[Clang] call HandleImmediateInvocation before checking for immediate …

…escacalating expressions (#124414)

HandleImmediateInvocation can call MarkExpressionAsImmediateEscalating
and should always be called before
CheckImmediateEscalatingFunctionDefinition.

However, we were not doing that in `ActFunctionBody`.

We simply move CheckImmediateEscalatingFunctionDefinition to
PopExpressionEvaluationContext.

Fixes #119046

clang/docs/ReleaseNotes.rst

@@ -1003,6 +1003,7 @@ Bug Fixes to C++ Support
 - Fixed assertions or false compiler diagnostics in the case of C++ modules for
   lambda functions or inline friend functions defined inside templates (#GH122493).
 - Clang now rejects declaring an alias template with the same name as its template parameter. (#GH123423)
+- Fix that some dependent immediate expressions did not cause immediate escalation (#GH119046)
 - Fixed the rejection of valid code when referencing an enumerator of an unscoped enum member with a prior declaration. (#GH124405)
 - Fixed immediate escalation of non-dependent expressions. (#GH123405)
 - Fix type of expression when calling a template which returns an ``__array_rank`` querying a type depending on a

clang/include/clang/Sema/Sema.h

@@ -13139,10 +13139,10 @@ class Sema final : public SemaBase {
     ~SynthesizedFunctionScope() {
       if (PushedCodeSynthesisContext)
         S.popCodeSynthesisContext();
-      if (auto *FD = dyn_cast<FunctionDecl>(S.CurContext)) {
+
+      if (auto *FD = dyn_cast<FunctionDecl>(S.CurContext))
         FD->setWillHaveBody(false);
-        S.CheckImmediateEscalatingFunctionDefinition(FD, S.getCurFunction());
-      }
+
       S.PopExpressionEvaluationContext();
       S.PopFunctionScopeInfo();
     }

clang/lib/Sema/SemaDecl.cpp

@@ -16019,7 +16019,6 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
       if (!FD->isDeletedAsWritten())
         FD->setBody(Body);
       FD->setWillHaveBody(false);
-      CheckImmediateEscalatingFunctionDefinition(FD, FSI);
 
       if (getLangOpts().CPlusPlus14) {
         if (!FD->isInvalidDecl() && Body && !FD->isDependentContext() &&

clang/lib/Sema/SemaExpr.cpp

@@ -17881,6 +17881,9 @@ void Sema::PopExpressionEvaluationContext() {
   WarnOnPendingNoDerefs(Rec);
   HandleImmediateInvocations(*this, Rec);
 
+  if (auto *FD = dyn_cast<FunctionDecl>(CurContext); FD && getCurFunction())
+    CheckImmediateEscalatingFunctionDefinition(FD, getCurFunction());
+
   // Warn on any volatile-qualified simple-assignments that are not discarded-
   // value expressions nor unevaluated operands (those cases get removed from
   // this list by CheckUnusedVolatileAssignment).

clang/test/CodeGenCXX/gh119046.cpp

@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 -std=c++2a -triple x86_64-elf-gnu %s -emit-llvm -o - | FileCheck %s
+
+struct S {
+    consteval void operator()() {}
+};
+
+template <class Fn>
+constexpr void dispatch(Fn fn) {
+    fn();
+}
+
+template <class Visitor>
+struct value_visitor {
+    constexpr void operator()() { visitor(); }
+    Visitor&& visitor;
+};
+
+template <class Visitor>
+constexpr auto make_dispatch() {
+    return dispatch<value_visitor<S>>;
+}
+
+template <class Visitor>
+constexpr void visit(Visitor&&) {
+    make_dispatch<Visitor>();
+}
+
+void f() { visit(S{}); }
+
+// CHECK: define {{.*}} @_Z1fv
+// CHECK-NOT: define {{.*}} @_Z5visitI1SEvOT_
+// CHECK-NOT: define {{.*}} @_Z13make_dispatchI1SEDav

clang/test/SemaCXX/cxx2b-consteval-propagate.cpp

@@ -529,6 +529,23 @@ D d(0); // expected-note {{in implicit initialization for inherited constructor
 
 }
 
+namespace GH119046 {
+
+template <typename Cls> constexpr auto tfn(int) {
+  return (unsigned long long)(&Cls::sfn);
+  //expected-note@-1 {{'tfn<GH119046::S>' is an immediate function because its body evaluates the address of a consteval function 'sfn'}}
+};
+struct S { static consteval void sfn() {} };
+
+int f() {
+  int a = 0; // expected-note{{declared here}}
+  return tfn<S>(a);
+  //expected-error@-1 {{call to immediate function 'GH119046::tfn<GH119046::S>' is not a constant expression}}
+  //expected-note@-2 {{read of non-const variable 'a' is not allowed in a constant expression}}
+}
+
+}
+
 namespace GH123405 {
 
 consteval void fn() {}