Objective-ARC++: infer template type arguments of

ownership-unqualified retainable object type as __strong. This allows
us to write, e.g.,

  std::vector<id>

and we'll infer that the vector's element types have __strong
ownership semantics, which is far nicer than requiring:

  std::vector<__strong id>

Note that we allow one to override the ownership qualifier of a
substituted template type parameter, e.g., given

  template<typename T>
  struct X {
    typedef __weak T type;
  };

X<id> is treated the same as X<__strong id>. At instantiation type,
the __weak in "__weak T" overrides the (inferred or specified)
__strong on the template argument type, so that we can still provide
metaprogramming transformations.

This is part of <rdar://problem/9595486>.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@133303 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 2 deletions

diff --git a/lib/Sema/SemaTemplate.cpp b/lib/Sema/SemaTemplate.cpp
index b8caad8af5..fa2182a2aa 100644
--- a/lib/Sema/SemaTemplate.cpp
+++ b/lib/Sema/SemaTemplate.cpp
@@ -2357,8 +2357,20 @@ bool Sema::CheckTemplateTypeArgument(TemplateTypeParmDecl *Param,
     return true;
 
   // Add the converted template type argument.
-  Converted.push_back(
-                 TemplateArgument(Context.getCanonicalType(Arg.getAsType())));
+  QualType ArgType = Context.getCanonicalType(Arg.getAsType());
+  
+  // Objective-C ARC:
+  //   If an explicitly-specified template argument type is a lifetime type
+  //   with no lifetime qualifier, the __strong lifetime qualifier is inferred.
+  if (getLangOptions().ObjCAutoRefCount &&
+      ArgType->isObjCLifetimeType() &&
+      !ArgType.getObjCLifetime()) {
+    Qualifiers Qs;
+    Qs.setObjCLifetime(Qualifiers::OCL_Strong);
+    ArgType = Context.getQualifiedType(ArgType, Qs);
+  }
+  
+  Converted.push_back(TemplateArgument(ArgType));
   return false;
 }