Return type of *(::Rational, ::Integer) changed in 1.5

[sostock]

#35483 introduced a new method for *(::Rational, ::Integer) which changed the return type of that operation. There was no specialized method for this before, so promotion was used.

Julia 1.4.2:

julia> Rational{Int64}(1,1) * UInt8(1) # returns Rational{Int64}
1//1

Julia 1.5.0-beta1:

julia> Rational{Int64}(1,1) * UInt8(1) # returns Rational{UInt64}
0x0000000000000001//0x0000000000000001

Should this return type be preserved between minor versions?

[Liozou]

I don't know if return types should be preserved in general, but for this particular case I would assume so, since, for this very reason, some computations that used to work now error:

Julia 1.0.5 (and probably up to 1.4.x)

julia> 0x1 * -1//1
-1//1

Julia 1.5.0-beta1:

julia> 0x1 * -1//1
ERROR: InexactError: check_top_bit(UInt64, -1)
Stacktrace:
 [1] throw_inexacterror(::Symbol, ::Type{UInt64}, ::Int64) at ./boot.jl:558
 [2] check_top_bit at ./boot.jl:572 [inlined]
 [3] toUInt64 at ./boot.jl:683 [inlined]
 [4] UInt64 at ./boot.jl:713 [inlined]
 [5] convert at ./number.jl:7 [inlined]
 [6] _promote at ./promotion.jl:259 [inlined]
 [7] promote at ./promotion.jl:282 [inlined]
 [8] checked_mul at ./checked.jl:21 [inlined]
 [9] *(::UInt8, ::Rational{Int64}) at /home/liozou/julia/base/rational.jl:318
 [10] top-level scope at none:1

A solution consists in using promotions when doing binary operations: see PR #36279

[StefanKarpinski]

This seems like a regression.