[Ada] Spurious ambiguity error on call returning an access type

[Ada] Spurious ambiguity error on call returning an access type

If F is a function with a single defaulted parameter that returns an
access_to_array type, then F (I) may designate either the return type or
an indexing of the result of the call, after implicit dereferencing.  If
the component type C of the array type AR is accces AR this is ambiguous
in a context whose expected type is C. If F is parameterless the call is
not ambiguous.

2018-08-21  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* sem_res.adb (Resolve_Call): Resolve correctly a parameterless
	call that returns an access type whose designated type is the
	component type of an array, when the function has no defaulted
	parameters.

gcc/testsuite/

	* gnat.dg/access5.adb, gnat.dg/access5.ads: New testcase.

From-SVN: r263726