MethodError message misleading/wrong on 0.4, very hard to read on 0.5

[IainNZ]

Reproduce with

type FooCon
    x
end
type BarCon
    x
end
function addConstraint(c::FooCon)
    println("addCon(FooCon)")
end
function addConstraint(c::BarCon; uncset=nothing)
    println("addCon(BarCon,$uncset)")
    # Oh, BarCon was suppossed to be a FooCon, let me erroneously pass
    # on this kwarg which isn't supported
    addConstraint(FooCon(c.x), uncset=uncset)
end
addConstraint(BarCon(1))

On Julia 0.4.5:

ERROR: LoadError: MethodError: `addConstraint` has no method matching addConstraint(::FooCon)
Closest candidates are:
  addConstraint(::FooCon)
 in include at ./boot.jl:261
 in include_from_node1 at ./loading.jl:304
 in process_options at ./client.jl:280
 in _start at ./client.jl:378

Julia 0.5 (from January 31st)

ERROR: LoadError: MethodError: `#addConstraint` has no method matching #addConstraint(::Array{Any,1}, ::#addConstraint, ::FooCon)
Closest candidates are:
  #addConstraint(::Array{T,N}, ::#addConstraint, ::BarCon)
 [inlined code] from ./boot.jl:331
 in #addConstraint#1(##addConstraint#1, Void, Any, BarCon) at /Users/idunning/.julia/v0.4/JuMPeR/rep.jl:14
 in include(Core.#include, ASCIIString) at ./boot.jl:264
 in include_from_node1 at ./loading.jl:417
 in process_options at ./client.jl:244
 in _start at ./client.jl:300

[dhoegh]

I have implemented a fix for this, see #16669.