lang: ast: fix expr type not being set when parsing a lambda

lang/ast/expr/arith.c

@@ -662,6 +662,20 @@ struct token_parse_result arith_parse_right_brace(
 struct token_parse_result arith_parse_left_bracket(
 	struct ivy_parser *ctx, struct ivy_token *tok)
 {
+	struct expr_parser_state *state
+		= parser_get_state(ctx, struct expr_parser_state);
+
+	if (state->s_type == EXPR_TYPE_STMT) {
+		return PARSE_RESULT(IVY_ERR_BAD_SYNTAX, 0);
+	}
+
+	if (state->s_prev_component == EXPR_CMP_OPERAND) {
+		return PARSE_RESULT(IVY_ERR_BAD_SYNTAX, 0);
+	}
+
+	state->s_prev_token = IVY_SYM_LEFT_BRACKET;
+	state->s_type = EXPR_TYPE_ARITH;
+
 	parser_push_state(ctx, IVY_AST_LAMBDA, 0);
 	return PARSE_RESULT(IVY_OK, 0);
 }