NestedClassTrait

rules/src/main/scala/fix/NestedClassTrait.scala

@@ -0,0 +1,41 @@
+package fix
+
+import scala.meta.Defn
+import scala.meta.Mod
+import scala.meta.Template
+import scala.meta.Tree
+import scala.meta.Type
+import scalafix.Patch
+import scalafix.lint.Diagnostic
+import scalafix.lint.LintSeverity
+import scalafix.v1.SyntacticDocument
+import scalafix.v1.SyntacticRule
+
+object NestedClassTrait {
+  private object ClassOrTrait {
+    def unapply(t: Tree): Option[(Type.Name, Template)] = PartialFunction.condOpt(t) {
+      case x: Defn.Trait if !x.mods.exists(_.is[Mod.Implicit]) =>
+        (x.name, x.templ)
+      case x: Defn.Class if !x.mods.exists(_.is[Mod.Implicit]) =>
+        (x.name, x.templ)
+    }
+  }
+}
+
+class NestedClassTrait extends SyntacticRule("NestedClassTrait") {
+  import NestedClassTrait.ClassOrTrait
+  override def fix(implicit doc: SyntacticDocument): Patch = {
+    doc.tree.collect { case ClassOrTrait(_, template) =>
+      template.stats.collect { case ClassOrTrait(typeName, _) =>
+        Patch.lint(
+          Diagnostic(
+            id = "",
+            message = "don't define nested class or trait",
+            position = typeName.pos,
+            severity = LintSeverity.Warning
+          )
+        )
+      }.asPatch
+    }.asPatch
+  }
+}