Catch null in if-condition cails at comptime.

[pmwhite]

const std = @import("std");

fn f(string: []const u8) ?f32 {
    if (std.fmt.parseFloat(f32, string) catch null) |decimal| {
        return decimal;
    }
    return null;
}

pub fn main() !void {
    if (comptime f("1")) |x| {
        std.debug.warn("x = {}\n", .{x});
    }
}

This code fails with the following compiler error:

Semantic Analysis [568/862] ./test.zig:4:41: error: expected optional type, found 'f32'
    if (std.fmt.parseFloat(f32, string) catch null) |decimal| {
                                        ^
./test.zig:11:19: note: called from here
    if (comptime f("1")) |x| {
                  ^
./test.zig:10:21: note: called from here
pub fn main() !void {
                    ^
./test.zig:4:5: note: referenced here
    if (std.fmt.parseFloat(f32, string) catch null) |decimal| {
    ^
./test.zig:11:19: note: referenced here
    if (comptime f("1")) |x| {
                  ^
/home/philip/Downloads/zig-linux-x86_64-latest/lib/zig/std/start.zig:252:40: note: referenced here
            const result = root.main() catch |err| {

Note that removing the comptime part from the call to f in main makes this code compile.

[Vexu]

This is another example of #5401. The result of parseFloat is known at compile time to not be an error so the catch branch is never evaluated. This skips the peer type resolution which would make it an optional type. You can avoid this by explicitly casting the condition @as(?[]const u8, ...).