
            ^

const expect = @import("std").testing.expect;

fn fibonacci(index: u32) u32 {
    if (index < 2) return index;
    return fibonacci(index - 1) + fibonacci(index - 2);
}

test "fibonacci" {
    // test fibonacci at run-time
    try expect(fibonacci(7) == 13);

    // test fibonacci at compile-time
    comptime {
        try expect(fibonacci(7) == 13);
    }
}

$ zig test fibonacci_recursion.zig
1/1 test "fibonacci"... OK
All 1 tests passed.

const expect = @import("std").testing.expect;

fn fibonacci(index: u32) u32 {
    //if (index < 2) return index;
    return fibonacci(index - 1) + fibonacci(index - 2);
}

test "fibonacci" {
    comptime {
        try expect(fibonacci(7) == 13);
    }
}

$ zig test test.zig
./docgen_tmp/test.zig:5:28: error: operation caused overflow
    return fibonacci(index - 1) + fibonacci(index - 2);
                           ^
./docgen_tmp/test.zig:5:21: note: called from here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:5:21: note: called from here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:5:21: note: called from here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:5:21: note: called from here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:5:21: note: called from here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:5:21: note: called from here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:5:21: note: called from here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:10:29: note: called from here
        try expect(fibonacci(7) == 13);
                            ^
./docgen_tmp/test.zig:8:18: note: called from here
test "fibonacci" {
                 ^
./docgen_tmp/test.zig:5:21: note: referenced here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:10:29: note: referenced here
        try expect(fibonacci(7) == 13);
                            ^

const expect = @import("std").testing.expect;

fn fibonacci(index: i32) i32 {
    //if (index < 2) return index;
    return fibonacci(index - 1) + fibonacci(index - 2);
}

test "fibonacci" {
    comptime {
        try expect(fibonacci(7) == 13);
    }
}

$ zig test test.zig
./docgen_tmp/test.zig:5:21: error: evaluation exceeded 1000 backwards branches
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:5:21: note: called from here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:5:21: note: called from here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:5:21: note: called from here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:5:21: note: called from here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:5:21: note: called from here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:5:21: note: called from here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:5:21: note: called from here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:5:21: note: called from here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:5:21: note: called from here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:5:21: note: called from here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:5:21: note: called from here
    return fibonacci(index - 1) + fibonacci(index - 2);
                    ^
./docgen_tmp/test.zig:10:29: note: referenced here
        try expect(fibonacci(7) == 13);
                            ^

const expect = @import("std").testing.expect;

fn fibonacci(index: i32) i32 {
    if (index < 2) return index;
    return fibonacci(index - 1) + fibonacci(index - 2);
}

test "fibonacci" {
    comptime {
        try expect(fibonacci(7) == 99999);
    }
}

$ zig test test.zig
1/1 test "fibonacci"... test "fibonacci"... FAIL (TestUnexpectedResult)
FAIL (TestUnexpectedResult)
0 passed; 0 skipped; 1 failed.
error: the following test command failed with exit code 1:
docgen_tmp/zig-cache/o/8e4964e05ddaf866e77360a551b3c05b/test /home/andy/Downloads/zig/build-release/zig

const first_25_primes = firstNPrimes(25);
const sum_of_first_25_primes = sum(&first_25_primes);

fn firstNPrimes(comptime n: usize) [n]i32 {
    var prime_list: [n]i32 = undefined;
    var next_index: usize = 0;
    var test_number: i32 = 2;
    while (next_index < prime_list.len) : (test_number += 1) {
        var test_prime_index: usize = 0;
        var is_prime = true;
        while (test_prime_index < next_index) : (test_prime_index += 1) {
            if (test_number % prime_list[test_prime_index] == 0) {
                is_prime = false;
                break;
            }
        }
        if (is_prime) {
            prime_list[next_index] = test_number;
            next_index += 1;
        }
    }
    return prime_list;
}

fn sum(numbers: []const i32) i32 {
    var result: i32 = 0;
    for (numbers) |x| {
        result += x;
    }
    return result;
}

test "variable values" {
    try @import("std").testing.expect(sum_of_first_25_primes == 1060);
}

$ zig test N_primes.zig
1/1 test "variable values"... OK
All 1 tests passed.

fn List(comptime T: type) type {
    return struct {
        items: []T,
        len: usize,
    };
}

const Node = struct {
    next: *Node,
    name: []u8,
};

const print = @import("std").debug.print;

const a_number: i32 = 1234;
const a_string = "foobar";

pub fn main() void {
    print("here is a string: '{s}' here is a number: {}\n", .{a_string, a_number});
}

$ zig build-exe print.zig

$ ./print
here is a string: 'foobar' here is a number: 1234

const Writer = struct {
    /// Calls print and then flushes the buffer.
    pub fn print(self: *Writer, comptime format: []const u8, args: anytype) anyerror!void {
        const State = enum {
            start,
            open_brace,
            close_brace,
        };

        comptime var start_index: usize = 0;
        comptime var state = State.start;
        comptime var next_arg: usize = 0;

        inline for (format) |c, i| {
            switch (state) {
                State.start => switch (c) {
                    '{' => {
                        if (start_index < i) try self.write(format[start_index..i]);
                        state = State.open_brace;
                    },
                    '}' => {
                        if (start_index < i) try self.write(format[start_index..i]);
                        state = State.close_brace;
                    },
                    else => {},
                },
                State.open_brace => switch (c) {
                    '{' => {
                        state = State.start;
                        start_index = i;
                    },
                    '}' => {
                        try self.printValue(args[next_arg]);
                        next_arg += 1;
                        state = State.start;
                        start_index = i + 1;
                    },
                    's' => {
                        continue;
                    },
                    else => @compileError("Unknown format character: " ++ [1]u8{c}),
                },
                State.close_brace => switch (c) {
                    '}' => {
                        state = State.start;
                        start_index = i;
                    },
                    else => @compileError("Single '}' encountered in format string"),
                },
            }
        }
        comptime {
            if (args.len != next_arg) {
                @compileError("Unused arguments");
            }
            if (state != State.start) {
                @compileError("Incomplete format string: " ++ format);
            }
        }
        if (start_index < format.len) {
            try self.write(format[start_index..format.len]);
        }
        try self.flush();
    }

    fn write(self: *Writer, value: []const u8) !void {
        _ = self;
        _ = value;
    }
    pub fn printValue(self: *Writer, value: anytype) !void {
        _ = self;
        _ = value;
    }
    fn flush(self: *Writer) !void {
        _ = self;
    }
};

pub fn print(self: *Writer, arg0: []const u8, arg1: i32) !void {
    try self.write("here is a string: '");
    try self.printValue(arg0);
    try self.write("' here is a number: ");
    try self.printValue(arg1);
    try self.write("\n");
    try self.flush();
}

const Writer = struct {
    pub fn printValue(self: *Writer, value: anytype) !void {
        switch (@typeInfo(@TypeOf(value))) {
            .Int => {
                return self.writeInt(value);
            },
            .Float => {
                return self.writeFloat(value);
            },
            .Pointer => {
                return self.write(value);
            },
            else => {
                @compileError("Unable to print type '" ++ @typeName(@TypeOf(value)) ++ "'");
            },
        }
    }

    fn write(self: *Writer, value: []const u8) !void {
        _ = self;
        _ = value;
    }
    fn writeInt(self: *Writer, value: anytype) !void {
        _ = self;
        _ = value;
    }
    fn writeFloat(self: *Writer, value: anytype) !void {
        _ = self;
        _ = value;
    }
};

const print = @import("std").debug.print;

const a_number: i32 = 1234;
const a_string = "foobar";

test "print too many arguments" {
    print("here is a string: '{s}' here is a number: {}\n", .{
        a_string,
        a_number,
        a_number,
    });
}

$ zig test test.zig
./lib/std/fmt.zig:360:18: error: Unused argument in 'here is a string: '{s}' here is a number: {}
'
            1 => @compileError("Unused argument in '" ++ fmt ++ "'"),
                 ^
./lib/std/io/writer.zig:28:34: note: called from here
            return std.fmt.format(self, format, args);
                                 ^
./lib/std/debug.zig:66:27: note: called from here
    nosuspend stderr.print(fmt, args) catch return;
                          ^
./docgen_tmp/test.zig:7:10: note: called from here
    print("here is a string: '{s}' here is a number: {}\n", .{
         ^
./docgen_tmp/test.zig:6:33: note: called from here
test "print too many arguments" {
                                ^
./lib/std/io/writer.zig:28:34: error: expected type 'std.os.WriteError!void', found '@typeInfo(@typeInfo(@TypeOf(std.fmt.format)).Fn.return_type.?).ErrorUnion.error_set!void'
            return std.fmt.format(self, format, args);
                                 ^
./lib/std/debug.zig:66:27: note: called from here
    nosuspend stderr.print(fmt, args) catch return;
                          ^
./docgen_tmp/test.zig:7:10: note: called from here
    print("here is a string: '{s}' here is a number: {}\n", .{
         ^
./docgen_tmp/test.zig:6:33: note: called from here
test "print too many arguments" {
                                ^
./lib/std/io/writer.zig:28:34: note: error set '@typeInfo(@typeInfo(@TypeOf(std.fmt.format)).Fn.return_type.?).ErrorUnion.error_set' cannot cast into error set 'std.os.WriteError'
            return std.fmt.format(self, format, args);
                                 ^

const print = @import("std").debug.print;

const a_number: i32 = 1234;
const a_string = "foobar";
const fmt = "here is a string: '{s}' here is a number: {}\n";

pub fn main() void {
    print(fmt, .{a_string, a_number});
}

$ zig build-exe print.zig

$ ./print
here is a string: 'foobar' here is a number: 1234

pub fn main() noreturn {
    const msg = "hello world\n";
    _ = syscall3(SYS_write, STDOUT_FILENO, @ptrToInt(msg), msg.len);
    _ = syscall1(SYS_exit, 0);
    unreachable;
}

pub const SYS_write = 1;
pub const SYS_exit = 60;

pub const STDOUT_FILENO = 1;

pub fn syscall1(number: usize, arg1: usize) usize {
    return asm volatile ("syscall"
        : [ret] "={rax}" (-> usize)
        : [number] "{rax}" (number),
          [arg1] "{rdi}" (arg1)
        : "rcx", "r11"
    );
}

pub fn syscall3(number: usize, arg1: usize, arg2: usize, arg3: usize) usize {
    return asm volatile ("syscall"
        : [ret] "={rax}" (-> usize)
        : [number] "{rax}" (number),
          [arg1] "{rdi}" (arg1),
          [arg2] "{rsi}" (arg2),
          [arg3] "{rdx}" (arg3)
        : "rcx", "r11"
    );
}

$ zig build-exe test.zig -target x86_64-linux

$ ./test
hello world

// Inline assembly is an expression which returns a value.
// the `asm` keyword begins the expression.
_ = asm
// `volatile` is an optional modifier that tells Zig this
// inline assembly expression has side-effects. Without
// `volatile`, Zig is allowed to delete the inline assembly
// code if the result is unused.
volatile (
// Next is a comptime string which is the assembly code.
// Inside this string one may use `%[ret]`, `%[number]`,
// or `%[arg1]` where a register is expected, to specify
// the register that Zig uses for the argument or return value,
// if the register constraint strings are used. However in
// the below code, this is not used. A literal `%` can be
// obtained by escaping it with a double percent: `%%`.
// Often multiline string syntax comes in handy here.
    \\syscall
// Next is the output. It is possible in the future Zig will
// support multiple outputs, depending on how
// https://github.com/ziglang/zig/issues/215 is resolved.
// It is allowed for there to be no outputs, in which case
// this colon would be directly followed by the colon for the inputs.
    :
// This specifies the name to be used in `%[ret]` syntax in
// the above assembly string. This example does not use it,
// but the syntax is mandatory.
    [ret]
// Next is the output constraint string. This feature is still
// considered unstable in Zig, and so LLVM/GCC documentation
// must be used to understand the semantics.
// http://releases.llvm.org/10.0.0/docs/LangRef.html#inline-asm-constraint-string
// https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html
// In this example, the constraint string means "the result value of
// this inline assembly instruction is whatever is in $rax".
    "={rax}"
// Next is either a value binding, or `->` and then a type. The
// type is the result type of the inline assembly expression.
// If it is a value binding, then `%[ret]` syntax would be used
// to refer to the register bound to the value.
    (-> usize)
// Next is the list of inputs.
// The constraint for these inputs means, "when the assembly code is
// executed, $rax shall have the value of `number` and $rdi shall have
// the value of `arg1`". Any number of input parameters is allowed,
// including none.
    : [number] "{rax}" (number),
        [arg1] "{rdi}" (arg1)
// Next is the list of clobbers. These declare a set of registers whose
// values will not be preserved by the execution of this assembly code.
// These do not include output or input registers. The special clobber
// value of "memory" means that the assembly writes to arbitrary undeclared
// memory locations - not only the memory pointed to by a declared indirect
// output. In this example we list $rcx and $r11 because it is known the
// kernel syscall does not preserve these registers.
    : "rcx", "r11"
);

const std = @import("std");
const expect = std.testing.expect;

comptime {
    asm (
        \\.global my_func;
        \\.type my_func, @function;
        \\my_func:
        \\  lea (%rdi,%rsi,1),%eax
        \\  retq
    );
}

extern fn my_func(a: i32, b: i32) i32;

test "global assembly" {
    try expect(my_func(12, 34) == 46);
}

$ zig test global-asm.zig -target x86_64-linux
1/1 test "global assembly"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

var x: i32 = 1;

test "suspend with no resume" {
    var frame = async func();
    try expect(x == 2);
    _ = frame;
}

fn func() void {
    x += 1;
    suspend {}
    // This line is never reached because the suspend has no matching resume.
    x += 1;
}

$ zig test suspend_no_resume.zig
1/1 test "suspend with no resume"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

var the_frame: anyframe = undefined;
var result = false;

test "async function suspend with block" {
    _ = async testSuspendBlock();
    try expect(!result);
    resume the_frame;
    try expect(result);
}

fn testSuspendBlock() void {
    suspend {
        comptime try expect(@TypeOf(@frame()) == *@Frame(testSuspendBlock));
        the_frame = @frame();
    }
    result = true;
}

$ zig test async_suspend_block.zig
1/1 test "async function suspend with block"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "resume from suspend" {
    var my_result: i32 = 1;
    _ = async testResumeFromSuspend(&my_result);
    try std.testing.expect(my_result == 2);
}
fn testResumeFromSuspend(my_result: *i32) void {
    suspend {
        resume @frame();
    }
    my_result.* += 1;
    suspend {}
    my_result.* += 1;
}

$ zig test resume_from_suspend.zig
1/1 test "resume from suspend"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "async and await" {
    // The test block is not async and so cannot have a suspend
    // point in it. By using the nosuspend keyword, we promise that
    // the code in amain will finish executing without suspending
    // back to the test block.
    nosuspend amain();
}

fn amain() void {
    var frame = async func();
    comptime try expect(@TypeOf(frame) == @Frame(func));

    const ptr: anyframe->void = &frame;
    const any_ptr: anyframe = ptr;

    resume any_ptr;
    await ptr;
}

fn func() void {
    suspend {}
}

$ zig test async_await.zig
1/1 test "async and await"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

var the_frame: anyframe = undefined;
var final_result: i32 = 0;

test "async function await" {
    seq('a');
    _ = async amain();
    seq('f');
    resume the_frame;
    seq('i');
    try expect(final_result == 1234);
    try expect(std.mem.eql(u8, &seq_points, "abcdefghi"));
}
fn amain() void {
    seq('b');
    var f = async another();
    seq('e');
    final_result = await f;
    seq('h');
}
fn another() i32 {
    seq('c');
    suspend {
        seq('d');
        the_frame = @frame();
    }
    seq('g');
    return 1234;
}

var seq_points = [_]u8{0} ** "abcdefghi".len;
var seq_index: usize = 0;

fn seq(c: u8) void {
    seq_points[seq_index] = c;
    seq_index += 1;
}

$ zig test async_await_sequence.zig
1/1 test "async function await"... OK
All 1 tests passed.

const std = @import("std");
const Allocator = std.mem.Allocator;

pub fn main() void {
    _ = async amainWrap();

    // Typically we would use an event loop to manage resuming async functions,
    // but in this example we hard code what the event loop would do,
    // to make things deterministic.
    resume global_file_frame;
    resume global_download_frame;
}

fn amainWrap() void {
    amain() catch |e| {
        std.debug.print("{}\n", .{e});
        if (@errorReturnTrace()) |trace| {
            std.debug.dumpStackTrace(trace.*);
        }
        std.process.exit(1);
    };
}

fn amain() !void {
    const allocator = std.heap.page_allocator;
    var download_frame = async fetchUrl(allocator, "https://example.com/");
    var awaited_download_frame = false;
    errdefer if (!awaited_download_frame) {
        if (await download_frame) |r| allocator.free(r) else |_| {}
    };

    var file_frame = async readFile(allocator, "something.txt");
    var awaited_file_frame = false;
    errdefer if (!awaited_file_frame) {
        if (await file_frame) |r| allocator.free(r) else |_| {}
    };

    awaited_file_frame = true;
    const file_text = try await file_frame;
    defer allocator.free(file_text);

    awaited_download_frame = true;
    const download_text = try await download_frame;
    defer allocator.free(download_text);

    std.debug.print("download_text: {s}\n", .{download_text});
    std.debug.print("file_text: {s}\n", .{file_text});
}

var global_download_frame: anyframe = undefined;
fn fetchUrl(allocator: Allocator, url: []const u8) ![]u8 {
    _ = url; // this is just an example, we don't actually do it!
    const result = try allocator.dupe(u8, "this is the downloaded url contents");
    errdefer allocator.free(result);
    suspend {
        global_download_frame = @frame();
    }
    std.debug.print("fetchUrl returning\n", .{});
    return result;
}

var global_file_frame: anyframe = undefined;
fn readFile(allocator: Allocator, filename: []const u8) ![]u8 {
    _ = filename; // this is just an example, we don't actually do it!
    const result = try allocator.dupe(u8, "this is the file contents");
    errdefer allocator.free(result);
    suspend {
        global_file_frame = @frame();
    }
    std.debug.print("readFile returning\n", .{});
    return result;
}

$ zig build-exe async.zig

$ ./async
readFile returning
fetchUrl returning
download_text: this is the downloaded url contents
file_text: this is the file contents

const std = @import("std");
const Allocator = std.mem.Allocator;

pub fn main() void {
    _ = async amainWrap();
}

fn amainWrap() void {
    amain() catch |e| {
        std.debug.print("{}\n", .{e});
        if (@errorReturnTrace()) |trace| {
            std.debug.dumpStackTrace(trace.*);
        }
        std.process.exit(1);
    };
}

fn amain() !void {
    const allocator = std.heap.page_allocator;
    var download_frame = async fetchUrl(allocator, "https://example.com/");
    var awaited_download_frame = false;
    errdefer if (!awaited_download_frame) {
        if (await download_frame) |r| allocator.free(r) else |_| {}
    };

    var file_frame = async readFile(allocator, "something.txt");
    var awaited_file_frame = false;
    errdefer if (!awaited_file_frame) {
        if (await file_frame) |r| allocator.free(r) else |_| {}
    };

    awaited_file_frame = true;
    const file_text = try await file_frame;
    defer allocator.free(file_text);

    awaited_download_frame = true;
    const download_text = try await download_frame;
    defer allocator.free(download_text);

    std.debug.print("download_text: {s}\n", .{download_text});
    std.debug.print("file_text: {s}\n", .{file_text});
}

fn fetchUrl(allocator: Allocator, url: []const u8) ![]u8 {
    _ = url; // this is just an example, we don't actually do it!
    const result = try allocator.dupe(u8, "this is the downloaded url contents");
    errdefer allocator.free(result);
    std.debug.print("fetchUrl returning\n", .{});
    return result;
}

fn readFile(allocator: Allocator, filename: []const u8) ![]u8 {
    _ = filename; // this is just an example, we don't actually do it!
    const result = try allocator.dupe(u8, "this is the file contents");
    errdefer allocator.free(result);
    std.debug.print("readFile returning\n", .{});
    return result;
}

$ zig build-exe blocking.zig

$ ./blocking
fetchUrl returning
readFile returning
download_text: this is the downloaded url contents
file_text: this is the file contents

const std = @import("std");
const expect = std.testing.expect;

test "async fn pointer in a struct field" {
    var data: i32 = 1;
    const Foo = struct {
        bar: fn (*i32) callconv(.Async) void,
    };
    var foo = Foo{ .bar = func };
    var bytes: [64]u8 align(@alignOf(@Frame(func))) = undefined;
    const f = @asyncCall(&bytes, {}, foo.bar, .{&data});
    try expect(data == 2);
    resume f;
    try expect(data == 4);
}

fn func(y: *i32) void {
    defer y.* += 2;
    y.* += 1;
    suspend {}
}

$ zig test async_struct_field_fn_pointer.zig
1/1 test "async fn pointer in a struct field"... OK
All 1 tests passed.

const expect = @import("std").testing.expect;

test "noinline function call" {
    try expect(@call(.{}, add, .{3, 9}) == 12);
}

fn add(a: i32, b: i32) i32 {
    return a + b;
}

$ zig test call.zig
1/1 test "noinline function call"... OK
All 1 tests passed.

pub const CallOptions = struct {
    modifier: Modifier = .auto,

    /// Only valid when `Modifier` is `Modifier.async_kw`.
    stack: ?[]align(std.Target.stack_align) u8 = null,

    pub const Modifier = enum {
        /// Equivalent to function call syntax.
        auto,

        /// Equivalent to async keyword used with function call syntax.
        async_kw,

        /// Prevents tail call optimization. This guarantees that the return
        /// address will point to the callsite, as opposed to the callsite's
        /// callsite. If the call is otherwise required to be tail-called
        /// or inlined, a compile error is emitted instead.
        never_tail,

        /// Guarantees that the call will not be inlined. If the call is
        /// otherwise required to be inlined, a compile error is emitted instead.
        never_inline,

        /// Asserts that the function call will not suspend. This allows a
        /// non-async function to call an async function.
        no_async,

        /// Guarantees that the call will be generated with tail call optimization.
        /// If this is not possible, a compile error is emitted instead.
        always_tail,

        /// Guarantees that the call will inlined at the callsite.
        /// If this is not possible, a compile error is emitted instead.
        always_inline,

        /// Evaluates the call at compile-time. If the call cannot be completed at
        /// compile-time, a compile error is emitted instead.
        compile_time,
    };
};

fn cmpxchgStrongButNotAtomic(comptime T: type, ptr: *T, expected_value: T, new_value: T) ?T {
    const old_value = ptr.*;
    if (old_value == expected_value) {
        ptr.* = new_value;
        return null;
    } else {
        return old_value;
    }
}

fn cmpxchgWeakButNotAtomic(comptime T: type, ptr: *T, expected_value: T, new_value: T) ?T {
    const old_value = ptr.*;
    if (old_value == expected_value and usuallyTrueButSometimesFalse()) {
        ptr.* = new_value;
        return null;
    } else {
        return old_value;
    }
}

const print = @import("std").debug.print;

const num1 = blk: {
    var val1: i32 = 99;
    @compileLog("comptime val1 = ", val1);
    val1 = val1 + 1;
    break :blk val1;
};

test "main" {
    @compileLog("comptime in main");

    print("Runtime in main, num1 = {}.\n", .{num1});
}

$ zig test test.zig
| *"comptime in main"
| *"comptime val1 = ", 99
./docgen_tmp/test.zig:11:5: error: found compile log statement
    @compileLog("comptime in main");
    ^
./docgen_tmp/test.zig:1:35: note: referenced here
const print = @import("std").debug.print;
                                  ^
./docgen_tmp/test.zig:13:5: note: referenced here
    print("Runtime in main, num1 = {}.\n", .{num1});
    ^
./docgen_tmp/test.zig:5:5: error: found compile log statement
    @compileLog("comptime val1 = ", val1);
    ^
./docgen_tmp/test.zig:13:46: note: referenced here
    print("Runtime in main, num1 = {}.\n", .{num1});
                                             ^

const print = @import("std").debug.print;

const num1 = blk: {
    var val1: i32 = 99;
    val1 = val1 + 1;
    break :blk val1;
};

test "main" {
    print("Runtime in main, num1 = {}.\n", .{num1});
}

$ zig test without_compileLog.zig
1/1 test "main"... Runtime in main, num1 = 100.
OK
All 1 tests passed.

comptime {
    @export(internalName, .{ .name = "foo", .linkage = .Strong });
}

fn internalName() callconv(.C) void {}

$ zig build-obj test.zig

export fn foo() void {}

$ zig build-obj test.zig

export fn @"A function name that is a complete sentence."() void {}

$ zig build-obj test.zig

const std = @import("std");

const Point = struct {
    x: u32,
    y: u32,

    pub var z: u32 = 1;
};

test "field access by string" {
    const expect = std.testing.expect;
    var p = Point{ .x = 0, .y = 0 };

    @field(p, "x") = 4;
    @field(p, "y") = @field(p, "x") + 1;

    try expect(@field(p, "x") == 4);
    try expect(@field(p, "y") == 5);
}

test "decl access by string" {
    const expect = std.testing.expect;

    try expect(@field(Point, "z") == 1);

    @field(Point, "z") = 2;
    try expect(@field(Point, "z") == 2);
}

$ zig test field_decl_access_by_string.zig
1/2 test "field access by string"... OK
2/2 test "decl access by string"... OK
All 2 tests passed.

const std = @import("std");

test "heap allocated frame" {
    const frame = try std.heap.page_allocator.create(@Frame(func));
    frame.* = async func();
}

fn func() void {
    suspend {}
}

$ zig test heap_allocated_frame.zig
1/1 test "heap allocated frame"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

const Foo = struct {
    nope: i32,

    pub var blah = "xxx";
    const hi = 1;
};

test "@hasDecl" {
    try expect(@hasDecl(Foo, "blah"));

    // Even though `hi` is private, @hasDecl returns true because this test is
    // in the same file scope as Foo. It would return false if Foo was declared
    // in a different file.
    try expect(@hasDecl(Foo, "hi"));

    // @hasDecl is for declarations; not fields.
    try expect(!@hasDecl(Foo, "nope"));
    try expect(!@hasDecl(Foo, "nope1234"));
}

$ zig test hasDecl.zig
1/1 test "@hasDecl"... OK
All 1 tests passed.

const std = @import("std");
const native_arch = @import("builtin").target.cpu.arch;
const expect = std.testing.expect;

test "@wasmMemoryGrow" {
    if (native_arch != .wasm32) return error.SkipZigTest;

    var prev = @wasmMemorySize(0);
    try expect(prev == @wasmMemoryGrow(0, 1));
    try expect(prev + 1 == @wasmMemorySize(0));
}

$ zig test wasmMemoryGrow.zig
1/1 test "@wasmMemoryGrow"... test "@wasmMemoryGrow"... SKIP
SKIP
0 passed; 1 skipped; 0 failed.

/// This data structure is used by the Zig language code generation and
/// therefore must be kept in sync with the compiler implementation.
pub const PrefetchOptions = struct {
    /// Whether the prefetch should prepare for a read or a write.
    rw: Rw = .read,
    /// 0 means no temporal locality. That is, the data can be immediately
    /// dropped from the cache after it is accessed.
    ///
    /// 3 means high temporal locality. That is, the data should be kept in
    /// the cache as it is likely to be accessed again soon.
    locality: u2 = 3,
    /// The cache that the prefetch should be preformed on.
    cache: Cache = .data,

    pub const Rw = enum {
        read,
        write,
    };

    pub const Cache = enum {
        instruction,
        data,
    };
};

test "foo" {
    comptime {
        var i = 0;
        while (i < 1001) : (i += 1) {}
    }
}

$ zig test test.zig
./docgen_tmp/test.zig:4:9: error: evaluation exceeded 1000 backwards branches
        while (i < 1001) : (i += 1) {}
        ^
./docgen_tmp/test.zig:1:12: note: referenced here
test "foo" {
           ^

test "foo" {
    comptime {
        @setEvalBranchQuota(1001);
        var i = 0;
        while (i < 1001) : (i += 1) {}
    }
}

$ zig test setEvalBranchQuota.zig
1/1 test "foo"... OK
All 1 tests passed.

pub const FloatMode = enum {
    Strict,
    Optimized,
};

test "@setRuntimeSafety" {
    // The builtin applies to the scope that it is called in. So here, integer overflow
    // will not be caught in ReleaseFast and ReleaseSmall modes:
    // var x: u8 = 255;
    // x += 1; // undefined behavior in ReleaseFast/ReleaseSmall modes.
    {
        // However this block has safety enabled, so safety checks happen here,
        // even in ReleaseFast and ReleaseSmall modes.
        @setRuntimeSafety(true);
        var x: u8 = 255;
        x += 1;

        {
            // The value can be overridden at any scope. So here integer overflow
            // would not be caught in any build mode.
            @setRuntimeSafety(false);
            // var x: u8 = 255;
            // x += 1; // undefined behavior in all build modes.
        }
    }
}

$ zig test test.zig -OReleaseFast
1/1 test "@setRuntimeSafety"... thread 797125 panic: integer overflow
error: the following test command crashed:
docgen_tmp/zig-cache/o/7b3f38578dd3c68a8e61771c6005cfea/test /home/andy/Downloads/zig/build-release/zig

const std = @import("std");
const Vector = std.meta.Vector;
const expect = std.testing.expect;

test "vector @shuffle" {
    const a: Vector(7, u8) = [_]u8{ 'o', 'l', 'h', 'e', 'r', 'z', 'w' };
    const b: Vector(4, u8) = [_]u8{ 'w', 'd', '!', 'x' };

    // To shuffle within a single vector, pass undefined as the second argument.
    // Notice that we can re-order, duplicate, or omit elements of the input vector
    const mask1: Vector(5, i32) = [_]i32{ 2, 3, 1, 1, 0 };
    const res1: Vector(5, u8) = @shuffle(u8, a, undefined, mask1);
    try expect(std.mem.eql(u8, &@as([5]u8, res1), "hello"));

    // Combining two vectors
    const mask2: Vector(6, i32) = [_]i32{ -1, 0, 4, 1, -2, -3 };
    const res2: Vector(6, u8) = @shuffle(u8, a, b, mask2);
    try expect(std.mem.eql(u8, &@as([6]u8, res2), "world!"));
}

$ zig test vector_shuffle.zig
1/1 test "vector @shuffle"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "vector @splat" {
    const scalar: u32 = 5;
    const result = @splat(4, scalar);
    comptime try expect(@TypeOf(result) == std.meta.Vector(4, u32));
    try expect(std.mem.eql(u32, &@as([4]u32, result), &[_]u32{ 5, 5, 5, 5 }));
}

$ zig test vector_splat.zig
1/1 test "vector @splat"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "vector @reduce" {
    const value: std.meta.Vector(4, i32) = [_]i32{ 1, -1, 1, -1 };
    const result = value > @splat(4, @as(i32, 0));
    // result is { true, false, true, false };
    comptime try expect(@TypeOf(result) == std.meta.Vector(4, bool));
    const is_all_true = @reduce(.And, result);
    comptime try expect(@TypeOf(is_all_true) == bool);
    try expect(is_all_true == false);
}

$ zig test vector_reduce.zig
1/1 test "vector @reduce"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "@src" {
    try doTheTest();
}

fn doTheTest() !void {
    const src = @src();

    try expect(src.line == 9);
    try expect(src.column == 17);
    try expect(std.mem.endsWith(u8, src.fn_name, "doTheTest"));
    try expect(std.mem.endsWith(u8, src.file, "source_location.zig"));
}

$ zig test source_location.zig
1/1 test "@src"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "@This()" {
    var items = [_]i32{ 1, 2, 3, 4 };
    const list = List(i32){ .items = items[0..] };
    try expect(list.length() == 4);
}

fn List(comptime T: type) type {
    return struct {
        const Self = @This();

        items: []T,

        fn length(self: Self) usize {
            return self.items.len;
        }
    };
}

$ zig test this_innermost.zig
1/1 test "@This()"... OK
All 1 tests passed.

test "integer cast panic" {
    var a: u16 = 0xabcd;
    var b: u8 = @intCast(u8, a);
    _ = b;
}

$ zig test test.zig
1/1 test "integer cast panic"... thread 797343 panic: integer cast truncated bits
/home/andy/Downloads/zig/docgen_tmp/test.zig:3:17: 0x207a05 in test "integer cast panic" (test)
    var b: u8 = @intCast(u8, a);
                ^
/home/andy/Downloads/zig/lib/std/special/test_runner.zig:80:28: 0x22f413 in std.special.main (test)
        } else test_fn.func();
                           ^
/home/andy/Downloads/zig/lib/std/start.zig:543:22: 0x227e0c in std.start.callMain (test)
            root.main();
                     ^
/home/andy/Downloads/zig/lib/std/start.zig:495:12: 0x20922e in std.start.callMainWithArgs (test)
    return @call(.{ .modifier = .always_inline }, callMain, .{});
           ^
/home/andy/Downloads/zig/lib/std/start.zig:409:17: 0x2082c6 in std.start.posixCallMainAndExit (test)
    std.os.exit(@call(.{ .modifier = .always_inline }, callMainWithArgs, .{ argc, argv, envp }));
                ^
/home/andy/Downloads/zig/lib/std/start.zig:322:5: 0x2080d2 in std.start._start (test)
    @call(.{ .modifier = .never_inline }, posixCallMainAndExit, .{});
    ^
error: the following test command crashed:
docgen_tmp/zig-cache/o/8e4964e05ddaf866e77360a551b3c05b/test /home/andy/Downloads/zig/build-release/zig

const std = @import("std");
const expect = std.testing.expect;

test "integer truncation" {
    var a: u16 = 0xabcd;
    var b: u8 = @truncate(u8, a);
    try expect(b == 0xcd);
}

$ zig test truncate.zig
1/1 test "integer truncation"... OK
All 1 tests passed.

const std = @import("std");
const expect = std.testing.expect;

test "no runtime side effects" {
    var data: i32 = 0;
    const T = @TypeOf(foo(i32, &data));
    comptime try expect(T == i32);
    try expect(data == 0);
}

fn foo(comptime T: type, ptr: *T) T {
    ptr.* += 1;
    return ptr.*;
}

$ zig test no_runtime_side_effects.zig
1/1 test "no runtime side effects"... OK
All 1 tests passed.

const Builder = @import("std").build.Builder;

pub fn build(b: *Builder) void {
    const exe = b.addExecutable("example", "example.zig");
    exe.setBuildMode(b.standardReleaseOptions());
    b.default_step.dependOn(&exe.step);
}

$ zig build-exe example.zig

$ zig build-exe example.zig -O ReleaseFast

$ zig build-exe example.zig -O ReleaseSafe

$ zig build-exe example.zig -O ReleaseSmall

test "safety check" {
    unreachable;
}

$ zig test test.zig
1/1 test "safety check"... thread 797490 panic: reached unreachable code
/home/andy/Downloads/zig/docgen_tmp/test.zig:2:5: 0x2079da in test "safety check" (test)
    unreachable;
    ^
/home/andy/Downloads/zig/lib/std/special/test_runner.zig:80:28: 0x22f3e3 in std.special.main (test)
        } else test_fn.func();
                           ^
/home/andy/Downloads/zig/lib/std/start.zig:543:22: 0x227ddc in std.start.callMain (test)
            root.main();
                     ^
/home/andy/Downloads/zig/lib/std/start.zig:495:12: 0x2091fe in std.start.callMainWithArgs (test)
    return @call(.{ .modifier = .always_inline }, callMain, .{});
           ^
/home/andy/Downloads/zig/lib/std/start.zig:409:17: 0x208296 in std.start.posixCallMainAndExit (test)
    std.os.exit(@call(.{ .modifier = .always_inline }, callMainWithArgs, .{ argc, argv, envp }));
                ^
/home/andy/Downloads/zig/lib/std/start.zig:322:5: 0x2080a2 in std.start._start (test)
    @call(.{ .modifier = .never_inline }, posixCallMainAndExit, .{});
    ^
error: the following test command crashed:
docgen_tmp/zig-cache/o/8e4964e05ddaf866e77360a551b3c05b/test /home/andy/Downloads/zig/build-release/zig

comptime {
    assert(false);
}
fn assert(ok: bool) void {
    if (!ok) unreachable; // assertion failure
}

$ zig test test.zig
./docgen_tmp/test.zig:5:14: error: reached unreachable code
    if (!ok) unreachable; // assertion failure
             ^
./docgen_tmp/test.zig:2:11: note: called from here
    assert(false);
          ^
./docgen_tmp/test.zig:1:10: note: called from here
comptime {
         ^
./docgen_tmp/test.zig:2:11: note: referenced here
    assert(false);
          ^

const std = @import("std");

pub fn main() void {
    std.debug.assert(false);
}

$ zig build-exe test.zig

$ ./test
thread 797551 panic: reached unreachable code
/home/andy/Downloads/zig/lib/std/debug.zig:224:14: 0x204e3b in std.debug.assert (test)
    if (!ok) unreachable; // assertion failure
             ^
/home/andy/Downloads/zig/docgen_tmp/test.zig:4:21: 0x22ce2a in main (test)
    std.debug.assert(false);
                    ^
/home/andy/Downloads/zig/lib/std/start.zig:543:22: 0x225bbc in std.start.callMain (test)
            root.main();
                     ^
/home/andy/Downloads/zig/lib/std/start.zig:495:12: 0x206fbe in std.start.callMainWithArgs (test)
    return @call(.{ .modifier = .always_inline }, callMain, .{});
           ^
/home/andy/Downloads/zig/lib/std/start.zig:409:17: 0x206056 in std.start.posixCallMainAndExit (test)
    std.os.exit(@call(.{ .modifier = .always_inline }, callMainWithArgs, .{ argc, argv, envp }));
                ^
/home/andy/Downloads/zig/lib/std/start.zig:322:5: 0x205e62 in std.start._start (test)
    @call(.{ .modifier = .never_inline }, posixCallMainAndExit, .{});
    ^
(process terminated by signal)