Remove hackery introduced for Swift 3 migration that should be in the 2.2 compiler.

Author: DougGregor

lib/ClangImporter/ImportDecl.cpp

@@ -5018,6 +5018,8 @@ canSkipOverTypedef(ClangImporter::Implementation &Impl,
 
 bool ClangImporter::Implementation::shouldTrySwift3Migration(
        Decl *swiftDecl, const clang::NamedDecl *clangDecl) {
+  if (!SwiftContext.LangOpts.Swift3Migration) return false;
+
   // Never map subscript declarations.
   if (isa<SubscriptDecl>(swiftDecl)) return false;
 

lib/Serialization/Deserialization.cpp

@@ -1051,47 +1051,11 @@ Decl *ModuleFile::resolveCrossReference(Module *M, uint32_t pathLen) {
     if (!isType)
       pathTrace.addType(filterTy);
 
-    bool retrying = false;
-    retry:
-
     M->lookupQualified(ModuleType::get(M), name,
                        NL_QualifiedDefault | NL_KnownNoDependency,
                        /*typeResolver=*/nullptr, values);
     filterValues(filterTy, nullptr, nullptr, isType, inProtocolExt, None,
                  values);
-
-    // HACK HACK HACK: Omit-needless-words hack to try to cope with
-    // the "NS" prefix being added/removed. No "real" compiler mode
-    // has to go through this path: a Swift 2 compiler will have the
-    // prefix, while a Swift 3 compiler will not have the
-    // prefix. However, one can set OmitNeedlessWords in a Swift 2
-    // compiler to get API dumps and perform basic testing; this hack
-    // keeps that working.
-    if (values.empty() && !retrying &&
-        getContext().LangOpts.OmitNeedlessWords &&
-        (M->getName().str() == "ObjectiveC" ||
-         M->getName().str() == "Foundation")) {
-      if (name.str().startswith("NS")) {
-        if (name.str().size() > 2 && name.str() != "NSCocoaError") {
-          auto known = getKnownFoundationEntity(name.str());
-          if (!known || !nameConflictsWithStandardLibrary(*known)) {
-            // FIXME: lowercasing magic for non-types.
-            name = getContext().getIdentifier(name.str().substr(2));
-            retrying = true;
-            goto retry;
-          }
-        }
-      } else {
-        SmallString<16> buffer;
-        buffer += "NS";
-        buffer += name.str();
-        // FIXME: Try uppercasing for non-types.
-        name = getContext().getIdentifier(buffer);
-        retrying = true;
-        goto retry;
-      }
-    }
-
     break;
   }