Is there a way to interpose on reading `#;`, `#|...|#`, and `#!` comments
with the standard e-expression reader? I can override the handling of
normal `;` line comments by adding a terminating macro to the reader, but
adding dispatch macros for the others doesn't seem to work (see below). I
wondered if they might be producing special comments
<https://docs.racket-lang.org/reference/special-comments.html>, but, if so,
I haven't managed to intercept them, and I also haven't seen any relevant
reader parameters.
#lang racket
(require syntax/readerr)
(define ((comment-error msg) ch in src line col pos)
(raise-read-error msg src line col pos 1))
(define readtable
(make-readtable #f
#\; 'terminating-macro (comment-error "line")
#\; 'dispatch-macro (comment-error "s-exp")
#\| 'dispatch-macro (comment-error "block")
#\! 'dispatch-macro (comment-error "unix")))
(parameterize ([current-readtable readtable])
(for ([str '("#;datum" "#|a block|#" "#!/usr/bin/env racket")])
(read (open-input-string str)))
(read (open-input-string ";only this works as expected")))
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