This patch fixes a bug in the handling of use_type_clauses
If a use_type_clause "use type X;" appears in the parent of
a generic child package, and "use type X;" also appears before an
instantiation of that generic child package, the second "use type X;"
is ineffective; the primitive operators of type X are not directly
visible where they should be.
The following test should compile quietly:
package Utl is
type Timerep_T is (Red);
function "+"
(Time : Timerep_T;
Interval : Timerep_T) return Timerep_T;
end Utl;
with Utl;
package Pfw is
use type Utl.Timerep_T;
end Pfw;
generic
package Pfw.Server is
end Pfw.Server;
with Pfw.Server;
with Utl;
package Beacon is
use type Utl.Timerep_T;
package Code_Server_Pkg is new Pfw.Server;
One_Hour : Utl.Timerep_T;
Two_hours : Utl.Timerep_T := One_Hour + One_Hour;
end Beacon;
Tested on x86_64-pc-linux-gnu, committed on trunk
2017-04-25 Bob Duff <d...@adacore.com>
* sem_ch8.adb (Use_One_Type): If a use_type_clause
is redundant, set its Used_Operations to empty. This is only
necessary for use clauses that appear in the parent of a generic
child unit, because those use clauses get reanalyzed when we
instantiate the generic, and we don't want the Used_Operations
carried over from the original context (where it was probably
not redundant).
Index: sem_ch8.adb
===================================================================
--- sem_ch8.adb (revision 247168)
+++ sem_ch8.adb (working copy)
@@ -9200,11 +9200,22 @@
("incomplete type from limited view "
& "cannot appear in use clause", Id);
+ -- If the use clause is redundant, Used_Operations will usually be
+ -- empty, but we need to set it to empty here in one case: If we are
+ -- instantiating a generic library unit, then we install the ancestors
+ -- of that unit in the scope stack, which involves reprocessing use
+ -- clauses in those ancestors. Such a use clause will typically have a
+ -- nonempty Used_Operations unless it was redundant in the generic unit,
+ -- even if it is redundant at the place of the instantiation.
+
+ elsif Redundant_Use (Id) then
+ Set_Used_Operations (Parent (Id), New_Elmt_List);
+
-- If the subtype mark designates a subtype in a different package,
-- we have to check that the parent type is visible, otherwise the
-- use type clause is a noop. Not clear how to do that???
- elsif not Redundant_Use (Id) then
+ else
Set_In_Use (T);
-- If T is tagged, primitive operators on class-wide operands
