Consider method-scoped companions in the implicit scope.

Fixes SI-4975.

I'll reproduce a relevant snippet of dialogue from Namers#companionSymbolOf:

/** The companion class or companion module of `original`.
   *  Calling .companionModule does not work for classes defined inside methods.
   *
   *  !!! Then why don't we fix companionModule? Does the presence of these
   *  methods imply all the places in the compiler calling sym.companionModule are
   *  bugs waiting to be reported? If not, why not? When exactly do we need to
   *  call this method?
   */
  def companionSymbolOf(original: Symbol, ctx: Context): Symbol = {

This was one such bug.

1 files changed, 12 insertions, 0 deletions

diff --git a/test/files/pos/t4975.scala b/test/files/pos/t4975.scala
new file mode 100644
index 0000000000..12d889c0d5
--- /dev/null
+++ b/test/files/pos/t4975.scala
@@ -0,0 +1,12 @@
+object ImplicitScope {
+  class A[T]
+
+  def foo {
+    trait B
+    object B {
+      implicit def ab = new A[B]
+    }
+
+    implicitly[A[B]]  // Error
+  }
+}