[Clang][Parse] Diagnose member template declarations with multiple declarators

Author: sdkrystian

clang/docs/ReleaseNotes.rst

@@ -611,6 +611,8 @@ Improvements to Clang's diagnostics
   inside namespace. The original diagnostic message is confusing.
   (`#73893: <https://github.com/llvm/llvm-project/issues/73893>`_)
 
+- Clang now diagnoses member template declarations with multiple declarators.
+
 Improvements to Clang's time-trace
 ----------------------------------
 - Two time-trace scope variables are added. A time trace scope variable of

clang/lib/Parse/ParseDeclCXX.cpp

@@ -3167,6 +3167,15 @@ Parser::ParseCXXClassMemberDeclaration(AccessSpecifier AS,
 
     DeclaratorInfo.complete(ThisDecl);
 
+    if (TemplateInfo.Kind != ParsedTemplateInfo::NonTemplate) {
+      if (Tok.is(tok::comma)) {
+        Diag(Tok, diag::err_multiple_template_declarators)
+            << (int)TemplateInfo.Kind;
+        SkipUntil(tok::semi, StopBeforeMatch);
+      }
+      break;
+    }
+
     // If we don't have a comma, it is either the end of the list (a ';')
     // or an error, bail out.
     SourceLocation CommaLoc;

clang/test/CXX/temp/p3.cpp

@@ -15,3 +15,9 @@ template<typename T> struct B { } f(); // expected-error {{expected ';' after st
 template<typename T> struct C { } // expected-error {{expected ';' after struct}}
 
 A<int> c;
+
+struct D {
+  template<typename T> static const int x = 0, f(); // expected-error {{can only declare a single entity}}
+
+  template<typename T> static const int g(), y = 0; // expected-error {{can only declare a single entity}}
+};

clang/test/OpenMP/declare_simd_messages.cpp

@@ -33,10 +33,9 @@ int main();
 int main();
 
 struct A {
-// expected-error@+1 {{function declaration is expected after 'declare simd' directive}}
   #pragma omp declare simd
   template<typename T>
-  T infunc1(T a), infunc2(T a);
+  T infunc1(T a);
 };
 
 // expected-error@+1 {{single declaration is expected after 'declare simd' directive}}