[m-rev.] for review: Bug fix for enumerated types in grade Java

[James Goddard]

Estimated hours taken: 9
Branches: main

Bug fix for enumerated type switch statements in Java.

compiler/mlds_to_java.m:
	Modified rval_is_enum_object/1 so that it considers field selections
	as well as vars.
	This fixes a problem that arose in producing the switch statement for
	fold_bits/7 in library/sparse_bitset, where the enumerated type was
	not detected, so it was trying to switch on an Object:

	(mercury.sparse_bitset.fold_bits_7_p_3_env_0) env_ptr).Dir_8

	as opposed to:

	(mercury.sparse_bitset.fold_bits_7_p_3_env_0) env_ptr).Dir_8.value

	which is what it should have.

	After making this change, it was also necessary to correct a call in
	output_initializer_body from output_rval_maybe_with_enum to just
	plain output_rval, since at that point it is known that the Rval is
	not an enum object.

	The standard library will now compile without error in grade java.

Index: mlds_to_java.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/mlds_to_java.m,v
retrieving revision 1.49
diff -u -d -r1.49 mlds_to_java.m
--- mlds_to_java.m	22 Dec 2003 23:37:33 -0000	1.49
+++ mlds_to_java.m	7 Jan 2004 04:26:43 -0000
@@ -212,9 +212,14 @@
 :- mode rval_is_enum_object(in) is semidet.
 
 rval_is_enum_object(Rval) :-
-		Rval = lval(Lval),
+	Rval = lval(Lval),
+	(
 		Lval = var(_, VarType),
-		type_is_enum(VarType).
+		type_is_enum(VarType)
+	;
+		Lval = field(_, _, _, FieldType, _),
+		type_is_enum(FieldType)
+	).
 
 	% Succeeds iff a given string matches the unqualified
 	% interface name of a interface in Mercury's Java runtime system.
@@ -1471,10 +1476,11 @@
 		io__write_string("("),
 		output_type(Type),
 		io__write_string(") "),
-		output_rval_maybe_with_enum(Rval, ModuleName)
+		output_rval(Rval, ModuleName)
 	;
 		output_rval_maybe_with_enum(Rval, ModuleName)
 	).
+
 output_initializer_body(init_struct(StructType, FieldInits), _MaybeType,
 		ModuleName) --> 
 	io__write_string("new "),
@@ -3219,6 +3225,13 @@
 	% Output an Rval and if the Rval is an enumeration object
 	% append the string ".value", so we can access its value
 	% field.
+	% XXX	Note that this is necessary in some places, but not in others.
+	%	For example, it is important to do so for switch statements, as
+	%	the argument of a switch _must_ be an integer in Java. However,
+	%	adding the .value to assignments breaks some casting...
+	%	At some point, we need to go through all the places where
+	%	output_rval and output_rval_maybe_with_enum are called and make
+	%	sure the correct one is being used.
 	%
 :- pred output_rval_maybe_with_enum(mlds__rval, mlds_module_name,
 		io__state, io__state).
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