checker: check generic struct using in non-generic fn (#12136)

vlib/v/checker/checker.v

@@ -4592,6 +4592,9 @@ pub fn (mut c Checker) array_init(mut node ast.ArrayInit) ast.Type {
 			c.ensure_sumtype_array_has_default_value(node)
 		}
 		c.ensure_type_exists(node.elem_type, node.elem_type_pos) or {}
+		if node.typ.has_flag(.generic) && c.table.cur_fn.generic_names.len == 0 {
+			c.error('generic struct cannot use in non-generic function', node.pos)
+		}
 		return node.typ
 	}
 	if node.is_fixed {

vlib/v/checker/tests/generics_struct_in_non_generic_fn_err.out

@@ -0,0 +1,6 @@
+vlib/v/checker/tests/generics_struct_in_non_generic_fn_err.vv:5:7: error: generic struct cannot use in non-generic function
+    3 |
+    4 | fn main() {
+    5 |     _ := []Example<T>{}
+      |          ~~~~~~~~~~~~~
+    6 | }

vlib/v/checker/tests/generics_struct_in_non_generic_fn_err.vv

@@ -0,0 +1,6 @@
+struct Example<T> {
+}
+
+fn main() {
+	_ := []Example<T>{}
+}