[Ada] Do not remove side-effects in an others_clause with function calls

[Ada] Do not remove side-effects in an others_clause with function calls

An aggregate can be handled by the backend if it consists of static
constants of an elementary type, or null. If a component is a type
conversion we must preanalyze and resolve it to determine whether the
ultimate value is in one of these categories.  Previously we did a full
analysis and resolution of the expression for the component, which could
lead to a removal of side-effects, which is semantically incorrect if
the expression includes functions with side-effects (e.g. a call to a
random generator).

2019-08-13  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* exp_aggr.adb (Aggr_Assignment_OK_For_Backend):  Preanalyze
	expression, rather do a full analysis, to prevent unwanted
	removal of side effects which mask the intent of the expression.

gcc/testsuite/

	* gnat.dg/aggr27.adb: New testcase.

From-SVN: r274355