vala: Fix assignment operators for element access

This transforms an assignment to element access other than `=' to a
binary expression i.e. `a[b] += 1' will become `a.set(a.get(b) + 1)'

Fixes https://gitlab.gnome.org/GNOME/vala/issues/135

1 files changed, 30 insertions, 0 deletions

diff --git a/vala/valaassignment.vala b/vala/valaassignment.vala
index 150c34723..929fa7b66 100644
--- a/vala/valaassignment.vala
+++ b/vala/valaassignment.vala
@@ -204,6 +204,36 @@ public class Vala.Assignment : Expression {
 				foreach (Expression e in ea.get_indices ()) {
 					set_call.add_argument (e);
 				}
+
+				if (operator != AssignmentOperator.SIMPLE && ea.container.value_type.get_member ("get") is Method) {
+					// transform into binary expression inside set call
+					var get_call = new MethodCall (new MemberAccess (ea.container, "get", source_reference), source_reference);
+					foreach (Expression e in ea.get_indices ()) {
+						get_call.add_argument (e);
+					}
+
+					BinaryOperator bop;
+
+					switch (operator) {
+					case AssignmentOperator.BITWISE_OR: bop = BinaryOperator.BITWISE_OR; break;
+					case AssignmentOperator.BITWISE_AND: bop = BinaryOperator.BITWISE_AND; break;
+					case AssignmentOperator.BITWISE_XOR: bop = BinaryOperator.BITWISE_XOR; break;
+					case AssignmentOperator.ADD: bop = BinaryOperator.PLUS; break;
+					case AssignmentOperator.SUB: bop = BinaryOperator.MINUS; break;
+					case AssignmentOperator.MUL: bop = BinaryOperator.MUL; break;
+					case AssignmentOperator.DIV: bop = BinaryOperator.DIV; break;
+					case AssignmentOperator.PERCENT: bop = BinaryOperator.MOD; break;
+					case AssignmentOperator.SHIFT_LEFT: bop = BinaryOperator.SHIFT_LEFT; break;
+					case AssignmentOperator.SHIFT_RIGHT: bop = BinaryOperator.SHIFT_RIGHT; break;
+					default:
+						error = true;
+						Report.error (source_reference, "internal error: unsupported assignment operator");
+						return false;
+					}
+
+					right = new BinaryExpression (bop, get_call, right, source_reference);
+				}
+
 				set_call.add_argument (right);
 				parent_node.replace_expression (this, set_call);
 				return set_call.check (context);