PR c++/67411

	* lambda.c (generic_lambda_fn_p): Split out from...
	(maybe_add_lambda_conv_op): ...here.
	* semantics.c (process_outer_var_ref): Don't defer maybe-constant
	variables in a generic lambda.
	* pt.c (instantiate_non_dependent_or_null): New.
	* init.c (constant_value_1): Use it.
	* cp-tree.h: Declare it and generic_lambda_fn_p.

From-SVN: r231863