[llvm-branch-commits] [clang] release/20.x: [Clang] Fix the trailing comma regression (#136273) (PR #136283)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/136283

Backport c7daab2

Requested by: @zyn0217

>From ca394968438dfd5a6227703fd4919682221240f8 Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Fri, 18 Apr 2025 16:27:27 +0800
Subject: [PATCH] [Clang] Fix the trailing comma regression (#136273)

925e195 introduced a regression since which we started to accept invalid
trailing commas in many expression lists where they're not allowed by
the grammar. The issue came from the fact that an additional invalid
state - previously handled by ParseExpressionList - was overlooked in
that patch.

Fixes https://github.com/llvm/llvm-project/issues/136254

No release entry because I want to backport it.

(cherry picked from commit c7daab259c3281cf8f649583993bad2536febc02)
---
 clang/lib/Parse/ParseExpr.cpp  |  3 ---
 clang/test/Parser/recovery.cpp | 18 ++++++++++++++++++
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/clang/lib/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
index 0cadede51a9b3..2fab1dfed4a00 100644
--- a/clang/lib/Parse/ParseExpr.cpp
+++ b/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) {
diff --git a/clang/test/Parser/recovery.cpp b/clang/test/Parser/recovery.cpp
index 2fce67a52c6b6..261f5dc99bad4 100644
--- a/clang/test/Parser/recovery.cpp
+++ b/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}}
+}
+
+}