unhelpful error when operand to error set merge is runtime

[xdBronch]

Zig Version

0.15.0-dev.762+3208c80f2

Steps to Reproduce and Observed Output

|| is often mistakenly used instead of or by newcomers to zig

pub fn main() void {
    var foo = true;
    _ = &foo;
    _ = foo || foo;
}

a.zig:4:9: error: unable to resolve comptime value
    _ = foo || foo;
        ^~~
a.zig:4:9: note: types must be comptime-known

this gives no real explanation as to why anything needs to be comptime since type seemingly isn't used

Expected Output

the error should give a more helpful message similar to here in the runtime case