[clang-tidy] modernize-pass-by-value bugfix

Modified the clang-tidy PassByValue check. It now stops adding std::move to type which is trivially copyable because that caused the clang-tidy MoveConstArg to complain and revert, thus creating a cycle.

I have also added a lit-style test to verify the bugfix.

This is the bug on bugzilla: https://llvm.org/bugs/show_bug.cgi?id=27731

This is the code review on phabricator: http://reviews.llvm.org/D20365

llvm-svn: 270565

1 files changed, 5 insertions, 0 deletions

diff --git a/clang-tools-extra/clang-tidy/modernize/PassByValueCheck.cpp b/clang-tools-extra/clang-tidy/modernize/PassByValueCheck.cpp
index c727deb7969..b8f83bbd7c1 100644
--- a/clang-tools-extra/clang-tidy/modernize/PassByValueCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/PassByValueCheck.cpp
@@ -181,6 +181,11 @@ void PassByValueCheck::check(const MatchFinder::MatchResult &Result) {
   if (!paramReferredExactlyOnce(Ctor, ParamDecl))
     return;
 
+  // If the parameter is trivial to copy, don't move it. Moving a trivivally
+  // copyable type will cause a problem with misc-move-const-arg
+  if (ParamDecl->getType().isTriviallyCopyableType(*Result.Context)) 
+    return;
+
   auto Diag = diag(ParamDecl->getLocStart(), "pass by value and use std::move");
 
   // Iterate over all declarations of the constructor.