checker: fix missing re-check of recursive generic function (fix #16962) (#17592)

vlib/v/checker/fn.v

@@ -1598,18 +1598,27 @@ fn (mut c Checker) method_call(mut node ast.CallExpr) ast.Type {
 				arg_sym := c.table.sym(c.comptime_fields_default_type)
 				if arg_sym.kind == .array
 					&& c.table.sym(method.params[param_idx].typ).kind == .array {
-					c.table.register_fn_concrete_types(method.fkey(), [
+					if c.table.register_fn_concrete_types(method.fkey(), [
 						(arg_sym.info as ast.Array).elem_type,
 					])
+					{
+						c.need_recheck_generic_fns = true
+					}
 				} else {
-					c.table.register_fn_concrete_types(method.fkey(), [
+					if c.table.register_fn_concrete_types(method.fkey(), [
 						c.comptime_fields_default_type,
 					])
+					{
+						c.need_recheck_generic_fns = true
+					}
 				}
 			} else if c.inside_for_in_any_cond && method.params[param_idx].typ.has_flag(.generic) {
-				c.table.register_fn_concrete_types(method.fkey(), [
+				if c.table.register_fn_concrete_types(method.fkey(), [
 					c.for_in_any_val_type,
 				])
+				{
+					c.need_recheck_generic_fns = true
+				}
 			}
 			if no_type_promotion {
 				if got_arg_typ != exp_arg_typ {

vlib/v/tests/generic_struct_test.v

@@ -0,0 +1,44 @@
+struct Test {}
+
+fn (t Test) test[T](val T) {
+	$for f in T.fields {
+		value := val.$(f.name)
+		$if f.is_option {
+			$if f.typ is $Struct {
+				_ := 1
+				t.test(value)
+			} $else $if f.typ is string {
+				_ := 2
+			} $else $if f.typ is ?string {
+				_ := 3
+			} $else {
+				_ := 4
+			}
+		} $else {
+			$if f.typ is $Struct {
+				t.test(value)
+			} $else $if f.typ is string {
+				_ := 5
+			}
+		}
+	}
+}
+
+struct Bb {
+	a ?string
+}
+
+struct Cc {
+	b Bb
+}
+
+struct Aa[T] {
+	a T
+}
+
+fn test_main() {
+	a := Aa[Cc]{}
+	t := Test{}
+	t.test(a)
+	assert true
+}