[Clang] Destructors should not be immediate-escalating

clang/docs/ReleaseNotes.rst

@@ -429,6 +429,7 @@ Bug Fixes to C++ Support
 - Suppress ``-Wdeprecated-declarations`` in implicitly generated functions. (#GH147293)
 - Fix a crash when deleting a pointer to an incomplete array (#GH150359).
 - Fixed a mismatched lambda scope bug when propagating up ``consteval`` within nested lambdas. (#GH145776)
+- Disallow immediate escalation in destructors. (#GH109096)
 - Fix an assertion failure when expression in assumption attribute
   (``[[assume(expr)]]``) creates temporary objects.
 - Fix the dynamic_cast to final class optimization to correctly handle

clang/lib/AST/Decl.cpp

@@ -3316,6 +3316,10 @@ bool FunctionDecl::isImmediateEscalating() const {
       CD && CD->isInheritingConstructor())
     return CD->getInheritedConstructor().getConstructor();
 
+  // Destructors are not immediate escalating.
+  if (isa<CXXDestructorDecl>(this))
+    return false;
+
   // - a function that results from the instantiation of a templated entity
   // defined with the constexpr specifier.
   TemplatedKind TK = getTemplatedKind();

clang/lib/Sema/SemaTemplateInstantiateDecl.cpp

@@ -5727,7 +5727,7 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
   Function->setDeclarationNameLoc(NameLocPointsToPattern());
 
   EnterExpressionEvaluationContextForFunction EvalContext(
-      *this, Sema::ExpressionEvaluationContext::PotentiallyEvaluated);
+      *this, Sema::ExpressionEvaluationContext::PotentiallyEvaluated, Function);
 
   Qualifiers ThisTypeQuals;
   CXXRecordDecl *ThisContext = nullptr;

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

@@ -626,3 +626,20 @@ void fn() {
 }
 
 }
+
+
+namespace GH109096 {
+consteval void undefined();
+template <typename T>
+struct scope_exit {
+    T t;
+    constexpr ~scope_exit() { t(); }
+    // expected-error@-1 {{call to immediate function 'GH109096::(anonymous class)::operator()' is not a constant expression}} \
+    // expected-note@-1 {{implicit use of 'this' pointer is only allowed within the evaluation}}
+};
+
+scope_exit guard( // expected-note {{in instantiation of member function}}
+    []() { undefined(); }
+);
+
+}