SI-6562 Fix crash with class nested in @inline method

e6b4204604 moved access widenings from ExplicitOuter to
SuperAccessors to reflect them in pickled signatures so
that the inliner can take advantage of them under separate
compilation.

The followup discussion [1] determined that this wasn't
the right solution: while it enabled new separate compilation
inlinings, it failed to widen access of outer pointers and
hence prevented certain inlinings.

A better solution was proposed: modify the inliner to know
that access widening is guaranteed to have happened in
ExplicitOuter for any field accessed by an @inline-d method
body, rather than relying solely on the pickled types.

But this hasn't happened yet. In the meantime 07f94297 / #1121
reinstated the access widening to SuperAccessors, but took a
slightly different approach, using `Symbol#enclMethod` rather
than `closestEnclMethod`. That deviation triggers SI-6562.

This commit goes back to `closestEnclMethod`.

[1] https://groups.google.com/forum/#!topic/scala-internals/iPkMCygzws4

1 files changed, 8 insertions, 0 deletions

diff --git a/src/reflect/scala/reflect/internal/Symbols.scala b/src/reflect/scala/reflect/internal/Symbols.scala
index a6f156f947..4afebab493 100644
--- a/src/reflect/scala/reflect/internal/Symbols.scala
+++ b/src/reflect/scala/reflect/internal/Symbols.scala
@@ -3269,6 +3269,14 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
    */
   def mapParamss[T](sym: Symbol)(f: Symbol => T): List[List[T]] = mmap(sym.info.paramss)(f)
 
+  /** Return closest enclosing method, unless shadowed by an enclosing class. */
+  // TODO Move back to ExplicitOuter when the other call site is removed.
+  // no use of closures here in the interest of speed.
+  final def closestEnclMethod(from: Symbol): Symbol =
+    if (from.isSourceMethod) from
+    else if (from.isClass) NoSymbol
+    else closestEnclMethod(from.owner)
+
   /** An exception for cyclic references of symbol definitions */
   case class CyclicReference(sym: Symbol, info: Type)
   extends TypeError("illegal cyclic reference involving " + sym) {