Hi,
I'm still building an ECMAScript parser, it's mostly running, except for
the Automatic Semicolon Insertion rule in the language: if a token stream
is invalid, but can be made valid by inserting a semicolon in front of the
current token, pretend that a semicolon is there.
For example inside a function:
function f() {
i = 5
}
the semicolon at the end of the assignment is implied, because a closing
brace is unexpected there. Similarly,
var foo = 4
var bar = 5
is legal, because the "var" token after the 4 is unexpected. At the same
time, if I make the semicolon optional, I'm in shift/reduce hell as the
next token could be unary or binary minus (as well as some other things).
Is there a way to create a last-resort alternative that always loses any
conflict, so I can do something similar to
variable_statement:
"var" variable_declaration_list ";" %prec WIN |
"var" variable_declaration_list %prec LOSE;
The expected result would be that anything that can be used to continue a
variable_declaration_list should go into it, anything that cannot be used
would terminate it, and a semicolon would terminate it nonetheless.
Alternatively, can I somehow use YYBACKUP or the error symbol here, by
allowing error productions instead of a semicolon, and inserting a
semicolon token as the next lookahead?
Simon
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