swift234

Parser: Parse operator decls.

At the top level, if 'operator' is followed by 'infix', 'prefix', or 'postfix', consider it a contextual keyword, and parse an operator decl following it that looks like:

  operator {infix|postfix|prefix} <+> {
    attributes…
  }

Prefix and postfix operator decls currently admit no attributes. Infix operators have 'associativity {left|right|none}' and 'precedence <int>' attributes.

This patch implements parsing for operator declarations but does not yet attach the declared attributes to func decls for the operators.

Swift SVN r4596