change promotion in rational conversion

[jishnub]

This lets one use an odd integer type as the numerator, which can't store 2. After this, one may use https://github.com/jishnub/OddEvenIntegers.jl to obtain

julia> Rational{Int}(half(Odd(1)))
1//2

This errors on master at present

[jishnub]

Test failure seems unrelated

[sostock]

Test failure seems unrelated

Yes, they are due to JuliaLang/julia#48735.

[sostock]

Some comments:

• There should be a test for this. I would just define a singleton type One <: Integer that represents the number 1, that way we don’t need to add OddEvenIntegers.jl as a test dependency.
• This only fixes the behavior on Julia 1.5 and newer. On older Julia versions, the following method is used, which still calls oftype(tx, 2):
  

  HalfIntegers.jl/src/HalfIntegers.jl

  Line 65 in 215556a

  (T::Type{<:Rational})(x::HalfInteger) = (tx=twice(x); T(tx,oftype(tx,2)))

  
  Since both HalfIntegers.jl and OddEvenIntegers.jl support Julia 1.0, I think we should change that method as well.
• This change allows Rational{Int}(half(Odd(1))), but not Rational(half(Odd(1))). For that, the following line would need to be changed as well:
  

  HalfIntegers.jl/src/HalfIntegers.jl

  Line 53 in 215556a

  Base.unsafe_rational(tx, oftype(tx, 2))

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and no project coverage change

Comparison is base (215556a) 99.20% compared to head (228551f) 99.20%.

❗ Current head 228551f differs from pull request most recent head 20d5b73. Consider uploading reports for the commit 20d5b73 to get more accurate results

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Additional details and impacted files

@@           Coverage Diff           @@
##           master      #49   +/-   ##
=======================================
  Coverage   99.20%   99.20%           
=======================================
  Files           1        1           
  Lines         250      250           
=======================================
  Hits          248      248           
  Misses          2        2           

Impacted Files	Coverage Δ
src/HalfIntegers.jl	99.20% <100.00%> (ø)

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[jishnub]

@sostock I've added tests and implemented the changes as suggested

[jishnub]

Gentle bump