C++ PATCH for c++/35255 (address of template-id)

C++ PATCH for c++/35255 (address of template-id)

[Jason Merrill]

Per DR 115, if the context of a template-id doesn't give enough type 
information to resolve it and the template-id fully resolves exactly one 
specialization, we should use that one.  The code in 
resolve_overloaded_unification was trying to do this, but was failing to 
handle the case where there are additional templates that aren't fully 
resolved.

Tested x86_64-pc-linux-gnu, applying to trunk.

Re: C++ PATCH for c++/35255 (address of template-id)

[Diego Novillo]

On Thu, Jun 23, 2011 at 22:10, Jason Merrill <jason@redhat.com> wrote:
> Per DR 115, if the context of a template-id doesn't give enough type
> information to resolve it and the template-id fully resolves exactly one
> specialization, we should use that one.  The code in
> resolve_overloaded_unification was trying to do this, but was failing to
> handle the case where there are additional templates that aren't fully
> resolved.
>
> Tested x86_64-pc-linux-gnu, applying to trunk.

Patch missing.

Re: C++ PATCH for c++/35255 (address of template-id)

[Jason Merrill]

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On 06/24/2011 08:33 AM, Diego Novillo wrote:
> Patch missing.

Oopt.

[-- Attachment #2: 35255.patch --]
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commit 124387ceea38a3c0204c9f91d17bbfa68063d42e
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Jun 22 16:07:10 2011 -0400

    	PR c++/35255
    	* pt.c (resolve_overloaded_unification): Fix DR 115 handling.

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 08ce5af..b3dd85f 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -14524,6 +14524,7 @@ resolve_overloaded_unification (tree tparms,
 	 the affected templates before we try to unify, in case the
 	 explicit args will completely resolve the templates in question.  */
 
+      int ok = 0;
       tree expl_subargs = TREE_OPERAND (arg, 1);
       arg = TREE_OPERAND (arg, 0);
 
@@ -14538,7 +14539,7 @@ resolve_overloaded_unification (tree tparms,
 	  ++processing_template_decl;
 	  subargs = get_bindings (fn, DECL_TEMPLATE_RESULT (fn),
 				  expl_subargs, /*check_ret=*/false);
-	  if (subargs)
+	  if (subargs && !any_dependent_template_arguments_p (subargs))
 	    {
 	      elem = tsubst (TREE_TYPE (fn), subargs, tf_none, NULL_TREE);
 	      if (try_one_overload (tparms, targs, tempargs, parm,
@@ -14549,8 +14550,16 @@ resolve_overloaded_unification (tree tparms,
 		  ++good;
 		}
 	    }
+	  else if (subargs)
+	    ++ok;
 	  --processing_template_decl;
 	}
+      /* If no templates (or more than one) are fully resolved by the
+	 explicit arguments, this template-id is a non-deduced context; it
+	 could still be OK if we deduce all template arguments for the
+	 enclosing call through other arguments.  */
+      if (good != 1)
+	good = ok;
     }
   else if (TREE_CODE (arg) != OVERLOAD
 	   && TREE_CODE (arg) != FUNCTION_DECL)
diff --git a/gcc/testsuite/g++.dg/template/partial10.C b/gcc/testsuite/g++.dg/template/partial10.C
new file mode 100644
index 0000000..53a48fb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/partial10.C
@@ -0,0 +1,18 @@
+// PR c++/35255, DR 115
+// { dg-do link }
+
+// 14.8.1: In contexts where deduction is done and fails, or in contexts
+// where deduction is not done, if a template argument list is specified
+// and it, along with any default template arguments, identifies a single
+// function template specialization, then the template-id is an lvalue for
+// the function template specialization.
+
+template <class Fn> void def(Fn fn) {}
+
+template <class T1, class T2> T2 fn(T1, T2);
+template <class T1> int fn(T1) { }
+
+int main()
+{
+  def(fn<int>);
+}
diff --git a/gcc/testsuite/g++.dg/template/partial11.C b/gcc/testsuite/g++.dg/template/partial11.C
new file mode 100644
index 0000000..b5ceaa8
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/partial11.C
@@ -0,0 +1,24 @@
+// DR 115
+
+// 14.8.1: In contexts where deduction is done and fails, or in contexts
+// where deduction is not done, if a template argument list is specified
+// and it, along with any default template arguments, identifies a single
+// function template specialization, then the template-id is an lvalue for
+// the function template specialization.
+
+// Here, deduction is not done to resolve fn<int> because the target type
+// is a template parameter, so we resolve to the second template, and then
+// the call to def fails because we deduce different values of Fn for the
+// two function arguments.
+
+template <class Fn> void def(Fn fn, Fn fn2);
+
+template <class T1, class T2> T2 fn(T1, T2);
+template <class T1> int fn(T1);
+
+int f(int,int);
+
+int main()
+{
+  def(fn<int>,f);		// { dg-error "" }
+}