[Clang Importer] Only strip common prefix for swift_newtype

Rather than do whole-word common-word stripping, we only strip common
prefixes. This is not as powerful as what was originally intended, but
much less magical in the mapping into Swift.

Test case adjusted, and common utility functions exposed.

Author: milseman

lib/ClangImporter/ClangImporter.cpp

@@ -2556,23 +2556,16 @@ auto ClangImporter::Implementation::importFullName(
   // swift_newtype-ed declarations may have common words with the type name
   // stripped.
   if (auto newtypeDecl = findSwiftNewtype(D)) {
-    SmallString<32> newNameBuffer;
-    auto newtypeNameWords = camel_case::getWords(newtypeDecl->getName());
-    auto declNameWords = camel_case::getWords(baseName);
-
-    // Scan the decl name, and drop any words that appear in order in the type
-    // name
-    for (auto wI = declNameWords.begin(), skipWI = newtypeNameWords.begin();
-         wI != declNameWords.end(); ++wI) {
-      if (skipWI != newtypeNameWords.end() && *wI == *skipWI) {
-        ++skipWI;
-        continue;
-      }
-      newNameBuffer.append(*wI);
-    }
-
-    if (newNameBuffer.str() != baseName) {
-      baseName = omitNeedlessWordsScratch.copyString(newNameBuffer);
+    // Skip a leading 'k' in a 'kConstant' pattern
+    if (baseName.size() >= 2 && baseName[0] == 'k' &&
+        clang::isUppercase(baseName[1]))
+      baseName.drop_front(1);
+
+    bool nonIdentifier = false;
+    auto pre =
+        getCommonWordPrefix(newtypeDecl->getName(), baseName, nonIdentifier);
+    if (pre.size()) {
+      baseName = baseName.drop_front(pre.size());
       strippedPrefix = true;
     }
   }

lib/ClangImporter/ImportEnumInfo.cpp

@@ -85,8 +85,8 @@ void EnumInfo::classifyEnum(const clang::EnumDecl *decl,
 ///
 /// This is used to derive the common prefix of enum constants so we can elide
 /// it from the Swift interface.
-static StringRef getCommonWordPrefix(StringRef a, StringRef b,
-                                     bool &followedByNonIdentifier) {
+StringRef importer::getCommonWordPrefix(StringRef a, StringRef b,
+                                        bool &followedByNonIdentifier) {
   auto aWords = camel_case::getWords(a), bWords = camel_case::getWords(b);
   auto aI = aWords.begin(), aE = aWords.end(), bI = bWords.begin(),
        bE = bWords.end();
@@ -124,7 +124,8 @@ static StringRef getCommonWordPrefix(StringRef a, StringRef b,
 /// in Cocoa and Cocoa Touch.
 ///
 /// \see getCommonWordPrefix
-static StringRef getCommonPluralPrefix(StringRef singular, StringRef plural) {
+StringRef importer::getCommonPluralPrefix(StringRef singular,
+                                          StringRef plural) {
   assert(!plural.empty());
 
   if (singular.empty())

lib/ClangImporter/ImportEnumInfo.h

@@ -97,6 +97,37 @@ class EnumInfo {
   void determineConstantNamePrefix(ASTContext &ctx, const clang::EnumDecl *);
   void classifyEnum(const clang::EnumDecl *, clang::Preprocessor &);
 };
+
+// Utility functions of primary interest to enum constant naming
+
+/// Returns the common prefix of two strings at camel-case word granularity.
+///
+/// For example, given "NSFooBar" and "NSFooBas", returns "NSFoo"
+/// (not "NSFooBa"). The returned StringRef is a slice of the "a" argument.
+///
+/// If either string has a non-identifier character immediately after the
+/// prefix, \p followedByNonIdentifier will be set to \c true. If both strings
+/// have identifier characters after the prefix, \p followedByNonIdentifier will
+/// be set to \c false. Otherwise, \p followedByNonIdentifier will not be
+/// changed from its initial value.
+///
+/// This is used to derive the common prefix of enum constants so we can elide
+/// it from the Swift interface.
+StringRef getCommonWordPrefix(StringRef a, StringRef b,
+                              bool &followedByNonIdentifier);
+
+/// Returns the common word-prefix of two strings, allowing the second string
+/// to be a common English plural form of the first.
+///
+/// For example, given "NSProperty" and "NSProperties", the full "NSProperty"
+/// is returned. Given "NSMagicArmor" and "NSMagicArmory", only
+/// "NSMagic" is returned.
+///
+/// The "-s", "-es", and "-ies" patterns cover every plural NS_OPTIONS name
+/// in Cocoa and Cocoa Touch.
+///
+/// \see getCommonWordPrefix
+StringRef getCommonPluralPrefix(StringRef singular, StringRef plural);
 }
 }
 

test/IDE/newtype.swift

@@ -11,7 +11,7 @@
 // PRINT-NEXT:    static let one: ErrorDomain
 // PRINT-NEXT:    static let errTwo: ErrorDomain
 // PRINT-NEXT:    static let three: ErrorDomain
-// PRINT-NEXT:    static let four: ErrorDomain
+// PRINT-NEXT:    static let fourErrorDomain: ErrorDomain
 // PRINT-NEXT:    static let stillAMember: ErrorDomain
 // PRINT-NEXT:  }
 // PRINT-NEXT:  struct Foo {
@@ -27,7 +27,7 @@
 // PRINT-NEXT:    let rawValue: NSString
 // PRINT-NEXT:  }
 // PRINT-NEXT:  extension ClosedEnum {
-// PRINT-NEXT:    static let firstEntry: ClosedEnum
+// PRINT-NEXT:    static let firstClosedEntryEnum: ClosedEnum
 // PRINT-NEXT:    static let secondEntry: ClosedEnum
 // PRINT-NEXT:    static let thirdEntry: ClosedEnum
 // PRINT-NEXT:  }