* lib/irb/context.rb (IRB::Context#evaluate): separate the code
from wrapping lines to propagate the given exception, not to show
the wrapping lines when SyntaxError.
The reason why we were checking lexer state in addition to token was
that we do not want to colorize local variable, method call, etc., while
they share the :on_ident token with a name of method definition which
should be colored as blue.
It means that we're concerned about the lexer state only for :on_ident.
Thus we can skip checking lexer state for non-:on_ident tokens. This
refactoring is based on that idea.
Also, now we manage Ripper's lexer state as Integer (use `|` if you
need to check multiple states). It should be faster than using Array of
Integer because #any? block call is not needed.
Symbol color was made blue as a workaround because it was hard to
distinguish `foo`s in `:foo` and `def foo; end` (both are :on_ident).
But I wanted to make it yellow like pry.
`:Struct` had the same problem in :on_const. Because the :on_const was
also blue (but underlined and bold), it was not a big issue.
While they're not so problematic since we got a workaround, we also had
a more serious issue for highlighting a symbol like `:"a#{b}c"`.
The first half was considered as Symbol and the last half was considered
as String, because the colorizer did not have a state like a parser.
To approach the last issue, I introduced `IRB::Color::SymbolState` which
is a thin state manager knowing only "the token is Symbol or not". Having
this module magically solves the first two problems as well. So now we
can highlight Symbol as yellow in the perfect manner.
We might need to do the same thing in IRB::Color now, but I'm not doing
that as I assume ANSI escape sequence does not come from a user input
though Reline.
