[Ada] Add -gnatX support for casing on discriminated values
gcc/ada/
* exp_ch5.adb (Expand_General_Case_Statement): Add new function
Else_Statements to handle the case of invalid data analogously
to how it is handled when casing on a discrete value.
* sem_case.adb (Has_Static_Discriminant_Constraint): A new
Boolean-valued function.
(Composite_Case_Ops.Scalar_Part_Count): Include discriminants
when traversing components.
(Composite_Case_Ops.Choice_Analysis.Traverse_Discrete_Parts):
Include discriminants when traversing components; the component
range for a constrained discriminant is a single value.
(Composite_Case_Ops.Choice_Analysis.Parse_Choice): Eliminate
Done variable and modify how Next_Part is computed so that it is
always correct (as opposed to being incorrect when Done is
True). This includes changes in Update_Result (a local
procedure). Add new local procedure
Update_Result_For_Box_Component and call it not just for box
components but also for "missing" components (components
associated with an inactive variant).
(Check_Choices.Check_Composite_Case_Selector.Check_Component_Subtype):
Instead of disallowing all discriminated component types, allow
those that are unconstrained or statically constrained. Check
discriminant subtypes along with other component subtypes.
* doc/gnat_rm/implementation_defined_pragmas.rst: Update
documentation to reflect current implementation status.
* gnat_rm.texi: Regenerate.