[ClangImporter] Remove importer-based NS stripping. (#3880)

* [ClangImporter] Remove importer-based NS stripping.

As Tony puts it, in the end we wound up with more Foundation
declarations imported as members or keeping "NS" than those that
dropped it, and any further decisions will be made on a case-by-case
basis. Move all of the existing cases of prefix-stripping into
Foundation's API notes and drop the logic from the compiler.

Tested by dumping the generated interface for Foundation and its
submodules for both macOS and the iOS simulator, and comparing the
results. A few cases did slip through here because of the interaction
between "SwiftName" and "Availability: nonswift".

The next commit will re-add "NS" to some stragglers that we missed.

rdar://problem/26880017

* APINotes: Add "NS" back to a few types.

NSKeyedUnarchiverDelegate
NSKeyedArchiverDelegate
NSTextCheckingTypes
NSBinarySearchingOptions
NSEnumerationOptions
NSSortOptions

More rdar://problem/26880017

* Remove now-redundant SwiftNames from API notes.

No change observed in the generated interface of Foundation and its
submodules.

Finishes rdar://problem/26880017.

Author: jrose-apple

apinotes/Foundation.apinotes

@@ -120,10 +120,6 @@ enum class KnownFoundationEntity {
 /// entity name.
 Optional<KnownFoundationEntity> getKnownFoundationEntity(StringRef name);
 
-/// Determine with the non-prefixed name of the given known Foundation
-/// entity conflicts with the Swift standard library.
-bool nameConflictsWithStandardLibrary(KnownFoundationEntity entity);
-
 /// Callback function used when referring to a type member of a given
 /// type variable.
 typedef std::function<Type(TypeVariableType *, AssociatedTypeDecl *)>

include/swift/AST/ASTContext.h

@@ -30,7 +30,6 @@ FOUNDATION_ENTITY(NSObject)
 FOUNDATION_ENTITY(NSRange)
 FOUNDATION_ENTITY(NSSet)
 FOUNDATION_ENTITY(NSString)
-FOUNDATION_ENTITY(NSStringEncoding)
 FOUNDATION_ENTITY(NSUInteger)
 FOUNDATION_ENTITY(NSURL)
 FOUNDATION_ENTITY(NSZone)

include/swift/AST/KnownFoundationEntities.def

@@ -161,9 +161,6 @@ namespace swift {
     /// and methods.
     bool InferImportAsMember = false;
 
-    /// Whether we are stripping the "NS" prefix from Foundation et al.
-    bool StripNSPrefix = true;
-
     /// Should 'id' in Objective-C be imported as 'Any' in Swift?
     bool EnableIdAsAny = true;
 

include/swift/Basic/LangOptions.h

@@ -247,10 +247,6 @@ def enable_swift_newtype :
   Flag<["-"], "enable-swift-newtype">,
   HelpText<"Enable the swift_newtype attribute">;
 
-def enable_strip_ns_prefix :
-  Flag<["-"], "enable-strip-ns-prefix">,
-  HelpText<"Strip 'NS' prefix from Foundation entities">;
-
 def swift3_migration :
   Flag<["-"], "swift3-migration">,
   HelpText<"Enable Fix-It based migration aids for Swift 3">;

include/swift/Option/FrontendOptions.td

@@ -2578,29 +2578,6 @@ Optional<KnownFoundationEntity> swift::getKnownFoundationEntity(StringRef name){
     .Default(None);
 }
 
-bool swift::nameConflictsWithStandardLibrary(KnownFoundationEntity entity) {
-  switch (entity) {
-  case KnownFoundationEntity::NSArray:
-  case KnownFoundationEntity::NSDictionary:
-  case KnownFoundationEntity::NSInteger:
-  case KnownFoundationEntity::NSRange:
-  case KnownFoundationEntity::NSSet:
-  case KnownFoundationEntity::NSString:
-  case KnownFoundationEntity::NSCopying:
-  case KnownFoundationEntity::NSError:
-  case KnownFoundationEntity::NSErrorPointer:
-  case KnownFoundationEntity::NSNumber:
-  case KnownFoundationEntity::NSObject:
-  case KnownFoundationEntity::NSUInteger:
-  case KnownFoundationEntity::NSURL:
-  case KnownFoundationEntity::NSZone:
-    return true;
-
-  case KnownFoundationEntity::NSStringEncoding:
-    return false;
-  }
-}
-
 StringRef ASTContext::getSwiftName(KnownFoundationEntity kind) {
   StringRef objcName;
   switch (kind) {
@@ -2610,13 +2587,6 @@ StringRef ASTContext::getSwiftName(KnownFoundationEntity kind) {
 #include "swift/AST/KnownFoundationEntities.def"
   }
 
-  // If we're omitting needless words and the name won't conflict with
-  // something in the standard library, strip the prefix off the Swift
-  // name.
-  if (LangOpts.StripNSPrefix &&
-      !nameConflictsWithStandardLibrary(kind))
-    return objcName.substr(2);
-
   return objcName;
 }
 

lib/AST/ASTContext.cpp

@@ -1309,13 +1309,6 @@ ClangImporter::Implementation::Implementation(ASTContext &ctx,
     DeprecatedAsUnavailableMessage =
       "APIs deprecated as of OS X 10.9 and earlier are unavailable in Swift";
   }
-
-  // Prepopulate the set of module prefixes.
-  // FIXME: Hard-coded list should move into the module map language.
-  if (ctx.LangOpts.StripNSPrefix) {
-    ModulePrefixes["Foundation"] = "NS";
-    ModulePrefixes["ObjectiveC"] = "NS";
-  }
 }
 
 
@@ -1817,8 +1810,7 @@ static unsigned stripModulePrefixLength(
   // Check whether this is a known Foundation entity that conflicts with the
   // standard library.
   if (auto known = getKnownFoundationEntity(baseName))
-    if (nameConflictsWithStandardLibrary(*known))
-      return 0;
+    return 0;
 
   // If the character following the prefix is a '_', eat that, too.
   unsigned prefixLen = prefixPos->second.size();
@@ -4436,7 +4428,6 @@ ClangImporter::Implementation::SwiftNameLookupExtension::hashExtension(
                             SWIFT_LOOKUP_TABLE_VERSION_MAJOR,
                             SWIFT_LOOKUP_TABLE_VERSION_MINOR,
                             Impl.InferImportAsMember,
-                            Impl.SwiftContext.LangOpts.StripNSPrefix,
                             Impl.HonorSwiftNewtypeAttr);
 }
 

lib/ClangImporter/ClangImporter.cpp

@@ -165,9 +165,7 @@ MAP_STDLIB_TYPE("CFIndex", SignedWord, 0, "Int", false, DefineAndUse)
 
 // Foundation types.
 // FIXME: <rdar://problem/16074941> NSStringEncoding doesn't work on 32-bit
-MAP_STDLIB_TYPE(
-  Impl.SwiftContext.getSwiftName(KnownFoundationEntity::NSStringEncoding),
-  UnsignedWord, 0, "UInt", false, DoNothing)
+MAP_STDLIB_TYPE("NSStringEncoding", UnsignedWord, 0, "UInt", false, DoNothing)
 
 #undef MAP_STDLIB_TYPE
 #undef MAP_TYPE

lib/ClangImporter/MappedTypes.def

@@ -771,7 +771,6 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
   Opts.Playground |= Args.hasArg(OPT_playground);
   Opts.Swift3Migration |= Args.hasArg(OPT_swift3_migration);
   Opts.WarnOmitNeedlessWords = Args.hasArg(OPT_warn_omit_needless_words);
-  Opts.StripNSPrefix |= Args.hasArg(OPT_enable_strip_ns_prefix);
   Opts.InferImportAsMember |= Args.hasArg(OPT_enable_infer_import_as_member);
 
   Opts.EnableThrowWithoutTry |= Args.hasArg(OPT_enable_throw_without_try);

lib/Frontend/CompilerInvocation.cpp

@@ -1100,13 +1100,12 @@ Decl *ModuleFile::resolveCrossReference(Module *M, uint32_t pathLen) {
     // has to go through this path, but it's an option we toggle for
     // testing.
     if (values.empty() && !retrying &&
-        getContext().LangOpts.StripNSPrefix &&
         (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)) {
+          if (!known) {
             name = getContext().getIdentifier(name.str().substr(2));
             retrying = true;
             goto retry;