backport: re PR c++/90108 (ICE: Segmentation fault (in c_tree_chain_next))

backport: re PR c++/90108 (ICE: Segmentation fault (in c_tree_chain_next))

	Backported from mainline
	2019-04-19  Jakub Jelinek  <jakub@redhat.com>

	PR c++/90108
	* c-decl.c (merge_decls): If remove is main variant and
	DECL_ORIGINAL_TYPE is some other type, remove a DECL_ORIGINAL_TYPE
	variant that has newdecl as TYPE_NAME if any.

	* decl.c (duplicate_decls): If remove is main variant and
	DECL_ORIGINAL_TYPE is some other type, remove a DECL_ORIGINAL_TYPE
	variant that has newdecl as TYPE_NAME if any.

	* c-c++-common/pr90108.c: New test.

From-SVN: r275150