Const-generic arguments are not printed in error messages

[jplatte]

This code (playground):

#![feature(const_generics)]

struct Generic<const C: usize>;

fn main() {
 let _: Generic<0> = Generic::<1>;
}

results in

error[E0308]: mismatched types
 --> src/main.rs:6:25
 |
6 | let _: Generic<0> = Generic::<1>;
 | ^^^^^^^^^^^^ expected `0usize`, found `1usize`
 |
 = note: expected type `Generic<>`
 found type `Generic<>`

with missing const arguments in the note: ... at the bottom.

[imbrem]

Hey guys could I take this on?

[imbrem]

Just FYI, same problem with messages involving const generics and matches, e.g.

#![feature(const_generics)]

struct Generic<const C: usize>;


fn main() {
 let x = Generic::<0>;
 let y = Generic::<1>;
 let _ = match 1 {
 0 => x,
 _ => y
 };
}

(Playground)
Also for functions:

#![feature(const_generics)]

struct Generic<const C: usize>;

fn foo(x : Generic::<1>) {}

fn main() {
 let x = Generic::<0>;
 foo(x);
}

(Playground)

[imbrem]

Interestingly, when I use concrete types for the function example, things display properly:

#![feature(const_generics)]

struct Generic<const C: usize>;

fn foo(x : usize) {}

fn main() {
 let x = Generic::<0>;
 foo(x);
}

gives

error[E0308]: mismatched types
 --> src/main.rs:9:9
 |
9 | foo(x);
 | ^ expected usize, found struct `Generic`
 |
 = note: expected type `usize`
 found type `Generic<0usize>`

(Playground)

[varkor]

@imbrem: you're welcome to look into fixing this! However, I'm not sure what might be causing this problem, so I don't have any suggestions for where to start looking yet.

[imbrem]

@varkor I spent a few hours doing some digging and I can't find anything yet as well, though I'm as of yet still quite unfamiliar with the code-base. I might have more time tomorrow to look things over again, or maybe the day after.