PR c++/40619
	* cp-tree.h (struct lang_decl_parm): New.
	(struct lang_decl): Add it.
	(LANG_DECL_PARM_CHECK): New.
	(DECL_PARM_INDEX): New.
	* decl2.c (parm_index): Remove.
	* lex.c (retrofit_lang_decl): Handle parms.
	(cxx_dup_lang_specific_decl): Likewise.
	* mangle.c (write_expression): Adjust.
	* tree.c (cp_tree_equal): Adjust.
	(decl_linkage): Only check DECL_COMDAT for functions and variables.
	* parser.c (cp_parser_parameter_declaration_list): Set
	DECL_PARM_INDEX.
	* pt.c (iterative_hash_template_arg): Hash it.

From-SVN: r149223