checker: fix selector with prefixed & structinit (#22689)

Author: felipensp

vlib/v/checker/checker.v

@@ -4498,6 +4498,9 @@ fn (mut c Checker) prefix_expr(mut node ast.PrefixExpr) ast.Type {
 		} else if mut node.right is ast.SelectorExpr {
 			if node.right.expr.is_literal() {
 				c.error('cannot take the address of a literal value', node.pos.extend(node.right.pos))
+			} else if node.right.expr is ast.StructInit {
+				c.error('should not create object instance on the heap to simply access a member',
+					node.pos.extend(node.right.pos))
 			}
 			right_sym := c.table.sym(right_type)
 			expr_sym := c.table.sym(node.right.expr_type)

vlib/v/checker/tests/selector_struct_init_amp_err.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/selector_struct_init_amp_err.vv:6:11: error: should not create object instance on the heap to simply access a member
+    4 | 
+    5 | fn test_main() {
+    6 |     field := &Object{}.a
+      |              ~~~~~~~~~~~
+    7 |     assert field == 123
+    8 | }

vlib/v/checker/tests/selector_struct_init_amp_err.vv

@@ -0,0 +1,8 @@
+struct Object {
+	a int = 123
+}
+
+fn test_main() {
+	field := &Object{}.a
+	assert field == 123
+}