BUG: clamp(typemax(UInt64), Int64) errors

[KlausC]

The call clamp(typemax(UInt64), Int64) should return typemax(Int64) but throws InexactError.

julia> clamp(typemax(UInt64), Int64)
ERROR: InexactError: check_top_bit(UInt64, -9223372036854775808)
Stacktrace:
 [1] throw_inexacterror(f::Symbol, ::Type{UInt64}, val::Int64)
   @ Core ./boot.jl:634
 [2] check_top_bit
   @ ./boot.jl:648 [inlined]
 [3] toUInt64
   @ ./boot.jl:759 [inlined]
 [4] UInt64
   @ ./boot.jl:789 [inlined]
 [5] convert
   @ ./number.jl:7 [inlined]
 [6] clamp
   @ ./math.jl:98 [inlined]
 [7] clamp(x::UInt64, ::Type{Int64})
   @ Base.Math ./math.jl:123
 [8] top-level scope
   @ REPL[1]:1

[KlausC]

The same happens for bit sizes 8, 16, 32, 64, 128.

[barucden]

It's due to ifelse being used in

julia/base/math.jl

Lines 99 to 102 in e9a24d4

	ifelse(x > hi, convert(promote_type(X,L,H), hi),
	ifelse(x < lo,
	convert(promote_type(X,L,H), lo),
	convert(promote_type(X,L,H), x)))

Since ifelse is a function, all arguments are evaluated. That is

convert(UInt64, typemax(Int64))
convert(UInt64, typemin(Int64))
convert(UInt64, typemax(UInt64))

with the second one throwing the reported error since typemin(Int64) is negative. We might replace ifelse with the ternary conditional operator (or normal conditional statements), but I am not sure whether it has some performance consequences.

[vtjnash]

Ternary is nearly always faster and usually generates better code

[KlausC]

See my comment in #54038.
Additionally something like clamp(x::Int64, ::Type{UInt64}) = UInt64(max(x, 0)) for all bit sizes would solve the issue, probably.