Throw OverflowError on typemin(Int)//(-1) (JuliaLang#51085)

Fixes JuliaLang#32443

Currently `typemin(Int)//(-1) == typemin(Int)//(1)`, ignoring an
overflow.

As noted by @JeffreySarnoff in
[JuliaLang#32443](JuliaLang#32443 (comment))
This should throw an error instead of silently overflowing.

To fix this I am using `checked_neg` instead of `-` in the Rational
constructor.

With this PR `(-one(T))//typemin(T)` will now also throw an
`OverflowError` instead of an `ArgumentError`

base/rational.jl

@@ -17,12 +17,10 @@ end
 unsafe_rational(num::T, den::T) where {T<:Integer} = unsafe_rational(T, num, den)
 unsafe_rational(num::Integer, den::Integer) = unsafe_rational(promote(num, den)...)
 
-@noinline __throw_rational_argerror_typemin(T) = throw(ArgumentError("invalid rational: denominator can't be typemin($T)"))
 function checked_den(::Type{T}, num::T, den::T) where T<:Integer
  if signbit(den)
- den = -den
- signbit(den) && __throw_rational_argerror_typemin(typeof(den))
- num = -num
+ den = checked_neg(den)
+ num = checked_neg(num)
  end
  return unsafe_rational(T, num, den)
 end

test/rational.jl

@@ -28,8 +28,8 @@ using Test
  @test (1//typemax(Int)) / (1//typemax(Int)) == 1
  @test_throws OverflowError (1//2)^63
  @test inv((1+typemin(Int))//typemax(Int)) == -1
- @test_throws ArgumentError inv(typemin(Int)//typemax(Int))
- @test_throws ArgumentError Rational(0x1, typemin(Int32))
+ @test_throws OverflowError inv(typemin(Int)//typemax(Int))
+ @test_throws OverflowError Rational(0x1, typemin(Int32))
 
  @test @inferred(rationalize(Int, 3.0, 0.0)) === 3//1
  @test @inferred(rationalize(Int, 3.0, 0)) === 3//1
@@ -43,10 +43,15 @@ using Test
  # issue 26823
  @test_throws InexactError rationalize(Int, NaN)
  # issue 32569
- @test_throws ArgumentError 1 // typemin(Int)
+ @test_throws OverflowError 1 // typemin(Int)
  @test_throws ArgumentError 0 // 0
  @test -2 // typemin(Int) == -1 // (typemin(Int) >> 1)
  @test 2 // typemin(Int) == 1 // (typemin(Int) >> 1)
+ # issue 32443
+ @test Int8(-128)//Int8(1) == -128
+ @test_throws OverflowError Int8(-128)//Int8(-1)
+ @test_throws OverflowError Int8(-1)//Int8(-128)
+ @test Int8(-128)//Int8(-2) == 64
 
  @test_throws InexactError Rational(UInt(1), typemin(Int32))
  @test iszero(Rational{Int}(UInt(0), 1))