Clean up Complex Rational division.

Fixes JuliaLang#15920 and JuliaLang#16282.

base/rational.jl

@@ -35,17 +35,9 @@ function //(x::Rational, y::Rational)
  checked_mul(xn,yd)//checked_mul(xd,yn)
 end
 
-//(x::Complex, y::Real ) = complex(real(x)//y,imag(x)//y)
-function //(x::Number, y::Complex)
- xr = complex(Rational(real(x)),Rational(imag(x)))
- yr = complex(Rational(real(y)),Rational(imag(y)))
- xr // yr
-end
-function //{Ra<:Rational,Rb<:Rational}(x::Complex{Ra}, y::Complex{Rb})
- xy = x*y'
- yy = real(y*y')
- complex(real(xy)//yy, imag(xy)//yy)
-end
+//(x::Complex, y::Real) = complex(real(x)//y,imag(x)//y)
+//(x::Number, y::Complex) = x*y'//abs2(y)
+
 
 //(X::AbstractArray, y::Number) = X .// y
 .//(X::AbstractArray, y::Number) = reshape([ x // y for x in X ], size(X))
@@ -196,7 +188,7 @@ function *(x::Rational, y::Rational)
  checked_mul(xn,yn) // checked_mul(xd,yd)
 end
 /(x::Rational, y::Rational) = x//y
-/(x::Rational, z::Complex ) = inv(z/x)
+/{T<:Union{Integer,Rational}}(x::Rational, y::Complex{T}) = x//y
 
 fma(x::Rational, y::Rational, z::Rational) = x*y+z
 

test/numbers.jl

@@ -2756,3 +2756,9 @@ testmi(typemax(UInt32)-UInt32(1000):typemax(UInt32), map(UInt32, 1:100))
 @test indices(1) == ()
 @test indices(1,1) == 1:1
 @test_throws BoundsError indices(1,-1)
+
+# issue #15920
+@test Rational(0, 1) / Complex(3, 2) == 0
+
+# issue #16282
+@test_throws MethodError 3 // 4.5im