Implement an immediate_identifier rule

[savq]

Many of the context-sensitive rules of the Julia grammar need to know whether a rule starts with an identifier.

For example, juxtaposition (implicit multiplication) work if the LHS is a number or if the RHS starts with an identifier:

2x         # ok
2(x + 1)   # ok. LHS is number
f()g()     # ok. RHS starts with identifier
(n - 1) n  # err. there's a space between the parenthesis and `n`
f(x).+(y)  # ok. Not a juxtaposition of function calls, but a binary expression

Other examples include:

• Quotations

  :foo   # ok
  : bar  # err

• Macro identifiers

  @foo   # ok
  @ foo  # err

• string suffixes

  r"^foo$"i  # ok
  r"^foo$" i # err

Currently, the scanner implements rules to check if there's an immediate opening brace/bracket/parenthesis. There's should be an similar rule for identifers and operators.

Note

This requires being able to check unicode categories in the scanner, like in Lezer-julia.