Omit needless words: allow removal of words following a gerund.

Identify gerunds by stripping off the "ing" and looking for a
verb. This lets us transform, e.g., "stringByAppendingString" to
"stringByAppending", since "append" is a verb.

Swift SVN r31660

include/swift/Basic/StringExtras.h

@@ -40,7 +40,8 @@ namespace swift {
   enum class PartOfSpeech {
     Unknown,
     Preposition,
-    Verb
+    Verb,
+    Gerund,
   };
 
   /// Determine the part of speech for the given word.

lib/Basic/StringExtras.cpp

@@ -48,6 +48,31 @@ PartOfSpeech swift::getPartOfSpeech(StringRef word) {
     return PartOfSpeech::Verb;
 #include "PartsOfSpeech.def"
 
+  // Identify gerunds, which always end in "ing".
+  if (word.endswith("ing") && word.size() > 4) {
+    StringRef possibleVerb = word.substr(0, word.size()-3);
+
+    // If what remains is a verb, we have a gerund.
+    if (getPartOfSpeech(possibleVerb) == PartOfSpeech::Verb)
+      return PartOfSpeech::Gerund;
+
+    // Try adding an "e" and look for that as a verb.
+    if (possibleVerb.back() != 'e') {
+      SmallString<16> possibleVerbWithE;
+      possibleVerbWithE += possibleVerb;
+      possibleVerbWithE += 'e';
+      if (getPartOfSpeech(possibleVerbWithE) == PartOfSpeech::Verb)
+        return PartOfSpeech::Gerund;
+    }
+
+    // If there is a repeated letter at the back, drop that second
+    // instance of that letter and try again.
+    unsigned count = possibleVerb.size();
+    if (possibleVerb[count-1] == possibleVerb[count-2] &&
+        getPartOfSpeech(possibleVerb.substr(0, count-1)) == PartOfSpeech::Verb)
+      return PartOfSpeech::Gerund;
+  }
+
   return PartOfSpeech::Unknown;
 }
 
@@ -362,6 +387,7 @@ StringRef swift::omitNeedlessWords(StringRef name, StringRef typeName,
     switch (getPartOfSpeech(*nameWordRevIter)) {
     case PartOfSpeech::Preposition:
     case PartOfSpeech::Verb:
+    case PartOfSpeech::Gerund:
       // Okay to strip off the part of the name that is redundant with
       // type information.
       break;

test/IDE/print_omit_needless_words.swift

@@ -61,6 +61,11 @@
 // Note: don't map base name down to a keyword.
 // CHECK-FOUNDATION: func doSelector(selector: Selector)
 
+// Note: Strip names preceded by a gerund.
+// CHECK-FOUNDATION: func startSquashing(bee: Bee)
+// CHECK-FOUNDATION: func startSoothing(bee: Bee)
+// CHECK-FOUNDATION: func startShopping(bee: Bee)
+
 // Note: class method name stripping result type.
 // CHECK-APPKIT: class func red() -> NSColor
 

test/Inputs/clang-importer-sdk/usr/include/Foundation.h

@@ -868,3 +868,9 @@ __attribute__((availability(macosx,introduced=10.11)))
 @interface NSObject (Silly)
 -(void)doSelector:(SEL)selector;
 @end
+
+@interface Bee (Gerunds)
+- (void)startSquashingBee:(nonnull Bee *)bee;
+- (void)startSoothingBee:(nonnull Bee *)bee;
+- (void)startShoppingBee:(nonnull Bee *)bee;
+@end