Point at coercion reason for `if` expressions without else clause if caused by return type
```
error[E0317]: if may be missing an else clause
--> $DIR/if-without-else-as-fn-expr.rs:2:5
|
LL | fn foo(bar: usize) -> usize {
| ----- found `usize` because of this return type
LL | / if bar % 5 == 0 {
LL | | return 3;
LL | | }
| |_____^ expected (), found usize
|
= note: expected type `()`
found type `usize`
= note: `if` expressions without `else` must evaluate to `()`
```
Fix#25228.
86466a397a