Make macros less weird by… (see inside)

[SuzanneSoy]

Make macros less weird and more like programs, by...

• [ ] Using unified matching and templates (syntax-parse/match/etc. and template/quasiquote/etc.) see https://github.com/jeapostrophe/remix/issues/16
• [ ] Using pattern matching everywhere

[SuzanneSoy]

In my experience, one of the hardest part about macros is getting the scopes right for unhygienic macros (e.g. macros which communicate with each other). Quite often I will end up with a spurious scope on one identifier, and figuring out what operation flipped that scope can be a painful task. Some of the issues I noted are:

• The tools to debug this are not great: the macro stepper just dumps a list of 7-digit numbers, and the snip% for syntax object when they are printed in DrRacket shows some useful info, but does not show the list of scopes present on that object. Opening the syntax debugger from the snip% would help tremendously when debugging.
• The available information is terse (it's impossible to give a name to a scope created with make-syntax-introducer, that would help when debugging by indicating which macro introduced the scope and for what purpose)
• Scopes feel too low-level as a concept. They are great in that the allow modelling nearly all macro behaviours with respect to hygiene, but I don't think in terms of sets of scopes when developing a macro.

To help with debugging, I wrote a small tool (unpackaged for now) which dumps a syntax object with its scopes in a concise way (I find it more readable than the representation in the macro stepper, when comparing two or more parts of the syntax object, looking for a scope that one has and the other lacks).