Auto merge of #121346 - m-ou-se:temp-lifetime-if-else-match, r=compiler-errors

Propagate temporary lifetime extension into if and match.

This PR makes this work:

```rust
let a = if true {
    ..;
    &temp() // used to error, but now gets lifetime extended
} else {
    ..;
    &temp() // used to error, but now gets lifetime extended
};
```

and

```rust
let a = match () {
    _ => {
        ..;
        &temp() // used to error, but now gets lifetime extended
    }
};
```

to make it consistent with:

```rust
let a = {
    ..;
    &temp() // lifetime is extended
};
```

This is one small part of [the temporary lifetimes work](https://github.com/rust-lang/lang-team/issues/253).

This part is backwards compatible (so doesn't need be edition-gated), because all code affected by this change previously resulted in a hard error.

compiler/rustc_hir_analysis/src/check/region.rs

@@ -689,6 +689,8 @@ fn resolve_local<'tcx>(
     ///        | [ ..., E&, ... ]
     ///        | ( ..., E&, ... )
     ///        | {...; E&}
+    ///        | if _ { ...; E& } else { ...; E& }
+    ///        | match _ { ..., _ => E&, ... }
     ///        | box E&
     ///        | E& as ...
     ///        | ( E& )
@@ -727,6 +729,17 @@ fn resolve_local<'tcx>(
                     record_rvalue_scope_if_borrow_expr(visitor, subexpr, blk_id);
                 }
             }
+            hir::ExprKind::If(_, then_block, else_block) => {
+                record_rvalue_scope_if_borrow_expr(visitor, then_block, blk_id);
+                if let Some(else_block) = else_block {
+                    record_rvalue_scope_if_borrow_expr(visitor, else_block, blk_id);
+                }
+            }
+            hir::ExprKind::Match(_, arms, _) => {
+                for arm in arms {
+                    record_rvalue_scope_if_borrow_expr(visitor, arm.body, blk_id);
+                }
+            }
             hir::ExprKind::Call(..) | hir::ExprKind::MethodCall(..) => {
                 // FIXME(@dingxiangfei2009): choose call arguments here
                 // for candidacy for extended parameter rule application