swift234

[Parser] Disambiguate between object literals and collection literals.

Now that we have expressions that start with #, the [# introducer for
object literals is no longer guaranteed to indicate an object
literal. For example:

    [#line, #column]

is an array literal and

    [#line : #column]

is a dictionary literal. Use additional lookahead in the parser to
disambiguate these cases from object literals. Fixes
rdar://problem/24533081.