@memoize cannot handle unnamed arguments

[matthias314]

Simple example:

julia> @memoize f(::Int) = 1;

julia> f(1)
ERROR: MethodError: no method matching var"##f_unmemoized"(::Nothing)
The function `##f_unmemoized` exists, but no method is defined for this combination of argument types.

Closest candidates are:
  var"##f_unmemoized"(::Int64)
   @ Main REPL[2]:1

A more realistic example is using Val:

julia> @memoize g(::Val{N}) where N = N;

julia> g(Val(1))
ERROR: MethodError: no method matching var"##g_unmemoized"(::Nothing)
The function `##g_unmemoized` exists, but no method is defined for this combination of argument types.

Closest candidates are:
  var"##g_unmemoized"(::Val{N}) where N
   @ Main REPL[4]:1

EDIT: Underscores don't work, either:

julia> @memoize h(_::Val{N}) where N = N
ERROR: syntax: all-underscore identifiers are write-only and their values cannot be used in expressions around /usr/local/julia-depot/packages/Memoize/12ANR/src/Memoize.jl:62

I'm using Memoize v0.4.4.

[cstjean]

Yes, that's a limitation that wouldn't be so hard to fix. PR welcome!