Fix and optimization in overriding logic.

Given:

  trait Foo { def f: Int = 5 }
  trait Bar extends Foo { def f: Int }

I noticed allOverriddenSymbols for the abstract f defined in Bar
was returning the method from Foo, even though an abstract method
cannot override a concrete one. There were other bits of code
which accidentally depended on this outcome. Now allOverriddenSymbols
for Bar is empty.

The optimization is that whether or not a symbol overrides
any other symbols is known at creation time and does not change.
We now spend a lot less time looking for overridden symbols in
base classes by storing that value, "isOverridingSymbol".

1 files changed, 1 insertions, 2 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Contexts.scala b/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
index 711085e6c9..b070bd1b49 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
@@ -573,8 +573,7 @@ trait Contexts { self: Analyzer =>
              (  superAccess
              || pre.isInstanceOf[ThisType]
              || phase.erasedTypes
-             || isProtectedAccessOK(sym)
-             || (sym.allOverriddenSymbols exists isProtectedAccessOK)
+             || (sym.overrideChain exists isProtectedAccessOK)
                 // that last condition makes protected access via self types work.
              )
         )