Auto merge of #118527 - Nadrieril:never_patterns_parse, r=compiler-errors

never_patterns: Parse match arms with no body

Never patterns are meant to signal unreachable cases, and thus don't take bodies:
```rust
let ptr: *const Option<!> = ...;
match *ptr {
    None => { foo(); }
    Some(!),
}
```
This PR makes rustc accept the above, and enforces that an arm has a body xor is a never pattern. This affects parsing of match arms even with the feature off, so this is delicate. (Plus this is my first non-trivial change to the parser).

~~The last commit is optional; it introduces a bit of churn to allow the new suggestions to be machine-applicable. There may be a better solution? I'm not sure.~~ EDIT: I removed that commit

r? `@compiler-errors`

compiler/rustc_resolve/src/late.rs

@@ -3297,7 +3297,7 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
         self.with_rib(ValueNS, RibKind::Normal, |this| {
             this.resolve_pattern_top(&arm.pat, PatternSource::Match);
             walk_list!(this, visit_expr, &arm.guard);
-            this.visit_expr(&arm.body);
+            walk_list!(this, visit_expr, &arm.body);
         });
     }