re PR c++/84768 (ICE with failed class template argument deduction because of invalid...

re PR c++/84768 (ICE with failed class template argument deduction because of invalid template parameter)

/cp
2018-04-03  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/84768
	* pt.c (rewrite_template_parm): If the first argument is
	error_mark_node return it immediately.
	(build_deduction_guide): Check the return value of the
	latter for error_mark_node.
	(do_class_deduction): Check the return value of the latter.

/testsuite
2018-04-03  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/84768
	* g++.dg/cpp1z/class-deduction52.C: New.

From-SVN: r259049