enhance ImplicitValueClasses rule to prevent implicit classes from being derived value classes and add corresponding tests

Author: halotukozak

analyzer/src/main/scala/com/avsystem/commons/analyzer/ImplicitValueClasses.scala

@@ -28,9 +28,14 @@ class ImplicitValueClasses(g: Global) extends AnalyzerRule(g, "implicitValueClas
 
         cls != cd.symbol && !isDefault && !isUniversalTrait
       }
-      def hasExactlyOneParam = paramLists.forall(lists => lists.size == 1 && lists.head.size == 1)
+      def hasExactlyOneParam = paramLists.exists(lists => lists.size == 1 && lists.head.size == 1)
 
-      if (!inheritsAnyVal && !inheritsOtherClass && hasExactlyOneParam) {
+      def paramIsValueClass = paramLists.exists { lists =>
+        /* lists.nonEmpty && lists.head.nonEmpty && */
+        lists.head.head.typeSignature.typeSymbol.isDerivedValueClass
+      }
+
+      if (!inheritsAnyVal && !inheritsOtherClass && hasExactlyOneParam && !paramIsValueClass) {
         val isNestedClass =
           //implicit classes are always nested classes, so we want to check if the outer class's an object
           /*cd.symbol.isNestedClass &&*/ !cd.symbol.isStatic

analyzer/src/test/scala/com/avsystem/commons/analyzer/ImplicitValueClassesTest.scala

@@ -112,13 +112,26 @@ class ImplicitValueClassesSuite extends AnyFunSuite with AnalyzerTest {
         |}
       """.stripMargin)
   }
+
+  test("implicit class for value class should not be affected") {
+    assertNoErrors(
+      //language=Scala
+      """
+        |object whatever {
+        |  implicit final class ValueClass(x: com.avsystem.commons.misc.Timestamp) {
+        |    def sth: Long = x.millis
+        |  }
+        |}
+      """.stripMargin)
+  }
 }
 
 class NestedImplicitValueClassesSuite extends AnyFunSuite with AnalyzerTest {
   settings.pluginOptions.value ++= List("AVSystemAnalyzer:+implicitValueClasses:true")
 
   test("nested implicit class not extending AnyVal should fail") {
     assertErrors(1,
+      //language=Scala
       """
         |object whatever {
         |  class Outer {
@@ -134,6 +147,8 @@ class NestedImplicitValueClassesSuite extends AnyFunSuite with AnalyzerTest {
   test("nested implicit class with type parameter not extending AnyVal should fail") {
     assertErrors(1,
       """
+        |      //language=Scala
+        |
         |object whatever {
         |  class Outer {
         |    implicit final class BadNestedImplicitClass[T <: Int](val x: T) {
@@ -146,6 +161,7 @@ class NestedImplicitValueClassesSuite extends AnyFunSuite with AnalyzerTest {
 
   test("deeply nested implicit class not extending AnyVal should fail") {
     assertErrors(1,
+      //language=Scala
       """
         |object whatever {
         |  class Outer {
@@ -161,6 +177,7 @@ class NestedImplicitValueClassesSuite extends AnyFunSuite with AnalyzerTest {
 
   test("regular class should not be affected") {
     assertNoErrors(
+      //language=Scala
       """
         |object whatever {
         |  class Outer {
@@ -174,6 +191,7 @@ class NestedImplicitValueClassesSuite extends AnyFunSuite with AnalyzerTest {
 
   test("implicit class extending other classes should not be affected") {
     assertNoErrors(
+      //language=Scala
       """
         |object whatever {
         |  class Outer {
@@ -194,6 +212,7 @@ class NestedImplicitValueClassesSuite extends AnyFunSuite with AnalyzerTest {
 
   test("implicit class extending AnyVal with traits should be handled correctly") {
     assertErrors(1,
+      //language=Scala
       """
         |object whatever {
         |  class Outer {