checker, orm: add error for unchecked option multi return types, fix undefined behavior

vlib/orm/orm.v

@@ -508,12 +508,13 @@ pub fn orm_table_gen(table string, q string, defaults bool, def_unique_len int,
 							return error("references attribute needs to be in the format [references], [references: 'tablename'], or [references: 'tablename(field_id)']")
 						}
 						if attr.arg.contains('(') {
-							ref_table, ref_field := attr.arg.split_once('(')
-							if !ref_field.ends_with(')') {
-								return error("explicit references attribute should be written as [references: 'tablename(field_id)']")
+							if ref_table, ref_field := attr.arg.split_once('(') {
+								if !ref_field.ends_with(')') {
+									return error("explicit references attribute should be written as [references: 'tablename(field_id)']")
+								}
+								references_table = ref_table
+								references_field = ref_field[..ref_field.len - 1]
 							}
-							references_table = ref_table
-							references_field = ref_field[..ref_field.len - 1]
 						} else {
 							references_table = attr.arg
 							references_field = 'id'

vlib/v/checker/checker.v

@@ -1161,17 +1161,20 @@ fn (mut c Checker) check_expr_option_or_result_call(expr ast.Expr, ret_type ast.
 				}
 			}
 			if expr_ret_type.has_option_or_result() {
-				if expr.or_block.kind == .absent && expr_ret_type.has_flag(.result) {
+				if expr.or_block.kind == .absent {
 					ret_sym := c.table.sym(expr_ret_type)
-					ret_typ_tok := if expr_ret_type.has_flag(.option) { '?' } else { '!' }
-					if c.inside_defer {
-						c.error('${expr.name}() returns `${ret_typ_tok}${ret_sym.name}`, so it should have an `or {}` block at the end',
-							expr.pos)
-					} else {
-						c.error('${expr.name}() returns `${ret_typ_tok}${ret_sym.name}`, so it should have either an `or {}` block, or `${ret_typ_tok}` at the end',
-							expr.pos)
+					if expr_ret_type.has_flag(.result)
+						|| (expr_ret_type.has_flag(.option) && ret_sym.kind == .multi_return) {
+						ret_typ_tok := if expr_ret_type.has_flag(.option) { '?' } else { '!' }
+						if c.inside_defer {
+							c.error('${expr.name}() returns `${ret_typ_tok}${ret_sym.name}`, so it should have an `or {}` block at the end',
+								expr.pos)
+						} else {
+							c.error('${expr.name}() returns `${ret_typ_tok}${ret_sym.name}`, so it should have either an `or {}` block, or `${ret_typ_tok}` at the end',
+								expr.pos)
+						}
 					}
-				} else if expr.or_block.kind != .absent {
+				} else {
 					c.check_or_expr(expr.or_block, ret_type, expr_ret_type, expr)
 				}
 				return ret_type.clear_flag(.result)

vlib/v/checker/tests/option_multi_return_err.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/option_multi_return_err.vv:6:14: error: split() returns `?(string, string)`, so it should have either an `or {}` block, or `?` at the end
+    4 | 
+    5 | fn main() {
+    6 |     foo, bar := split('foo/bar')
+      |                 ~~~~~~~~~~~~~~~~
+    7 |     println('${foo}.${bar}')
+    8 | }

vlib/v/checker/tests/option_multi_return_err.vv

@@ -0,0 +1,8 @@
+fn split(str string) ?(string, string) {
+	return none
+}
+
+fn main() {
+	foo, bar := split('foo/bar')
+	println('${foo}.${bar}')
+}