SI-8054 Fix regression in TypeRef rebind with val overriding object

Regressed in 8076738 / SI-7928

The condition added in that commit are necessary after refchecks but
poisonous before.

This still seems rather fragile: I wonder if `eliminateModuleDefs`
in `RefChecks` ought to flag the module symbol as `ARTIFACT` after
creating the accessor, so as to signal that it shouldn't be bound
anymore?

Author: retronym

src/reflect/scala/reflect/internal/Types.scala

@@ -3392,11 +3392,14 @@ trait Types
   /** Rebind symbol `sym` to an overriding member in type `pre`. */
   private def rebind(pre: Type, sym: Symbol): Symbol = {
     if (!sym.isOverridableMember || sym.owner == pre.typeSymbol) sym
-    else pre.nonPrivateMember(sym.name).suchThat(sym =>
-      // SI-7928 `isModuleNotMethod` is here to avoid crashing with overloaded module accessor and module symbols
-      //         after refchecks eliminates a ModuleDef that implements and interface.
-      sym.isType || (!sym.isModuleNotMethod && sym.isStable && !sym.hasVolatileType)
-    ) orElse sym
+    else pre.nonPrivateMember(sym.name).suchThat { sym =>
+      // SI-7928 `isModuleNotMethod` is here to avoid crashing with spuriously "overloaded" module accessor and module symbols.
+      //         These appear after refchecks eliminates ModuleDefs that implement an interface.
+      //         Here, we exclude the module symbol, which allows us to bind to the accessor.
+      // SI-8054 We must only do this after refchecks, otherwise we exclude the module symbol which does not yet have an accessor!
+      val isModuleWithAccessor = phase.refChecked && sym.isModuleNotMethod
+      sym.isType || (!isModuleWithAccessor && sym.isStable && !sym.hasVolatileType)
+    } orElse sym
   }
 
   /** Convert a `super` prefix to a this-type if `sym` is abstract or final. */

test/files/pos/t8054.scala

@@ -0,0 +1,31 @@
+trait D {
+  trait Manifest {
+    class Entry
+  }
+
+  val M: Manifest
+
+  def m: M.Entry = ???
+}
+
+object D1 extends D {
+  object M extends Manifest
+}
+
+object D2 extends D {
+  val M: Manifest = ???
+}
+
+object Hello {
+
+  def main(args: Array[String]) {
+    // 2.10.3 - ok
+    // 2.11.0-M7 - type mismatch; found : Seq[DB1.MANIFEST.Entry]
+    // required: Seq[DB1.MANIFEST.Entry]
+    val t1: D1.M.Entry = D1.m
+
+    // 2.10.3 - ok
+    // 2.11.0-M7 - ok
+    val t2: D2.M.Entry = D2.m
+  }
+}