Syntax quirks: documentation & debug mode

[fcard]

Trying to match Julia syntax has some quirks that I think are worth documenting in some way, with maybe also a debug mode that warns when patterns that might not mean what they seem are used.

• (*{args}) does not match a tuple, (*{args},) does, so things like (*{args}) -> ... could be warned against. Also, (*{args},) -> body will not match (x) -> y.
• (x...) does match a tuple, so (a, b, (x...)) is suspicious and @metafunction f((args...)) = ... and @metafunction f(args...) = ... mean different things and either could not be what the author intended.
• @m x *{args} matches @m x * {args}, with * unintentionally used in its binary form, same with
  [x *{elements}]. (maybe I should just change it to :*{args})
• f() = expr; *{exprs} is the same as (f() = expr); *{exprs} instead of
  f() = (expr; *{exprs}).

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There are more probably, will add to the list if I remember.