FP equatable_if_let: no longer able to infer type

Summary

.

Lint Name

equatable_if_let

Reproducer

I tried this code:

#![warn(clippy::redundant_else)]
#![allow(clippy::needless_return, clippy::if_same_then_else, clippy::needless_late_init)]

fn main() {
   
    // inside if let
    let _ = if let Some(1) = foo() {
        let _ = 1;
        if foo() {
            return;
        } else {
            1
        }
    } else {
        1
    };

}

fn foo<T>() -> T {
    unimplemented!("I'm not Santa Claus")
}

I saw this happen:
cargo clippy --fix -- -Wclippy::equatable_if_let

warning: failed to automatically apply fixes suggested by rustc to crate `a`

after fixes were automatically applied the compiler reported errors within these files:

  * src/main.rs

This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag

The following errors were reported:
warning: redundant else block
  --> src/main.rs:11:16
   |
11 |           } else {
   |  ________________^
12 | |             1
13 | |         }
   | |_________^
   |
   = help: remove the `else` block and move the contents out
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#redundant_else
note: the lint level is defined here
  --> src/main.rs:1:9
   |
1  | #![warn(clippy::redundant_else)]
   |         ^^^^^^^^^^^^^^^^^^^^^^

error[E0282]: type annotations needed
 --> src/main.rs:7:16
  |
7 |     let _ = if foo() == Some(1) {
  |                ^^^ cannot infer type of the type parameter `T` declared on the function `foo`
  |
help: consider specifying the generic argument
  |
7 |     let _ = if foo::<T>() == Some(1) {
  |                   +++++

error: aborting due to previous error; 1 warning emitted

For more information about this error, try `rustc --explain E0282`.
Original diagnostics will follow.

warning: redundant else block
  --> src/main.rs:11:16
   |
11 |           } else {
   |  ________________^
12 | |             1
13 | |         }
   | |_________^
   |
   = help: remove the `else` block and move the contents out
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#redundant_else
note: the lint level is defined here
  --> src/main.rs:1:9
   |
1  | #![warn(clippy::redundant_else)]
   |         ^^^^^^^^^^^^^^^^^^^^^^

warning: this pattern matching can be expressed using equality
 --> src/main.rs:7:16
  |
7 |     let _ = if let Some(1) = foo() {
  |                ^^^^^^^^^^^^^^^^^^^ help: try: `foo() == Some(1)`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#equatable_if_let
  = note: requested on the command line with `-W clippy::equatable-if-let`

warning: `a` (bin "a") generated 2 warnings (run `cargo fix --bin "a"` to apply 1 suggestion)

Version

rustc 1.67.0-nightly (b833ad56f 2022-11-18)
binary: rustc
commit-hash: b833ad56f46a0bbe0e8729512812a161e7dae28a
commit-date: 2022-11-18
host: x86_64-unknown-linux-gnu
release: 1.67.0-nightly
LLVM version: 15.0.4

Additional Labels

No response

Start with the equatable_if_let lint and the supplied generic foo() reproducer, then run cargo clippy --fix with the shown lint settings. Trace the suggested transformation and add or update a regression test so the fix preserves type inference and the reproducer compiles without the reported E0282 error.