Currently, unexpected tokens in the parser are shown as the text
found, plus the internal token name, including the notorious
"unexpected '::' (T_PAAMAYIM_NEKUDOTAYIM)".
This commit replaces that with a more user-friendly format, with
two main types of token:
* Tokens which always represent the same text are shown like
'unexpected token "::"' and 'expected "::"'
* Tokens which have variable text are given a user-friendly
name, and show like 'unexpected identifier "foo"', and
'expected identifer'.
A few tokens have special cases:
* unexpected token """ -> unexpected double-quote mark
* unexpected quoted string "'foo'" -> unexpected single-quoted
string "foo"
* unexpected quoted string ""foo"" -> unexpected double-quoted
string "foo"
* unexpected illegal character "_" -> unexpected character 0xNN
(where _ is almost certainly a control character, and NN is the
hexadecimal value of the byte)
The \ token has a special case in the implementation just to stop
bison making a mess of escaping it and it coming out as \\
Some of these are entirely unnecessary. Some specify an associativity
for operators where the concept doesn't make sense and has no effect:
Explicit associativity is only meaningful for binary operators. For
unary operators and constrained operations like instanceof or assignment
the associativity specification has no effect and only serves to confuse.
For example assignments were specified as %left, even though they will
actually behave as right-associative due to the variable requirement on
the LHS. Similarly instanceof was specified as %nonassoc, but it will
behave as left-associative, due to the restrictions places on the RHS.
