Incorrect return type for @abs

[ArnaudPare-Vogt]

Zig Version

0.13.0

Steps to Reproduce and Observed Behavior

This test:

const std = @import("std");
test "abs" {
    const a: i32 = std.crypto.random.int(i32); // random to prevent comptime evaluation
    const b: i32 = @abs(a);
    try std.testing.expect(a == b or a == -b);
}

Fails to compile with:

test.zig:4:20: error: expected type 'i32', found 'u32'
    const b: i32 = @abs(a);
                   ^~~~~~~
test.zig:4:20: note: signed 32-bit int cannot represent all possible unsigned 32-bit values

Expected Behavior

I expect the test to compile.

As far as I can tell, this is because abs returns a u32 when it should return a u31, but I am not super certain about the type system.

[mlugg]

when it should return a u31

Unfortunately, it has to be a u32, because signed integer have a negative range one larger than their positive range. For instance, an i8 can represent the value -128, but a u7 can only represent values up to 127.

This code will work if we accept #3806.

[ArnaudPare-Vogt]

For instance, an i8 can represent the value -128, but a u7 can only represent values up to 127.

Damn, I did not think about that, but now the error makes sense.

Thanks for the super fast answer :)