[m-rev.] for review: Allow pred or func containing coerce to be opt-exported.

[Peter Wang]

compiler/intermod.m:
    Make the presence of a coerce goal not disqualify a predicate or
    function from being written out to a .opt file.

compiler/hlds_out_goal.m:
    Write coerce goal using function call syntax "X = coerce(Y)".
    instead of predicate call syntax "coerce(X, Y)".

diff --git a/compiler/hlds_out_goal.m b/compiler/hlds_out_goal.m
index 3a4c437ae..1ffc54747 100644
--- a/compiler/hlds_out_goal.m
+++ b/compiler/hlds_out_goal.m
@@ -1522,10 +1522,12 @@ write_goal_generic_call(Info, Stream, _ModuleInfo, VarSet, _TypeQual,
     ;
         (
             GenericCall = cast(CastType),
-            CastTypeString = cast_type_to_string(CastType)
+            CastTypeString = cast_type_to_string(CastType),
+            PredOrFunc = pf_predicate
         ;
             GenericCall = subtype_coerce,
-            CastTypeString = "coerce"
+            CastTypeString = "coerce",
+            PredOrFunc = pf_function
         ),
         ( if string.contains_char(DumpOptions, 'l') then
             write_indent(Stream, Indent, !IO),
@@ -1544,12 +1546,25 @@ write_goal_generic_call(Info, Stream, _ModuleInfo, VarSet, _TypeQual,
         else
             true
         ),
-        Functor = term.atom(CastTypeString),
-        term.var_list_to_term_list(ArgVars, ArgTerms),
-        term.context_init(Context),
-        Term = term.functor(Functor, ArgTerms, Context),
-        write_indent(Stream, Indent, !IO),
-        mercury_output_term(VarSet, VarNamePrint, Term, Stream, !IO),
+        (
+            PredOrFunc = pf_predicate,
+            Functor = term.atom(CastTypeString),
+            term.var_list_to_term_list(ArgVars, ArgTerms),
+            term.context_init(Context),
+            Term = term.functor(Functor, ArgTerms, Context),
+            write_indent(Stream, Indent, !IO),
+            mercury_output_term(VarSet, VarNamePrint, Term, Stream, !IO)
+        ;
+            PredOrFunc = pf_function,
+            pred_args_to_func_args(ArgVars, FuncArgVars, FuncRetVar),
+            write_indent(Stream, Indent, !IO),
+            mercury_output_var(VarSet, VarNamePrint, FuncRetVar, Stream, !IO),
+            io.write_string(Stream, " = ", !IO),
+            io.write_string(Stream,
+                functor_to_string(VarSet, VarNamePrint,
+                    term.atom(CastTypeString), FuncArgVars),
+                !IO)
+        ),
         io.write_string(Stream, Follow, !IO)
     ).
 
diff --git a/compiler/intermod.m b/compiler/intermod.m
index f466d94ff..1fd75855c 100644
--- a/compiler/intermod.m
+++ b/compiler/intermod.m
@@ -628,8 +628,7 @@ gather_entities_to_opt_export_in_goal_expr(GoalExpr, DoWrite,
             DoWrite = no
         ;
             CallType = subtype_coerce,
-            % XXX SUBTYPE consider this later
-            DoWrite = no
+            DoWrite = yes
         )
     ;
         GoalExpr = call_foreign_proc(Attrs, _, _, _, _, _, _),
-- 
2.30.0