einfo.ads (Extra_Accessibility_Of_Result): New function...

einfo.ads (Extra_Accessibility_Of_Result): New function...

2011-09-06  Steve Baird  <baird@adacore.com>

	* einfo.ads (Extra_Accessibility_Of_Result): New function; in the
	(Ada2012) cases described in AI05-0234 where the accessibility
	level of a function result is "determined by the point of
	call", an implicit parameter representing that accessibility
	level is passed in. Extra_Accessibilty_Of_Result yields this
	additional formal parameter. Extra_Accessibility_Of_Result
	is analogous to the existing Extra_Accessibility
	function used in the implementation of access parameters.
	(Set_Extra_Accessibility_Of_Result): New procedure; sets
	Extra_Accessibility_Of_Result attribute.
	* einfo.adb (Extra_Accessibility_Of_Result): New function.
	(Set_Extra_Accessibility_Of_Result): New procedure.
	(Write_Field19_Name): Display Extra_Accessibilty_Of_Result attribute.
	* sem_util.adb (Dynamic_Accessibility_Level): Set Etype of
	an accessibility level literal to Natural; introduce a nested
	function, Make_Level_Literal, to do this.
	* exp_ch6.ads (Needs_Result_Accessibility_Level): New function;
	determines whether a given function (or access-to-function
	type) needs to have an implicitly-declared accessibility-level
	parameter added to its profile.
	(Add_Extra_Actual_To_Call): Export an existing procedure which was
	previously declared in the body of Exp_Ch6.
	* exp_ch6.adb (Add_Extra_Actual_To_Call): Export declaration by moving
	it to exp_ch6.ads.
	(Has_Unconstrained_Access_Discriminants): New Function; a
	predicate on subtype entities which returns True if the given
	subtype is unconstrained and has one or more access discriminants.
	(Expand_Call): When expanding a call to a function which takes an
	Extra_Accessibility_Of_Result parameter, pass in the appropriate
	actual parameter value. In the case of a function call which is
	used to initialize an allocator, this may not be possible because
	the Etype of the allocator may not have been set yet. In this
	case, we defer passing in the parameter and handle it later in
	Expand_Allocator_Expression.
	(Expand_Simple_Function_Return): When returning from a function which
	returns an unconstrained subtype having at least one access
	discriminant, generate the accessibility check needed to ensure that
	the function result will not outlive any objects designated by its
	discriminants.
	(Needs_Result_Accessibility_Level): New function; see exp_ch6.ads
	description.
	* exp_ch4.adb (Expand_Allocator_Expression): When a function call
	is used to initialize an allocator, we may need to pass in "the
	accessibility level determined by the point of call" (AI05-0234)
	to the function. Expand_Call, where such actual parameters are
	usually generated, is too early in this case because the Etype of
	the allocator (which is used in determining the level to be passed
	in) may not have been set yet when Expand_Call executes. Instead,
	we generate code to pass in the appropriate actual parameter
	in Expand_Allocator_Expression.
	* sem_ch6.adb (Create_Extra_Formals): Create
	the new Extra_Accessibility_Of_Result formal if
	Needs_Result_Accessibility_Level returns True. This includes the
	introduction of a nested procedure, Check_Against_Result_Level.

From-SVN: r178567