Simplify type bounds. #2405
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Simplify type bounds. #2405
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This will impact anyone who parses TypeBoundsTrees and never expects to see an EmptyTree in there. I don't know what can be done about that beyond alerting/preparing the usual parties. |
I started out looking to limit the noise from empty type
bounds, i.e. the endless repetition of
class A[T >: _root_.scala.Nothing <: _root_.scala.Any]
This led me to be reminded of all the unnecessary and
in fact damaging overreaches which are performed during parsing.
Why should a type parameter for which no bounds are
specified be immediately encoded with this giant tree:
TypeBounds(
Select(Select(Ident(nme.ROOTPKG), tpnme.scala_), tpnme.Nothing),
Select(Select(Ident(nme.ROOTPKG), tpnme.scala_), tpnme.Any)
)
...which must then be manually recognized as empty type bounds?
Truly, this is madness.
- It deftly eliminates the possibility of recognizing
whether the user wrote "class A[T]" or "class A[T >: Nothing]"
or "class A[T <: Any]" or specified both bounds. The fact
that these work out the same internally does not imply the
information should be exterminated even before parsing completes.
- It burdens everyone who must recognize type bounds trees,
such as this author
- It is far less efficient than the obvious encoding
- It offers literally no advantage whatsoever
Encode empty type bounds as
TypeBounds(EmptyTree, EmptyTree)
What could be simpler.
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I hope I can screw around with the position of this tree for the rest of my natural life. |
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Fuck. This. |
This was referenced Apr 19, 2013
Merged
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I started out looking to limit the noise from empty type
bounds, i.e. the endless repetition of
class A[T >: _root_.scala.Nothing <: _root_.scala.Any]This led me to be reminded of all the unnecessary and
in fact damaging overreaches which are performed during parsing.
Why should a type parameter for which no bounds are
specified be immediately encoded with this giant tree:
...which must then be manually recognized as empty type bounds?
Truly, this is madness.
whether the user wrote "class A[T]" or "class A[T >: Nothing]"
or "class A[T <: Any]" or specified both bounds. The fact
that these work out the same internally does not imply the
information should be exterminated even before parsing completes.
such as this author
Encode empty type bounds as
TypeBounds(EmptyTree, EmptyTree)What could be simpler.