Expected/Found does not point to point where type parameter was inferred
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A-diagnostics
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T-compiler
- Dominant language
- Rust
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Description
Code
fn foo<'a, T>(b: &'a T) -> &'a T { b }
fn main() {
let f = foo;
f(&String::new());
f(&Vec::new());
}
Current output
error[E0308]: mismatched types
--> src/main.rs:7:7
|
7 | f(&Vec::new());
| - ^^^^^^^^^^^ expected `&String`, found `&Vec<_>`
| |
| arguments to this function are incorrect
|
= note: expected reference `&String`
found reference `&Vec<_>`
note: function defined here
--> src/main.rs:1:4
|
1 | fn foo<'a, T>(b: &'a T) -> &'a T { b }
| ^^^ --------
Desired output
error[E0308]: mismatched types
--> src/main.rs:7:7
|
7 | f(&Vec::new());
| - ^^^^^^^^^^^ expected `&String`, found `&Vec<_>`
| |
| arguments to this function are incorrect
|
= note: expected reference `&String`
found reference `&Vec<_>`
note: function defined here
--> src/main.rs:1:4
|
1 | fn foo<'a, T>(b: &'a T) -> &'a T { b }
| ^^^ --------
note: generic argument was inferred to `String` here
--> src/main.rs:6:7
|
6 | f(&String::new());
| ^^^^^^^^^^^^^
Rationale and extra context
No response
Other cases
Rust Version
playground version:
Build using the Nightly version: 1.85.0-nightly
(2024-12-08 4d669fb34e7db6f3825d)
Anything else?
No response
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Reproduce the diagnostic using the example in src/main.rs and the listed nightly Rust version. Compare the current and desired output, focusing on the missing inference note and its source location. Done means the diagnostic points to the call where String was inferred as the generic argument.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100