Provide context when type error happens due to different fn arguments with the same type parameter are called with different types

[estebank]

Code

fn main() {
    foo(1, 2.);
}
fn foo<T>(a: T, b: T) {}

Current output

error[E0308]: mismatched types
 --> src/main.rs:2:12
  |
2 |     foo(1, 2.);
  |     ---    ^^ expected integer, found floating-point number
  |     |
  |     arguments to this function are incorrect
  |
note: function defined here
 --> src/main.rs:4:4
  |
4 | fn foo<T>(a: T, b: T) {}
  |    ^^^          ----

Desired output

error[E0308]: mismatched types
 --> src/main.rs:2:12
  |
2 |     foo(1, 2.);
  |     --- -  ^^ expected integer, found floating-point number
  |     |   |
  |     |   expected because that argument needs to match the integer type of this parameter
  |     |
  |     arguments to this function are incorrect
  |
note: function defined here
 --> src/main.rs:4:4
  |
4 | fn foo<T>(a: T, b: T) {}
  |    ^^^ -  ----  ----
  |        |  |     |
  |        |  |     this parameter needs to match the type of `a`
  |        |  `b` needs to match the type of this parameter
  |        `a` and `b` both reference type parameter `T`

Rationale and extra context

No response

Other cases

No response

Anything else?

No response

[strottos]

@rustbot claim

I think I can see how to implement this, will give it a go and unassign if it doesn't work.

[strottos]

Spent the last week on this now and put a draft PR here for feedback at this stage, though not essential if I don't get it at this stage: #121595

It's mostly working now, though there are likely to be improvements yet and I'd like to do a review of it myself before pushing even which I'll probably do later next week.

[strottos]

This has been merged now, I believe the issue can be closed.