For an object X of a composite type, the attribute X'Valid_Scalars should
return False if and only if there exists at least one invalid scalar
subcomponent of X. The validity test for a scalar part may include a
range test. In some cases involving a private type that is implemented as
a signed integer type, this range test was incorrectly implemented using
unsigned comparisons. For an enclosing object X, this could result in
X'Valid_Scalars yielding the wrong Boolean result. Such an incorrect
result would almost always be False, although an incorrect True result is
theoretically possible (this would require that both bounds of the
component subtype are negative and that the invalid component has a positive
value).

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

	* exp_attr.adb
	(Make_Range_Test): In determining which subtype's First and Last
	attributes are to be queried as part of a range test, call
	Validated_View in order to get a scalar (as opposed to private)
	subtype.
	(Attribute_Valid): In determining whether to perform a signed or
	unsigned comparison for a range test, call Validated_View in order
	to get a scalar (as opposed to private) type. Also correct a typo
	which, by itself, is the source of the problem reported for this
	ticket.