Overflows are ignored in some cases when checked-converting from Int128 to SignedInteger

[skyoxZ]

Description

runtime/src/libraries/System.Private.CoreLib/src/System/Int128.cs

Lines 311 to 317 in 82dac28

	public static explicit operator checked long(Int128 value)
	{
	if (~value._upper == 0)
	{
	long lower = (long)value._lower;
	return lower;
	}

Overflows are ignored when lower >= 0.

Search if (~value._upper == 0) in that file to find more.

Reproduction Steps

Int128 a = new(ulong.MaxValue, 42);
var b = checked((long)a);
Console.WriteLine(b);

Expected behavior

OverflowException

Actual behavior

42

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response