Update base/rational.jl

Author: stevengj

base/rational.jl

@@ -145,8 +145,12 @@ function (::Type{T})(x::Rational{S}) where T<:AbstractFloat where S
     P = promote_type(T,S)
     convert(T, convert(P,x.num)/convert(P,x.den))::T
 end
-Float16(x::Rational{<:Union{Int16,Int32,Int64,Int128,UInt16,UInt32,UInt64,UInt128}}) =
-    Float16(Float32(x)) # avoid spurious overflow (#52394)
+ # avoid spurious overflow (#52394).  (Needed for UInt16 or larger;
+ # we also include Int16 for consistency of accuracy.)
+Float16(x::Rational{<:Union{Int16,Int32,Int64,UInt16,UInt32,UInt64}}) =
+    Float16(Float32(x))
+Float16(x::Rational{<:Union{Int128,UInt128}}) =
+    Float16(Float64(x)) # UInt128 overflows Float32, include Int128 for consistency
 
 function Rational{T}(x::AbstractFloat) where T<:Integer
     r = rationalize(T, x, tol=0)