func makeUserFoldFn()

in gotype/fold_user.go [32:58]

• 22 lines of code
• 7 McCabe index (conditional complexity)

func makeUserFoldFn(fn reflect.Value) (userFoldFn, error) {
	t := fn.Type()

	if fn.Kind() != reflect.Func {
		return nil, errors.New("function type required")
	}

	if t.NumIn() != 2 {
		return nil, fmt.Errorf("function '%v' must accept 2 arguments", t.Name())
	}
	if t.NumOut() != 1 || t.Out(0) != tError {
		return nil, fmt.Errorf("function '%v' does not return errors", t.Name())
	}

	ta0 := t.In(0)
	if ta0.Kind() != reflect.Ptr {
		return nil, fmt.Errorf("first argument in function '%v' must be a pointer", t.Name())
	}

	ta1 := t.In(1)
	if ta1 != tExtVisitor {
		return nil, fmt.Errorf("second arument in function '%v' must be structform.ExtVisitor", t.Name())
	}

	fptr := *((*userFoldFn)(stunsafe.UnsafeFnPtr(fn)))
	return fptr, nil
}