PR c++/86993
	* cp-tree.h (cxx_readonly_error): Add location_t argument.
	* typeck2.c (cxx_readonly_error): Add LOC argument, pass it to
	ERROR_FOR_ASSIGNMENT macro and readonly_error.  Add LOC argument
	to ERROR_FOR_ASSIGNMENT macro, use error_at instead of error and
	pass LOC to it.  Formatting fixes.
	* typeck.c (cp_build_unary_op): Pass location to cxx_readonly_error.
	(cp_build_modify_expr): Pass loc to cxx_readonly_error.
	* semantics.c (finish_asm_stmt): Pass input_location to
	cxx_readonly_error.

	* g++.dg/diagnostic/pr86993.C: New test.

From-SVN: r263891