SI-8862 Fix treatment of inherited implicits in package objects

Two spots in implicit search fell prey to a trap with package
objects. Members of a package object are entered into the scope
of the enclosing package, but that doesn't form a suitable prefix
for determing the member type.

A REPL transcript paints a picture that speaks a 1000 words:

```
scala> :paste -raw
// Entering paste mode (ctrl-D to finish)

package p { class C[A] { def foo: A = ??? }; object `package` extends C[String] }

// Exiting paste mode, now interpreting.

scala> val p = rootMirror.getPackageIfDefined("p")
warning: there was one deprecation warning; re-run with -deprecation for details
p: $r.intp.global.Symbol = package p

scala> p.info.decls
res0: $r.intp.global.Scope = Scopes(class C, package object p, method foo)

scala> val foo = p.info.decl(TermName("foo"))
foo: $r.intp.global.Symbol = method foo

scala> p.typeOfThis memberType foo
res1: $r.intp.global.Type = => A

scala> val fooOwner = foo.owner
fooOwner: $r.intp.global.Symbol = class C

scala> p.info.decl(nme.PACKAGE).typeOfThis memberType foo
res3: $r.intp.global.Type = => String
```

This commit detects if we find an implicit in a package module,
and then uses the self type of the corresponding package object
as the prefix for the `ImplicitInfo`. This is done in both
`Context.implicitss` (which collects in-scope implicits), and
in `companionImplicitMap` (which harvests them from the implicit
scope.) In addition, it was necessary / possible to remove a special
case that excluded package object implicits, the referenced tests for
SI-3999 now pass without this.

1 files changed, 47 insertions, 0 deletions

diff --git a/test/files/pos/t8862a.scala b/test/files/pos/t8862a.scala
new file mode 100644
index 0000000000..f9576707ba
--- /dev/null
+++ b/test/files/pos/t8862a.scala
@@ -0,0 +1,47 @@
+package p {
+
+  abstract class C[A] {
+    def x: A
+    implicit def oops: A = x
+    implicit def oopso: Option[A] = None
+  }
+
+  package q {
+
+    class Oops
+
+    object `package` extends C[Oops] {
+      override def x = new Oops
+    }
+
+    object Blah {
+      oops
+      oopso
+
+      // implicits found in enclosing context
+      implicitly[Oops]
+      implicitly[Option[Oops]]
+    }
+  }
+}
+
+package other {
+
+  object Blah {
+    // implicits found through this import
+    import p.q._
+
+    oops
+    oopso
+
+    implicitly[Oops]
+    implicitly[Option[Oops]]
+  }
+
+
+  object Blee {
+    // implicits found through the companion implicits
+    implicitly[p.q.Oops]
+    implicitly[Option[p.q.Oops]]
+  }
+}