2005-03-17  Thomas Quinot  <quinot@adacore.com>

	* exp_ch3.adb (Check_Attr): New subprogram.
	(Check_Stream_Attribute): Move the code for 13.13.2(9/1) enforcement
	into a new Check_Attr subprogram, in order to provide a more
	explanatory error message (including the name of the missing attribute).
	(Stream_Operation_OK): Renamed from Stream_Operations_OK. This
	subprogram determines whether a default implementation exists for a
	given stream attribute.
	(Make_Predefined_Primitive_Specs, Predefined_Primitive_Bodies):
	Determine whether to generate a default implementation for each stream
	attribute separately, as this depends on the specific attribute.

	* exp_strm.adb (Make_Field_Attribute): For the case of an illegal
	limited extension where a stream attribute is missing for a limited
	component (which will have been flagged in Exp_Ch3.Sem_Attr), do not
	generate a bogus reference to the missing attribute to prevent
	cascaded errors. Instead, generate a null statement.

	* sem_attr.adb (Check_Stream_Attribute): A stream attribute is
	available for a limited type if it has been specified for an ancestor
	of the type.

From-SVN: r96666