[AST] Eliminate two simple uses of (NominalType|Extension)Decl::getInheritedType().

Simple checks for the presence of a protocol in the “inherited” list should only
require a scan through that list + name lookup; use those facilities instead of
recursing through the type checker.

Author: DougGregor

lib/AST/DeclContext.cpp

@@ -91,6 +91,16 @@ ProtocolDecl *DeclContext::getAsProtocolExtensionContext() const {
 GenericTypeParamType *DeclContext::getProtocolSelfType() const {
   assert(getAsProtocolOrProtocolExtensionContext() && "not a protocol");
 
+  auto genericParams = getGenericParamsOfContext();
+
+  if (!genericParams) {
+    if (auto proto = dyn_cast<ProtocolDecl>(this)) {
+      getASTContext().getLazyResolver()
+          ->resolveDeclSignature(const_cast<ProtocolDecl *>(proto));
+      genericParams = getGenericParamsOfContext();
+    }
+  }
+
   return getGenericParamsOfContext()->getParams().front()
       ->getDeclaredInterfaceType()
       ->castTo<GenericTypeParamType>();

lib/ClangImporter/ImportDecl.cpp

@@ -5168,21 +5168,15 @@ Decl *SwiftDeclConverter::importCompatibilityTypeAlias(
 namespace {
   template<typename D>
   bool inheritanceListContainsProtocol(D decl, const ProtocolDecl *proto) {
-    return llvm::any_of(range(decl->getInherited().size()),
-                        [decl, proto](unsigned index) -> bool {
-      Type type = decl->getInheritedType(index);
-      if (!type || !type->isExistentialType())
-        return false;
-
-      auto layout = type->getExistentialLayout();
-      for (auto protoTy : layout.getProtocols()) {
-        auto *protoDecl = protoTy->getDecl();
+    bool anyObject = false;
+    for (const auto &found :
+            getDirectlyInheritedNominalTypeDecls(decl, anyObject)) {
+      if (auto protoDecl = dyn_cast<ProtocolDecl>(found.second))
         if (protoDecl == proto || protoDecl->inheritsFrom(proto))
           return true;
-      }
+    }
 
-      return false;
-    });
+    return false;
   }
 }
 

lib/Sema/TypeCheckDecl.cpp

@@ -560,16 +560,11 @@ getInheritedForCycleCheck(TypeChecker &tc,
                           ProtocolDecl **scratch) {
   TinyPtrVector<ProtocolDecl *> result;
 
-  for (unsigned index : indices(proto->getInherited())) {
-    if (auto type = proto->getInheritedType(index)) {
-      if (type->isExistentialType()) {
-        auto layout = type->getExistentialLayout();
-        for (auto protoTy : layout.getProtocols()) {
-          auto *protoDecl = protoTy->getDecl();
-          result.push_back(protoDecl);
-        }
-      }
-    }
+  bool anyObject = false;
+  for (const auto &found :
+         getDirectlyInheritedNominalTypeDecls(proto, anyObject)) {
+    if (auto protoDecl = dyn_cast<ProtocolDecl>(found.second))
+      result.push_back(protoDecl);
   }
 
   return result;