release/20.x: [Clang] Fix the trailing comma regression (#136273)

clang/lib/Parse/ParseExpr.cpp

@@ -2237,8 +2237,6 @@ Parser::ParsePostfixExpressionSuffix(ExprResult LHS) {
             if (PP.isCodeCompletionReached() && !CalledSignatureHelp)
               RunSignatureHelp();
             LHS = ExprError();
-          } else if (!HasError && HasTrailingComma) {
-            Diag(Tok, diag::err_expected_expression);
           } else if (LHS.isInvalid()) {
             for (auto &E : ArgExprs)
               Actions.CorrectDelayedTyposInExpr(E);
@@ -3738,7 +3736,6 @@ bool Parser::ParseExpressionList(SmallVectorImpl<Expr *> &Exprs,
     if (Tok.is(tok::r_paren)) {
       if (HasTrailingComma)
         *HasTrailingComma = true;
-      break;
     }
   }
   if (SawError) {

clang/test/Parser/recovery.cpp

@@ -222,3 +222,21 @@ void k() {
   func(1, ); // expected-error {{expected expression}}
 }
 }
+
+namespace GH136254 {
+
+void call() {
+  [a(42, )]() {} (); // expected-error {{expected expression}}
+
+  int *b = new int(42, ); // expected-error {{expected expression}}
+
+  struct S {
+    int c;
+
+    S() : c(42, ) {} // expected-error {{expected expression}}
+  };
+
+  int d(42, ); // expected-error {{expected expression}}
+}
+
+}