Objective-C ARC++: Prefer references to __strong/__weak over __unsafe_unretained.

Fixes <rdar://problem/15713945>.

llvm-svn: 198343

1 files changed, 11 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index d87254483d0..71826d6799b 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -981,6 +981,17 @@ DeduceTemplateArgumentsByTypeMatch(Sema &S,
         Comparison.Qualifiers = ParamMoreQualified;
       else if (ArgQuals.isStrictSupersetOf(ParamQuals))
         Comparison.Qualifiers = ArgMoreQualified;
+      else if (ArgQuals.getObjCLifetime() != ParamQuals.getObjCLifetime() &&
+               ArgQuals.withoutObjCLifetime()
+                 == ParamQuals.withoutObjCLifetime()) {
+        // Prefer binding to non-__unsafe_autoretained parameters.
+        if (ArgQuals.getObjCLifetime() == Qualifiers::OCL_ExplicitNone &&
+            ParamQuals.getObjCLifetime())
+          Comparison.Qualifiers = ParamMoreQualified;
+        else if (ParamQuals.getObjCLifetime() == Qualifiers::OCL_ExplicitNone &&
+                 ArgQuals.getObjCLifetime())
+          Comparison.Qualifiers = ArgMoreQualified;
+      }
       RefParamComparisons->push_back(Comparison);
     }