Formatting a byte as a hexadecimal integer produces an incorrect result for a negative value about scala-js

[sjrd]

This is working as designed. The behavior is indeed a consequence of value-based type tests for numeric types. The fact that it behaves like Int instead of Byte/Short is the better trade-off. As mentioned in the issue description, portable behavior is recoverable by converting to Int; if we had chosen the other way around, no workaround would exist for the Int behavior.

[gzm0]

Hrm. I was going to write that this is a direct consequence of "Runtime type tests are based on values" documented here: https://www.scala-js.org/doc/semantics.html

However, one would expect the JVM result in this case. It seems that the relevant code simply only considers ints and longs:

scala-js/javalib/src/main/scala/java/util/Formatter.scala

Lines 433 to 442 in b5158b2

	val str = arg match {
	case arg: Int =>
	if (isOctal) java.lang.Integer.toOctalString(arg)
	else java.lang.Integer.toHexString(arg)
	case arg: Long =>
	if (isOctal) java.lang.Long.toOctalString(arg)
	else java.lang.Long.toHexString(arg)
	case _ =>
	illegalFormatConversion()
	}

I vaguely recall that we needed to make this decision a long time ago, but I do not remember why we settled on this. I'll try and dig in the commit history.

[gzm0]

Commit removing the handling of Byte/Short: 000fb14 / #434

[sjrd]

Also Duplicate of #2206.