PR c++/77656
	* pt.c (convert_template_argument): Call convert_nontype_argument
	on value-dependent but not type-dependent arguments.
	(convert_nontype_argument): Handle value-dependent arguments.
	(canonicalize_expr_argument): New.
	(deducible_expression, unify): Skip CONVERT_EXPR.
	* error.c (dump_template_argument): Likewise.
	* mangle.c (write_expression): Likewise.

From-SVN: r241425