Integer /: restrict fallback to same-type case (fix #19714)

The principle here is that if there's an implementation of a promoted operator for some type and promotions for that type, unless other methods are defined, the operation should always be "funnelled" through the core operator definition for that type. The method for `/(::Integer, ::Integer)` violated that principle since it would take precedence in mixed-integer-type division cases even in the presence of a same-type method definition for a custom integer type and the appropriate promotion rules.
JuliaLang · Dec 31, 2016 · 2166ec6 · 2166ec6 · sairus7 · Dec 1, 2017
1 parent 9ce0aca
commit 2166ec6
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diff --git a/base/int.jl b/base/int.jl
@@ -32,8 +32,9 @@ typealias BitUnsigned64T Union{Type{UInt8},Type{UInt16},Type{UInt32},Type{UInt64
 +{T<:BitInteger}(x::T, y::T) = box(T, add_int(unbox(T,x),unbox(T,y)))
 *{T<:BitInteger}(x::T, y::T) = box(T, mul_int(unbox(T,x),unbox(T,y)))
 
-/(x::Integer, y::Integer) = float(x)/float(y)
 inv(x::Integer) = float(one(x))/float(x)
+/{T<:Integer}(x::T, y::T) = float(x)/float(y)
+/(x::BitInteger, y::BitInteger) = float(x)/float(y)
 
 """
     isodd(x::Integer) -> Bool

diff --git a/test/operators.jl b/test/operators.jl
@@ -71,3 +71,11 @@ let xs = [[i:i+4;] for i in 1:10]
         @test max.(xs[1:n]...) == [n:n+4;]
     end
 end
+
+# issue #19714
+immutable T19714 <: Integer end
+Base.float(::T19714) = 19714.0
+Base.:/(::T19714, ::T19714) = T19714()
+Base.convert(::Type{T19714}, ::Int) = T19714()
+Base.promote_rule(::Type{T19714}, ::Type{Int}) = T19714
+@test T19714()/1 === 1/T19714() === T19714()