Fix loop-convert for const references to containers.

Previously we would use a non-const loop variable in the range-based
loop for:
void f(const std::vector<int> &v) {
  for (size_t i = 0; i < v.size(); ++i) {
Now we use const auto&.

Note that we'll also want to use a copy at least for simple types.

llvm-svn: 248418

1 files changed, 6 insertions, 0 deletions

diff --git a/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp b/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp
index 2c623727119..054e5ce94d9 100644
--- a/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp
@@ -391,6 +391,12 @@ static bool containerIsConst(const Expr *ContainerExpr, bool Dereference) {
         return false;
       CType = CType->getPointeeType();
     }
+    // If VDec is a reference to a container, Dereference is false,
+    // but we still need to check the const-ness of the underlying container
+    // type.
+    if (const auto &RT = CType->getAs<ReferenceType>()) {
+      CType = RT->getPointeeType();
+    }
     return CType.isConstQualified();
   }
   return false;