[clang] Fix the local parameter of void type inside the Requires expression.

clang/docs/ReleaseNotes.rst

@@ -359,6 +359,8 @@ Improvements to Clang's diagnostics
 
 - Clang now diagnoses cases where a dangling ``GSLOwner<GSLPointer>`` object is constructed, e.g. ``std::vector<string_view> v = {std::string()};`` (#GH100526).
 
+- Clang now diagnoses when a ``requires`` expression has a local parameter of void type, aligning with the function parameter (#GH109831).
+
 Improvements to Clang's time-trace
 ----------------------------------
 

clang/lib/AST/ExprConcepts.cpp

@@ -153,6 +153,10 @@ RequiresExpr::RequiresExpr(ASTContext &C, SourceLocation RequiresKWLoc,
   std::copy(Requirements.begin(), Requirements.end(),
             getTrailingObjects<concepts::Requirement *>());
   RequiresExprBits.IsSatisfied |= Dependent;
+  RequiresExprBits.IsSatisfied &=
+      llvm::none_of(LocalParameters, [](const ParmVarDecl *Param) {
+        return Param->isInvalidDecl();
+      });
   // FIXME: move the computing dependency logic to ComputeDependence.h
   if (ContainsUnexpandedParameterPack)
     setDependence(getDependence() | ExprDependence::UnexpandedPack);

clang/lib/Sema/SemaExprCXX.cpp

@@ -9509,6 +9509,19 @@ Sema::ActOnStartRequiresExpr(SourceLocation RequiresKWLoc,
   PushDeclContext(BodyScope, Body);
 
   for (ParmVarDecl *Param : LocalParameters) {
+    if (Param->getType()->isVoidType()) {
+      if (LocalParameters.size() > 1) {
+        Diag(Param->getBeginLoc(), diag::err_void_only_param);
+        Param->setInvalidDecl();
+      } else if (Param->getIdentifier()) {
+        Diag(Param->getBeginLoc(), diag::err_param_with_void_type);
+        Param->setInvalidDecl();
+      } else if (Param->getType().hasQualifiers()) {
+        Diag(Param->getBeginLoc(), diag::err_void_param_qualified);
+        Param->setInvalidDecl();
+      }
+    }
+
     if (Param->hasDefaultArg())
       // C++2a [expr.prim.req] p4
       //     [...] A local parameter of a requires-expression shall not have a

clang/test/CXX/expr/expr.prim/expr.prim.req/requires-expr.cpp

@@ -65,4 +65,18 @@ template<typename T> requires requires { T::value; S<T>::s; }
 struct r4 { };
 
 using r4i = r4<int>;
-// expected-error@-1 {{constraints not satisfied for class template 'r4' [with T = int]}}
+// expected-error@-1 {{constraints not satisfied for class template 'r4' [with T = int]}}
+
+namespace GH109538 {
+static_assert(requires(void *t) { t; });
+static_assert(requires(void) { 42; });
+static_assert(!requires(void t) { // expected-error {{argument may not have 'void' type}}
+  t;
+});
+static_assert(!requires(void t, int a) {  // expected-error {{'void' must be the first and only parameter if specified}}
+  t;
+});
+static_assert(!requires(const void) { // expected-error {{'void' as parameter must not have type qualifiers}}
+  42;
+});
+} // namespace GH109538