[clang-tidy] Ignore incomplete types when determining whether they are expensive...

Summary: IsExpensiveToCopy can return false positives for incomplete types, so ignore them.

All existing ClangTidy tests that depend on this function still pass as the types are complete.

Reviewers: alexfh, aaron.ballman

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D26195

llvm-svn: 286008

diff --git a/clang-tools-extra/clang-tidy/utils/TypeTraits.cpp b/clang-tools-extra/clang-tidy/utils/TypeTraits.cpp
index 03b05d1..88e4a82 100644 (file)
--- a/clang-tools-extra/clang-tidy/utils/TypeTraits.cpp
+++ b/clang-tools-extra/clang-tidy/utils/TypeTraits.cpp
@@ -41,7 +41,7 @@ bool hasDeletedCopyConstructor(QualType Type) {
 
 llvm::Optional<bool> isExpensiveToCopy(QualType Type,
                                        const ASTContext &Context) {
-  if (Type->isDependentType())
+  if (Type->isDependentType() || Type->isIncompleteType())
     return llvm::None;
   return !Type.isTriviallyCopyableType(Context) &&
          !classHasTrivialCopyAndDestroy(Type) &&

diff --git a/clang-tools-extra/test/clang-tidy/performance-unnecessary-value-param.cpp b/clang-tools-extra/test/clang-tidy/performance-unnecessary-value-param.cpp
index e33f449..75c8e10 100644 (file)
--- a/clang-tools-extra/test/clang-tidy/performance-unnecessary-value-param.cpp
+++ b/clang-tools-extra/test/clang-tidy/performance-unnecessary-value-param.cpp
@@ -1,4 +1,4 @@
-// RUN: %check_clang_tidy %s performance-unnecessary-value-param %t
+// RUN: %check_clang_tidy %s performance-unnecessary-value-param %t -- -fix-errors -- --std=c++11
 
 // CHECK-FIXES: #include <utility>
 
@@ -237,3 +237,10 @@ void PositiveConstRefNotMoveAssignable(ExpensiveToCopyType A) {
   ExpensiveToCopyType B;
   B = A;
 }
+
+// Ensure that incomplete types result in an error from the frontend and not a
+// clang-tidy diagnostic about IncompleteType being expensive to copy.
+struct IncompleteType;
+void NegativeForIncompleteType(IncompleteType I) {
+  // CHECK-MESSAGES: [[@LINE-1]]:47: error: variable has incomplete type 'IncompleteType' [clang-diagnostic-error]
+}