Weird method overwritten warning on 0.5

[JaredCrean2]

I get a weird warning when using julia 0.5 (on the 0.5update branch of PETSc.jl)

WARNING: Method definition (::Type{PETSc.Mat})(Type{#T<:Any}) in module PETSc at /home/jared/.julia/v0.5/PETSc/src/mat.jl:58 overwritten at /home/jared/.julia/v0.5/PETSc/src/mat.jl:75.

I don't know quite what is going on, because line 75 is not defining a new method, it is calling the one on line 57.

cc @stevengj

[stevengj]

Not sure...

[JaredCrean2]

I narrowed it down to this example:

module C

  global const PETSC_DECIDE = -1
  typealias PetscInt Int64
  MATMPIAIJ = "matmpiaij"
  MatType = Symbol


end  # end module C

module MPI
  typealias Comm Cint
  COMM_WORLD = Cint(42)
end

module PETSc

using MPI
using C

function Mat{T}(::Type{T}, mtype::C.MatType=C.MATSEQAIJ; comm::MPI.Comm=MPI.COMM_WORLD)

  println("I found the other half of the problem")
end


function Mat{T}(::Type{T}, m::Integer=C.PETSC_DECIDE, n::Integer=C.PETSC_DECIDE;
                mlocal::Integer=C.PETSC_DECIDE, nlocal::Integer=C.PETSC_DECIDE,
                bs=1, nz::Integer=0, nnz::AbstractVector=PetscInt[],
                onz::Integer=0, onnz::AbstractVector=PetscInt[],
                comm::MPI.Comm=MPI.COMM_WORLD,
                mtype::Symbol=C.MATMPIAIJ)


  println("I finally found the problem")

  return nothing
end

end  # end module PETSc

using PETSc

producing output:

WARNING: Method definition Mat(Type{#T<:Any}) in module PETSc at /home/jared/.julia/v0.4/PETSc_current/src/tmp.jl:24 overwritten at /home/jared/.julia/v0.4/PETSc_current/src/tmp.jl:36.
WARNING: Method definition #Mat(Array{Any, 1}, PETSc.#Mat, Type{#T<:Any}) in module PETSc overwritten.

For the invocation Mat(Float64) the methods are actually ambiguous, explaining the first warning. Not providing default arguments for m and n in the second function fixes both (although I'm not really sure what the second one is complaining about). That will make calling the function with local sizes a bit more verbose, but I guess its unavoidable.

ref JuliaLang/julia#18273

[simonbyrne]

code replaced in #99.