[clang][Interp] Control InitStack activity state in visitInitList

Summary:
This doesn't change anything about the current tests, but helps
once those tests change because of #97308

Test Plan: 

Reviewers: 

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Tasks: 

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Differential Revision: https://phabricator.intern.facebook.com/D60251512

Author: tbaederr

clang/lib/AST/Interp/Compiler.cpp

@@ -1334,6 +1334,7 @@ bool Compiler<Emitter>::visitInitList(ArrayRef<const Expr *> Inits,
 
     auto initPrimitiveField = [=](const Record::Field *FieldToInit,
                                   const Expr *Init, PrimType T) -> bool {
+      InitStackScope<Emitter> ISS(this, isa<CXXDefaultInitExpr>(Init));
       if (!this->visit(Init))
         return false;
 
@@ -1344,6 +1345,7 @@ bool Compiler<Emitter>::visitInitList(ArrayRef<const Expr *> Inits,
 
     auto initCompositeField = [=](const Record::Field *FieldToInit,
                                   const Expr *Init) -> bool {
+      InitStackScope<Emitter> ISS(this, isa<CXXDefaultInitExpr>(Init));
       InitLinkScope<Emitter> ILS(this, InitLink::Field(FieldToInit->Offset));
       // Non-primitive case. Get a pointer to the field-to-initialize
       // on the stack and recurse into visitInitializer().
@@ -4088,12 +4090,7 @@ template <class Emitter>
 bool Compiler<Emitter>::VisitCXXDefaultInitExpr(const CXXDefaultInitExpr *E) {
   SourceLocScope<Emitter> SLS(this, E);
 
-  bool Old = InitStackActive;
-  InitStackActive =
-      !(E->getUsedContext()->getDeclKind() == Decl::CXXConstructor);
-  bool Result = this->delegate(E->getExpr());
-  InitStackActive = Old;
-  return Result;
+  return this->delegate(E->getExpr());
 }
 
 template <class Emitter>
@@ -4151,6 +4148,9 @@ bool Compiler<Emitter>::VisitCXXThisExpr(const CXXThisExpr *E) {
   // instance pointer of the current function frame, but e.g. to the declaration
   // currently being initialized. Here we emit the necessary instruction(s) for
   // this scenario.
+  if (!InitStackActive || !E->isImplicit())
+    return this->emitThis(E);
+
   if (InitStackActive && !InitStack.empty()) {
     unsigned StartIndex = 0;
     for (StartIndex = InitStack.size() - 1; StartIndex > 0; --StartIndex) {

clang/lib/AST/Interp/Compiler.h

@@ -33,6 +33,7 @@ template <class Emitter> class DestructorScope;
 template <class Emitter> class VariableScope;
 template <class Emitter> class DeclScope;
 template <class Emitter> class InitLinkScope;
+template <class Emitter> class InitStackScope;
 template <class Emitter> class OptionScope;
 template <class Emitter> class ArrayIndexScope;
 template <class Emitter> class SourceLocScope;
@@ -298,6 +299,7 @@ class Compiler : public ConstStmtVisitor<Compiler<Emitter>, bool>,
   friend class DestructorScope<Emitter>;
   friend class DeclScope<Emitter>;
   friend class InitLinkScope<Emitter>;
+  friend class InitStackScope<Emitter>;
   friend class OptionScope<Emitter>;
   friend class ArrayIndexScope<Emitter>;
   friend class SourceLocScope<Emitter>;
@@ -612,6 +614,20 @@ template <class Emitter> class InitLinkScope final {
   Compiler<Emitter> *Ctx;
 };
 
+template <class Emitter> class InitStackScope final {
+public:
+  InitStackScope(Compiler<Emitter> *Ctx, bool Active)
+      : Ctx(Ctx), OldValue(Ctx->InitStackActive) {
+    Ctx->InitStackActive = Active;
+  }
+
+  ~InitStackScope() { this->Ctx->InitStackActive = OldValue; }
+
+private:
+  Compiler<Emitter> *Ctx;
+  bool OldValue;
+};
+
 } // namespace interp
 } // namespace clang