Description
in very recent 2.13.x nightlies,
scala> (+0): Byte
^
error: type mismatch;
found : Int(0)
required: Byte
as Byte, so also Short and Char. this code has been accepted since Scala 2.8 (the version that introduced weak conformance). Dotty also accepts it.
note that while an initial - is part of the syntax for numeric literals, + is not (SLS 1.3). +0 parses as 0.unary_+. (0.unary_+): Byte gives the same error (and was accepted in previous Scala versions).
@sjrd this was uncovered by Scala.js's test suite, via the community build 🏅
@milessabin I haven't bisected to pinpoint when this regressed, but I bet this has to do with one of your recent changes to ConstantFolder made as part of SIP-23 (PR scala/scala#5310)
SLS 6.24, "Constant Expressions", gives plenty of wiggle room here:
Constant expressions are expressions that the Scala compiler can evaluate to a constant. The definition of "constant expression" depends on the platform
regardless, I think it would be peculiar if +0 weren't covered, given that 0 + 0 is covered ((0 + 0): Byte still compiles)