wrong error when using a unit struct as length of a repeat expression

[oli-obk]

struct A { i: i32};
let a = [0; A{i: 42}];

yields the expected

error: expected positive integer for repeat count, found struct [E0306]

while

struct B;
let b = [0; B];

thinks that B is a variable

error: expected constant integer for repeat count, found variable [E0307]

PlayPen

[rick68]

I hope this can help you http://is.gd/NzhhNN

[Aatch]

This is due to the fact that while B is a path expression, it doesn't refer to a constant, so the relevant code fails, and the check that produces the error assumes that B is a variable.

[Detegr]

What would be the proper way to fix this (rustc newbie here)? Is it possible to check if a non-constant path expression refers to an integer or to a struct, or should the error message just be changed to contain the two possibilities?

[oli-obk]

It's probably necessary to change https://github.com/rust-lang/rust/blob/master/src/librustc/middle/const_eval.rs#L875-935 to account for unit-struct-names