[m-rev.] for review: do not allow non-abstract instance decls in interfaces

[Julien Fischer]

For review by anyone.

Estimated hours taken: 2
Branches: main, release

Fix a long standing problem where the compiler would accept
non-abstract instance declarations in module interfaces, despite
the reference manual disallowing these.

compiler/modules.m:
	Emit an error message when a non-abstract instance
	declaration occurs in a module interface.

tests/invalid/Mmakefile:
tests/invalid/instance_bug.m:
tests/invalid/instance_bug.err_exp:
	Test case for the above.

Julien.

Workspace:/home/swordfish/juliensf/ws75
Index: compiler/modules.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/modules.m,v
retrieving revision 1.325
diff -u -r1.325 modules.m
--- compiler/modules.m	11 Apr 2005 02:50:58 -0000	1.325
+++ compiler/modules.m	11 Apr 2005 03:41:26 -0000
@@ -463,7 +463,9 @@
     % - report an error if the `implementation' section of a sub-module
     %   is contained inside the `interface' section of its parent module
     % - check for modules declared as both nested and separate sub-modules.
-
+    % - check for non-abstract typeclass instance declarations in module
+    %   interfaces.
+    %
 :- type module_list == list(pair(module_name, item_list)).

 :- pred split_into_submodules(module_name::in, item_list::in, module_list::out,
@@ -6797,6 +6799,7 @@
     InParentInterface = no,
     split_into_submodules_2(ModuleName, Items0, InParentInterface,
         Items, ModuleList, !IO),
+
     %
     % Check that there are no items after the end_module declaration.
     %
@@ -6896,11 +6899,11 @@
         %
         ( Item = module_defn(_, interface) - _Context ->
             InInterface1 = yes
-        ; Item = module_defn(_, implementation) - Context ->
+        ; Item = module_defn(_, implementation) - ImplContext ->
             (
                 InParentInterface = yes,
-                report_error_implementation_in_interface(ModuleName, Context,
-                    !IO)
+                report_error_implementation_in_interface(ModuleName,
+                    ImplContext, !IO)
             ;
                 InParentInterface = no
             ),
@@ -6909,6 +6912,20 @@
             InInterface1 = InInterface0
         ),
         %
+        % Check to make sure that a non-abstract instance declaration
+        % does not occur in a module interface.
+        %
+        (
+            InInterface1 = yes,
+            Item = instance(_, _, _, Body, _, _) - InstanceContext,
+            Body \= abstract
+        ->
+            report_non_abstract_instance_in_interface(InstanceContext, !IO)
+        ;
+            true
+        ),
+
+        %
         % parse the remaining items for this module,
         %
         split_into_submodules_3(ModuleName, Items1,
@@ -7019,6 +7036,15 @@

 report_items_after_end_module(Context, !IO) :-
     ErrorPieces = [words("Error: item(s) after end_module declaration.")],
+    write_error_pieces(Context, 0, ErrorPieces, !IO),
+    io.set_exit_status(1, !IO).
+
+:- pred report_non_abstract_instance_in_interface(prog_context::in,
+    io::di, io::uo) is det.
+
+report_non_abstract_instance_in_interface(Context, !IO) :-
+    ErrorPieces = [words("Error: non-abstract instance declaration"),
+        words("in module interface.")],
     write_error_pieces(Context, 0, ErrorPieces, !IO),
     io.set_exit_status(1, !IO).

Index: tests/invalid/Mmakefile
===================================================================
RCS file: /home/mercury1/repository/tests/invalid/Mmakefile,v
retrieving revision 1.161
diff -u -r1.161 Mmakefile
--- tests/invalid/Mmakefile	6 Apr 2005 05:08:08 -0000	1.161
+++ tests/invalid/Mmakefile	11 Apr 2005 03:36:49 -0000
@@ -85,6 +85,7 @@
 	impure_method_impl \
 	inline_conflict \
 	inst_list_dup \
+	instance_bug \
 	invalid_export_detism \
 	invalid_import_detism \
 	invalid_main \
Index: tests/invalid/instance_bug.err_exp
===================================================================
RCS file: tests/invalid/instance_bug.err_exp
diff -N tests/invalid/instance_bug.err_exp
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ tests/invalid/instance_bug.err_exp	11 Apr 2005 03:37:43 -0000
@@ -0,0 +1,3 @@
+instance_bug.m:009: Error: non-abstract instance declaration in module
+instance_bug.m:009:   interface.
+For more information, try recompiling with `-E'.
Index: tests/invalid/instance_bug.m
===================================================================
RCS file: tests/invalid/instance_bug.m
diff -N tests/invalid/instance_bug.m
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ tests/invalid/instance_bug.m	11 Apr 2005 03:36:21 -0000
@@ -0,0 +1,18 @@
+:- module instance_bug.
+
+:- interface.
+
+:- typeclass foo(T) where [
+	func id(T) = T
+].
+	% Compiler should complain about this.
+:- instance foo(int) where [
+	id(X) = X
+].
+
+:- implementation.
+
+	% Compiler shouldn't complain about this.
+:- instance foo(float) where [
+	id(X) = X
+].

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