Rollup merge of rust-lang#30375 - aaronkeen:issue_28777, r=eddyb

RESTRICTION_STMT_EXPR restriction to allow subsequent expressions to
contain braces.

rust-lang#28777

Author: Manishearth

src/libsyntax/parse/parser.rs

@@ -2813,16 +2813,25 @@ impl<'a> Parser<'a> {
 
 
             let rhs = try!(match op.fixity() {
-                Fixity::Right => self.with_res(restrictions, |this|{
-                    this.parse_assoc_expr_with(op.precedence(), LhsExpr::NotYetParsed)
+                Fixity::Right => self.with_res(
+                    restrictions - Restrictions::RESTRICTION_STMT_EXPR,
+                    |this| {
+                        this.parse_assoc_expr_with(op.precedence(),
+                            LhsExpr::NotYetParsed)
                 }),
-                Fixity::Left => self.with_res(restrictions, |this|{
-                    this.parse_assoc_expr_with(op.precedence() + 1, LhsExpr::NotYetParsed)
+                Fixity::Left => self.with_res(
+                    restrictions - Restrictions::RESTRICTION_STMT_EXPR,
+                    |this| {
+                        this.parse_assoc_expr_with(op.precedence() + 1,
+                            LhsExpr::NotYetParsed)
                 }),
                 // We currently have no non-associative operators that are not handled above by
                 // the special cases. The code is here only for future convenience.
-                Fixity::None => self.with_res(restrictions, |this|{
-                    this.parse_assoc_expr_with(op.precedence() + 1, LhsExpr::NotYetParsed)
+                Fixity::None => self.with_res(
+                    restrictions - Restrictions::RESTRICTION_STMT_EXPR,
+                    |this| {
+                        this.parse_assoc_expr_with(op.precedence() + 1,
+                            LhsExpr::NotYetParsed)
                 }),
             });