Regression in empty constructor falling back to defined convert method

[jakebolewski]

The following fails on 0.5-dev but works on 0.4

julia/julia-dev [master] » julia-dev
               _
   _       _ _(_)_     |  A fresh approach to technical computing
  (_)     | (_) (_)    |  Documentation: http://docs.julialang.org
   _ _   _| |_  __ _   |  Type "?help" for help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 0.5.0-dev+4646 (2016-06-10 11:00 UTC)
 _/ |\__'_|_|_|\__'_|  |  Commit 56d7d66* (1 day old master)
|__/                   |  x86_64-apple-darwin15.5.0

julia> bitstype 8 ThreeWay

julia> Base.convert(::Type{ThreeWay}, x::Bool) = reinterpret(ThreeWay, x)

julia> Base.convert(::Type{ThreeWay}) = reinterpret(ThreeWay, 0xff)

julia> ThreeWay()
ERROR: MethodError: no method matching ThreeWay()
 in eval(::Module, ::Any) at ./boot.jl:225
 in macro expansion at ./REPL.jl:92 [inlined]
 in (::Base.REPL.##1#2{Base.REPL.REPLBackend})() at ./event.jl:46

Julia/julia-dev [master] » julia
               _
   _       _ _(_)_     |  A fresh approach to technical computing
  (_)     | (_) (_)    |  Documentation: http://docs.julialang.org
   _ _   _| |_  __ _   |  Type "?help" for help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 0.4.5 (2016-03-18 00:58 UTC)
 _/ |\__'_|_|_|\__'_|  |
|__/                   |  x86_64-apple-darwin15.4.0

LoadError("/Users/jacobbolewski/.julia/v0.4/TerminalExtensions/src/TerminalExtensions.jl",237,InitError(:TerminalExtensions,ErrorException("Timed out!")))
julia> bitstype 8 ThreeWay

julia> Base.convert(::Type{ThreeWay}, x::Bool) = reinterpret(ThreeWay, x)
convert (generic function with 535 methods)

julia> Base.convert(::Type{ThreeWay}) = reinterpret(ThreeWay, 0xff)
convert (generic function with 536 methods)

julia> ThreeWay()
ThreeWay(0xff)

[JeffBezanson]

I think the fallback definition used to use args..., and we switched it to take a single argument, since it seemed to make the most sense to convert a single value.

[jakebolewski]

That makes sense, maybe there are bits of documentation that need updating? Otherwise feel free to close.

[jakebolewski]

I think that if you are limiting yourself to one argument convert method fallbacks, the error message could be updated to ...fall back to convert(::Type{AType}, x) methods

[JeffBezanson]

This fallback has been removed.