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.
```
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 `()`
```
- Point at the body expression of the match arm with the type error.
- Point at the prior match arms explicitely stating the evaluated type.
- Point at the entire match expr in a secondary span, instead of primary.
- For type errors in the first match arm, the cause is outside of the
match, treat as implicit block error to give a more appropriate error.
- Point at opening mismatched formatting brace
- Account for differences between raw and regular strings
- Account for differences between the code snippet and `InternedString`
- Add more tests
I also added `// skip-codegen` to each one, to address potential concerns
that this change would otherwise slow down our test suite spending time
generating code for files that are really just meant to be checks of
compiler diagnostics.
(However, I will say: My preference is to not use `// skip-codegen` if
one can avoid it. We can use all the testing of how we drive LLVM that
we can get...)
(Updated post rebase.)
