AST: Remove DeclContext::isExtensionContext()

It's identical in every way to isa<ExtensionDecl>(), so
make code less confusing by only having one way of doing
that check.

Author: slavapestov

include/swift/AST/Decl.h

@@ -6795,12 +6795,6 @@ inline const GenericContext *Decl::getAsGenericContext() const {
   }
 }
 
-inline bool DeclContext::isExtensionContext() const {
-  if (auto D = getAsDecl())
-    return ExtensionDecl::classof(D);
-  return false;
-}
-
 inline bool DeclContext::classof(const Decl *D) {
   switch (D->getKind()) { //
   default: return false;

include/swift/AST/DeclContext.h

@@ -277,10 +277,6 @@ class alignas(1 << DeclContextAlignInBits) DeclContext {
   LLVM_READONLY
   bool isTypeContext() const;
 
-  /// \brief Determine whether this is an extension context.
-  LLVM_READONLY
-  bool isExtensionContext() const; // see swift/AST/Decl.h
-
   /// If this DeclContext is a NominalType declaration or an
   /// extension thereof, return the NominalTypeDecl.
   LLVM_READONLY

lib/IDE/IDETypeChecking.cpp

@@ -28,7 +28,7 @@ using namespace swift;
 
 static bool shouldPrintAsFavorable(const Decl *D, const PrintOptions &Options) {
   if (!Options.TransformContext ||
-      !D->getDeclContext()->isExtensionContext() ||
+      !isa<ExtensionDecl>(D->getDeclContext()) ||
       !Options.TransformContext->isPrintingSynthesizedExtension())
     return true;
   auto DC = Options.TransformContext->getDeclContext();

lib/SIL/SILDeclRef.cpp

@@ -883,7 +883,7 @@ SubclassScope SILDeclRef::getSubclassScope() const {
   DeclContext *context = FD->getDeclContext();
 
   // Methods from extensions don't go into vtables (yet).
-  if (context->isExtensionContext())
+  if (isa<ExtensionDecl>(context))
     return SubclassScope::NotApplicable;
 
   // Various forms of thunks don't either.

lib/SILGen/SILGen.cpp

@@ -507,7 +507,7 @@ SILGenModule::getOrCreateProfilerForConstructors(DeclContext *ctx,
   // distinct files. For extensions, just pass in the constructor, because
   // there are no stored property initializers to visit.
   Decl *decl = nullptr;
-  if (ctx->isExtensionContext())
+  if (isa<ExtensionDecl>(ctx))
     decl = cd;
   else
     decl = ctx->getSelfNominalTypeDecl();

lib/SILGen/SILGenApply.cpp

@@ -150,8 +150,7 @@ static bool canUseStaticDispatch(SILGenFunction &SGF,
 
   // Extension methods currently must be statically dispatched, unless they're
   // @objc or dynamic.
-  if (funcDecl->getDeclContext()->isExtensionContext()
-      && !constant.isForeign)
+  if (isa<ExtensionDecl>(funcDecl->getDeclContext()) && !constant.isForeign)
     return true;
 
   // We cannot form a direct reference to a method body defined in

lib/Sema/CSSolver.cpp

@@ -1787,10 +1787,7 @@ void ConstraintSystem::partitionForDesignatedTypes(
     auto *funcDecl = cast<FuncDecl>(decl);
 
     auto *parentDC = funcDecl->getParent();
-    auto *parentDecl = parentDC->getAsDecl();
-
-    if (parentDC->isExtensionContext())
-      parentDecl = cast<ExtensionDecl>(parentDecl)->getExtendedNominal();
+    auto *parentDecl = parentDC->getSelfNominalTypeDecl();
 
     for (auto designatedTypeIndex : indices(designatedNominalTypes)) {
       auto *designatedNominal =
@@ -1800,7 +1797,7 @@ void ConstraintSystem::partitionForDesignatedTypes(
         continue;
 
       auto &constraints =
-          parentDC->isExtensionContext()
+          isa<ExtensionDecl>(parentDC)
               ? definedInExtensionOfDesignatedType[designatedTypeIndex]
               : definedInDesignatedType[designatedTypeIndex];
 

lib/Sema/TypeCheckAttr.cpp

@@ -2050,7 +2050,7 @@ void TypeChecker::checkDynamicReplacementAttribute(ValueDecl *D) {
   auto *attr = D->getAttrs().getAttribute<DynamicReplacementAttr>();
   assert(attr);
 
-  if (!D->getDeclContext()->isExtensionContext() &&
+  if (!isa<ExtensionDecl>(D->getDeclContext()) &&
       !D->getDeclContext()->isModuleScopeContext()) {
     diagnose(attr->getLocation(), diag::dynamic_replacement_not_in_extension,
                 D->getBaseName());

lib/Sema/TypeCheckDecl.cpp

@@ -972,7 +972,7 @@ static void validatePatternBindingEntry(TypeChecker &tc,
   // Validate 'static'/'class' on properties in nominal type decls.
   auto StaticSpelling = binding->getStaticSpelling();
   if (StaticSpelling != StaticSpellingKind::None &&
-      binding->getDeclContext()->isExtensionContext()) {
+      isa<ExtensionDecl>(binding->getDeclContext())) {
     if (auto *NTD = binding->getDeclContext()->getSelfNominalTypeDecl()) {
       if (!isa<ClassDecl>(NTD)) {
         if (StaticSpelling == StaticSpellingKind::KeywordClass) {
@@ -4186,7 +4186,7 @@ void TypeChecker::validateDecl(ValueDecl *D) {
     // Validate 'static'/'class' on functions in extensions.
     auto StaticSpelling = FD->getStaticSpelling();
     if (StaticSpelling != StaticSpellingKind::None &&
-        FD->getDeclContext()->isExtensionContext()) {
+        isa<ExtensionDecl>(FD->getDeclContext())) {
       if (auto *NTD = FD->getDeclContext()->getSelfNominalTypeDecl()) {
         if (!isa<ClassDecl>(NTD)) {
           if (StaticSpelling == StaticSpellingKind::KeywordClass) {

lib/Sema/TypeCheckDeclOverride.cpp

@@ -1510,12 +1510,12 @@ static bool checkSingleOverride(ValueDecl *override, ValueDecl *base) {
   // Non-Objective-C declarations in extensions cannot override or
   // be overridden.
   if (!isAccessor &&
-      (base->getDeclContext()->isExtensionContext() ||
-       override->getDeclContext()->isExtensionContext()) &&
+      (isa<ExtensionDecl>(base->getDeclContext()) ||
+       isa<ExtensionDecl>(override->getDeclContext())) &&
       !base->isObjC()) {
     bool baseCanBeObjC = canBeRepresentedInObjC(base);
     diags.diagnose(override, diag::override_decl_extension, baseCanBeObjC,
-                   !base->getDeclContext()->isExtensionContext());
+                   !isa<ExtensionDecl>(base->getDeclContext()));
     if (baseCanBeObjC) {
       SourceLoc insertionLoc =
         override->getAttributeInsertionLoc(/*forModifier=*/false);
@@ -1559,8 +1559,7 @@ static bool checkSingleOverride(ValueDecl *override, ValueDecl *base) {
     if (!isAccessor &&
         baseDecl->hasKnownSwiftImplementation() &&
         !base->isObjCDynamic() &&
-        override->getDeclContext()->isExtensionContext()) {
-      // For compatibility, only generate a warning in Swift 3
+        isa<ExtensionDecl>(override->getDeclContext())) {
       diags.diagnose(override, diag::override_class_declaration_in_extension);
       diags.diagnose(base, diag::overridden_here);
     }

lib/Sema/TypeCheckProtocol.cpp

@@ -2466,10 +2466,10 @@ printRequirementStub(ValueDecl *Requirement, DeclContext *Adopter,
                      Type AdopterTy, SourceLoc TypeLoc, raw_ostream &OS) {
   if (isa<ConstructorDecl>(Requirement)) {
     if (auto CD = Adopter->getSelfClassDecl()) {
-      if (!CD->isFinal() && Adopter->isExtensionContext()) {
-          // In this case, user should mark class as 'final' or define
-          // 'required' initializer directly in the class definition.
-          return false;
+      if (!CD->isFinal() && isa<ExtensionDecl>(Adopter)) {
+        // In this case, user should mark class as 'final' or define
+        // 'required' initializer directly in the class definition.
+        return false;
       }
     }
   }
@@ -2508,7 +2508,7 @@ printRequirementStub(ValueDecl *Requirement, DeclContext *Adopter,
       if (auto CD = Adopter->getSelfClassDecl()) {
         if (!CD->isFinal()) {
           Printer << "required ";
-        } else if (Adopter->isExtensionContext()) {
+        } else if (isa<ExtensionDecl>(Adopter)) {
           Printer << "convenience ";
         }
       }
@@ -2530,7 +2530,7 @@ printRequirementStub(ValueDecl *Requirement, DeclContext *Adopter,
     };
     Options.setBaseType(AdopterTy);
     Options.CurrentModule = Adopter->getParentModule();
-    if (!Adopter->isExtensionContext()) {
+    if (!isa<ExtensionDecl>(Adopter)) {
       // Create a variable declaration instead of a computed property in
       // nominal types
       Options.PrintPropertyAccessors = false;