[clang-tidy] Fix some false positives in google-readability-casting

Summary:
Ignore C-style casts in extern "C" {} sections. Be more careful when
detecting redundant casts between typedefs to the same type - emit a more
specific warning and don't automatically fix them.

Reviewers: klimek

Reviewed By: klimek

Subscribers: curdeius, cfe-commits

Differential Revision: http://reviews.llvm.org/D7247

llvm-svn: 227444

1 files changed, 18 insertions, 6 deletions

diff --git a/clang-tools-extra/clang-tidy/google/AvoidCStyleCastsCheck.cpp b/clang-tools-extra/clang-tidy/google/AvoidCStyleCastsCheck.cpp
index 093250d541f..20440fe618c 100644
--- a/clang-tools-extra/clang-tidy/google/AvoidCStyleCastsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/AvoidCStyleCastsCheck.cpp
@@ -68,19 +68,30 @@ void AvoidCStyleCastsCheck::check(const MatchFinder::MatchResult &Result) {
   if (CastExpr->getTypeAsWritten()->isVoidType())
     return;
 
-  QualType SourceType =
-      CastExpr->getSubExprAsWritten()->getType().getCanonicalType();
-  QualType DestType = CastExpr->getTypeAsWritten().getCanonicalType();
+  QualType SourceType = CastExpr->getSubExprAsWritten()->getType();
+  QualType DestType = CastExpr->getTypeAsWritten();
 
   if (SourceType == DestType) {
-    diag(CastExpr->getLocStart(), "Redundant cast to the same type.")
+    diag(CastExpr->getLocStart(), "redundant cast to the same type")
         << FixItHint::CreateRemoval(ParenRange);
     return;
   }
+  SourceType = SourceType.getCanonicalType();
+  DestType = DestType.getCanonicalType();
+  if (SourceType == DestType) {
+    diag(CastExpr->getLocStart(),
+         "possibly redundant cast between typedefs of the same type");
+    return;
+  }
+
 
   // The rest of this check is only relevant to C++.
   if (!Result.Context->getLangOpts().CPlusPlus)
     return;
+  // Ignore code inside extern "C" {} blocks.
+  if (!match(expr(hasAncestor(linkageSpecDecl())), *CastExpr, *Result.Context)
+           .empty())
+    return;
 
   // Leave type spelling exactly as it was (unlike
   // getTypeAsWritten().getAsString() which would spell enum types 'enum X').
@@ -94,7 +105,7 @@ void AvoidCStyleCastsCheck::check(const MatchFinder::MatchResult &Result) {
       diag(CastExpr->getLocStart(), "C-style casts are discouraged. %0");
 
   auto ReplaceWithCast = [&](StringRef CastType) {
-    diag_builder << ("Use " + CastType + ".").str();
+    diag_builder << ("Use " + CastType).str();
 
     const Expr *SubExpr = CastExpr->getSubExprAsWritten()->IgnoreImpCasts();
     std::string CastText = (CastType + "<" + DestTypeString + ">").str();
@@ -108,6 +119,7 @@ void AvoidCStyleCastsCheck::check(const MatchFinder::MatchResult &Result) {
     }
     diag_builder << FixItHint::CreateReplacement(ParenRange, CastText);
   };
+
   // Suggest appropriate C++ cast. See [expr.cast] for cast notation semantics.
   switch (CastExpr->getCastKind()) {
   case CK_NoOp:
@@ -145,7 +157,7 @@ void AvoidCStyleCastsCheck::check(const MatchFinder::MatchResult &Result) {
     break;
   }
 
-  diag_builder << "Use static_cast/const_cast/reinterpret_cast.";
+  diag_builder << "Use static_cast/const_cast/reinterpret_cast";
 }
 
 } // namespace readability