[PATCH 1/3] [lambda] Support template-parameter-list in lambda-declarator.

[Adam Butcher]

---
 gcc/cp/decl2.c  |  5 +++--
 gcc/cp/lambda.c |  9 ++++++++-
 gcc/cp/parser.c | 36 ++++++++++++++++++++++++++++++++++--
 gcc/cp/pt.c     |  4 +++-
 4 files changed, 48 insertions(+), 6 deletions(-)

diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index 1573ced..c166f6e 100644
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -507,8 +507,9 @@ check_member_template (tree tmpl)
       || (TREE_CODE (decl) == TYPE_DECL
 	  && MAYBE_CLASS_TYPE_P (TREE_TYPE (decl))))
     {
-      /* The parser rejects template declarations in local classes.  */
-      gcc_assert (!current_function_decl);
+      /* The parser rejects template declarations in local classes
+	 (with the exception of generic lambdas).  */
+      gcc_assert (!current_function_decl || LAMBDA_FUNCTION_P (decl));
       /* The parser rejects any use of virtual in a function template.  */
       gcc_assert (!(TREE_CODE (decl) == FUNCTION_DECL
 		    && DECL_VIRTUAL_P (decl)));
diff --git a/gcc/cp/lambda.c b/gcc/cp/lambda.c
index a53e692..98a7925 100644
--- a/gcc/cp/lambda.c
+++ b/gcc/cp/lambda.c
@@ -196,7 +196,7 @@ lambda_function (tree lambda)
 			  /*protect=*/0, /*want_type=*/false,
 			  tf_warning_or_error);
   if (lambda)
-    lambda = BASELINK_FUNCTIONS (lambda);
+    lambda = STRIP_TEMPLATE (get_first_fn (lambda));
   return lambda;
 }
 
@@ -759,6 +759,13 @@ maybe_add_lambda_conv_op (tree type)
   if (processing_template_decl)
     return;
 
+  if (DECL_TEMPLATE_INFO (callop) && DECL_TEMPLATE_RESULT
+        (DECL_TI_TEMPLATE (callop)) == callop)
+    {
+      warning (0, "Conversion of a generic lambda to a function pointer is not currently implemented.");
+      return;
+    }
+
   if (DECL_INITIAL (callop) == NULL_TREE)
     {
       /* If the op() wasn't instantiated due to errors, give up.  */
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 4b683bf..48c95e6 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -8790,6 +8790,7 @@ cp_parser_lambda_introducer (cp_parser* parser, tree lambda_expr)
 /* Parse the (optional) middle of a lambda expression.
 
    lambda-declarator:
+     < template-parameter-list [opt] >
      ( parameter-declaration-clause [opt] )
        attribute-specifier [opt]
        mutable [opt]
@@ -8809,10 +8810,32 @@ cp_parser_lambda_declarator_opt (cp_parser* parser, tree lambda_expr)
   tree param_list = void_list_node;
   tree attributes = NULL_TREE;
   tree exception_spec = NULL_TREE;
+  tree template_param_list = NULL_TREE;
   tree t;
 
-  /* The lambda-declarator is optional, but must begin with an opening
-     parenthesis if present.  */
+  /* The template-parameter-list is optional, but must begin with
+     an opening angle if present.  */
+  if (cp_lexer_next_token_is (parser->lexer, CPP_LESS))
+    {
+      cp_lexer_consume_token (parser->lexer);
+
+      if (cxx_dialect < cxx1y)
+	cp_parser_error (parser,
+			 "Generic lambdas are only supported in C++1y mode.");
+
+      push_deferring_access_checks (dk_deferred);
+
+      template_param_list = cp_parser_template_parameter_list (parser);
+
+      cp_parser_skip_to_end_of_template_parameter_list (parser);
+
+      /* We just processed one more parameter list.  */
+      ++parser->num_template_parameter_lists;
+    }
+
+  /* The parameter-declaration-clause is optional (unless
+     template-parameter-list was given), but must begin with an
+     opening parenthesis if present.  */
   if (cp_lexer_next_token_is (parser->lexer, CPP_OPEN_PAREN))
     {
       cp_lexer_consume_token (parser->lexer);
@@ -8858,6 +8881,8 @@ cp_parser_lambda_declarator_opt (cp_parser* parser, tree lambda_expr)
 
       leave_scope ();
     }
+  else if (template_param_list != NULL_TREE) // generate diagnostic
+    cp_parser_require (parser, CPP_OPEN_PAREN, RT_OPEN_PAREN);
 
   /* Create the function call operator.
 
@@ -8901,6 +8926,13 @@ cp_parser_lambda_declarator_opt (cp_parser* parser, tree lambda_expr)
 	DECL_ARTIFICIAL (fco) = 1;
 	/* Give the object parameter a different name.  */
 	DECL_NAME (DECL_ARGUMENTS (fco)) = get_identifier ("__closure");
+	if (template_param_list)
+	  {
+	    pop_deferring_access_checks ();
+	    fco = finish_member_template_decl (fco);
+	    finish_template_decl (template_param_list);
+	    --parser->num_template_parameter_lists;
+	  }
       }
 
     finish_member_declaration (fco);
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index de054ac..3694ccc 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -9028,7 +9028,9 @@ instantiate_class_template_1 (tree type)
       tree decl = lambda_function (type);
       if (decl)
 	{
-	  instantiate_decl (decl, false, false);
+	  if (!DECL_TEMPLATE_INFO (decl) || DECL_TEMPLATE_RESULT
+	      (DECL_TI_TEMPLATE (decl)) != decl)
+	    instantiate_decl (decl, false, false);
 
 	  /* We need to instantiate the capture list from the template
 	     after we've instantiated the closure members, but before we
-- 
1.8.3