[m-rev.] for review: Fix MR_named_arg_num for RTTI changes introduced with subtypes.

[Peter Wang]

runtime/mercury_deconstruct.c:
    Use MR_index_or_search_ptag_layout to search du type layouts by
    primary tag and MR_index_or_search_sectag_functor to search
    sectag_alternatives by secondary tag, as required for subtypes.

    (MR_named_arg_num is used by the debugger.)
---
 runtime/mercury_deconstruct.c | 21 ++++++---------------
 1 file changed, 6 insertions(+), 15 deletions(-)

diff --git a/runtime/mercury_deconstruct.c b/runtime/mercury_deconstruct.c
index 7888cefa7..01c104247 100644
--- a/runtime/mercury_deconstruct.c
+++ b/runtime/mercury_deconstruct.c
@@ -127,7 +127,6 @@ MR_named_arg_num(MR_TypeInfo type_info, MR_Word *term_ptr,
     const char *arg_name, int *arg_num_ptr)
 {
     MR_TypeCtorInfo             type_ctor_info;
-    MR_DuTypeLayout             du_type_layout;
     const MR_DuPtagLayout       *ptag_layout;
     const MR_DuFunctorDesc      *functor_desc;
     const MR_NotagFunctorDesc   *notag_functor_desc;
@@ -147,39 +146,28 @@ MR_named_arg_num(MR_TypeInfo type_info, MR_Word *term_ptr,
         case MR_TYPECTOR_REP_DU_USEREQ:
         case MR_TYPECTOR_REP_DU:
             data = *term_ptr;
-            du_type_layout = MR_type_ctor_layout(type_ctor_info).MR_layout_du;
+
             ptag = MR_tag(data);
-            // XXX SUBTYPE cannot index du_type_layout for subtypes
-            ptag_layout = &du_type_layout[ptag];
+            MR_index_or_search_ptag_layout(ptag, ptag_layout);
 
             switch (ptag_layout->MR_sectag_locn) {
                 case MR_SECTAG_NONE:
                 case MR_SECTAG_NONE_DIRECT_ARG:
-                    // We can index MR_sectag_alternatives for
-                    // MR_SECTAG_NONE_*.
-                    functor_desc = ptag_layout->MR_sectag_alternatives[0];
+                    sectag = 0;
                     break;
                 case MR_SECTAG_LOCAL_REST_OF_WORD:
                     sectag = MR_unmkbody(data);
-                    // XXX SUBTYPE cannot index MR_sectag_alternatives
-                    functor_desc = ptag_layout->MR_sectag_alternatives[sectag];
                     break;
                 case MR_SECTAG_LOCAL_BITS:
                     sectag = MR_unmkbody(data) &
                         ((1 << ptag_layout->MR_sectag_numbits) - 1);
-                    // XXX SUBTYPE cannot index MR_sectag_alternatives
-                    functor_desc = ptag_layout->MR_sectag_alternatives[sectag];
                     break;
                 case MR_SECTAG_REMOTE_FULL_WORD:
                     sectag = MR_field(ptag, data, 0);
-                    // XXX SUBTYPE cannot index MR_sectag_alternatives
-                    functor_desc = ptag_layout->MR_sectag_alternatives[sectag];
                     break;
                 case MR_SECTAG_REMOTE_BITS:
                     sectag = MR_field(ptag, data, 0) &
                         ((1 << ptag_layout->MR_sectag_numbits) - 1);
-                    // XXX SUBTYPE cannot index MR_sectag_alternatives
-                    functor_desc = ptag_layout->MR_sectag_alternatives[sectag];
                     break;
                 case MR_SECTAG_VARIABLE:
                     MR_fatal_error("MR_named_arg_num(): unexpected variable");
@@ -187,6 +175,9 @@ MR_named_arg_num(MR_TypeInfo type_info, MR_Word *term_ptr,
                     MR_fatal_error("MR_named_arg_num(): invalid sectag_locn");
             }
 
+            MR_index_or_search_sectag_functor(ptag_layout, sectag,
+                functor_desc);
+
             if (functor_desc->MR_du_functor_arg_names == NULL) {
                 return MR_FALSE;
             }
-- 
2.30.0