[m-rev.] for review: fix singleton variable warning problem

[Peter Ross]

Hi,

For Simon to review.

This solution isn't very elegant but I couldn't think of a better way to fix
it, suggestions welcome.

===================================================================


Estimated hours taken: 4
Branches: main

Avoid a bug where predicates defined in both Mercury and a foreign
language were issuing warnings about underscore variables occuring
more than once.  This is because if the foreign clause appears first
than its varset is used for the names of the variables and hence a
variable could be given an underscore name.

mcpp/compiler/make_hlds.m:
	If a clause has foreign clauses don't check for singleton
	variables.
	
tests/hard_coded/Mmakefile:
tests/hard_coded/no_warn_singleton.exp:
tests/hard_coded/no_warn_singleton.m:
	A test case.

Index: mcpp/compiler/make_hlds.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/make_hlds.m,v
retrieving revision 1.411
diff -u -r1.411 make_hlds.m
--- mcpp/compiler/make_hlds.m	9 May 2002 16:30:55 -0000	1.411
+++ mcpp/compiler/make_hlds.m	28 May 2002 17:02:47 -0000
@@ -3887,7 +3887,10 @@
 		module_info_set_predicate_table(ModuleInfo3, PredicateTable,
 			ModuleInfo)
 		},
-		( { Status \= opt_imported } ->
+		(
+			{ Status \= opt_imported },
+			{ Clauses ^ have_foreign_clauses = no }
+		->
 			% warn about singleton variables 
 			maybe_warn_singletons(VarSet,
 				PredOrFunc - PredName/Arity, ModuleInfo, Goal),
Index: tests/hard_coded/Mmakefile
===================================================================
RCS file: /home/mercury1/repository/tests/hard_coded/Mmakefile,v
retrieving revision 1.144
diff -u -r1.144 Mmakefile
--- tests/hard_coded/Mmakefile	3 Mar 2002 13:45:47 -0000	1.144
+++ tests/hard_coded/Mmakefile	28 May 2002 17:02:47 -0000
@@ -88,6 +88,7 @@
 	name_mangling \
 	no_fully_strict \
 	no_inline \
+	no_warn_singleton \
 	nondet_ctrl_vn \
 	nondet_copy_out \
 	nullary_ho_func \
@@ -238,6 +239,7 @@
 MCFLAGS-intermod_type_qual2 =	--intermodule-optimization
 MCFLAGS-intermod_multimode =	--intermodule-optimization
 MCFLAGS-intermod_multimode_main = --intermodule-optimization
+MCFLAGS-no_warn_singleton =	--halt-at-warn
 MCFLAGS-nondet_copy_out =	--no-inlining --nondet-copy-out
 MCFLAGS-redoip_clobber	=	--no-inlining
 MCFLAGS-rnd		=	-O6
Index: tests/hard_coded/no_warn_singleton.exp
===================================================================
RCS file: tests/hard_coded/no_warn_singleton.exp
diff -N tests/hard_coded/no_warn_singleton.exp
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ tests/hard_coded/no_warn_singleton.exp	28 May 2002 17:02:47 -0000
@@ -0,0 +1 @@
+5
Index: tests/hard_coded/no_warn_singleton.m
===================================================================
RCS file: tests/hard_coded/no_warn_singleton.m
diff -N tests/hard_coded/no_warn_singleton.m
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ tests/hard_coded/no_warn_singleton.m	28 May 2002 17:02:47 -0000
@@ -0,0 +1,25 @@
+% A regression test to ensure that we don't get warnings about the variables
+% _IO0 and _IO occuring more than once.
+:- module no_warn_singleton.
+
+:- interface.
+
+:- import_module io.
+
+:- pred main(io::di, io::uo) is det.
+
+:- implementation.
+
+main -->
+	f(X),
+	io__write_int(X),
+	io__nl.
+
+:- pred f(int::out, io::di, io::uo) is det.
+
+:- pragma foreign_proc("C", f(X::out, _IO0::di, _IO::uo),
+        [will_not_call_mercury, promise_pure], "
+    X = 5;
+").
+
+f(5) --> [].

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