checker: fix autocast in complex if conditions 3 (#18710)

vlib/v/checker/infix.v

@@ -24,7 +24,6 @@ fn (mut c Checker) infix_expr(mut node ast.InfixExpr) ast.Type {
 					to_type := c.expr(left_node.right.right)
 					c.autocast_in_if_conds(mut node.right, left_node.right.left, from_type,
 						to_type)
-					break
 				}
 			}
 			if left_node.op == .key_is {
@@ -823,8 +822,18 @@ fn (mut c Checker) invalid_operator_error(op token.Kind, left_type ast.Type, rig
 }
 
 // `if node is ast.Ident && node.is_mut { ... }` -> `if node is ast.Ident && (node as ast.Ident).is_mut { ... }`
-fn (mut c Checker) autocast_in_if_conds(mut right ast.Expr, from_expr ast.Expr, from_type ast.Type, to_type ast.Type) {
+fn (mut c Checker) autocast_in_if_conds(mut right_ ast.Expr, from_expr ast.Expr, from_type ast.Type, to_type ast.Type) {
+	mut right := right_
 	match mut right {
+		ast.Ident {
+			if right.name == from_expr.str() {
+				right_ = ast.AsCast{
+					typ: to_type
+					expr: from_expr
+					expr_type: from_type
+				}
+			}
+		}
 		ast.SelectorExpr {
 			if right.expr.str() == from_expr.str() {
 				right.expr = ast.ParExpr{
@@ -855,7 +864,6 @@ fn (mut c Checker) autocast_in_if_conds(mut right ast.Expr, from_expr ast.Expr,
 					}
 				}
 			}
-			c.autocast_in_if_conds(mut right.left, from_expr, from_type, to_type)
 			for mut arg in right.args {
 				c.autocast_in_if_conds(mut arg.expr, from_expr, from_type, to_type)
 			}

vlib/v/tests/autocast_in_if_conds_4_test.v

@@ -0,0 +1,32 @@
+type MySumType = S1 | S2
+
+struct Info {
+	name string
+}
+
+struct S1 {
+	is_info bool
+	info    Info
+}
+
+struct S2 {
+	field2 string
+}
+
+fn get_name(s1 S1) string {
+	return s1.info.name
+}
+
+fn test_autocast_in_if_conds() {
+	s := MySumType(S1{
+		is_info: false
+		info: Info{'foo'}
+	})
+
+	if s is S1 && !s.is_info && get_name(s) == 'foo' {
+		println('ok')
+		assert true
+	} else {
+		assert false
+	}
+}