method seems to get dropped when precompilation is enabled

[jrevels]

For ease of reproducibility, I made an MRE package here: https://github.com/jrevels/DispatchError.jl. The bug can be "toggled" by turning precompilation on/off.

Here's the code:

__precompile__()

module DispatchError

immutable Foo{A,B}
    a::A
    b::B
    c::Int
    # disable default outer constructor
    Foo(a, b, c) = new(a, b, c)
end

Foo(args...) = error("boo!")

Foo{A<:AbstractArray,B<:AbstractArray}(a::A, b::B, c::Int) = info("yay!")

end # module

...and here's the test which exhibits the bug:

using DispatchError

# if you run this with precompilation enabled, 
# it errors out with "boo!" even though it should 
# just call the non-erroring constructor
#
# if precompilation is disabled, it calls the correct method
DispatchError.Foo(rand(3), rand(3), 1)

versioninfo:

julia> versioninfo()
Julia Version 0.6.0-dev.2478
Commit dbf41c0 (2017-01-30 18:58 UTC)
Platform Info:
  OS: macOS (x86_64-apple-darwin13.4.0)
  CPU: Intel(R) Core(TM) i5-4288U CPU @ 2.60GHz
  WORD_SIZE: 64
  BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Haswell)
  LAPACK: libopenblas64_
  LIBM: libopenlibm
  LLVM: libLLVM-3.9.1 (ORCJIT, haswell)

EDIT: simplified the example further

[jrevels]

Note that switching the order of the outer constructor definitions also circumvents the bug.

[jrevels]

Checked this at the request of @vtjnash, and it seems like the more specific constructor gets totally dropped when precompilation is enabled (but the method table seems to have the right number of methods either way...?).

Precompilation on:

julia> n_methods = length(typeof(Type).name.mt)
1387

julia> using DispatchError

julia> methods(DispatchError.Foo)
# 1 method for generic function "(::Type)":
(::Type{DispatchError.Foo})(args...) in DispatchError at /Users/jarrettrevels/.julia/v0.6/DispatchError/src/DispatchError.jl:13

julia> length(typeof(Type).name.mt) - n_methods
3

Precompilation off:

julia> n_methods = length(typeof(Type).name.mt)
1387

julia> using DispatchError

julia> methods(DispatchError.Foo)
# 2 methods for generic function "(::Type)":
(::Type{DispatchError.Foo}){A<:AbstractArray, B<:AbstractArray}(a::A, b::B, c::Int64) in DispatchError at /Users/jarrettrevels/.julia/v0.6/DispatchError/src/DispatchError.jl:15
(::Type{DispatchError.Foo})(args...) in DispatchError at /Users/jarrettrevels/.julia/v0.6/DispatchError/src/DispatchError.jl:13

julia> length(typeof(Type).name.mt) - n_methods
3

[vtjnash]

fixed by #20665