Clang importer: Swift 2 lowercased subsequent argument names coming from Objective-C selectors. Mimic this.

Author: DougGregor

include/swift/Basic/StringExtras.h

@@ -51,6 +51,14 @@ namespace swift {
   /// Determine the part of speech for the given word.
   PartOfSpeech getPartOfSpeech(StringRef word);
 
+  /// Scratch space used for returning a set of StringRefs.
+  class StringScratchSpace {
+    llvm::BumpPtrAllocator Allocator;
+
+  public:
+    StringRef copyString(StringRef string);
+  };
+
   namespace camel_case {
     class WordIterator;
 
@@ -219,6 +227,16 @@ namespace swift {
     /// unchanged.
     StringRef toLowercaseWord(StringRef string, SmallVectorImpl<char> &scratch);
 
+    /// Lowercase the first word within the given camelCase string.
+    ///
+    /// \param string The string to lowercase.
+    /// \param scratch Scratch buffer used to form the resulting string.
+    ///
+    /// \returns the string with the first word lowercased. When the
+    /// first word is an acronym, the string will be returned
+    /// unchanged.
+    StringRef toLowercaseWord(StringRef string, StringScratchSpace &scratch);
+
     /// Sentence-case the given camelCase string by turning the first
     /// letter into an uppercase letter.
     ///
@@ -358,14 +376,6 @@ struct OmissionTypeName {
 /// would produce "ByAppendingString".
 StringRef matchLeadingTypeName(StringRef name, OmissionTypeName typeName);
 
-/// Scratch space used for returning a set of StringRefs.
-class StringScratchSpace {
-  llvm::BumpPtrAllocator Allocator;
-
-public:
-  StringRef copyString(StringRef string);
-};
-
 /// Describes a set of names with an inheritance relationship.
 class InheritedNameSet {
   const InheritedNameSet *Parent;

lib/Basic/StringExtras.cpp

@@ -442,9 +442,10 @@ bool InheritedNameSet::contains(StringRef name) const {
 }
 
 /// Wrapper for camel_case::toLowercaseWord that uses string scratch space.
-static StringRef toLowercaseWord(StringRef string, StringScratchSpace &scratch){
+StringRef camel_case::toLowercaseWord(StringRef string,
+                                      StringScratchSpace &scratch){
   llvm::SmallString<32> scratchStr;
-  StringRef result = camel_case::toLowercaseWord(string, scratchStr);
+  StringRef result = toLowercaseWord(string, scratchStr);
   if (string == result)
     return string;
 

lib/ClangImporter/ClangImporter.cpp

@@ -2150,6 +2150,7 @@ auto ClangImporter::Implementation::importFullName(
   StringRef baseName;
   SmallVector<StringRef, 4> argumentNames;
   SmallString<16> selectorSplitScratch;
+  StringScratchSpace stringScratch;
   ArrayRef<const clang::ParmVarDecl *> params;
   switch (D->getDeclName().getNameKind()) {
   case clang::DeclarationName::CXXConstructorName:
@@ -2205,7 +2206,15 @@ auto ClangImporter::Implementation::importFullName(
       if (index == 0) {
         argumentNames.push_back(StringRef());
       } else {
-        argumentNames.push_back(selector.getNameForSlot(index));
+        StringRef argName = selector.getNameForSlot(index);
+
+        // Swift 2 lowercased all subsequent argument names.
+        // Swift 3 may handle this as part of omitting needless words, below,
+        // but don't preempt that here.
+        if (!OmitNeedlessWords)
+          argName = camel_case::toLowercaseWord(argName, stringScratch);
+
+        argumentNames.push_back(argName);
       }
     }
 

test/IDE/Inputs/swift_name_objc.h

@@ -17,7 +17,7 @@ SWIFT_NAME(SomeClass)
 @interface SNSomeClass : NSObject
 - (instancetype)initWithFloat:(float)f;
 - (instancetype)initWithDefault;
-- (void)instanceMethodWithX:(float)x y:(float)y z:(float)z;
+- (void)instanceMethodWithX:(float)x Y:(float)y Z:(float)z;
 + (instancetype)someClassWithDouble:(double)d;
 + (instancetype)someClassWithTry:(BOOL)shouldTry;
 + (NSObject *)buildWithObject:(NSObject *)object SWIFT_NAME(init(object:));

test/IDE/dump_swift_lookup_tables_objc.swift

@@ -84,7 +84,7 @@
 // CHECK-NEXT:   init(withTry:):
 // CHECK-NEXT:     SNSomeClass: +[SNSomeClass someClassWithTry:]
 // CHECK-NEXT:   instanceMethodWithX(_:y:z:):
-// CHECK-NEXT:     SNSomeClass: -[SNSomeClass instanceMethodWithX:y:z:]
+// CHECK-NEXT:     SNSomeClass: -[SNSomeClass instanceMethodWithX:Y:Z:]
 // CHECK-NEXT:   method():
 // CHECK-NEXT:     NSErrorImports: -[NSErrorImports methodAndReturnError:]
 // CHECK-NEXT:   methodWithFloat(_:):
@@ -95,6 +95,7 @@
 // CHECK-NEXT:     NSAccessibility: -[NSAccessibility setAccessibilityFloat:]
 
 // CHECK-OMIT-NEEDLESS-WORDS: Base -> full name mappings:
+// CHECK-OMIT-NEEDLESS-WORDS:   instanceMethodWithX --> instanceMethodWithX(_:y:z:)
 // CHECK-OMIT-NEEDLESS-WORDS:   methodWith --> methodWith(_:)
 
 // CHECK-OMIT-NEEDLESS-WORDS: Full name -> entry mappings: