Java methods: JavaMethodType instead of MethodType, convert Object to Any

Fixes two bugs needed for java-override test:

Namer was creating a MethodType instead of a JavaMethodType even though
the JavaDefined flag was set on the DefDef.

Following Scalac, Namer needs to convert Java method parameters
of type j.l.Object to s.Any.

Author: olhotak

src/dotty/tools/dotc/typer/Namer.scala

@@ -654,9 +654,14 @@ class Namer { typer: Typer =>
         else restpe
       val monotpe =
         (paramSymss :\ restpe1) { (params, restpe) =>
+          val isJava = ddef.mods is JavaDefined
           val make =
             if (params.nonEmpty && (params.head is Implicit)) ImplicitMethodType
+            else if(isJava) JavaMethodType
             else MethodType
+          if(isJava) params.foreach { symbol =>
+            if(symbol.info == defn.ObjectType) symbol.info = defn.AnyType
+          }
           make.fromSymbols(params, restpe)
         }
       if (typeParams.nonEmpty) PolyType.fromSymbols(typeParams, monotpe)

test/dotc/tests.scala

@@ -57,6 +57,7 @@ class tests extends CompilerTest {
   @Test def pos_packageobject() = compileFile(posDir, "packageobject")
   @Test def pos_overloaded() = compileFile(posDir, "overloaded")
   @Test def pos_overrides() = compileFile(posDir, "overrides")
+  @Test def pos_javaOverride() = compileDir(posDir + "java-override")
   @Test def pos_templateParents() = compileFile(posDir, "templateParents")
   @Test def pos_structural() = compileFile(posDir, "structural")
   @Test def pos_overloadedAccess = compileFile(posDir, "overloadedAccess")