New format for trait redefined final method from AnyRef error message…

[thebignet]

Further enhancement : explanation could be enhanced by telling which method from AnyRef was redefined

[dottybot]

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[allanrenucci]

I think we should only have on error message for overridden final value/def. We should not special case for traits that override a method in AnyRef

[thebignet]

I understand what you mean. I had the same thought as to why should there be such a specific check. I think it is explained by this comment.

Have to use matchingSymbol, not a method involving overridden symbols, because the scala type system understands that an abstract method here does not override a concrete method in Object. The jvm, however, does not.

According to notes on RefsChecks.scala:127, 1.2 says that final members of classes should not be overriden. Maybe it is because AnyRef is a trait (and not a class), so implementing a final def should normally work, but since methods like wait are implemented in the JVM for all Objects, there is a special case.

This is my first PR on dotty and I have no claim to be an expert. Is this explanation correct ?