Don't override fields defined with Java

Fields defined with Java can't be overridden on the Scala side, therefore
it shouldn't be done automatically.

Fixes #1002240

org.scala-ide.sdt.core.tests/src/org/scalaide/extensions/saveactions/AddMissingOverrideTest.scala

@@ -245,4 +245,82 @@ class AddMissingOverrideTest {
       override var f = 0
     }
     """ after SaveEvent
+
+  @Test
+  def add_override_to_def_that_overrides_java_method() = {
+    val jPkg = uniquePkgName()
+    val sPkg = uniquePkgName()
+    mkJavaCompilationUnit(s"""
+      package $jPkg;
+      public class T {
+        public String f() { return ""; }
+      }
+    """)
+
+    s"""^
+    package $sPkg
+    import $jPkg.T
+    trait TT extends T {
+      def f = ""
+    }
+    """ becomes s"""^
+    package $sPkg
+    import $jPkg.T
+    trait TT extends T {
+      override def f = ""
+    }
+    """ after SaveEvent
+  }
+
+  @Test
+  def add_no_override_to_val_that_overrides_java_field() = {
+    val jPkg = uniquePkgName()
+    val sPkg = uniquePkgName()
+    mkJavaCompilationUnit(s"""
+      package $jPkg;
+      public class T {
+        public String f = "";
+      }
+    """)
+
+    s"""^
+    package $sPkg
+    import $jPkg.T
+    trait TT extends T {
+      val f = ""
+    }
+    """ becomes s"""^
+    package $sPkg
+    import $jPkg.T
+    trait TT extends T {
+      val f = ""
+    }
+    """ after SaveEvent
+  }
+
+  @Test
+  def add_no_override_to_def_that_overrides_java_field() = {
+    val jPkg = uniquePkgName()
+    val sPkg = uniquePkgName()
+    mkJavaCompilationUnit(s"""
+      package $jPkg;
+      public class T {
+        public String f = "";
+      }
+    """)
+
+    s"""^
+    package $sPkg
+    import $jPkg.T
+    trait TT extends T {
+      def f = ""
+    }
+    """ becomes s"""^
+    package $sPkg
+    import $jPkg.T
+    trait TT extends T {
+      def f = ""
+    }
+    """ after SaveEvent
+  }
 }

org.scala-ide.sdt.core/src/org/scalaide/extensions/saveactions/AddMissingOverride.scala

@@ -29,6 +29,12 @@ trait AddMissingOverride extends SaveAction with CompilerSupport {
     def canOverride(sym: Symbol) = sym.isOverridingSymbol && !sym.isOverride && !sym.isAbstractOverride
 
     val symbolWithoutOverride = filter {
+      case d: ValDef if isJavaField(getterOf(d.symbol)) ⇒
+        false
+
+      case d: DefDef if isJavaField(d.symbol) ⇒
+        false
+
       case d: ValDef if d.mods.positions.contains(Tokens.VAR) && !overridesVar(getterOf(d.symbol)) ⇒
         false
 
@@ -90,4 +96,15 @@ trait AddMissingOverride extends SaveAction with CompilerSupport {
       symbol.matchingSymbol(sym, baseType).setterIn(sym) != NoSymbol
     }
   }
+
+  private def isJavaField(symbol: Symbol): Boolean = {
+    val base = symbol.owner
+    val baseType = base.toType
+    val bcs = base.info.baseClasses dropWhile (symbol.owner != _) drop 1
+
+    bcs exists { sym ⇒
+      val s = symbol.matchingSymbol(sym, baseType)
+      s.isJava && !s.isMethod
+    }
+  }
 }