[clang] [Clang] Do not try to transform invalid bindings (PR #125658)

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https://github.com/cor3ntin updated https://github.com/llvm/llvm-project/pull/125658

>From 70d7bd8fe791210a6e83389c7e33e17d1fed0c77 Mon Sep 17 00:00:00 2001
From: Corentin Jabot <corentinjabot at gmail.com>
Date: Tue, 4 Feb 2025 10:14:12 +0100
Subject: [PATCH] [Clang] Do not try to transform invalid bindings

In the presence of an invalid structured binding decomposition,
some binding packs may be invalid and trying to transform them
would produce a recovery expression that does not contains a pack,
leading to assertions in places where we would expect a pack
at that stage.

Fixes #125165
---
 clang/lib/Sema/TreeTransform.h            |  2 +-
 clang/test/SemaCXX/cxx2c-binding-pack.cpp | 15 +++++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 05cac8db3c42c..eaabfae2409f4 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -12716,7 +12716,7 @@ TreeTransform<Derived>::TransformDeclRefExpr(DeclRefExpr *E) {
   ValueDecl *ND
     = cast_or_null<ValueDecl>(getDerived().TransformDecl(E->getLocation(),
                                                          E->getDecl()));
-  if (!ND)
+  if (!ND || ND->isInvalidDecl())
     return ExprError();
 
   NamedDecl *Found = ND;
diff --git a/clang/test/SemaCXX/cxx2c-binding-pack.cpp b/clang/test/SemaCXX/cxx2c-binding-pack.cpp
index 62e1da565f2b5..0f10dad3937ba 100644
--- a/clang/test/SemaCXX/cxx2c-binding-pack.cpp
+++ b/clang/test/SemaCXX/cxx2c-binding-pack.cpp
@@ -218,3 +218,18 @@ auto X = [] <typename = void> () {
     static_assert(sizeof...(pack3) == 5);
 };
 }  // namespace
+
+namespace GH125165 {
+
+template <typename = void>
+auto f(auto t) {
+    const auto& [...pack] = t;
+    // expected-error at -1 {{cannot decompose non-class, non-array type 'char const'}}
+    (pack, ...);
+};
+
+void g() {
+    f('x'); // expected-note {{in instantiation}}
+}
+
+}