#1736: Incomplete SRFI-46/R7RS tail pattern support

[Chicken Trac]

#1736: Incomplete SRFI-46/R7RS tail pattern support
---------------------------------+----------------------------------
            Reporter:  wasamasa  |       Type:  defect
              Status:  new       |   Priority:  minor
           Milestone:  someday   |  Component:  core libraries
             Version:  5.2.0     |   Keywords:  syntax-rules srfi-46
Estimated difficulty:            |
---------------------------------+----------------------------------
 I've run into an expansion error when trying to install {{{(chibi
 optional)}}}. It's using a tail pattern of the {{{(binding ... . rest)}}}
 kind. SRFI-46 only shows one tail pattern example of the {{{((binding ...)
 . rest)}}} kind, but R7RS is explicit about allowing both:

 {{{
 ⟨transformer spec⟩ −→
 (syntax-rules (⟨identifier⟩*) ⟨syntax rule⟩*)
 | (syntax-rules ⟨identifier⟩ (⟨identifier⟩*)
 ⟨syntax rule⟩*)
 ⟨syntax rule⟩ −→ (⟨pattern⟩ ⟨template⟩)
 ⟨pattern⟩ −→ ⟨pattern identifier⟩
 | ⟨underscore⟩
 | (⟨pattern⟩*)
 | (⟨pattern⟩+ . ⟨pattern⟩)
 | (⟨pattern⟩* ⟨pattern⟩ ⟨ellipsis⟩ ⟨pattern⟩*)
 | (⟨pattern⟩* ⟨pattern⟩ ⟨ellipsis⟩ ⟨pattern⟩*
 . ⟨pattern⟩)
 | #(⟨pattern⟩*)
 | #(⟨pattern⟩* ⟨pattern⟩ ⟨ellipsis⟩ ⟨pattern⟩*)
 | ⟨pattern datum⟩
 }}}

 According to SRFI-46 alexpander does support both patterns just fine, the
 error message originates from synrules.scm. I've attached a file with
 simplified examples for both the working and not working pattern. I've
 also done a brief check across R7RS-compliant Scheme implementations, it
 seems that Cyclone doesn't support it either, while Chibi, Kawa, Gauche,
 Sagittarius and Foment do.

-- 
Ticket URL: <https://bugs.call-cc.org/ticket/1736>
CHICKEN Scheme <https://www.call-cc.org/>
CHICKEN Scheme is a compiler for the Scheme programming language.