[m-rev.] diff: improve error checking for instance decls

[Julien Fischer]

Estimated hours taken: 1
Branches: main, release

Emit an error if abstract instances in the implementation of a module do
not have a corresponding concrete instance.

compiler/check_typeclass.m:
 	Check that abstract instance declarations in the implementation
 	section of a module have a corresponding concrete instance
 	declaration somewhere.  Emit an error if they don't.

tests/invalid/missing_concrete_instance.{m,err_exp}:
 	Extend this test case to cover the above situation.

Julien.

Index: compiler/check_typeclass.m
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/compiler/check_typeclass.m,v
retrieving revision 1.104
diff -u -r1.104 check_typeclass.m
--- compiler/check_typeclass.m	22 Oct 2006 09:14:23 -0000	1.104
+++ compiler/check_typeclass.m	25 Oct 2006 08:47:43 -0000
@@ -891,27 +891,25 @@

  %---------------------------------------------------------------------------%

-    % Check that every abstract instance in the interface of a module
-    % has a corresponding concrete instance in the implementation.
+    % Check that every abstract instance in the module has a
+    % corresponding concrete instance in the implementation.
      %
  :- pred check_for_missing_concrete_instances(module_info::in, module_info::out,
      list(error_spec)::in, list(error_spec)::out) is det.

  check_for_missing_concrete_instances(!ModuleInfo, !Specs) :-
      module_info_get_instance_table(!.ModuleInfo, InstanceTable),
-    % Grab all the abstract instance declarations in the interface of this
-    % module and all the concrete instances defined in the implementation.
+    % Grab all the instance declarations that occur in this module
+    % and partition them into two sets: abstract instance declarations
+    % and concrete instance declarations.
      gather_abstract_and_concrete_instances(InstanceTable,
          AbstractInstances, ConcreteInstances),
      map.foldl(check_for_corresponding_instances(ConcreteInstances),
          AbstractInstances, !Specs).

-    % gather_abstract_and_concrete_instances(Table,
-    %   AbstractInstances, ConcreteInstances).
-    %
      % Search the instance_table and create a table of abstract
-    % instances that occur in the module interface and a table of
-    % concrete instances that occur in the module implementation.
+    % instances that occur in the module and a table of concrete
+    % instances that occur in the module.
      % Imported instances are not included at all.
      %
  :- pred gather_abstract_and_concrete_instances(instance_table::in,
@@ -923,10 +921,8 @@
          multi_map.init, Abstracts, multi_map.init, Concretes).

      % Partition all the non-imported instances for a particular
-    % class into two groups, those that are abstract and in the
-    % module interface and those that are concrete and in the module
-    % implementation.  Concrete instances cannot occur in the
-    % interface and we ignore abstract instances in the implementation.
+    % class into two groups, those that are abstract and those that
+    % are concrete.
      %
  :- pred partition_instances_for_class(class_id::in,
      list(hlds_instance_defn)::in, instance_table::in, instance_table::out,
@@ -949,13 +945,7 @@
          Body = InstanceDefn ^ instance_body,
          (
              Body = instance_body_abstract,
-            IsExported = status_is_exported_to_non_submodules(ImportStatus),
-            (
-                IsExported = yes,
-                svmulti_map.add(ClassId, InstanceDefn, !Abstracts)
-            ;
-                IsExported = no
-            )
+            svmulti_map.add(ClassId, InstanceDefn, !Abstracts)
          ;
              Body = instance_body_concrete(_),
              svmulti_map.add(ClassId, InstanceDefn, !Concretes)
Index: tests/invalid/missing_concrete_instance.err_exp
===================================================================
RCS file: /home/mercury/mercury1/repository/tests/invalid/missing_concrete_instance.err_exp,v
retrieving revision 1.2
diff -u -r1.2 missing_concrete_instance.err_exp
--- tests/invalid/missing_concrete_instance.err_exp	14 Sep 2005 05:26:48 -0000	1.2
+++ tests/invalid/missing_concrete_instance.err_exp	25 Oct 2006 08:44:36 -0000
@@ -2,3 +2,7 @@
  missing_concrete_instance.m:011:   `missing_concrete_instance.foo(int)' has no
  missing_concrete_instance.m:011:   corresponding concrete instance in the
  missing_concrete_instance.m:011:   implementation.
+missing_concrete_instance.m:015: Error: abstract instance declaration for
+missing_concrete_instance.m:015:   `missing_concrete_instance.foo(float)' has
+missing_concrete_instance.m:015:   no corresponding concrete instance in the
+missing_concrete_instance.m:015:   implementation.
Index: tests/invalid/missing_concrete_instance.m
===================================================================
RCS file: /home/mercury/mercury1/repository/tests/invalid/missing_concrete_instance.m,v
retrieving revision 1.1
diff -u -r1.1 missing_concrete_instance.m
--- tests/invalid/missing_concrete_instance.m	13 Apr 2005 07:41:28 -0000	1.1
+++ tests/invalid/missing_concrete_instance.m	25 Oct 2006 08:44:10 -0000
@@ -9,3 +9,7 @@
  :- typeclass foo(T) where [].

  :- instance foo(int).
+
+:- implementation.
+
+:- instance foo(float).

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