Implement C++17 constexpr lambda.

gcc/c-family/
	* c-cppbuiltin.c (c_cpp_builtins): Update __cpp_constexpr for
	C++17 constexpr lambdas.
gcc/cp/
	* class.c (finalize_literal_type_property): Handle lambdas.
	* constexpr.c (is_valid_constexpr_fn): Likewise.  No longer static.
	(explain_invalid_constexpr_fn, cxx_eval_call_expression): Handle
	lambdas.
	(cxx_eval_constant_expression): Handle capture proxy.
	(var_in_constexpr_fn): Don't check for C++14.
	(var_in_maybe_constexpr_fn): New.
	(potential_constant_expression_1): Use it.  Check DECL_EXPR for
	declarations not allowed in constexpr function.
	* decl.c (make_rtl_for_nonlocal_decl): Use var_in_maybe_constexpr_fn.
	(finish_function): Set DECL_DECLARED_CONSTEXPR_P on lambda members.
	* lambda.c (begin_lambda_type): Set CLASSTYPE_LITERAL_P.
	(maybe_add_lambda_conv_op): Clear thunk CALL_EXPR location.
	(lambda_static_thunk_p): New.
	* parser.c (cp_keyword_starts_decl_specifier_p): Add RID_CONSTEXPR.
	(CP_PARSER_FLAGS_ONLY_MUTABLE_OR_CONSTEXPR): New enumerator.
	(cp_parser_decl_specifier_seq): Handle it.
	(cp_parser_lambda_declarator_opt): Use cp_parser_decl_specifier_seq.
	* pt.c (instantiate_class_template_1): Set CLASSTYPE_LITERAL_P.
	(tsubst_copy_and_build) [CALL_EXPR]: Propagate CALL_FROM_THUNK_P.
	* error.c (dump_function_decl): Check TFF_NO_TEMPLATE_BINDINGS.
	(dump_expr) [FUNCTION_DECL]: Pass it.

From-SVN: r239268

1 files changed, 18 insertions, 0 deletions

diff --git a/gcc/cp/lambda.c b/gcc/cp/lambda.c
index 978fa0d..d511185 100644
--- a/gcc/cp/lambda.c
+++ b/gcc/cp/lambda.c
@@ -154,6 +154,11 @@ begin_lambda_type (tree lambda)
   LAMBDA_EXPR_CLOSURE (lambda) = type;
   CLASSTYPE_LAMBDA_EXPR (type) = lambda;
 
+  /* In C++17, assume the closure is literal; we'll clear the flag later if
+     necessary.  */
+  if (cxx_dialect >= cxx1z)
+    CLASSTYPE_LITERAL_P (type) = true;
+
   /* Clear base types.  */
   xref_basetypes (type, /*bases=*/NULL_TREE);
 
@@ -1004,6 +1009,7 @@ maybe_add_lambda_conv_op (tree type)
 			 direct_argvec->address ());
 
   CALL_FROM_THUNK_P (call) = 1;
+  SET_EXPR_LOCATION (call, UNKNOWN_LOCATION);
 
   tree stattype = build_function_type (fn_result, FUNCTION_ARG_CHAIN (callop));
   stattype = (cp_build_type_attribute_variant
@@ -1141,6 +1147,18 @@ maybe_add_lambda_conv_op (tree type)
     --function_depth;
 }
 
+/* True if FN is the static function "_FUN" that gets returned from the lambda
+   conversion operator.  */
+
+bool
+lambda_static_thunk_p (tree fn)
+{
+  return (fn && TREE_CODE (fn) == FUNCTION_DECL
+	  && DECL_ARTIFICIAL (fn)
+	  && DECL_STATIC_FUNCTION_P (fn)
+	  && LAMBDA_TYPE_P (CP_DECL_CONTEXT (fn)));
+}
+
 /* Returns true iff VAL is a lambda-related declaration which should
    be ignored by unqualified lookup.  */