[clang] NFC: NNS getLocalSourceRange user cleanup

This adds a note to the documentation of getLocalSourceRange,
and cleans up one of the users of this function which was
changed in #147835

Author: mizvekov

clang-tools-extra/clangd/FindTarget.cpp

@@ -1040,16 +1040,11 @@ class ExplicitReferenceCollector
     if (auto *S = N.get<Stmt>())
       return refInStmt(S, Resolver);
     if (auto *NNSL = N.get<NestedNameSpecifierLoc>()) {
+      if (auto TL = NNSL->getAsTypeLoc())
+        return refInTypeLoc(NNSL->getAsTypeLoc(), Resolver);
       // (!) 'DeclRelation::Alias' ensures we do not lose namespace aliases.
-      NestedNameSpecifierLoc Qualifier;
-      SourceLocation NameLoc;
-      if (auto TL = NNSL->getAsTypeLoc()) {
-        Qualifier = TL.getPrefix();
-        NameLoc = TL.getNonPrefixBeginLoc();
-      } else {
-        Qualifier = NNSL->getAsNamespaceAndPrefix().Prefix;
-        NameLoc = NNSL->getLocalBeginLoc();
-      }
+      NestedNameSpecifierLoc Qualifier = NNSL->getAsNamespaceAndPrefix().Prefix;
+      SourceLocation NameLoc = NNSL->getLocalBeginLoc();
       return {
           ReferenceLoc{Qualifier, NameLoc, false,
                        explicitReferenceTargets(

clang/include/clang/AST/NestedNameSpecifierBase.h

@@ -361,6 +361,9 @@ class NestedNameSpecifierLoc {
   /// Retrieve the source range covering just the last part of
   /// this nested-name-specifier, not including the prefix.
   ///
+  /// Note that this is the source range of this NestedNameSpecifier chunk,
+  // and for a type this includes the prefix of that type.
+  ///
   /// For example, if this instance refers to a nested-name-specifier
   /// \c \::std::vector<int>::, the returned source range would cover
   /// from "vector" to the last '::'.