REQUEST FOR COMMENTS: Change to future Ruby hash literal syntax
In 1.9, if you prefer to omit parentheses and you write this:
h = { a: Array.new 5, ‘A’, b: 0, c: 1 } # Syntax error
you will get a syntax error. The following works:
h = { a: Array.new(5, ‘A’), b: 0, c: 1 }
because the parser is not confused by the argument-separating comma
and the element-separating comma.
I propose that the owners consider changing the syntax.
ALTERNATIVE 1: Same input, different interpretation
If the scanner does lookahead and returns tASSOC_SEP for a comma
that is followed by a label, then there is no ambiguity.
ALTERNATIVE 2: Use ‘;’ to separate elements, use ‘,’ for arguments
h = { a: Array.new 5, ‘A’; b: 0; c: 1 } # Proposal 2
This avoids shift-reduce conflicts by a simple change to the assocs
production in parse.y, perhaps. Unfortunately the semicolon looks
strange, especially in array literals, when we address those, too.
ALTERNATIVE 3: Allow ‘;’ as an element separator, but keep ‘,’
h = { a: Array.new 5, ‘A’; b: 0, c: 1 } # Proposal 3
This does not break working code. It is like ‘or’ versus ‘||’,
and ‘do’ vs. ‘{’, i.e., same role, different precedence.
