[Chicken-janitors] #1354: Clean up the expander a bit

[Chicken Trac]

#1354: Clean up the expander a bit
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 Reporter:  sjamaan   |                 Owner:  sjamaan
     Type:  task      |                Status:  new
 Priority:  minor     |             Milestone:  5.1
Component:  expander  |               Version:  5.0
 Keywords:  expander  |  Estimated difficulty:  hard
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 Currently the expander is full of hooks and hacks, mostly for maintaining
 the line number database and various syntactic environments.  It would be
 nice if we can clean things up a bit. A few ideas:

 * {{{##sys#syntax-context}}} and {{{##sys#syntax-error/context}}} are
 weird and can maybe be cleaned up if we can make {{{##sys#check-syntax}}}
 work better with line number info.
 * {{{##sys#syntax-error-culprit}}} seems to be unnecessary, because while
 expanding {{{##sys#check-syntax}}} should have access to the input form
 already?
 * {{{##sys#line-number-database}}} is defined in expander, but only really
 used in {{{core.scm}}} (except for getting the line number)
 * The new {{{expansion-result-hook}}} is yet another hook, and can perhaps
 be combined with the previous two.
 * The special-cased hack in {{{##sys#canonicalize-body}}} that prevents
 expansion of {{{import}}} and hands back control to the compiler after
 expansion of {{{##core#module}}}) (in a currently pending patch) needs to
 die. No clue yet how to do this...

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Ticket URL: <https://bugs.call-cc.org/ticket/1354>
CHICKEN Scheme <https://www.call-cc.org/>
CHICKEN Scheme is a compiler for the Scheme programming language.