Fix context for type checking early initializers

Before:

scala> class A { class C extends { val x: A = this } with AnyRef }
<console>:7: error: type mismatch;
 found   : A.this.C
 required: A
       class A { class C extends { val x: A = this } with AnyRef }
                                              ^

Note that the same thing is necessary and already done in Namers (see
def createNamer). The whole logic of when and how to create contexts
should be factored out and reused in Namer and Typer.

(
My Hobby [1]: detecting compiler by just looking at its soruce
[1] http://www.explainxkcd.com/wiki/index.php?title=Category:My_Hobby
)

src/compiler/scala/tools/nsc/typechecker/Typers.scala

@@ -2069,7 +2069,7 @@ trait Typers extends Modes with Adaptations with Tags {
       val sym = vdef.symbol
       val valDefTyper = {
         val maybeConstrCtx =
-          if (sym.isParameter && sym.owner.isConstructor) context.makeConstructorContext
+          if ((sym.isParameter || sym.isEarlyInitialized) && sym.owner.isConstructor) context.makeConstructorContext
           else context
         newTyper(maybeConstrCtx.makeNewScope(vdef, sym))
       }

test/files/pos/presuperContext.scala

@@ -0,0 +1,13 @@
+class A {
+  class C extends { val x: A = this } with AnyRef
+}
+
+class B(x: Int)
+
+class D {
+  class C(x: Int) extends B({val test: D = this; x}) {
+    def this() {
+      this({val test: D = this; 1})
+    }
+  }
+}