Omit needless words: only omit words when they are preceded by a verb or preposition.

The presence of a verb or preposition prior to the redundant part
provides a firm linguistic split that lets the actual argument fill in
for the reader. For other parts of speech (adjectives, especially)
it's awkward to transition from "reading part of the name" to "reading
the argument". This eliminates a significant number of bad omissions,
e.g., "setTextColor()" -> "setText()", and generally makes the
transformation more conservative.

Swift SVN r31656

lib/Basic/StringExtras.cpp

@@ -33,11 +33,24 @@ PrepositionKind swift::getPrepositionKind(StringRef word) {
 #define PREPOSITION(Word)                       \
   if (word.equals_lower(#Word))                 \
     return PK_Nondirectional;
-#include "Prepositions.def"
+#include "PartsOfSpeech.def"
 
   return PK_None;
 }
 
+PartOfSpeech swift::getPartOfSpeech(StringRef word) {
+  // FIXME: This implementation is woefully inefficient.
+#define PREPOSITION(Word)                       \
+  if (word.equals_lower(#Word))                 \
+    return PartOfSpeech::Preposition;
+#define VERB(Word)                              \
+  if (word.equals_lower(#Word))                 \
+    return PartOfSpeech::Verb;
+#include "PartsOfSpeech.def"
+
+  return PartOfSpeech::Unknown;
+}
+
 void WordIterator::computeNextPosition() const {
   assert(Position < String.size() && "Already at end of string");
 
@@ -343,6 +356,22 @@ StringRef swift::omitNeedlessWords(StringRef name, StringRef typeName,
     return name;
   }
 
+  if (role != NameRole::Property) {
+    // Classify the part of speech of the word before the type
+    // information we would strip off.
+    switch (getPartOfSpeech(*nameWordRevIter)) {
+    case PartOfSpeech::Preposition:
+    case PartOfSpeech::Verb:
+      // Okay to strip off the part of the name that is redundant with
+      // type information.
+      break;
+
+    case PartOfSpeech::Unknown:
+      // Assume it's a noun or adjective; don't strip anything.
+      return name;
+    }
+  }
+
   // Go back to the last matching word and chop off the name at that
   // point.
   StringRef newName = name.substr(0, nameWordRevIter.base().getPosition());
@@ -371,7 +400,7 @@ bool swift::omitNeedlessWords(StringRef &baseName,
         return false;
 
       StringRef oldBaseName = baseName;
-      baseName = omitNeedlessWords(baseName, typeName, NameRole::BaseName);
+      baseName = omitNeedlessWords(baseName, typeName, NameRole::Property);
       return baseName != oldBaseName;
     }