Fix AddMissingOverride for constructor parameter

Fixes #1002225

Author: kiritsuku

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

@@ -126,4 +126,51 @@ class AddMissingOverrideTest {
       abstract override def f = super.f+0
     }
     """ after SaveEvent
+
+  @Test
+  def add_override_modifier_to_constructor_param() = """^
+    trait T {
+      def meth: Int
+    }
+    case class C(val meth: Int) extends T
+    class D(val meth: Int) extends T
+    """ becomes """^
+    trait T {
+      def meth: Int
+    }
+    case class C(override val meth: Int) extends T
+    class D(override val meth: Int) extends T
+    """ after SaveEvent
+
+  @Test
+  def add_val_keyword_when_override_modifier_is_added_to_constructor_param() = """^
+    trait T {
+      def meth: Int
+    }
+    case class C(meth: Int) extends T
+    class D(meth: Int) extends T
+    """ becomes """^
+    trait T {
+      def meth: Int
+    }
+    case class C(override val meth: Int) extends T
+    class D(override val meth: Int) extends T
+    """ after SaveEvent
+
+  @Test
+  def no_change_to_constructor_param_when_nothing_is_overriden() = """^
+    trait T {
+      def meth: Int
+    }
+    case class B(meth: Int)
+    class C(meth: Int)
+    class D(meth: Int, func: Int) extends T
+    """ becomes """^
+    trait T {
+      def meth: Int
+    }
+    case class B(meth: Int)
+    class C(meth: Int)
+    class D(override val meth: Int, func: Int) extends T
+    """ after SaveEvent
 }

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

@@ -1,6 +1,8 @@
 package org.scalaide.extensions
 package saveactions
 
+import scala.tools.nsc.ast.parser.Tokens
+
 object AddMissingOverrideSetting extends SaveActionSetting(
   id = ExtensionSetting.fullyQualifiedName[AddMissingOverride],
   name = "Add missing override keyword",
@@ -29,7 +31,7 @@ trait AddMissingOverride extends SaveAction with CompilerSupport {
     val symbolWithoutOverride = filter {
       case d: ValDef =>
         val getter = d.symbol.getterIn(d.symbol.owner)
-        canOverride(getter)
+        canOverride(if (getter != NoSymbol) getter else d.symbol)
 
       case d @ (_: DefDef | _: TypeDef) =>
         canOverride(d.symbol)
@@ -39,9 +41,15 @@ trait AddMissingOverride extends SaveAction with CompilerSupport {
       case d: MemberDef =>
         val mods = d.mods.withFlag(Flag.OVERRIDE)
         d match {
-          case d: DefDef => d.copy(mods = mods) replaces d
-          case d: ValDef => d.copy(mods = mods) replaces d
-          case d: TypeDef => d.copy(mods = mods) replaces d
+          case d: DefDef =>
+            d.copy(mods = mods) replaces d
+
+          case d: ValDef =>
+            val valMods = if (mods.positions.contains(Tokens.VAL)) mods else mods.withFlag(Tokens.VAL)
+            d.copy(mods = valMods) replaces d
+
+          case d: TypeDef =>
+            d.copy(mods = mods) replaces d
         }
     }