inline modifier rejected under Scala2 mode

[allanrenucci]

The following code snippet fails to compile under Scala2 mode:

class Foo {
  inline def foo = 1
}

dotc Foo.scala -language:Scala2
-- [E040] Syntax Error: Foo.scala:41:13 ---------------------------
41 |  inline def foo = 1
   |             ^^^
   |             ';' expected, but identifier found
-- [E006] Unbound Identifier Error: Foo.scala:41:2 ----------------
41 |  inline def foo = 1
   |  ^^^^^^
   |  not found: inline

The issue is that the scanner treats the inline keyword as an ident under Scala2 mode.

[allanrenucci]

We don't have the issue with enums:

enum Foo { case F0, F1 }

To fix this issue, one could have a look at how we handle enums and replicate the behavior to inline

[manshengyang]

@allanrenucci this is due to Scanner.scala:199. And the commit(d575e58) says this was done intentionally.
What should be the expected behavior?

[allanrenucci]

Hum, indeed inline is treated as an identifier under Scala2 mode as opposed to enum which is always treated as keyword. For instance under Scala2 mode you cannot write:

class Foo {
  val enum = 1
}

@smarter What do you think? Should we treat enum like inline and parse it as an identifier under Scala2 mode? But that would mean we can't write enums under this mode...

[smarter]

No, requiring users to put backquotes around enum is not a big deal. For inline, we should be able to support both @inline and inline since they can be distinguished by checking if there's an at or not.