from_over_into auto fix breaks type inference

[zaneduffield]

Summary

Accepting the fix to convert impl Into to impl From causes a type inference error in the following example

struct WrapErr(String);

impl Into<WrapErr> for &str {
    fn into(self) -> WrapErr {
        todo!()
    }
}

// impl From<&str> for WrapErr {
//     fn from(val: &str) -> Self {
//         todo!()
//     }
// }

fn foo() -> Result<(), WrapErr> {
    None.ok_or("".into())?;
    Ok(())
}

I'm not 100% sure whether this is a clippy bug or a rustc bug.

Lint Name

from_over_into

Reproducer

I tried this code (as generated by the fix):

struct WrapErr(String);

impl From<&str> for WrapErr {
    fn from(val: &str) -> Self {
        todo!()
    }
}

fn foo() -> Result<(), WrapErr> {
    None.ok_or("".into())?;
    Ok(())
}

I saw this happen:

playground

error[E0283]: type annotations needed
  --> src/lib.rs:10:10
   |
10 |     None.ok_or("".into())?;
   |          ^^^^^    ---- type must be known at this point
   |          |
   |          cannot infer type of the type parameter `E` declared on the method `ok_or`
   |
   = note: cannot satisfy `_: From<&str>`
   = note: required for `&str` to implement `Into<_>`
help: consider specifying the generic argument
   |
10 |     None.ok_or::<E>("".into())?;
   |               +++++

error[E0283]: type annotations needed
  --> src/lib.rs:10:10
   |
10 |     None.ok_or("".into())?;
   |          ^^^^^           - type must be known at this point
   |          |
   |          cannot infer type of the type parameter `E` declared on the method `ok_or`
   |
note: multiple `impl`s satisfying `WrapErr: From<_>` found
  --> src/lib.rs:3:1
   |
3  | impl From<&str> for WrapErr {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
   = note: and another `impl` found in the `core` crate: `impl<T> From<T> for T;`
   = note: required for `Result<(), WrapErr>` to implement `FromResidual<Result<Infallible, _>>`
help: consider specifying the generic argument
   |
10 |     None.ok_or::<E>("".into())?;
   |               +++++

I expected to see this happen:
compile without errors

Version

rustc 1.83.0 (90b35a623 2024-11-26)
binary: rustc
commit-hash: 90b35a6239c3d8bdabc530a6a0816f7ff89a0aaf
commit-date: 2024-11-26
host: x86_64-pc-windows-msvc
release: 1.83.0
LLVM version: 19.1.1

Additional Labels

No response