# Imported syntax class works different from syntax class copy-pasted into file **URL:** \ **Category:** Questions & Answers\ **Created:** [January 21, 2025, 7:35pm UTC](https://racket.discourse.group/t/imported-syntax-class-works-different-from-syntax-class-copy-pasted-into-file/3507 "2025-01-21T19:35:45Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![sora22](https://yyz2.discourse-cdn.com/free1/user_avatar/racket.discourse.group/sora22/32/2622_2.png) [@sora22](https://racket.discourse.group/u/sora22)\ **Post date:** [January 21, 2025, 7:35pm UTC](https://racket.discourse.group/t/imported-syntax-class-works-different-from-syntax-class-copy-pasted-into-file/3507/1 "2025-01-21T19:35:45Z")
I'm currently trying to reuse some syntax classes that I've made, and want to match certain identifiers within them. These syntax classes produce an error if I attempt to import them rather than defining them directly within the macro I am writing. This is a small breaking example I could come up with: This works fine ```scheme #lang racket/base (require (for-syntax racket/base syntax/parse)) (define-syntax (test stx) (define-syntax-class test-class (pattern ((~literal list) (~var x) (~var y)))) (syntax-parse stx [(_ (~var list-expr test-class)) #'(void)])) (test (list '(a b c) 1)) ``` This produces an error stating "expected the identifier `list' parsing context: while parsing test-class in: list": ```scheme ;; some-syntax-classes.rkt #lang racket/base (require syntax/parse) (provide (all-defined-out)) (define-syntax-class test-class (pattern ((~literal list) (~var x) (~var y)))) ``` ```scheme #lang racket/base (require (for-syntax racket/base syntax/parse "some-syntax-classes.rkt")) (define-syntax (test stx) (syntax-parse stx [(_ (~var list-expr test-class)) #'(void)])) (test (list '(a b c) 1)) ``` Any idea what I'm doing wrong? ---
**Author:** ![greghendershott](https://yyz2.discourse-cdn.com/free1/user_avatar/racket.discourse.group/greghendershott/32/98_2.png) [@greghendershott](https://racket.discourse.group/u/greghendershott)\ **Post date:** [January 21, 2025, 8:47pm UTC](https://racket.discourse.group/t/imported-syntax-class-works-different-from-syntax-class-copy-pasted-into-file/3507/2 "2025-01-21T20:47:48Z")
So `~literal` matches an _identifier_ -- including a phase as well as a symbol: It's "`list` _at some specific phase level_". In your first example, where the syntax class is defined at phase 1 inside the `define-syntax`, the `list` identifier in `(~literal list)` is the one at phase 1. But in your second example, where the syntax class is defined at phase 0, the `list` identifier in `(~literal list)` is the one at phase 0. That doesn't match the `list` at phase 1 in the expansion of `test`. So the error. * * * One thing you could do, in your second example, is change `(~literal list)` to `(~literal list #:phase 1)`. As in the following. [Note: Just for my own convenience, I changed your two-file example into one file -- with a submodule `m` playing the role of `some-syntax-classes.rkt`.] ```scheme #lang racket/base (module m racket/base ;~= some-syntax-classes.rkt (require syntax/parse) (provide (all-defined-out)) (define-syntax-class test-class (pattern ((~literal list #:phase 1) (~var x) (~var y))))) (require (for-syntax racket/base syntax/parse 'm)) ;~= some-syntax-classes.rkt (define-syntax (test stx) (syntax-parse stx [(_ (~var list-expr test-class)) #'(void)])) (test (list '(a b c) 1)) ``` ---
**Author:** ![sora22](https://yyz2.discourse-cdn.com/free1/user_avatar/racket.discourse.group/sora22/32/2622_2.png) [@sora22](https://racket.discourse.group/u/sora22)\ **Post date:** [January 21, 2025, 9:10pm UTC](https://racket.discourse.group/t/imported-syntax-class-works-different-from-syntax-class-copy-pasted-into-file/3507/3 "2025-01-21T21:10:13Z")
That solved my problem! Didn't know I could specify a phase level for it, thank you so much for your help ---
**Author:** ![greghendershott](https://yyz2.discourse-cdn.com/free1/user_avatar/racket.discourse.group/greghendershott/32/98_2.png) [@greghendershott](https://racket.discourse.group/u/greghendershott)\ **Post date:** [January 21, 2025, 9:18pm UTC](https://racket.discourse.group/t/imported-syntax-class-works-different-from-syntax-class-copy-pasted-into-file/3507/4 "2025-01-21T21:18:43Z")
Keep in mind there are various ways to handle this. Some may be more "ergonomic" solutions, if you're writing a lot of this stuff. For example you could: 1. Use `define-literal-set` to name a variety of symbols (`list`, `cons`, whatever, etc.). 2. Use the `#:literal-sets` option to use that whole set at a certain phase level. 3. Now in your patterns you can just write `list` (not even need `(~literal list)` anymore, much less `(~literal list #:phase 1)`). ---
**Author:** ![benknoble](https://yyz2.discourse-cdn.com/free1/user_avatar/racket.discourse.group/benknoble/32/16_2.png) [@benknoble](https://racket.discourse.group/u/benknoble)\ **Post date:** [January 21, 2025, 9:21pm UTC](https://racket.discourse.group/t/imported-syntax-class-works-different-from-syntax-class-copy-pasted-into-file/3507/5 "2025-01-21T21:21:37Z")
2 other options I can think of: - use `~datum`. A bit discouraged, but useful when you only care about the textual content and don't want to allow it to be renamed (`cond` recognizes `else` by binding, which means it works through renames but is a bit confusing if `else` is lexically shadowed). - create, provide, and consistently use your _own_ binding. If you don't need its value, it can be as simple as `(define my-marker #f)`, as long as you're consistent about the phasing use as Greg pointed out.