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

// comptime array passed as slice argument
comptime {
    const S = struct {
        fn indexOfScalarPos(comptime T: type, slice: []const T, start_index: usize, value: T) ?usize {
            var i: usize = start_index;
            while (i < slice.len) : (i += 1) {
                if (slice[i] == value) return i;
            }
            return null;
        }

        fn indexOfScalar(comptime T: type, slice: []const T, value: T) ?usize {
            return indexOfScalarPos(T, slice, 0, value);
        }
    };
    const unsigned = [_]type{ c_uint, c_ulong, c_ulonglong };
    const list: []const type = &unsigned;
    var pos = S.indexOfScalar(type, list, c_ulong).?;
    if (pos != 1) @compileError("bad pos");
}

test "slicing" {
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    var array: [20]i32 = undefined;

    array[5] = 1234;

    var slice = array[5..10];

    if (slice.len != 5) unreachable;

    const ptr = &slice[0];
    if (ptr.* != 1234) unreachable;

    var slice_rest = array[10..];
    if (slice_rest.len != 10) unreachable;
}

test "const slice" {
    comptime {
        const a = "1234567890";
        try expect(a.len == 10);
        const b = a[1..2];
        try expect(b.len == 1);
        try expect(b[0] == '2');
    }
}

test "comptime slice of undefined pointer of length 0" {
    const slice1 = @as([*]i32, undefined)[0..0];
    try expect(slice1.len == 0);
    const slice2 = @as([*]i32, undefined)[100..100];
    try expect(slice2.len == 0);
}

test "implicitly cast array of size 0 to slice" {
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    var msg = [_]u8{};
    try assertLenIsZero(&msg);
}

fn assertLenIsZero(msg: []const u8) !void {
    try expect(msg.len == 0);
}

test "access len index of sentinel-terminated slice" {
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO

    const S = struct {
        fn doTheTest() !void {
            var slice: [:0]const u8 = "hello";

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

test "comptime slice of slice preserves comptime var" {
    comptime {
        var buff: [10]u8 = undefined;
        buff[0..][0..][0] = 1;
        try expect(buff[0..][0..][0] == 1);
    }
}

test "slice of type" {
    comptime {
        var types_array = [_]type{ i32, f64, type };
        for (types_array, 0..) |T, i| {
            switch (i) {
                0 => try expect(T == i32),
                1 => try expect(T == f64),
                2 => try expect(T == type),
                else => unreachable,
            }
        }
        for (types_array[0..], 0..) |T, i| {
            switch (i) {
                0 => try expect(T == i32),
                1 => try expect(T == f64),
                2 => try expect(T == type),
                else => unreachable,
            }
        }
    }
}

test "generic malloc free" {
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    const a = memAlloc(u8, 10) catch unreachable;
    memFree(u8, a);
}
var some_mem: [100]u8 = undefined;
fn memAlloc(comptime T: type, n: usize) anyerror![]T {
    return @as([*]T, @ptrCast(&some_mem[0]))[0..n];
}
fn memFree(comptime T: type, memory: []T) void {
    _ = memory;
}

test "slice of hardcoded address to pointer" {
    const S = struct {
        fn doTheTest() !void {
            const pointer = @as([*]u8, @ptrFromInt(0x04))[0..2];
            try comptime expect(@TypeOf(pointer) == *[2]u8);
            const slice: []const u8 = pointer;
            try expect(@intFromPtr(slice.ptr) == 4);
            try expect(slice.len == 2);
        }
    };

    try S.doTheTest();
}

test "comptime slice of pointer preserves comptime var" {
    comptime {
        var buff: [10]u8 = undefined;
        var a = @as([*]u8, @ptrCast(&buff));
        a[0..1][0] = 1;
        try expect(buff[0..][0..][0] == 1);
    }
}

test "comptime pointer cast array and then slice" {
    const array = [_]u8{ 1, 2, 3, 4, 5, 6, 7, 8 };

    const ptrA: [*]const u8 = @as([*]const u8, @ptrCast(&array));
    const sliceA: []const u8 = ptrA[0..2];

    const ptrB: [*]const u8 = &array;
    const sliceB: []const u8 = ptrB[0..2];

    try expect(sliceA[1] == 2);
    try expect(sliceB[1] == 2);
}

test "slicing zero length array" {
    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    const s1 = ""[0..];
    const s2 = ([_]u32{})[0..];
    try expect(s1.len == 0);
    try expect(s2.len == 0);
    try expect(mem.eql(u8, s1, ""));
    try expect(mem.eql(u32, s2, &[_]u32{}));
}

test "slicing pointer by length" {
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    const array = [_]u8{ 1, 2, 3, 4, 5, 6, 7, 8 };
    const ptr: [*]const u8 = @as([*]const u8, @ptrCast(&array));
    const slice = ptr[1..][0..5];
    try expect(slice.len == 5);
    var i: usize = 0;
    while (i < slice.len) : (i += 1) {
        try expect(slice[i] == i + 2);
    }
}

const x = @as([*]i32, @ptrFromInt(0x1000))[0..0x500];
const y = x[0x100..];
test "compile time slice of pointer to hard coded address" {
    try expect(@intFromPtr(x) == 0x1000);
    try expect(x.len == 0x500);

    try expect(@intFromPtr(y) == 0x1400);
    try expect(y.len == 0x400);
}

test "slice string literal has correct type" {
    comptime {
        try expect(@TypeOf("aoeu"[0..]) == *const [4:0]u8);
        const array = [_]i32{ 1, 2, 3, 4 };
        try expect(@TypeOf(array[0..]) == *const [4]i32);
    }
    var runtime_zero: usize = 0;
    try comptime expect(@TypeOf("aoeu"[runtime_zero..]) == [:0]const u8);
    const array = [_]i32{ 1, 2, 3, 4 };
    try comptime expect(@TypeOf(array[runtime_zero..]) == []const i32);
}

test "result location zero sized array inside struct field implicit cast to slice" {
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    const E = struct {
        entries: []u32,
    };
    var foo = E{ .entries = &[_]u32{} };
    try expect(foo.entries.len == 0);
}

test "runtime safety lets us slice from len..len" {
    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    var an_array = [_]u8{ 1, 2, 3 };
    try expect(mem.eql(u8, sliceFromLenToLen(an_array[0..], 3, 3), ""));
}

fn sliceFromLenToLen(a_slice: []u8, start: usize, end: usize) []u8 {
    return a_slice[start..end];
}

test "C pointer" {
    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    var buf: [*c]const u8 = "kjdhfkjdhfdkjhfkfjhdfkjdhfkdjhfdkjhf";
    var len: u32 = 10;
    var slice = buf[0..len];
    try expect(mem.eql(u8, "kjdhfkjdhf", slice));
}

test "C pointer slice access" {
    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    var buf: [10]u32 = [1]u32{42} ** 10;
    const c_ptr = @as([*c]const u32, @ptrCast(&buf));

    var runtime_zero: usize = 0;
    try comptime expectEqual([]const u32, @TypeOf(c_ptr[runtime_zero..1]));
    try comptime expectEqual(*const [1]u32, @TypeOf(c_ptr[0..1]));

    for (c_ptr[0..5]) |*cl| {
        try expect(@as(u32, 42) == cl.*);
    }
}

test "comptime slices are disambiguated" {
    try expect(sliceSum(&[_]u8{ 1, 2 }) == 3);
    try expect(sliceSum(&[_]u8{ 3, 4 }) == 7);
}

fn sliceSum(comptime q: []const u8) i32 {
    comptime var result = 0;
    inline for (q) |item| {
        result += item;
    }
    return result;
}

test "slice type with custom alignment" {
    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    const LazilyResolvedType = struct {
        anything: i32,
    };
    var slice: []align(32) LazilyResolvedType = undefined;
    var array: [10]LazilyResolvedType align(32) = undefined;
    slice = &array;
    slice[1].anything = 42;
    try expect(array[1].anything == 42);
}

test "obtaining a null terminated slice" {
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    // here we have a normal array
    var buf: [50]u8 = undefined;

    buf[0] = 'a';
    buf[1] = 'b';
    buf[2] = 'c';
    buf[3] = 0;

    // now we obtain a null terminated slice:
    const ptr = buf[0..3 :0];
    _ = ptr;

    var runtime_len: usize = 3;
    const ptr2 = buf[0..runtime_len :0];
    // ptr2 is a null-terminated slice
    try comptime expect(@TypeOf(ptr2) == [:0]u8);
    try comptime expect(@TypeOf(ptr2[0..2]) == *[2]u8);
    var runtime_zero: usize = 0;
    try comptime expect(@TypeOf(ptr2[runtime_zero..2]) == []u8);
}

test "empty array to slice" {
    const S = struct {
        fn doTheTest() !void {
            const empty: []align(16) u8 = &[_]u8{};
            const align_1: []align(1) u8 = empty;
            const align_4: []align(4) u8 = empty;
            const align_16: []align(16) u8 = empty;
            try expect(1 == @typeInfo(@TypeOf(align_1)).Pointer.alignment);
            try expect(4 == @typeInfo(@TypeOf(align_4)).Pointer.alignment);
            try expect(16 == @typeInfo(@TypeOf(align_16)).Pointer.alignment);
        }
    };

    try S.doTheTest();
    try comptime S.doTheTest();
}

test "@ptrCast slice to pointer" {
    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    const S = struct {
        fn doTheTest() !void {
            var array align(@alignOf(u16)) = [5]u8{ 0xff, 0xff, 0xff, 0xff, 0xff };
            var slice: []align(@alignOf(u16)) u8 = &array;
            var ptr = @as(*u16, @ptrCast(slice));
            try expect(ptr.* == 65535);
        }
    };

    try S.doTheTest();
    try comptime S.doTheTest();
}

test "slice syntax resulting in pointer-to-array" {
    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    const S = struct {
        fn doTheTest() !void {
            try testArray();
            try testArrayZ();
            try testArray0();
            try testArrayAlign();
            try testPointer();
            try testPointerZ();
            try testPointer0();
            try testPointerAlign();
            try testSlice();
            try testSliceZ();
            try testSliceOpt();
            try testSliceAlign();
            try testConcatStrLiterals();
            try testSliceLength();
            try testSliceLengthZ();
            try testArrayLength();
            try testArrayLengthZ();
            try testMultiPointer();
            try testMultiPointerLengthZ();
        }

        fn testArray() !void {
            var array = [5]u8{ 1, 2, 3, 4, 5 };
            var slice = array[1..3];
            try comptime expect(@TypeOf(slice) == *[2]u8);
            try expect(slice[0] == 2);
            try expect(slice[1] == 3);
        }

        fn testArrayZ() !void {
            var array = [5:0]u8{ 1, 2, 3, 4, 5 };
            try comptime expect(@TypeOf(array[1..3]) == *[2]u8);
            try comptime expect(@TypeOf(array[1..5]) == *[4:0]u8);
            try comptime expect(@TypeOf(array[1..]) == *[4:0]u8);
            try comptime expect(@TypeOf(array[1..3 :4]) == *[2:4]u8);
        }

        fn testArray0() !void {
            {
                var array = [0]u8{};
                var slice = array[0..0];
                try comptime expect(@TypeOf(slice) == *[0]u8);
            }
            {
                var array = [0:0]u8{};
                var slice = array[0..0];
                try comptime expect(@TypeOf(slice) == *[0:0]u8);
                try expect(slice[0] == 0);
            }
        }

        fn testArrayAlign() !void {
            var array align(4) = [5]u8{ 1, 2, 3, 4, 5 };
            var slice = array[4..5];
            try comptime expect(@TypeOf(slice) == *align(4) [1]u8);
            try expect(slice[0] == 5);
            try comptime expect(@TypeOf(array[0..2]) == *align(4) [2]u8);
        }

        fn testPointer() !void {
            var array = [5]u8{ 1, 2, 3, 4, 5 };
            var pointer: [*]u8 = &array;
            var slice = pointer[1..3];
            try comptime expect(@TypeOf(slice) == *[2]u8);
            try expect(slice[0] == 2);
            try expect(slice[1] == 3);
        }

        fn testPointerZ() !void {
            var array = [5:0]u8{ 1, 2, 3, 4, 5 };
            var pointer: [*:0]u8 = &array;
            try comptime expect(@TypeOf(pointer[1..3]) == *[2]u8);
            try comptime expect(@TypeOf(pointer[1..3 :4]) == *[2:4]u8);
        }

        fn testPointer0() !void {
            var pointer: [*]const u0 = &[1]u0{0};
            var slice = pointer[0..1];
            try comptime expect(@TypeOf(slice) == *const [1]u0);
            try expect(slice[0] == 0);
        }

        fn testPointerAlign() !void {
            var array align(4) = [5]u8{ 1, 2, 3, 4, 5 };
            var pointer: [*]align(4) u8 = &array;
            var slice = pointer[4..5];
            try comptime expect(@TypeOf(slice) == *align(4) [1]u8);
            try expect(slice[0] == 5);
            try comptime expect(@TypeOf(pointer[0..2]) == *align(4) [2]u8);
        }

        fn testSlice() !void {
            var array = [5]u8{ 1, 2, 3, 4, 5 };
            var src_slice: []u8 = &array;
            var slice = src_slice[1..3];
            try comptime expect(@TypeOf(slice) == *[2]u8);
            try expect(slice[0] == 2);
            try expect(slice[1] == 3);
        }

        fn testSliceZ() !void {
            var array = [5:0]u8{ 1, 2, 3, 4, 5 };
            var slice: [:0]u8 = &array;
            try comptime expect(@TypeOf(slice[1..3]) == *[2]u8);
            try comptime expect(@TypeOf(slice[1..3 :4]) == *[2:4]u8);
            if (@inComptime()) {
                try comptime expect(@TypeOf(slice[1..]) == *[4:0]u8);
            } else {
                try comptime expect(@TypeOf(slice[1..]) == [:0]u8);
            }
        }

        fn testSliceOpt() !void {
            var array: [2]u8 = [2]u8{ 1, 2 };
            var slice: ?[]u8 = &array;
            try comptime expect(@TypeOf(&array, slice) == ?[]u8);
            try comptime expect(@TypeOf(slice, &array) == ?[]u8);
            try comptime expect(@TypeOf(slice.?[0..2]) == *[2]u8);
        }

        fn testSliceAlign() !void {
            var array align(4) = [5]u8{ 1, 2, 3, 4, 5 };
            var src_slice: []align(4) u8 = &array;
            var slice = src_slice[4..5];
            try comptime expect(@TypeOf(slice) == *align(4) [1]u8);
            try expect(slice[0] == 5);
            try comptime expect(@TypeOf(src_slice[0..2]) == *align(4) [2]u8);
        }

        fn testConcatStrLiterals() !void {
            try expectEqualSlices(u8, "ab", "a"[0..] ++ "b"[0..]);
            try expectEqualSlices(u8, "ab", "a"[0.. :0] ++ "b"[0.. :0]);
        }

        fn testSliceLength() !void {
            var array = [5]u8{ 1, 2, 3, 4, 5 };
            var slice: []u8 = &array;
            try comptime expect(@TypeOf(slice[1..][0..2]) == *[2]u8);
            try comptime expect(@TypeOf(slice[1..][0..4]) == *[4]u8);
            try comptime expect(@TypeOf(slice[1..][0..2 :4]) == *[2:4]u8);
        }

        fn testSliceLengthZ() !void {
            var array = [5:0]u8{ 1, 2, 3, 4, 5 };
            var slice: [:0]u8 = &array;
            try comptime expect(@TypeOf(slice[1..][0..2]) == *[2]u8);
            try comptime expect(@TypeOf(slice[1..][0..2 :4]) == *[2:4]u8);
            try comptime expect(@TypeOf(slice[1.. :0][0..2]) == *[2]u8);
            try comptime expect(@TypeOf(slice[1.. :0][0..2 :4]) == *[2:4]u8);
        }

        fn testArrayLength() !void {
            var array = [5]u8{ 1, 2, 3, 4, 5 };
            try comptime expect(@TypeOf(array[1..][0..2]) == *[2]u8);
            try comptime expect(@TypeOf(array[1..][0..4]) == *[4]u8);
            try comptime expect(@TypeOf(array[1..][0..2 :4]) == *[2:4]u8);
        }

        fn testArrayLengthZ() !void {
            var array = [5:0]u8{ 1, 2, 3, 4, 5 };
            try comptime expect(@TypeOf(array[1..][0..2]) == *[2]u8);
            try comptime expect(@TypeOf(array[1..][0..4]) == *[4:0]u8);
            try comptime expect(@TypeOf(array[1..][0..2 :4]) == *[2:4]u8);
            try comptime expect(@TypeOf(array[1.. :0][0..2]) == *[2]u8);
            try comptime expect(@TypeOf(array[1.. :0][0..4]) == *[4:0]u8);
            try comptime expect(@TypeOf(array[1.. :0][0..2 :4]) == *[2:4]u8);
        }

        fn testMultiPointer() !void {
            var array = [5]u8{ 1, 2, 3, 4, 5 };
            var ptr: [*]u8 = &array;
            try comptime expect(@TypeOf(ptr[1..][0..2]) == *[2]u8);
            try comptime expect(@TypeOf(ptr[1..][0..4]) == *[4]u8);
            try comptime expect(@TypeOf(ptr[1..][0..2 :4]) == *[2:4]u8);
        }

        fn testMultiPointerLengthZ() !void {
            var array = [5:0]u8{ 1, 2, 3, 4, 5 };
            var ptr: [*]u8 = &array;
            try comptime expect(@TypeOf(ptr[1..][0..2]) == *[2]u8);
            try comptime expect(@TypeOf(ptr[1..][0..4]) == *[4]u8);
            try comptime expect(@TypeOf(ptr[1..][0..2 :4]) == *[2:4]u8);
            try comptime expect(@TypeOf(ptr[1.. :0][0..2]) == *[2]u8);
            try comptime expect(@TypeOf(ptr[1.. :0][0..4]) == *[4]u8);
            try comptime expect(@TypeOf(ptr[1.. :0][0..2 :4]) == *[2:4]u8);

            var ptr_z: [*:0]u8 = &array;
            try comptime expect(@TypeOf(ptr_z[1..][0..2]) == *[2]u8);
            try comptime expect(@TypeOf(ptr_z[1..][0..4]) == *[4]u8);
            try comptime expect(@TypeOf(ptr_z[1..][0..2 :4]) == *[2:4]u8);
            try comptime expect(@TypeOf(ptr_z[1.. :0][0..2]) == *[2]u8);
            try comptime expect(@TypeOf(ptr_z[1.. :0][0..4]) == *[4]u8);
            try comptime expect(@TypeOf(ptr_z[1.. :0][0..2 :4]) == *[2:4]u8);
        }
    };

    try S.doTheTest();
    try comptime S.doTheTest();
}

test "slice pointer-to-array null terminated" {
    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    comptime {
        var array = [5:0]u8{ 1, 2, 3, 4, 5 };
        var slice: [:0]u8 = &array;
        try expect(@TypeOf(slice[1..3]) == *[2]u8);
        try expect(@TypeOf(slice[1..3 :4]) == *[2:4]u8);
        try expect(@TypeOf(slice[1..]) == *[4:0]u8);
    }

    var array = [5:0]u8{ 1, 2, 3, 4, 5 };
    var slice: [:0]u8 = &array;
    try comptime expect(@TypeOf(slice[1..3]) == *[2]u8);
    try comptime expect(@TypeOf(slice[1..3 :4]) == *[2:4]u8);
    try comptime expect(@TypeOf(slice[1..]) == [:0]u8);
}

test "slice pointer-to-array zero length" {
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    comptime {
        {
            var array = [0]u8{};
            var src_slice: []u8 = &array;
            var slice = src_slice[0..0];
            try expect(@TypeOf(slice) == *[0]u8);
        }
        {
            var array = [0:0]u8{};
            var src_slice: [:0]u8 = &array;
            var slice = src_slice[0..0];
            try expect(@TypeOf(slice) == *[0:0]u8);
        }
    }

    {
        var array = [0]u8{};
        var src_slice: []u8 = &array;
        var slice = src_slice[0..0];
        try comptime expect(@TypeOf(slice) == *[0]u8);
    }
    {
        var array = [0:0]u8{};
        var src_slice: [:0]u8 = &array;
        var slice = src_slice[0..0];
        try comptime expect(@TypeOf(slice) == *[0]u8);
    }
}

test "type coercion of pointer to anon struct literal to pointer to slice" {
    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    const S = struct {
        const U = union {
            a: u32,
            b: bool,
            c: []const u8,
        };

        fn doTheTest() !void {
            var x1: u8 = 42;
            const t1 = &.{ x1, 56, 54 };
            var slice1: []const u8 = t1;
            try expect(slice1.len == 3);
            try expect(slice1[0] == 42);
            try expect(slice1[1] == 56);
            try expect(slice1[2] == 54);

            var x2: []const u8 = "hello";
            const t2 = &.{ x2, ", ", "world!" };
            // @compileLog(@TypeOf(t2));
            var slice2: []const []const u8 = t2;
            try expect(slice2.len == 3);
            try expect(mem.eql(u8, slice2[0], "hello"));
            try expect(mem.eql(u8, slice2[1], ", "));
            try expect(mem.eql(u8, slice2[2], "world!"));
        }
    };
    try S.doTheTest();
    try comptime S.doTheTest();
}

test "array concat of slices gives ptr to array" {
    comptime {
        var a: []const u8 = "aoeu";
        var b: []const u8 = "asdf";
        const c = a ++ b;
        try expect(std.mem.eql(u8, c, "aoeuasdf"));
        try expect(@TypeOf(c) == *const [8]u8);
    }
}

test "array mult of slice gives ptr to array" {
    comptime {
        var a: []const u8 = "aoeu";
        const c = a ** 2;
        try expect(std.mem.eql(u8, c, "aoeuaoeu"));
        try expect(@TypeOf(c) == *const [8]u8);
    }
}

test "slice bounds in comptime concatenation" {
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO

    const bs = comptime blk: {
        const b = "........1........";
        break :blk b[8..9];
    };
    const str = "" ++ bs;
    try expect(str.len == 1);
    try expect(std.mem.eql(u8, str, "1"));

    const str2 = bs ++ "";
    try expect(str2.len == 1);
    try expect(std.mem.eql(u8, str2, "1"));
}

test "slice sentinel access at comptime" {
    {
        const str0 = &[_:0]u8{ '1', '2', '3' };
        const slice0: [:0]const u8 = str0;

        try expect(slice0.len == 3);
        try expect(slice0[slice0.len] == 0);
    }
    {
        const str0 = "123";
        _ = &str0[0];
        const slice0: [:0]const u8 = str0;

        try expect(slice0.len == 3);
        try expect(slice0[slice0.len] == 0);
    }
}

test "slicing array with sentinel as end index" {
    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    const S = struct {
        fn do() !void {
            var array = [_:0]u8{ 1, 2, 3, 4 };
            var slice = array[4..5];
            try expect(slice.len == 1);
            try expect(slice[0] == 0);
            try expect(@TypeOf(slice) == *[1]u8);
        }
    };

    try S.do();
    try comptime S.do();
}

test "slicing slice with sentinel as end index" {
    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    const S = struct {
        fn do() !void {
            var array = [_:0]u8{ 1, 2, 3, 4 };
            var src_slice: [:0]u8 = &array;
            var slice = src_slice[4..5];
            try expect(slice.len == 1);
            try expect(slice[0] == 0);
            try expect(@TypeOf(slice) == *[1]u8);
        }
    };

    try S.do();
    try comptime S.do();
}

test "slice len modification at comptime" {
    comptime {
        var buf: [10]u8 = .{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
        var items: []u8 = buf[0..0];
        items.len += 2;
        try expect(items.len == 2);
        try expect(items[0] == 0);
        try expect(items[1] == 1);
    }
}

test "slice field ptr const" {
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    const const_slice: []const u8 = "string";

    const const_ptr_const_slice = &const_slice;
    try expectEqual(*const []const u8, @TypeOf(&const_ptr_const_slice.*));
    try expectEqual(*const [*]const u8, @TypeOf(&const_ptr_const_slice.ptr));

    var var_ptr_const_slice = &const_slice;
    try expectEqual(*const []const u8, @TypeOf(&var_ptr_const_slice.*));
    try expectEqual(*const [*]const u8, @TypeOf(&var_ptr_const_slice.ptr));
}

test "slice field ptr var" {
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    var var_slice: []const u8 = "string";

    var var_ptr_var_slice = &var_slice;
    try expectEqual(*[]const u8, @TypeOf(&var_ptr_var_slice.*));
    try expectEqual(*[*]const u8, @TypeOf(&var_ptr_var_slice.ptr));

    const const_ptr_var_slice = &var_slice;
    try expectEqual(*[]const u8, @TypeOf(&const_ptr_var_slice.*));
    try expectEqual(*[*]const u8, @TypeOf(&const_ptr_var_slice.ptr));
}

test "global slice field access" {
    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    const S = struct {
        var slice: []const u8 = undefined;
    };
    S.slice = "string";
    S.slice.ptr += 1;
    S.slice.len -= 2;
    try expectEqualStrings("trin", S.slice);
}

test "slice of void" {
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    var n: usize = 10;
    var arr: [12]void = undefined;
    const slice = @as([]void, &arr)[0..n];
    try expect(slice.len == n);
}

test "slice with dereferenced value" {
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    var a: usize = 0;
    var idx: *usize = &a;
    _ = blk: {
        var array = [_]u8{};
        break :blk array[idx.*..];
    };
    const res = blk: {
        var array = [_]u8{};
        break :blk array[idx.*..];
    };
    try expect(res.len == 0);
}

test "empty slice ptr is non null" {
    if (builtin.zig_backend == .stage2_aarch64 and builtin.os.tag == .macos) return error.SkipZigTest; // TODO
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    {
        const empty_slice: []u8 = &[_]u8{};
        const p: [*]u8 = empty_slice.ptr + 0;
        const t = @as([*]i8, @ptrCast(p));
        try expect(@intFromPtr(t) == @intFromPtr(empty_slice.ptr));
    }
    {
        const empty_slice: []u8 = &.{};
        const p: [*]u8 = empty_slice.ptr + 0;
        const t = @as([*]i8, @ptrCast(p));
        try expect(@intFromPtr(t) == @intFromPtr(empty_slice.ptr));
    }
}

test "slice decays to many pointer" {
    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    var buf: [8]u8 = "abcdefg\x00".*;
    const p: [*:0]const u8 = buf[0..7 :0];
    try expectEqualStrings(buf[0..7], std.mem.span(p));
}

test "write through pointer to optional slice arg" {
    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest;
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    const S = struct {
        fn bar(foo: *?[]const u8) !void {
            foo.* = try baz();
        }

        fn baz() ![]const u8 {
            return "ok";
        }
    };
    var foo: ?[]const u8 = null;
    try S.bar(&foo);
    try expectEqualStrings(foo.?, "ok");
}

test "modify slice length at comptime" {
    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest;
    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;

    const arr: [2]u8 = .{ 10, 20 };
    comptime var s: []const u8 = arr[0..0];
    s.len += 1;
    const a = s;
    s.len += 1;
    const b = s;

    try expectEqualSlices(u8, &.{10}, a);
    try expectEqualSlices(u8, &.{ 10, 20 }, b);
}