Extends syntax inconsistent

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In the syntax summary of the Scala Specification (as of May 5th, 2008), the syntax for subclassing is given as:

ClassTemplateOpt ::= Extends ClassTemplate | [[Extends] TemplateBody]
TraitTemplateOpt ::= Extends TraitTemplate | [[Extends] TemplateBody]
Extends          ::= `extends' | `<:'

However, the alternative <: token doesn't seem to be supported by the compiler. Moreover, the Extends non-terminal is not mentioned elsewhere in the specification, and in 5.3 we have

ClassTemplateOpt ::= `extends' ClassTemplate | [[`extends'] TemplateBody]
TraitTemplateOpt ::= `extends' TraitTemplate | [[`extends'] TemplateBody]

Hence the syntax summary seems to be erroneous.

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Imported From: https://issues.scala-lang.org/browse/SI-902?orig=1
Reporter: Lauri Alanko (lealanko)

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Geoffrey Alan Washburn (washburn) said:
The token <: can be used in some cases in trunk, though the semantics are completely undefined until virtual classes are implemented.

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Lauri Alanko (lealanko) said:
Quite right. A braino on my part to forget virtual classes.

However, I'd still say that, in a reference document linked to from the Scala site's front page, it is a bad idea to describe a syntax that is not supported by the current release version, and that is not explained in detail anywhere in the specification.

If the May 5th version of the spec is a "work in progress", not even supposed to be a coherent text, or consistent with any release of the implementation, then I think it should be listed under "nightly builds" or the like.

Yes, granted, it does say "draft", but it also says "version 2.7", strongly indicating that it's somehow related to the language supported by the 2.7.x series of the implementation.

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@odersky said:
Milestone next_bugfix deleted