[Clang] disallow attributes on void parameters

clang/docs/ReleaseNotes.rst

@@ -100,6 +100,8 @@ Removed Compiler Flags
 Attribute Changes in Clang
 --------------------------
 
+- Clang now disallows the use of attributes on void parameters. (#GH108819)
+
 Improvements to Clang's diagnostics
 -----------------------------------
 

clang/lib/Parse/ParseDecl.cpp

@@ -7986,6 +7986,12 @@ void Parser::ParseParameterDeclarationClause(
     if (getLangOpts().HLSL)
       MaybeParseHLSLAnnotations(DS.getAttributes());
 
+    if (ParmDeclarator.getDeclarationAttributes().size() &&
+        ParmDeclarator.getDeclSpec().getTypeSpecType() == DeclSpec::TST_void) {
+      SourceRange AttrRange = ParmDeclarator.getDeclarationAttributes().Range;
+      Diag(AttrRange.getBegin(), diag::err_attributes_not_allowed) << AttrRange;
+    }
+
     if (Tok.is(tok::kw_requires)) {
       // User tried to define a requires clause in a parameter declaration,
       // which is surely not a function declaration.

clang/test/Parser/cxx0x-attributes.cpp

@@ -453,3 +453,12 @@ namespace P2361 {
 }
 
 alignas(int) struct AlignAsAttribute {}; // expected-error {{misplaced attributes; expected attributes here}}
+
+namespace GH108819 {
+void a([[maybe_unused]] void) {}                 // expected-error {{an attribute list cannot appear here}} \
+                                                 // expected-warning {{use of the 'maybe_unused' attribute is a C++17 extension}}
+void b([[deprecated]] void) {}                   // expected-error {{an attribute list cannot appear here}} \
+                                                 // expected-warning {{use of the 'deprecated' attribute is a C++14 extension}}
+void c([[clang::lifetimebound]] void) {}         // expected-error {{an attribute list cannot appear here}}
+void d([[clang::annotate("a", "b", 1)]] void) {} // expected-error {{an attribute list cannot appear here}}
+}