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, 0 deletions

diff --git a/docs/AutomaticReferenceCounting.html b/docs/AutomaticReferenceCounting.html
index 3d34ddb310..e7b8f22365 100644
--- a/docs/AutomaticReferenceCounting.html
+++ b/docs/AutomaticReferenceCounting.html
@@ -978,9 +978,23 @@ pointer type.  Such code is still ill-formed.</p>
 to be intentional in template code.</p></div>
 
 </div> <!-- ownership.inference.indirect_parameters -->
+
+<div id="ownership.inference.template_arguments">
+<h1>Template arguments</h1>
+
+<p>If a template argument for a template type parameter is an
+retainable object owner type that does not have an explicit ownership
+qualifier, it is adjusted to have <tt>__strong</tt>
+qualification. This adjustment occurs both regardless of whether the
+template argument was deduced or explicitly specified. </p>
+
+<div class="rationale"><p>Rationale: <tt>__strong</tt> is a useful default for containers (e.g., <tt>std::vector&lt;id&gt;</tt>), which would otherwise require explicit qualification. Moreover, unqualified retainable object pointer types are unlikely to be useful within templates, since they generally need to have a qualifier applied to the before being used.</p></div>
+
+</div> <!-- ownership.inference.template_arguments -->
 </div> <!-- ownership.inference -->
 </div> <!-- ownership -->
 
+
 <div id="family">
 <h1>Method families</h1>