ada: Fix internal error on concatenation of discriminant-dependent component

This only occurs with optimization enabled, but the expanded code is always
wrong because it reuses the formal parameter of an initialization procedure
associated with a discriminant (a discriminal in GNAT parlance) outside of
the initialization procedure.

gcc/ada/

	* checks.adb (Selected_Length_Checks.Get_E_Length): For a
	component of a record with discriminants and if the expression is
	a selected component, try to build an actual subtype from its
	prefix instead of from the discriminal.

1 files changed, 9 insertions, 1 deletions

diff --git a/gcc/ada/checks.adb b/gcc/ada/checks.adb
index 2fb750c..5d7f4cc 100644
--- a/gcc/ada/checks.adb
+++ b/gcc/ada/checks.adb
@@ -9861,7 +9861,15 @@ package body Checks is
          if Ekind (Scope (E)) = E_Record_Type
            and then Has_Discriminants (Scope (E))
          then
-            N := Build_Discriminal_Subtype_Of_Component (E);
+            --  If the expression is a selected component, in other words,
+            --  has a prefix, then build an actual subtype from the prefix.
+            --  Otherwise, build an actual subtype from the discriminal.
+
+            if Nkind (Expr) = N_Selected_Component then
+               N := Build_Actual_Subtype_Of_Component (E, Expr);
+            else
+               N := Build_Discriminal_Subtype_Of_Component (E);
+            end if;
 
             if Present (N) then
                Insert_Action (Expr, N);