Support rewriting |to##macroArg()| into |To##macroArg()|.

tools/clang/rewrite_to_chrome_style/RewriteToChromeStyle.cpp

Index: tools/clang/rewrite_to_chrome_style/RewriteToChromeStyle.cpp
diff --git a/tools/clang/rewrite_to_chrome_style/RewriteToChromeStyle.cpp b/tools/clang/rewrite_to_chrome_style/RewriteToChromeStyle.cpp
index e142dc2639c45afd7f2c4de72e8e0d8feb3899b8..4d171711b024338d754e0e9b2b81c51c2c1de0f1 100644
--- a/tools/clang/rewrite_to_chrome_style/RewriteToChromeStyle.cpp
+++ b/tools/clang/rewrite_to_chrome_style/RewriteToChromeStyle.cpp
@@ -692,8 +692,49 @@ class RewriterBase : public MatchFinder::MatchCallback {
 
     clang::SourceLocation loc =
         TargetNodeTraits<TargetNode>::GetLoc(GetTargetNode(result));
-    clang::CharSourceRange range = clang::CharSourceRange::getTokenRange(loc);
-    replacements_->emplace(*result.SourceManager, range, new_name);
+
+    if (loc.isMacroID()) {
+      // Try to jump "above" the scratch buffer if |loc| is inside
+      // token##Concatenation.
+      const int kMaxJumps = 5;
+      bool verified_out_of_scratch_space = false;
+      for (int i = 0; i < kMaxJumps && !verified_out_of_scratch_space; i++) {
+        clang::SourceLocation spell = result.SourceManager->getSpellingLoc(loc);
+        verified_out_of_scratch_space =
+            result.SourceManager->getBufferName(spell) != "<scratch space>";

[dcheng, 2016/12/22 21:32:42]

I think I would prefer that we just use the file entry, rather than comparing
against this internal string constant.

(It would be nice to share this helper with the edit tracker code, which I think
we can do just by having the utility helper return a SourceLocation, and having
it not really deal with filenames at all. But we can poke at this in a followup)

[Łukasz Anforowicz, 2016/12/23 00:17:48]

I can't make it work without actually looking at "<scratch space>" string :-(  
I give up?

+        if (!verified_out_of_scratch_space)
+          loc = result.SourceManager->getImmediateMacroCallerLoc(loc);
+      }
+      if (!verified_out_of_scratch_space)
+        return;
+    }
+
+    // If the edit affects only the first character of the identifier, then
+    // narrow down the edit to only this single character.  This is important
+    // for dealing with toFooBar -> ToFooBar method renaming when the method
+    // name is built using macro token concatenation like to##macroArgument - in
+    // this case we should only rewrite "t" -> "T" and leave "o##macroArgument"
+    // untouched.
+    llvm::StringRef expected_old_text = old_name;
+    llvm::StringRef new_text = new_name;
+    if (expected_old_text.substr(1) == new_text.substr(1)) {
+      expected_old_text = expected_old_text.substr(0, 1);
+      new_text = new_text.substr(0, 1);
+    }
+    clang::SourceLocation spell = result.SourceManager->getSpellingLoc(loc);
+    clang::CharSourceRange range = clang::CharSourceRange::getCharRange(
+        spell, spell.getLocWithOffset(expected_old_text.size()));
+
+    // We need to ensure that |actual_old_text| is the same as
+    // |expected_old_text| - it can be different if |actual_old_text| contains
+    // a macro argument (see DEFINE_WITH_TOKEN_CONCATENATION2 in
+    // macros-original.cc testcase).
+    StringRef actual_old_text = clang::Lexer::getSourceText(
+        range, *result.SourceManager, result.Context->getLangOpts());
+    if (actual_old_text != expected_old_text)
+      return;
+
+    replacements_->emplace(*result.SourceManager, range, new_text);
     replacement_names_.emplace(old_name.str(), std::move(new_name));
   }
 
@@ -721,18 +762,6 @@ class DeclRewriterBase : public RewriterBase<TargetNode> {
     // If false, there's no name to be renamed.
     if (!decl->getIdentifier())
       return;
-    clang::SourceLocation decl_loc =
-        TargetNodeTraits<clang::NamedDecl>::GetLoc(*decl);
-    if (decl_loc.isMacroID()) {
-      // Get the location of the spelling of the declaration. If token pasting
-      // was used this will be in "scratch space" and we don't know how to get
-      // from there back to/ the actual macro with the foo##bar text. So just
-      // don't replace in that case.
-      clang::SourceLocation spell =
-          result.SourceManager->getSpellingLoc(decl_loc);
-      if (result.SourceManager->getBufferName(spell) == "<scratch space>")
-        return;
-    }
     clang::ASTContext* context = result.Context;
     std::string new_name;
     if (!GetNameForDecl(*decl, *context, new_name))