zig/test/cases/null.zig

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Zig

const assert = @import("std").debug.assert;
test "nullable type" {
const x : ?bool = true;
if (x) |y| {
if (y) {
// OK
} else {
unreachable;
}
} else {
unreachable;
}
const next_x : ?i32 = null;
const z = next_x ?? 1234;
assert(z == 1234);
const final_x : ?i32 = 13;
const num = final_x ?? unreachable;
assert(num == 13);
}
test "test maybe object and get a pointer to the inner value" {
var maybe_bool: ?bool = true;
if (maybe_bool) |*b| {
*b = false;
}
assert(??maybe_bool == false);
}
test "rhs maybe unwrap return" {
const x: ?bool = true;
const y = x ?? return;
}
test "maybe return" {
maybeReturnImpl();
comptime maybeReturnImpl();
}
fn maybeReturnImpl() void {
assert(??foo(1235));
if (foo(null) != null)
unreachable;
assert(!??foo(1234));
}
fn foo(x: ?i32) ?bool {
const value = x ?? return null;
return value > 1234;
}
test "if var maybe pointer" {
assert(shouldBeAPlus1(Particle {.a = 14, .b = 1, .c = 1, .d = 1}) == 15);
}
fn shouldBeAPlus1(p: &const Particle) u64 {
var maybe_particle: ?Particle = *p;
if (maybe_particle) |*particle| {
particle.a += 1;
}
if (maybe_particle) |particle| {
return particle.a;
}
return 0;
}
const Particle = struct {
a: u64,
b: u64,
c: u64,
d: u64,
};
test "null literal outside function" {
const is_null = here_is_a_null_literal.context == null;
assert(is_null);
const is_non_null = here_is_a_null_literal.context != null;
assert(!is_non_null);
}
const SillyStruct = struct {
context: ?i32,
};
const here_is_a_null_literal = SillyStruct {
.context = null,
};
test "test null runtime" {
testTestNullRuntime(null);
}
fn testTestNullRuntime(x: ?i32) void {
assert(x == null);
assert(!(x != null));
}
test "nullable void" {
nullableVoidImpl();
comptime nullableVoidImpl();
}
fn nullableVoidImpl() void {
assert(bar(null) == null);
assert(bar({}) != null);
}
fn bar(x: ?void) ?void {
if (x) |_| {
return {};
} else {
return null;
}
}
const StructWithNullable = struct {
field: ?i32,
};
var struct_with_nullable: StructWithNullable = undefined;
test "unwrap nullable which is field of global var" {
struct_with_nullable.field = null;
if (struct_with_nullable.field) |payload| {
unreachable;
}
struct_with_nullable.field = 1234;
if (struct_with_nullable.field) |payload| {
assert(payload == 1234);
} else {
unreachable;
}
}
test "null with default unwrap" {
const x: i32 = null ?? 1;
assert(x == 1);
}