[Ada] Crash on Loop_Entry for while_loop involving substrings

[Ada] Crash on Loop_Entry for while_loop involving substrings

When expanding a loop entry attribute for a while_loop we construct a
function that incorporates the expanded condition of the loop. The
itypes that may be generated in that expansion must carry the scope of
the constructed function for proper handling in the backend.

2019-08-20  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* exp_attr.adb (Expand_Loop_Entry_Attribute): When expanding a
	loop entry attribute for a while_loop we construct a function
	that incorporates the expanded condition of the loop. The itypes
	that may be generated in that expansion must carry the scope of
	the constructed function for proper handling in gigi.

gcc/testsuite/

	* gnat.dg/loop_entry2.adb: New testcase.

From-SVN: r274734