round(Int, -Inf16) doesn't throw

[LilithHafner]

julia> round(Int32, -Inf16)
-2147483648

julia> round(Int64, -Inf16)
-9223372036854775808

julia> round(Int128, -Inf16)
0

julia> versioninfo()
Julia Version 1.10.0-beta2
Commit a468aa198d0 (2023-08-17 06:27 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: macOS (arm64-apple-darwin22.4.0)
  CPU: 8 × Apple M2
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, apple-m1)
  Threads: 1 on 4 virtual cores
Environment:
  JULIA_EDITOR = code

[ararslan]

Looks like this is because Float16(typemin(Int)) is -Inf16 and the check in trunc is inclusive on the lower bound. Compare that to Float32 for which Float32(typemin(Int)) > -Inf32. In fact, this is touched on in a comment in the code:

This assumes that Tf(typemin(Ti)) > -Inf, which is true for these types, but not for Float16 or larger integer types.

Perhaps that assumption should be explicit as part of the condition? Like

--- a/base/float.jl
+++ b/base/float.jl
@@ -953,7 +953,7 @@ for Ti in (Int8, Int16, Int32, Int64, Int128, UInt8, UInt16, UInt32, UInt64, UIn
             # these types, but not for `Float16` or larger integer types.
             @eval begin
                 function trunc(::Type{$Ti},x::$Tf)
-                    if $(Tf(typemin(Ti))) <= x < $(Tf(typemax(Ti)))
+                    if isfinite(x) && $(Tf(typemin(Ti))) <= x < $(Tf(typemax(Ti)))
                         return unsafe_trunc($Ti,x)
                     else
                         throw(InexactError(:trunc, $Ti, x))

[LilithHafner]

I noticed this issue when writing tests for #51095, but #50812 should already fix it.