Spurious method ambiguity error

[nalimilan]

On current master the following code generates an ambiguity error which does not happen on 0.5. Commenting out the second convert method and uncommenting the third one fixes the problem. Yet adding free type parameters shouldn't make any difference.

immutable CategoricalValue{T, R <: Integer}
    pool::T
    level::R
end

Base.convert{T, R}(::Type{CategoricalValue{T, R}}, x::CategoricalValue{T, R}) = 1
Base.convert{T}(::Type{T}, x::CategoricalValue) = 2
#Base.convert{S, T, R}(::Type{T}, x::CategoricalValue{S, R}) = 3

x = CategoricalValue{String, Int}("a", 1);

convert(CategoricalValue{String, Int}, x)

[yuyichao]

Dup of #11597 (comment)

[nalimilan]

I suspected this was already known, but it's hard for me to tell. Feel free to close.

[JeffBezanson]

Dup of #6383