Deprecate object $ to avoid unsoundess
#1395
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This was referenced Feb 16, 2024
lihaoyi
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Jun 10, 2024
Added 3.4.2 to targets in a fairly straightforward, formulaic fashion. 3.4.0 and 3.4.1, for good reason, fail to parse `$` as a class file, but a [temporary ad-hoc workaround was added in 3.4.2](scala/scala3#19705), so this needn't block 3.4 support for now. Reliance on `object $` still needs to be [fixed in Ammonite](#1395). Several internals changes required fixes also; I used the most obvious solution (e.g. if Y extends X and Y is now private, use X instead), but someone who knows more might want to read it over. Tests pass on my machine for 3.3 and 3.4.2 (under Java 21). If accepted, this patch would supersede #1394
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The Scala spec states that identifiers that contain the
$characters are reserved for compiler-generated names. Any other use has undefined behavior.One of these (
object $) caused a bug in scala/scala3#19702. We are trying to add an ad-hoc patch to support these broken classes from Ammonite. But this patch cannot be guaranteed to work forever and there is no guarantee that these definitions do not introduce more issues (that may not be by the compiler).The following names can cause undefined behavior:
object $,package $file,package $exec,package $ivy,package $url,package $stub,package $cp,package $plugin,package $repo. These are defined in https://github.com/com-lihaoyi/Ammonite/blob/main/amm/interp/api/src/main/scala/ammonite/Stubs.scala. There might be more problematic names.The only possible solution is to deprecate these objects and migrate to some sound naming scheme.
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