[clang] [clang] fix incorrect assumption about function type 's ExtInfo (PR #157925)

[Matheus Izvekov via cfe-commits]

https://github.com/mizvekov created https://github.com/llvm/llvm-project/pull/157925

This fixes an assumption that the ExtInfo for two same function types would have referential equality.

This should compare these ExtInfos by value instead.

The bug is pre-existing to https://github.com/llvm/llvm-project/pull/147835, but that PR adds another way to reproduce it.

>From 489383e2a500812894f0714cbcb30d8d3289147d Mon Sep 17 00:00:00 2001
From: Matheus Izvekov <mizvekov at gmail.com>
Date: Wed, 10 Sep 2025 15:26:53 -0300
Subject: [PATCH] [clang] fix incorrect assumption about function type 's
 ExtInfo

This fixes an assumption that the ExtInfo for two same function types
would have referential equality.

This should compare these ExtInfos by value instead.

The bug is pre-existing to https://github.com/llvm/llvm-project/pull/147835,
but that PR adds another way to reproduce it.
---
 clang/docs/ReleaseNotes.rst               |  3 +++
 clang/lib/AST/ASTContext.cpp              |  6 +++++-
 clang/test/SemaCXX/sugar-common-types.cpp | 24 +++++++++++++++++++++++
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index a20b1ab298f9c..c0e3fafc379c6 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -350,6 +350,9 @@ Bug Fixes to C++ Support
   authentication enabled. (#GH152601)
 - Fix the check for narrowing int-to-float conversions, so that they are detected in
   cases where converting the float back to an integer is undefined behaviour (#GH157067).
+- Fix a crash when applying binary or ternary operators to two same function types with different spellings,
+  where at least one of the function parameters has an attribute which affects
+  the function type.
 - Fix an assertion failure when a ``constexpr`` variable is only referenced through
   ``__builtin_addressof``, and related issues with builtin arguments. (#GH154034)
 
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index c04de4e132739..ed4c6b0e38be3 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -14195,7 +14195,11 @@ static QualType getCommonNonSugarTypeNode(const ASTContext &Ctx, const Type *X,
     FunctionProtoType::ExtProtoInfo EPIX = FX->getExtProtoInfo(),
                                     EPIY = FY->getExtProtoInfo();
     assert(EPIX.ExtInfo == EPIY.ExtInfo);
-    assert(EPIX.ExtParameterInfos == EPIY.ExtParameterInfos);
+    assert(!EPIX.ExtParameterInfos == !EPIY.ExtParameterInfos);
+    assert(!EPIX.ExtParameterInfos ||
+           llvm::equal(
+               llvm::ArrayRef(EPIX.ExtParameterInfos, FX->getNumParams()),
+               llvm::ArrayRef(EPIY.ExtParameterInfos, FY->getNumParams())));
     assert(EPIX.RefQualifier == EPIY.RefQualifier);
     assert(EPIX.TypeQuals == EPIY.TypeQuals);
     assert(EPIX.Variadic == EPIY.Variadic);
diff --git a/clang/test/SemaCXX/sugar-common-types.cpp b/clang/test/SemaCXX/sugar-common-types.cpp
index dd5fc4a654795..4db0d2ac2f2ae 100644
--- a/clang/test/SemaCXX/sugar-common-types.cpp
+++ b/clang/test/SemaCXX/sugar-common-types.cpp
@@ -203,3 +203,27 @@ namespace member_pointers {
   N t3 = 0 ? &W1::a : &W2::b;
   // expected-error at -1 {{rvalue of type 'B1 member_pointers::W<void>::*'}}
 } // namespace member_pointers
+
+namespace FunctionTypeExtInfo {
+  namespace RecordType {
+    class A;
+    void (*x)(__attribute__((swift_async_context)) A *);
+
+    class A;
+    void (*y)(__attribute__((swift_async_context)) A *);
+
+    N t1 = 0 ? x : y;
+    // expected-error at -1 {{lvalue of type 'void (*)(__attribute__((swift_async_context)) A *)'}}
+  } // namespace RecordType
+  namespace TypedefType {
+    class A;
+    using B = A;
+    void (*x)(__attribute__((swift_async_context)) B *);
+
+    using B = A;
+    void (*y)(__attribute__((swift_async_context)) B *);
+
+    N t1 = 0 ? x : y;
+    // expected-error at -1 {{lvalue of type 'void (*)(__attribute__((swift_async_context)) B *)'}}
+  } // namespace TypedefType
+} // namespace FunctionTypeExtInfo