[ASTMatchers] Allow file-based narrowing matches to work with NestedNameSpecifierLocs.

[dlj]

Summary

The narrowing matchers isExpansionInMainFile, isExpansionInSystemHeader, and
isExpansionInFileMatching work for TypeLocs, but not NestedNameSpecifierLocs.
This changes the matchers to use getSourceRange() to get location information,
which not only works for the previous cases, but also for NNSLocs.

[rsmith]

Please add some test coverage for the NNS case.

include/clang/ASTMatchers/ASTMatchers.h

 ///   class Y {};
 /// \endcode
 ///
-/// Usable as: Matcher<Decl>, Matcher<Stmt>, Matcher<TypeLoc>
+/// Usable as: Matcher<Decl>, Matcher<Stmt>, Matcher<TypeLoc>,
+/// Matcher<NestedNameSpecifierLoc>
 AST_POLYMORPHIC_MATCHER(isExpansionInMainFile,
-                        AST_POLYMORPHIC_SUPPORTED_TYPES(Decl, Stmt, TypeLoc)) {
+                        AST_POLYMORPHIC_SUPPORTED_TYPES(
+                            Decl, Stmt, TypeLoc, NestedNameSpecifierLoc)) {
   auto &SourceManager = Finder->getASTContext().getSourceManager();
   return SourceManager.isInMainFile(
-      SourceManager.getExpansionLoc(Node.getLocStart()));
+      SourceManager.getExpansionLoc(Node.getSourceRange().getBegin()));
 }
 
 /// \brief Matches AST nodes that were expanded within system-header-files.

 ///   class Y {};
 /// \endcode
 ///
-/// Usable as: Matcher<Decl>, Matcher<Stmt>, Matcher<TypeLoc>
+/// Usable as: Matcher<Decl>, Matcher<Stmt>, Matcher<TypeLoc>,
+/// Matcher<NestedNameSpecifierLoc>
 AST_POLYMORPHIC_MATCHER(isExpansionInSystemHeader,
-                        AST_POLYMORPHIC_SUPPORTED_TYPES(Decl, Stmt, TypeLoc)) {
+                        AST_POLYMORPHIC_SUPPORTED_TYPES(
+                            Decl, Stmt, TypeLoc, NestedNameSpecifierLoc)) {
   auto &SourceManager = Finder->getASTContext().getSourceManager();
-  auto ExpansionLoc = SourceManager.getExpansionLoc(Node.getLocStart());
+  auto ExpansionLoc =
+      SourceManager.getExpansionLoc(Node.getSourceRange().getBegin());
   if (ExpansionLoc.isInvalid()) {
     return false;
   }

 ///   class Y {};
 /// \endcode
 ///
-/// Usable as: Matcher<Decl>, Matcher<Stmt>, Matcher<TypeLoc>
+/// Usable as: Matcher<Decl>, Matcher<Stmt>, Matcher<TypeLoc>,
+/// Matcher<NestedNameSpecifierLoc>
 AST_POLYMORPHIC_MATCHER_P(isExpansionInFileMatching,
-                          AST_POLYMORPHIC_SUPPORTED_TYPES(Decl, Stmt, TypeLoc),
+                          AST_POLYMORPHIC_SUPPORTED_TYPES(
+                              Decl, Stmt, TypeLoc, NestedNameSpecifierLoc),
                           std::string, RegExp) {
   auto &SourceManager = Finder->getASTContext().getSourceManager();
-  auto ExpansionLoc = SourceManager.getExpansionLoc(Node.getLocStart());
+  auto ExpansionLoc =
+      SourceManager.getExpansionLoc(Node.getSourceRange().getBegin());
   if (ExpansionLoc.isInvalid()) {
     return false;
   }