[clang] [clang] fix crash when casting a parenthesized unresolved template-id (PR #183633)

[via cfe-commits]

https://github.com/Serosh-commits updated https://github.com/llvm/llvm-project/pull/183633

>From 4f2a394c925a34d9037825683c0a9fe07702499e Mon Sep 17 00:00:00 2001
From: Serosh-commits <janmejayapanda400 at gmail.com>
Date: Fri, 27 Feb 2026 03:34:44 +0530
Subject: [PATCH 1/2] add release note and remove extra checks

---
 clang/docs/ReleaseNotes.rst     |  1 +
 clang/lib/Sema/SemaExpr.cpp     | 12 ++++++------
 clang/test/SemaCXX/gh183505.cpp | 12 ++++++++++++
 3 files changed, 19 insertions(+), 6 deletions(-)
 create mode 100644 clang/test/SemaCXX/gh183505.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 613d87668be18..def7f6c3d32c2 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -262,6 +262,7 @@ Miscellaneous Clang Crashes Fixed
 - Fixed a crash when using loop hint with a value dependent argument inside a
   generic lambda. (#GH172289)
 - Fixed a crash in C++ overload resolution with ``_Atomic``-qualified argument types. (#GH170433)
+- Fixed a crash when casting a parenthesized unresolved template-id or array section. (#GH183505)
 
 OpenACC Specific Changes
 ------------------------
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 27f1cce88897b..4f614ca317b38 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -21522,7 +21522,7 @@ ExprResult Sema::CheckPlaceholderExpr(Expr *E) {
 
   switch (placeholderType->getKind()) {
   case BuiltinType::UnresolvedTemplate: {
-    auto *ULE = cast<UnresolvedLookupExpr>(E);
+    auto *ULE = cast<UnresolvedLookupExpr>(E->IgnoreParens());
     const DeclarationNameInfo &NameInfo = ULE->getNameInfo();
     // There's only one FoundDecl for UnresolvedTemplate type. See
     // BuildTemplateIdExpr.
@@ -21565,7 +21565,7 @@ ExprResult Sema::CheckPlaceholderExpr(Expr *E) {
           /*CanonicalArgs=*/{},
           HasAnyDependentTA ? Context.DependentTy : Context.IntTy);
     return CreateRecoveryExpr(NameInfo.getBeginLoc(), NameInfo.getEndLoc(), {},
-                              TST);
+                               TST);
   }
 
   // Overloaded expressions.
@@ -21629,11 +21629,11 @@ ExprResult Sema::CheckPlaceholderExpr(Expr *E) {
       unsigned BuiltinID = FD->getBuiltinID();
       if (BuiltinID == Builtin::BI__noop) {
         E = ImpCastExprToType(E, Context.getPointerType(FD->getType()),
-                              CK_BuiltinFnToFnPtr)
+                               CK_BuiltinFnToFnPtr)
                 .get();
         return CallExpr::Create(Context, E, /*Args=*/{}, Context.IntTy,
-                                VK_PRValue, SourceLocation(),
-                                FPOptionsOverride());
+                                 VK_PRValue, SourceLocation(),
+                                 FPOptionsOverride());
       }
 
       if (Context.BuiltinInfo.isInStdNamespace(BuiltinID)) {
@@ -21689,7 +21689,7 @@ ExprResult Sema::CheckPlaceholderExpr(Expr *E) {
     // shouldn't need to do any further diagnostic here.
     if (!E->containsErrors())
       Diag(E->getBeginLoc(), diag::err_array_section_use)
-          << cast<ArraySectionExpr>(E)->isOMPArraySection();
+          << cast<ArraySectionExpr>(E->IgnoreParens())->isOMPArraySection();
     return ExprError();
 
   // Expressions of unknown type.
diff --git a/clang/test/SemaCXX/gh183505.cpp b/clang/test/SemaCXX/gh183505.cpp
new file mode 100644
index 0000000000000..94c70c3270f72
--- /dev/null
+++ b/clang/test/SemaCXX/gh183505.cpp
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+int ab[7];
+int[(int)(abc<>)]; // expected-error {{use of undeclared identifier 'abc'}} \
+                   // expected-error {{expected expression}}
+
+int[(int)(undefined_name<>)]; // expected-error {{use of undeclared identifier 'undefined_name'}} \
+                              // expected-error {{expected expression}}
+
+int[(int)(<>)]; // expected-error {{expected expression}}
+
+int[(int)(123<>)]; // expected-error {{expected expression}}

>From 91755b1300887d8382d287eade099e31b64731a1 Mon Sep 17 00:00:00 2001
From: Serosh-commits <janmejayapanda400 at gmail.com>
Date: Fri, 27 Feb 2026 15:08:48 +0530
Subject: [PATCH 2/2] some nits and ci fixes

---
 clang/lib/Sema/SemaExpr.cpp     |  8 ++++----
 clang/test/SemaCXX/gh183505.cpp | 14 +++++++++-----
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 4f614ca317b38..20e95d8982781 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -21565,7 +21565,7 @@ ExprResult Sema::CheckPlaceholderExpr(Expr *E) {
           /*CanonicalArgs=*/{},
           HasAnyDependentTA ? Context.DependentTy : Context.IntTy);
     return CreateRecoveryExpr(NameInfo.getBeginLoc(), NameInfo.getEndLoc(), {},
-                               TST);
+                              TST);
   }
 
   // Overloaded expressions.
@@ -21629,11 +21629,11 @@ ExprResult Sema::CheckPlaceholderExpr(Expr *E) {
       unsigned BuiltinID = FD->getBuiltinID();
       if (BuiltinID == Builtin::BI__noop) {
         E = ImpCastExprToType(E, Context.getPointerType(FD->getType()),
-                               CK_BuiltinFnToFnPtr)
+                              CK_BuiltinFnToFnPtr)
                 .get();
         return CallExpr::Create(Context, E, /*Args=*/{}, Context.IntTy,
-                                 VK_PRValue, SourceLocation(),
-                                 FPOptionsOverride());
+                                VK_PRValue, SourceLocation(),
+                                FPOptionsOverride());
       }
 
       if (Context.BuiltinInfo.isInStdNamespace(BuiltinID)) {
diff --git a/clang/test/SemaCXX/gh183505.cpp b/clang/test/SemaCXX/gh183505.cpp
index 94c70c3270f72..f170b29ed0cb8 100644
--- a/clang/test/SemaCXX/gh183505.cpp
+++ b/clang/test/SemaCXX/gh183505.cpp
@@ -1,12 +1,16 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s
 
-int ab[7];
+int ab[7]; // expected-note {{'ab' declared here}} \
+           // expected-note {{class template declared here}}
 int[(int)(abc<>)]; // expected-error {{use of undeclared identifier 'abc'}} \
-                   // expected-error {{expected expression}}
+                   // expected-error {{'ab' is expected to be a non-type template, but instantiated to a class template}} \
+                   // expected-error {{expected unqualified-id}}
 
 int[(int)(undefined_name<>)]; // expected-error {{use of undeclared identifier 'undefined_name'}} \
-                              // expected-error {{expected expression}}
+                              // expected-error {{expected unqualified-id}}
 
-int[(int)(<>)]; // expected-error {{expected expression}}
+int[(int)(<>)]; // expected-error 3 {{expected expression}} \
+                // expected-error {{expected unqualified-id}}
 
-int[(int)(123<>)]; // expected-error {{expected expression}}
+int[(int)(123<>)]; // expected-error 2 {{expected expression}} \
+                   // expected-error {{expected unqualified-id}}