'comptime_int' error when switching on caught Error

[tau-dev]

Trying to compile

fn test() error{A}!usize {
    return 1;
}

test "switch" {
    var x = test() catch |err| switch (err) {
        error.A => 2,
        else => 3,
    };
}

results in

error: values of type 'comptime_int' must be comptime known
    var x = test3() catch |err| switch (err) {
                                ^

I'm fairly new to Zig, so maybe I need to solve this differently and the error is intended behavior, but it feels like it shouldn't be.

[LemonBoy]

This section on ZigLearn explains that literal values are of type comptime_int, you need to tell the compiler what type you want by:

• Using var x: <type> = ...
• Having at least one branch a cast such as @as(<type>, <number>)

Oh well, I didn't see the test3() has type usize. This looks like a compiler bug, the switch doesn't understand the LHS of the catch already has a well-defined type.

[nektro]

This also seems like a bug because it should be showing the error that the else => is invalid due to the switch already being exhaustive first.

[renatoathaydes]

I think I have the same kind of error... I am trying to compile this:

fn center(text: u8, out: *[5]u8) !void {
    const left_pad: usize = if (text < 10) 3 else if (text < 100) 2 else 1;
...

Looks straightforward but doesn't compile because the if expression tries to take the type comptime_int despite the explicit type on the resulting variable.

I also tried this:

fn center(text: u8, out: *[5]u8) !void {
    const left_pad = @as(usize, if (text < 10) 3 else if (text < 100) 2 else 1);
...

Which still fails with the same error.

./color8.zig:8:55: error: values of type 'comptime_int' must be comptime known
    const left_pad = @as(usize, if (text < 10) 3 else if (text < 100) 2 else 1);
                                                      ^
simple...The following command exited with error code 1:
zig-macos-x86_64-0.10.0-dev.2577+5816d3eae/zig build-exe projects/ansi-escapes.zig/examples/simple/color8.zig --cache-dir projects/ansi-escapes.zig/examples/simple/zig-cache --global-cache-dir /Users/renato/.cache/zig --name simple --pkg-begin ansi-escapes projects/ansi-escapes.zig/src/ansi-escapes.zig --pkg-end --enable-cache 
error: the following build command failed with exit code 1:

I have to unfortunately case every single value instead:

const left_pad = if (text < 10) @as(usize, 3) else if (text < 100) @as(usize, 2) else @as(usize, 1);

Which is really awkward.

Hope this kind of issue with comptime can be improved.

[Vexu]

Stage2 issue in #11812