Add flag to forbid recovery in the parser

compiler/rustc_parse/src/parser/expr.rs

@@ -2112,6 +2112,8 @@ impl<'a> Parser<'a> {
             // HACK: This is needed so we can detect whether we're inside a macro,
             // where regular assumptions about what tokens can follow other tokens
             // don't necessarily apply.
+            && self.may_recover()
+            // FIXME(Nilstrieb): Remove this check once `may_recover` actually stops recovery
             && self.subparser_name.is_none()
         {
             // It is likely that the closure body is a block but where the