Skip parameter replacements where old text != old name.

tools/clang/rewrite_to_chrome_style/RewriteToChromeStyle.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // Changes Blink-style names to Chrome-style names. Currently transforms:
 //   fields:
 //     int m_operationCount => int operation_count_
 //   variables (including parameters):
 //     int mySuperVariable => int my_super_variable
 //   constants:
@@ skipping 324 matching lines @@
 
   return true;
 }
 
 bool GetNameForDecl(const clang::VarDecl& decl,
                     const clang::ASTContext& context,
                     std::string& name) {
   StringRef original_name = decl.getName();
 
   // Nothing to do for unnamed parameters.
-  if (clang::isa<clang::ParmVarDecl>(decl) && original_name.empty())
-    return false;
+  if (clang::isa<clang::ParmVarDecl>(decl)) {
+    if (original_name.empty())
+      return false;
+
+    // Check if |decl| really covers text of |original_name|.  See also
+    // https://llvm.org/bugs/show_bug.cgi?id=29145

[dcheng, 2016/08/26 20:28:02]

Perhaps describe the actual bug a bit here: a method of a templated class is
declared with a param with no name, and the definition has a name, and we
somehow end up trying to replace the parameter in the declaration as well.

Btw, did you try experimenting with checks to determine the SourceLocation is
"in range"? I tried that to and I recall it didn't work... but maybe its' worth
a shot now that we have a test case.

[Łukasz Anforowicz, 2016/08/26 22:39:51]

Done.
Good idea.  I cooked up something that only looks at the AST (checks if source
range of ParmVarDecl's parent contains ParmVarDecl - it doesn't in case of the
bug).

Wanna take one final look?

+    clang::SourceLocation loc =
+        context.getSourceManager().getSpellingLoc(decl.getLocation());
+    clang::CharSourceRange range = clang::CharSourceRange::getTokenRange(loc);
+    StringRef old_text = clang::Lexer::getSourceText(
+        range, context.getSourceManager(), context.getLangOpts());
+    if (old_text != original_name)
+      return false;
+  }
 
   // static class members match against VarDecls. Blink style dictates that
   // these should be prefixed with `s_`, so strip that off. Also check for `m_`
   // and strip that off too, for code that accidentally uses the wrong prefix.
   if (original_name.startswith(kBlinkStaticMemberPrefix))
     original_name = original_name.substr(strlen(kBlinkStaticMemberPrefix));
   else if (original_name.startswith(kBlinkFieldPrefix))
     original_name = original_name.substr(strlen(kBlinkFieldPrefix));
 
   bool is_const = IsProbablyConst(decl, context);
@@ skipping 522 matching lines @@
   for (const auto& r : replacements) {
     std::string replacement_text = r.getReplacementText().str();
     std::replace(replacement_text.begin(), replacement_text.end(), '\n', '\0');
     llvm::outs() << "r:::" << r.getFilePath() << ":::" << r.getOffset()
                  << ":::" << r.getLength() << ":::" << replacement_text << "\n";
   }
   llvm::outs() << "==== END EDITS ====\n";
 
   return 0;
 }