Skip parameter replacements where old text != old name.

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 dddccd1741bb968b0c99fec10af2bda8a3a5ec5a..596c1582e84f408e7836bdd418fc5227085ceea4 100644
--- a/tools/clang/rewrite_to_chrome_style/RewriteToChromeStyle.cpp
+++ b/tools/clang/rewrite_to_chrome_style/RewriteToChromeStyle.cpp
@@ -342,8 +342,20 @@ bool GetNameForDecl(const clang::VarDecl& decl,
   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_`