[clang] Support __is_trivially_copyable(int()&)==false (llvm#81298)

IMHO it would be productive to make a similar change for `typeid`, in
`ParseCXXTypeid`, in order to improve Clang's error message for
https://godbolt.org/z/oKKWxeYra
But that might be better done by adding a new DeclaratorContext
specifically for TypeidArg, instead of pretending that the argument to
`typeid` is a template argument, because I don't know what else that
change might affect.

Fixes llvm#77585

clang/docs/ReleaseNotes.rst

@@ -265,6 +265,8 @@ Bug Fixes to C++ Support
 - Fix a crash when trying to call a varargs function that also has an explicit object parameter. (#GH80971)
 - Fixed a bug where abbreviated function templates would append their invented template parameters to
   an empty template parameter lists.
+- Fix parsing of abominable function types inside type traits.
+  Fixes (`#77585 <https://github.com/llvm/llvm-project/issues/77585>`_)
 - Clang now classifies aggregate initialization in C++17 and newer as constant
   or non-constant more accurately. Previously, only a subset of the initializer
   elements were considered, misclassifying some initializers as constant. Partially fixes

clang/lib/Parse/ParseExprCXX.cpp

@@ -3908,7 +3908,10 @@ ExprResult Parser::ParseTypeTrait() {
   SmallVector<ParsedType, 2> Args;
   do {
     // Parse the next type.
-    TypeResult Ty = ParseTypeName();
+    TypeResult Ty =
+        ParseTypeName(/*SourceRange=*/nullptr,
+                      getLangOpts().CPlusPlus ? DeclaratorContext::TemplateArg
+                                              : DeclaratorContext::TypeName);
     if (Ty.isInvalid()) {
       Parens.skipToEnd();
       return ExprError();
@@ -3950,7 +3953,8 @@ ExprResult Parser::ParseArrayTypeTrait() {
   if (T.expectAndConsume())
     return ExprError();
 
-  TypeResult Ty = ParseTypeName();
+  TypeResult Ty =
+      ParseTypeName(/*SourceRange=*/nullptr, DeclaratorContext::TemplateArg);
   if (Ty.isInvalid()) {
     SkipUntil(tok::comma, StopAtSemi);
     SkipUntil(tok::r_paren, StopAtSemi);

clang/test/Sema/static-assert.c

@@ -1,6 +1,6 @@
-// RUN: %clang_cc1 -std=c11 -Wgnu-folding-constant -fsyntax-only -verify %s
-// RUN: %clang_cc1 -fms-compatibility -Wgnu-folding-constant -DMS -fsyntax-only -verify=expected,ms %s
-// RUN: %clang_cc1 -std=c99 -pedantic -Wgnu-folding-constant -fsyntax-only -verify=expected,ext %s
+// RUN: %clang_cc1 -std=c11 -Wgnu-folding-constant -fsyntax-only -verify=expected,c %s
+// RUN: %clang_cc1 -fms-compatibility -Wgnu-folding-constant -DMS -fsyntax-only -verify=expected,ms,c %s
+// RUN: %clang_cc1 -std=c99 -pedantic -Wgnu-folding-constant -fsyntax-only -verify=expected,ext,c %s
 // RUN: %clang_cc1 -xc++ -std=c++11 -pedantic -fsyntax-only -verify=expected,ext,cxx %s
 
 _Static_assert("foo", "string is nonzero"); // ext-warning {{'_Static_assert' is a C11 extension}}
@@ -57,7 +57,8 @@ UNION(char[2], short) u2 = { .one = { 'a', 'b' } }; // ext-warning 3 {{'_Static_
 typedef UNION(char, short) U3; // expected-error {{static assertion failed due to requirement 'sizeof(char) == sizeof(short)': type size mismatch}} \
                                // expected-note{{evaluates to '1 == 2'}} \
                                // ext-warning 3 {{'_Static_assert' is a C11 extension}}
-typedef UNION(float, 0.5f) U4; // expected-error {{expected a type}} \
+typedef UNION(float, 0.5f) U4; // c-error {{expected a type}} \
+                               // cxx-error {{type name requires a specifier or qualifier}} \
                                // ext-warning 3 {{'_Static_assert' is a C11 extension}}
 
 // After defining the assert macro in MS-compatibility mode, we should

clang/test/SemaCXX/type-traits-nonobject.cpp

@@ -6,11 +6,14 @@
 static_assert(!__is_pod(void), "");
 static_assert(!__is_pod(int&), "");
 static_assert(!__is_pod(int()), "");
+static_assert(!__is_pod(int()&), "");
 
 static_assert(!__is_trivially_copyable(void), "");
 static_assert(!__is_trivially_copyable(int&), "");
 static_assert(!__is_trivially_copyable(int()), "");
+static_assert(!__is_trivially_copyable(int()&), "");
 
 static_assert(!__is_trivially_relocatable(void), "");
 static_assert(!__is_trivially_relocatable(int&), "");
 static_assert(!__is_trivially_relocatable(int()), "");
+static_assert(!__is_trivially_relocatable(int()&), "");