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override val + super difference between 2.7.0 and 2.7.1 #899

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scabug opened this issue May 13, 2008 · 6 comments
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override val + super difference between 2.7.0 and 2.7.1 #899

scabug opened this issue May 13, 2008 · 6 comments
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@scabug
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scabug commented May 13, 2008

Take the example:

class Top {
  val o = "Hi there!"
}

class Bot extends Top {
  override val o = "Ha! " + super.o
}

And try compiling it with the different versions:

dietlw@scarab:~/tmp$$ /opt/scala-2.6.1-final/bin/scalac OverrideVal.scala 
dietlw@scarab:~/tmp$$ /opt/scala-2.7.0-final/bin/scalac OverrideVal.scala 
dietlw@scarab:~/tmp$$ /opt/scala-2.7.1.final/bin/scalac OverrideVal.scala 
OverrideVal.scala:6: error: super may be not be used on value o
  override val o = "Ha! " + super.o
                                  ^
one error found

Why is this an error now?
The error message text could be changed to something like
"super may not be used on value o".
I did not see an entry in the change logs that would explain this
change of behavior and guess it's an error introduced in 2.7.1.
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scabug commented May 13, 2008

Imported From: https://issues.scala-lang.org/browse/SI-899?orig=1
Reporter: wdietl

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scabug commented May 13, 2008

Geoffrey Alan Washburn (washburn) said:
This is the intended behavior, and it was changed so that traits could override vals to be more uniform with classes.

I don't know why it didn't make it into the ChangeLog. Probably it was a small item in a larger set of changes someone committed.

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scabug commented May 13, 2008

wdietl said:
The Scala Reference, page 81, has Example 6.5.1, which does not
compile any more under this changed rule.
(Also the example contains superfluous "}" in classes C and D).

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scabug commented May 14, 2008

Geoffrey Alan Washburn (washburn) said:
I am pretty sure Martin made the change, so it would probably be better for him to document it.

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scabug commented May 22, 2008

@odersky said:
I changed the spec to explain.

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scabug commented Jan 14, 2009

@odersky said:
Milestone next_bugfix deleted

@scabug scabug closed this as completed May 18, 2011
@scabug scabug added the docs label Apr 6, 2017
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