Check for stubs in NeedsNewVTableEntryRequest

This lets us remove `setNeedsNewVTableEntry`.

Author: hamishknight

include/swift/AST/Decl.h

@@ -5824,11 +5824,6 @@ class AbstractFunctionDecl : public GenericContext, public ValueDecl {
     return getBodyKind() == BodyKind::MemberwiseInitializer;
   }
 
-  void setNeedsNewVTableEntry(bool value) {
-    LazySemanticInfo.NeedsNewVTableEntryComputed = true;
-    LazySemanticInfo.NeedsNewVTableEntry = value;
-  }
-
   /// For a method of a class, checks whether it will require a new entry in the
   /// vtable.
   bool needsNewVTableEntry() const;

lib/Sema/CodeSynthesis.cpp

@@ -702,8 +702,6 @@ createDesignatedInitOverride(ClassDecl *classDecl,
     // Note that this is a stub implementation.
     ctor->setStubImplementation(true);
 
-    // Stub constructors don't appear in the vtable.
-    ctor->setNeedsNewVTableEntry(false);
     return ctor;
   }
 

lib/Sema/TypeCheckDecl.cpp

@@ -1392,6 +1392,10 @@ NeedsNewVTableEntryRequest::evaluate(Evaluator &evaluator,
     if (!ctor->isRequired() && !ctor->isDesignatedInit()) {
       return false;
     }
+
+    // Stub constructors don't appear in the vtable.
+    if (ctor->hasStubImplementation())
+      return false;
   }
 
   if (auto *accessor = dyn_cast<AccessorDecl>(decl)) {