Auto merge of #29398 - jonas-schievink:if-let-arms, r=arielb1

Closes #29314

The code from #29314:
```rust
fn main() {
    if let Some(b) = None {
        ()
    } else {
        1
    };
}
```
now prints this:
```
test.rs:2:5: 6:6 error: `if let` arms have incompatible types: expected `()`, found `_` (expected (), found integral variable) [E0308]
test.rs:2     if let Some(b) = None {
test.rs:3         ()
test.rs:4     } else {
test.rs:5         1
test.rs:6     };
test.rs:2:5: 6:6 help: run `rustc --explain E0308` to see a detailed explanation
test.rs:4:12: 6:6 note: `if let` arm with an incompatible type
test.rs:4     } else {
test.rs:5         1
test.rs:6     };
error: aborting due to previous error
```

0 files changed, 0 insertions, 0 deletions