diff --git a/input/src/main/scala/fix/DivideByOne.scala b/input/src/main/scala/fix/DivideByOne.scala
new file mode 100644
index 0000000..72bcf9e
--- /dev/null
+++ b/input/src/main/scala/fix/DivideByOne.scala
@@ -0,0 +1,31 @@
+/*
+rule = DivideByOne
+ */
+package fix
+
+object DivideByOne {
+  var a = 14
+  val b = a / 1 // assert: DivideByOne
+  a /= 1 // assert: DivideByOne
+  a = a / 2 // scalafix: ok;
+  a /= 2 // scalafix: ok;
+
+  var c = 10.0
+  val d = c / 1 // assert: DivideByOne
+  c /= 1 // assert: DivideByOne
+  c = c / 2 // scalafix: ok;
+  c /= 2 // scalafix: ok;
+
+  var e = 100L
+  val f = e / 1 // assert: DivideByOne
+  e /= 1 // assert: DivideByOne
+  e = e / 2 // scalafix: ok;
+  e /= 2 // scalafix: ok;
+
+  var g = 5.0d
+  val h = g / 1 // assert: DivideByOne
+  g /= 1 // assert: DivideByOne
+  g = g / 2 // scalafix: ok;
+  g /= 2 // scalafix: ok;
+
+}
diff --git a/input/src/main/scala/fix/DoubleNegation.scala b/input/src/main/scala/fix/DoubleNegation.scala
new file mode 100644
index 0000000..144e50f
--- /dev/null
+++ b/input/src/main/scala/fix/DoubleNegation.scala
@@ -0,0 +1,12 @@
+/*
+rule = DoubleNegation
+ */
+package fix
+
+object DoubleNegation {
+  val b = true
+  val c = !(!b) // assert: DoubleNegation
+  val d = !(!(!b)) // assert: DoubleNegation
+  val f = !b // scalafix: ok;
+
+}
diff --git a/input/src/main/scala/fix/DuplicateMapKey.scala b/input/src/main/scala/fix/DuplicateMapKey.scala
new file mode 100644
index 0000000..756e81f
--- /dev/null
+++ b/input/src/main/scala/fix/DuplicateMapKey.scala
@@ -0,0 +1,12 @@
+/*
+rule = DuplicateMapKey
+ */
+package fix
+
+object DuplicateMapKey {
+  Map("name" -> "sam", "location" -> "aylesbury", "name" -> "bob") // assert: DuplicateMapKey
+  Map("name" -> "sam", "location" -> "aylesbury", "name2" -> "bob") // scalafix: ok;
+
+  val tuples = List((1, 2), (3, 4))
+  Map(tuples: _*) // scalafix: ok;
+}
diff --git a/input/src/main/scala/fix/DuplicateSetValue.scala b/input/src/main/scala/fix/DuplicateSetValue.scala
new file mode 100644
index 0000000..e11c3ed
--- /dev/null
+++ b/input/src/main/scala/fix/DuplicateSetValue.scala
@@ -0,0 +1,21 @@
+/*
+rule = DuplicateSetValue
+ */
+package fix
+
+object DuplicateSetValue {
+  Set("sam", "aylesbury", "sam") // assert: DuplicateSetValue
+  Set("name", "location", "aylesbury", "bob")
+
+  // Works for different types of literals
+  Set(1, 2, 1) // assert: DuplicateSetValue
+  Set(2.4, 3.5, 2.4) // assert: DuplicateSetValue
+  Set(2.4f, 3.5f, 2.4f) // assert: DuplicateSetValue
+  Set(true, false, true) // assert: DuplicateSetValue
+  Set('a', 'b', 'a') // assert: DuplicateSetValue
+  Set("olivia", 2, "olivia") // assert: DuplicateSetValue
+  Set(2L, 3, 2L) // assert: DuplicateSetValue
+
+  def name = "could be random" // We could have def name calling random.nextInt, hence we exclude variables and only check literals
+  Set(name, "middle", name) // scalafix: ok;
+}
diff --git a/input/src/main/scala/fix/EmptyCaseClass.scala b/input/src/main/scala/fix/EmptyCaseClass.scala
new file mode 100644
index 0000000..028939a
--- /dev/null
+++ b/input/src/main/scala/fix/EmptyCaseClass.scala
@@ -0,0 +1,31 @@
+/*
+rule = EmptyCaseClass
+ */
+package fix
+
+object EmptyCaseClass {
+  case class Empty() // assert: EmptyCaseClass
+  case class Empty2() {} // assert: EmptyCaseClass
+
+  case class Empty3() { // assert: EmptyCaseClass
+    def foo = "boo"
+  }
+
+  case class NonEmpty() { // scalafix: ok;
+    def foo = "boo"
+    val myVal = 42
+  }
+  class NonEmpty2() // scalafix: ok;
+
+  case class Empty4(name: String) // scalafix: ok;
+  case object Empty5 // scalafix: ok;
+
+  abstract class Attr(val name: String) {
+    override def toString: String = name
+    override def hashCode: Int = name.hashCode
+    override def equals(obj: Any): Boolean = false
+  }
+  // We don't look at case classes extending something because we could have some fields in the parent class
+  case class TestClass() extends Attr("test") // scalafix: ok;
+  case class TestClass2(bool: Boolean) extends Attr("test") // scalafix: ok;
+}
diff --git a/rules/src/main/resources/META-INF/services/scalafix.v1.Rule b/rules/src/main/resources/META-INF/services/scalafix.v1.Rule
index 5ab490d..b88dfbd 100644
--- a/rules/src/main/resources/META-INF/services/scalafix.v1.Rule
+++ b/rules/src/main/resources/META-INF/services/scalafix.v1.Rule
@@ -62,4 +62,9 @@ fix.BrokenOddness
 fix.ClassNames
 fix.CollectionNamingConfusion
 fix.ComparisonToEmptyList
-fix.ComparisonToEmptySet
\ No newline at end of file
+fix.ComparisonToEmptySet
+fix.DivideByOne
+fix.DoubleNegation
+fix.DuplicateMapKey
+fix.DuplicateSetValue
+fix.EmptyCaseClass
\ No newline at end of file
diff --git a/rules/src/main/scala/fix/DivideByOne.scala b/rules/src/main/scala/fix/DivideByOne.scala
new file mode 100644
index 0000000..d900e79
--- /dev/null
+++ b/rules/src/main/scala/fix/DivideByOne.scala
@@ -0,0 +1,27 @@
+/*
+rule = DivideByOne
+ */
+package fix
+
+import scalafix.lint.LintSeverity
+import scalafix.v1._
+
+import scala.meta._
+
+class DivideByOne extends SemanticRule("DivideByOne") {
+
+  private def diag(pos: Position) = Diagnostic(
+    "",
+    "Checks for division by one.",
+    pos,
+    "Divide by one will always return the original value.",
+    LintSeverity.Warning
+  )
+
+  override def fix(implicit doc: SemanticDocument): Patch = {
+    doc.tree.collect {
+      case t @ Term.ApplyInfix.After_4_6_0(_, Term.Name("/" | "/="), _, Term.ArgClause(List(Lit.Int(1)), _)) => Patch.lint(diag(t.pos))
+    }.asPatch
+  }
+
+}
diff --git a/rules/src/main/scala/fix/DoubleNegation.scala b/rules/src/main/scala/fix/DoubleNegation.scala
new file mode 100644
index 0000000..0f9304f
--- /dev/null
+++ b/rules/src/main/scala/fix/DoubleNegation.scala
@@ -0,0 +1,27 @@
+/*
+rule = DoubleNegation
+ */
+package fix
+
+import scalafix.lint.LintSeverity
+import scalafix.v1._
+
+import scala.meta._
+
+class DoubleNegation extends SemanticRule("DoubleNegation") {
+
+  private def diag(pos: Position) = Diagnostic(
+    "",
+    "Checks for code like !(!b).",
+    pos,
+    "Double negation can be removed, e.g. !(!b) it equal to just b.",
+    LintSeverity.Info
+  )
+
+  override def fix(implicit doc: SemanticDocument): Patch = {
+    doc.tree.collect {
+      case t @ Term.ApplyUnary(Term.Name("!"), Term.ApplyUnary(Term.Name("!"), _)) => Patch.lint(diag(t.pos))
+    }.asPatch
+  }
+
+}
diff --git a/rules/src/main/scala/fix/DuplicateMapKey.scala b/rules/src/main/scala/fix/DuplicateMapKey.scala
new file mode 100644
index 0000000..c8aa679
--- /dev/null
+++ b/rules/src/main/scala/fix/DuplicateMapKey.scala
@@ -0,0 +1,34 @@
+/*
+rule = DuplicateMapKey
+ */
+package fix
+
+import scalafix.lint.LintSeverity
+import scalafix.v1._
+
+import scala.collection.mutable
+import scala.meta._
+
+class DuplicateMapKey extends SemanticRule("DuplicateMapKey") {
+
+  private def diag(pos: Position) = Diagnostic(
+    "",
+    "Checks for duplicate key names in Map literals.",
+    pos,
+    "A map key is overwritten by a later entry.",
+    LintSeverity.Warning
+  )
+
+  override def fix(implicit doc: SemanticDocument): Patch = {
+    doc.tree.collect {
+      case t @ Term.Apply.After_4_6_0(Term.Name("Map"), Term.ArgClause(args, _)) =>
+        val seen = mutable.HashSet.empty[String]
+        args.collect {
+          // Simply look at the args, try to add them in the sent, will fail if already present.
+          // We chose not to support the unicode arrow (→) because it has been deprecated in Scala 2.13.
+          case Term.ApplyInfix.After_4_6_0(Lit.String(key), Term.Name("->"), _, _) if !seen.add(key) => Patch.lint(diag(t.pos))
+        }
+    }.flatten.asPatch
+  }
+
+}
diff --git a/rules/src/main/scala/fix/DuplicateSetValue.scala b/rules/src/main/scala/fix/DuplicateSetValue.scala
new file mode 100644
index 0000000..6e32aa0
--- /dev/null
+++ b/rules/src/main/scala/fix/DuplicateSetValue.scala
@@ -0,0 +1,35 @@
+/*
+rule = DuplicateSetValue
+ */
+package fix
+
+import scalafix.lint.LintSeverity
+import scalafix.v1._
+
+import scala.collection.mutable
+import scala.meta._
+
+class DuplicateSetValue extends SemanticRule("DuplicateSetValue") {
+
+  private def diag(pos: Position) = Diagnostic(
+    "",
+    "Checks for duplicate values in set literals.",
+    pos,
+    "A set value is overwritten by a later entry.",
+    LintSeverity.Warning
+  )
+
+  override def fix(implicit doc: SemanticDocument): Patch = {
+    doc.tree.collect {
+      case t @ Term.Apply.After_4_6_0(Term.Name("Set"), Term.ArgClause(args, _)) =>
+        val seen = mutable.HashSet.empty[Any]
+        args.collect {
+          // Simply look at the args, try to add them in the sent, will fail if already present.
+          // We limit ourselves to literals, as variables could change at runtime, see tests.
+          // We work with the value, not the literal, as otherwise comparisons do not function.
+          case value: Lit if !seen.add(value.value) => Patch.lint(diag(t.pos))
+        }
+    }.flatten.asPatch
+  }
+
+}
diff --git a/rules/src/main/scala/fix/EmptyCaseClass.scala b/rules/src/main/scala/fix/EmptyCaseClass.scala
new file mode 100644
index 0000000..678e586
--- /dev/null
+++ b/rules/src/main/scala/fix/EmptyCaseClass.scala
@@ -0,0 +1,38 @@
+/*
+rule = EmptyCaseClass
+ */
+package fix
+
+import scalafix.lint.LintSeverity
+import scalafix.v1._
+
+import scala.meta._
+
+class EmptyCaseClass extends SemanticRule("EmptyCaseClass") {
+
+  private def diag(pos: Position) = Diagnostic(
+    "",
+    "Checks for empty case classes like, e.g. case class Faceman().",
+    pos,
+    "An empty case class can be rewritten as a case object.",
+    LintSeverity.Info
+  )
+
+  override def fix(implicit doc: SemanticDocument): Patch = {
+
+    // For a case class to be empty, it should either have an empty body or no accessors (i.e. just methods, in which case we can have a case object)
+    def hasAccessor(body: List[Stat]): Boolean = body.exists {
+      case _: Defn.Val => true
+      case _: Defn.Var => true
+      case _           => false
+    }
+
+    def isCaseClass(mods: List[Mod]) = mods.exists { case Mod.Case() => true; case _ => false }
+
+    doc.tree.collect {
+      // Corresponds to case class Empty() {} or only with methods, see above
+      // We should consider only cases class with empty constructors, no body / accessors and no extending classes
+      case c @ Defn.Class.After_4_6_0(mods, _, _, Ctor.Primary.After_4_6_0(_, _, List(Term.ParamClause(Nil, _))), Template.After_4_4_0(_, Nil, _, body, _)) if isCaseClass(mods) && (body.isEmpty || !hasAccessor(body)) => Patch.lint(diag(c.pos))
+    }.asPatch
+  }
+}