For review: Fix inappropriate warning message for purity markers.

[Peter Schachte]

I'm on leave through the end of December starting next week, so I may
not be online to respond to comments on this diff until then (though I
may).  I'll wrap this up next year (it's not a terribly significant
bug, anyway).


Fix inappropriate warning message for purity markers.

Estimated hours taken:  0.5

Ripped out code to warn if impurity markers were put before non-atomic
goals.  Such errors are now handled in prog_io_goal.m, and a suitable
error message is printed by typecheck.m.  So the code in purity.m was
vestigial.  It was triggered by implied modes of semipure or impure
goals, because they are turned into conjunctions, which then appear to
have been marked {im,semi}pure.

purity.m:
	Ripped out no-longer-needed error checking code.

Index: purity.m
===================================================================
RCS file: /home/staff/zs/imp/mercury/compiler/purity.m,v
retrieving revision 1.1
diff -u -r1.1 purity.m
--- purity.m	1997/12/09 04:01:33	1.1
+++ purity.m	1997/12/12 06:13:53
@@ -325,7 +325,6 @@
 
 compute_expr_purity(conj(Goals0), conj(Goals), GoalInfo, PredInfo, ModuleInfo,
 		InClosure, Purity, NumErrors0, NumErrors) -->
-	warn_if_body_purity_indicated(GoalInfo, PredInfo, InClosure),
 	compute_goals_purity(Goals0, Goals, PredInfo, ModuleInfo,
 			     InClosure, pure, Purity, NumErrors0, NumErrors).
 compute_expr_purity(call(PredId0,ProcId,Vars,BIState,UContext,Name0),
@@ -362,51 +361,42 @@
 		{ NumErrors = NumErrors0 }
 	).
 compute_expr_purity(HOCall, HOCall, GoalInfo, _, _, InClosure, pure,
-		NumErrors0, NumErrors) -->
-	{ HOCall = higher_order_call(_,_,_,_,_,_) },
-	error_if_body_purity_indicated(GoalInfo, NumErrors0, NumErrors,
-				       InClosure, "higher order goal").
+		NumErrors, NumErrors) -->
+	{ HOCall = higher_order_call(_,_,_,_,_,_) }.
 compute_expr_purity(switch(Var,Canfail,Cases0,Storemap),
 		switch(Var,Canfail,Cases,Storemap), GoalInfo, PredInfo,
 		ModuleInfo, InClosure, Purity, NumErrors0, NumErrors) -->
-	warn_if_body_purity_indicated(GoalInfo, PredInfo, InClosure),
 	compute_cases_purity(Cases0, Cases, PredInfo, ModuleInfo,
 			     InClosure, pure, Purity, NumErrors0, NumErrors).
 compute_expr_purity(Unif0, Unif, GoalInfo, PredInfo, ModuleInfo, InClosure,
 		pure, NumErrors0, NumErrors) -->
 	{ Unif0 = unify(A,RHS0,C,D,E) },
 	{ Unif  = unify(A,RHS,C,D,E) },
-	error_if_body_purity_indicated(GoalInfo, NumErrors0, NumErrors1,
-				       InClosure, "unification"),
 	(   { RHS0 = lambda_goal(F, G, H, I, Goal0 - Info0) } ->
 		{ RHS = lambda_goal(F, G, H, I, Goal - Info0) },
 		compute_expr_purity(Goal0, Goal, Info0, PredInfo, ModuleInfo,
-				    yes, Purity, NumErrors1, NumErrors2),
+				    yes, Purity, NumErrors0, NumErrors1),
 		error_if_closure_impure(GoalInfo, Purity,
-					NumErrors2, NumErrors)
+					NumErrors1, NumErrors)
 	;
 		{ RHS = RHS0 },
 		{ NumErrors = NumErrors0 }
 	).
 compute_expr_purity(disj(Goals0,Store), disj(Goals,Store), GoalInfo, PredInfo,
 		ModuleInfo, InClosure, Purity, NumErrors0, NumErrors) -->
-	warn_if_body_purity_indicated(GoalInfo, PredInfo, InClosure),
 	compute_goals_purity(Goals0, Goals, PredInfo, ModuleInfo,
 			     InClosure, pure, Purity, NumErrors0, NumErrors).
 compute_expr_purity(not(Goal0), not(Goal), GoalInfo, PredInfo, ModuleInfo,
 		InClosure, Purity, NumErrors0, NumErrors) -->
-	warn_if_body_purity_indicated(GoalInfo, PredInfo, InClosure),
 	compute_goal_purity(Goal0, Goal, PredInfo, ModuleInfo, 
 			    InClosure, Purity, NumErrors0, NumErrors).
 compute_expr_purity(some(Vars,Goal0), some(Vars,Goal), GoalInfo, PredInfo,
 		ModuleInfo, InClosure, Purity, NumErrors0, NumErrors) -->
-	warn_if_body_purity_indicated(GoalInfo, PredInfo, InClosure),
 	compute_goal_purity(Goal0, Goal, PredInfo, ModuleInfo, 
 			    InClosure, Purity, NumErrors0, NumErrors).
 compute_expr_purity(if_then_else(Vars,Goali0,Goalt0,Goale0,Store),
 		if_then_else(Vars,Goali,Goalt,Goale,Store), GoalInfo, PredInfo,
 		ModuleInfo, InClosure, Purity, NumErrors0, NumErrors) -->
-	warn_if_body_purity_indicated(GoalInfo, PredInfo, InClosure),
 	compute_goal_purity(Goali0, Goali, PredInfo, ModuleInfo,
 			    InClosure, Purity1, NumErrors0, NumErrors1),
 	compute_goal_purity(Goalt0, Goalt, PredInfo, ModuleInfo,
@@ -613,73 +603,6 @@
 		io__write_string("' is sufficient.\n")
 	).
 	
-
-:- pred warn_if_body_purity_indicated(hlds_goal_info, pred_info, bool,
-	io__state, io__state).
-:- mode warn_if_body_purity_indicated(in, in, in, di, uo) is det.
-
-warn_if_body_purity_indicated(GoalInfo, PredInfo, InClosure) -->
-	(   { InClosure = yes } ->
-		[]
-	;   { code_util__compiler_generated(PredInfo) } ->
-		[]
-	;   { infer_goal_info_purity(GoalInfo, Purity) },
-	    (   { Purity = pure } ->
-		    []
-	    ;	
-		    { goal_info_get_context(GoalInfo, Context) },
-		    prog_out__write_context(Context),
-		    io__write_string("Warning: inappropriate placement of `"),
-		    write_purity(Purity),
-		    io__write_string("' indicator.\n"),
-		    globals__io_lookup_bool_option(verbose_errors,
-						   VerboseErrors),
-		    (   { VerboseErrors = yes } ->
-			    prog_out__write_context(Context),
-			    io__write_string(
-	    "  Impurity indicators only belong before predicate calls.\n")
-		    ;   
-			    []
-		    )
-	    )
-	).
-
-
-
-:- pred error_if_body_purity_indicated(hlds_goal_info, int, int, bool,
-	string, io__state, io__state).
-:- mode error_if_body_purity_indicated(in, in, out, in, in, di, uo) is det.
-
-error_if_body_purity_indicated(GoalInfo, NumErrors0, NumErrors, InClosure,
-		Kind) -->
-	{ infer_goal_info_purity(GoalInfo, Purity) },
-	(   { Purity = pure } ->
-		{ NumErrors = NumErrors0 }
-	;   { InClosure = yes } ->
-		% Don't report purity errors inside a closure
-		{ NumErrors = NumErrors0 }
-	;
-		{ NumErrors is NumErrors0 + 1 },
-		{ goal_info_get_context(GoalInfo, Context) },
-		prog_out__write_context(Context),
-		io__write_string("Error: inappropriate placement of `"),
-		write_purity(Purity),
-		io__write_string("' indicator.\n"),
-		prog_out__write_context(Context),
-		io__write_string("  A "),
-		io__write_string(Kind),
-		io__write_string(" can never be "),
-		write_purity(Purity),
-		io__write_string(".\n"),
-		globals__io_lookup_bool_option(verbose_errors, VerboseErrors),
-		(   { VerboseErrors = yes } ->
-			prog_out__write_context(Context),
-			io__write_string("  Impurity indicators only belong before predicate calls.\n")
-		;   
-			[]
-		)
-	).
-
 
 :- pred error_if_closure_impure(hlds_goal_info, purity, int, int,
 	io__state, io__state).