[m-rev.] Re: for review: check for pred methods with no modes

[Fergus Henderson]

On 25-Apr-2001, Fergus Henderson <fjh at cs.mu.oz.au> wrote:
> Fix a bug where the compiler was silently accepting invalid code.
> 
> doc/reference_manual.texi:
> 	Document that type class methods must have their modes and
> 	determinism explicitly declared.
> 
> compiler/make_hlds.m:
> 	Report errors for predicate type class methods with no modes
> 	or with modes but no determinism.

After further testing, I found that in some cases the compiler was
getting internal errors and (after I fixed that) producing spurious
flow-on error messages.  Hence I made the following additional
changes.  I'll go ahead and commit this now.

--- CHANGES2.old	Sun Apr 29 16:25:54 2001
+++ CHANGES2	Sun Apr 29 16:26:52 2001
@@ -1,5 +1,5 @@
 
-Estimated hours taken: 4
+Estimated hours taken: 6
 Branches: main, release
 
 Fix a bug where the compiler was silently accepting invalid code.
@@ -12,6 +12,12 @@
 	Report errors for predicate type class methods with no modes
 	or with modes but no determinism.
 
+compiler/check_typeclass.m:
+compiler/polymorphism.m:
+	Handle the case where a method has no declared determinism:
+	since make_hlds.m will have already reported the error,
+	we just need to avoid aborting or issuing spurious flow-on errors.
+
 tests/invalid/Mmakefile:
 tests/invalid/typeclass_missing_mode.m:
 tests/invalid/typeclass_missing_mode.err_exp:
@@ -21,6 +27,8 @@
 tests/invalid/typeclass_missing_det.err_exp:
 tests/invalid/typeclass_missing_det_2.m:
 tests/invalid/typeclass_missing_det_2.err_exp:
+tests/invalid/typeclass_missing_det_3.m:
+tests/invalid/typeclass_missing_det_3.err_exp:
 	Add some regression tests.
 

Index: check_typeclass.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/check_typeclass.m,v
retrieving revision 1.39
diff -u -d -u -r1.39 check_typeclass.m
--- check_typeclass.m	2001/01/15 07:15:28	1.39
+++ check_typeclass.m	2001/04/29 06:17:37
@@ -395,11 +395,15 @@
 			(
 				map__lookup(ProcTable, TheProcId, ProcInfo), 
 				proc_info_argmodes(ProcInfo, Modes),
-				proc_info_interface_determinism(ProcInfo, 
-					Detism),
+				% if the determinism declaration on the method
+				% was omitted, then make_hlds.m will have
+				% already issued an error message, so
+				% don't complain here.
+				proc_info_declared_determinism(ProcInfo, 
+					MaybeDetism),
 				proc_info_inst_varset(ProcInfo, InstVarSet),
 				ModesAndDetism = modes_and_detism(Modes,
-						InstVarSet, Detism)
+						InstVarSet, MaybeDetism)
 			)),
 		ProcIds, 
 		ArgModes),
@@ -428,7 +432,7 @@
 				OrderedMethods, Errors, ModuleInfo, QualInfo).
 
 :- type modes_and_detism
-	--->	modes_and_detism(list(mode), inst_varset, determinism).
+	--->	modes_and_detism(list(mode), inst_varset, maybe(determinism)).
 
 :- pred check_instance_pred_procs(class_id, list(tvar), sym_name, pred_markers,
 	hlds_instance_defn, hlds_instance_defn, 
@@ -713,9 +717,9 @@
 	AddProc = lambda([ModeAndDet::in, NewProcId::out,
 			OldPredInfo::in, NewPredInfo::out] is det,
 	(
-		ModeAndDet = modes_and_detism(Modes, InstVarSet, Det),
+		ModeAndDet = modes_and_detism(Modes, InstVarSet, MaybeDet),
 		add_new_proc(OldPredInfo, InstVarSet, PredArity, Modes,
-			yes(Modes), no, yes(Det), Context, address_is_taken,
+			yes(Modes), no, MaybeDet, Context, address_is_taken,
 			NewPredInfo, NewProcId)
 	)),
 	list__map_foldl(AddProc, ArgModes, InstanceProcIds, 
Index: polymorphism.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/polymorphism.m,v
retrieving revision 1.208
diff -u -d -u -r1.208 polymorphism.m
--- polymorphism.m	2001/04/07 14:04:53	1.208
+++ polymorphism.m	2001/04/29 06:10:03
@@ -3318,9 +3318,17 @@
 	(
 		Detism0 = yes(Detism1)
 	->
-		Detism = Detism1
+		Detism = Detism1,
+		ModuleInfo1 = ModuleInfo0
 	;
-		error("missing determinism decl. How did we get this far?")
+		% Omitting the determinism for a method is not allowed.
+		% But make_hlds.m will have already detected and reported
+		% the error.  So here we can just pick some value at random;
+		% hopefully something that won't cause flow-on errors.
+		% We also mark the predicate as invalid, also to avoid
+		% flow-on errors.
+		Detism = nondet,
+		module_info_remove_predid(ModuleInfo0, PredId, ModuleInfo1)
 	),
 
 		% Work out which argument corresponds to the constraint which
@@ -3365,7 +3373,7 @@
 	),
 
 	map__det_update(PredTable0, PredId, PredInfo, PredTable),
-	module_info_set_preds(ModuleInfo0, PredTable, ModuleInfo),
+	module_info_set_preds(ModuleInfo1, PredTable, ModuleInfo),
 
 	ProcNum is ProcNum0 + 1.
 	
Index: ../tests/invalid/typeclass_missing_det_3.m
===================================================================
RCS file: typeclass_missing_det_3.m
diff -N typeclass_missing_det_3.m
--- /dev/null	Wed Apr 11 00:52:25 2001
+++ typeclass_missing_det_3.m	Sun Apr 29 16:21:06 2001
@@ -0,0 +1,20 @@
+% test the case of a type class mode declaration without any determinism,
+% and with an instance declaration in the same module.
+
+:- module typeclass_missing_det_3.
+
+:- interface.
+
+:- implementation.
+
+:- import_module io.
+    
+:- typeclass writeable(T) where [
+    pred write(T::in, io__state::di, io__state::uo)
+].
+    
+:- instance writeable(int) where [
+    (write(V) -->
+        write_string("a"),
+        write_int(V))
+].
Index: ../tests/invalid/typeclass_missing_det_3.err_exp
===================================================================
RCS file: typeclass_missing_det_3.err_exp
diff -N typeclass_missing_det_3.err_exp
--- /dev/null	Wed Apr 11 00:52:25 2001
+++ typeclass_missing_det_3.err_exp	Sun Apr 29 16:28:24 2001
@@ -0,0 +1,4 @@
+typeclass_missing_det_3.m:  1: Warning: interface for module `typeclass_missing_det_3' does not export anything.
+typeclass_missing_det_3.m:013: Error: no determinism declaration for type class method
+typeclass_missing_det_3.m:013:   predicate `typeclass_missing_det_3:write/3'.
+For more information, try recompiling with `-E'.
-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
                                    |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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