Spurious UndefVarError when converting a vector of tuples

[rdeits]

Here's a MWE:

module Foo

abstract type A end

struct B <: A
end

convert(Vector{Tuple{C}} where C <: A, [(B(),)])

end

on v0.6, this works, but on the latest nightly it fails with:

UndefVarError: T not defined

Stacktrace:
 [1] convert(::Type{Array{Tuple{C},1} where C<:Main.Foo.A}, ::Array{Tuple{Main.Foo.B},1}) at ./array.jl:406
 [2] top-level scope

The relevant line is: https://github.com/JuliaLang/julia/tree/ff0e1f7fcf324d4e1598e30dac91f13609d7e04e/base/array.jl#L406 in which T appears to be properly defined.

julia> versioninfo()
Julia Version 0.7.0-DEV.3018
Commit ff0e1f7fcf* (2017-12-15 23:34 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Core(TM) i7-3920XM CPU @ 2.90GHz
  WORD_SIZE: 64
  BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Sandybridge)
  LAPACK: libopenblas64_
  LIBM: libopenlibm
  LLVM: libLLVM-3.9.1 (ORCJIT, ivybridge)
Environment:

(sorry if this is already fixed in master -- I don't have a working source build on my current machine).

[KristofferC]

Work on latest master for me. Closing.

[vtjnash]

different repro:

julia> abstract type A end

julia> convert(Vector{Tuple{C}} where C <: A, [])
ERROR: UndefVarError: T not defined
Stacktrace:
 [1] Array{Tuple{C},1} where C<:A(::Array{Any,1}) at ./array.jl:411
 [2] convert(::Type{Array{Tuple{C},1} where C<:A}, ::Array{Any,1}) at ./abstractarray.jl:15
 [3] top-level scope

[JeffBezanson]

I think that case should give an error, though perhaps a more useful error. It's not clear what concrete array type to return.

[vtjnash]

seems okay now

julia> convert(Vector{Tuple{C}} where C <: A, [])
ERROR: MethodError: no method matching (Array{Tuple{C}, 1} where C<:A)(::Vector{Any})
Stacktrace:
 [1] convert(::Type{Array{Tuple{C}, 1} where C<:A}, a::Vector{Any})
   @ Base ./array.jl:663
 [2] top-level scope
   @ REPL[2]:1

(we do have a better version of convert for NamedTuple that handles this case, but unclear if that is really useful in general like this)