change :: parsing

[Keno]

Currently :: parses as an identifier, allowing e.g.

julia> h(::) = ::
h (generic function with 1 method)

julia> h(1)
1

@JeffBezanson has suggested changing parsing of :: from Symbol("::") to Expr(Symbol("::")), which would give the same error as

julia> ::Any
ERROR: syntax: invalid "::" syntax

The one thing that does make this a little tricky is that packages have been using :(::) for Symbol("::") though arguably those packages should just change to the latter.