Move ValueClass checking errors to case class scheme

compiler/src/dotty/tools/dotc/reporting/diagnostic/ErrorMessageID.java

@@ -77,6 +77,15 @@ public enum ErrorMessageID {
     OnlyClassesCanHaveDeclaredButUndefinedMembersID,
     CannotExtendAnyValID,
     CannotHaveSameNameAsID,
+    ValueClassesMayNotDefineInnerID,
+    ValueClassesMayNotDefineNonParameterFieldID,
+    ValueClassesMayNotDefineASecondaryConstructorID,
+    ValueClassesMayNotContainInitalizationID,
+    ValueClassesMayNotBeAbstractID,
+    ValueClassesMayNotBeContaintedID,
+    ValueClassesMayNotWrapItselfID,
+    ValueClassParameterMayNotBeAVarID,
+    ValueClassNeedsExactlyOneValParamID,
     ;
 
     public int errorNumber() {

compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala

@@ -1484,5 +1484,70 @@ object messages {
     val explanation = ""
   }
 
+  case class ValueClassesMayNotDefineInner(valueClass: Symbol, inner: Symbol)(implicit ctx: Context)
+    extends Message(ValueClassesMayNotDefineInnerID) {
+    val msg = hl"""value classes may not define an inner class"""
+    val kind = "Syntax"
+    val explanation = ""
+  }
+
+  case class ValueClassesMayNotDefineNonParameterField(valueClass: Symbol, field: Symbol)(implicit ctx: Context)
+    extends Message(ValueClassesMayNotDefineNonParameterFieldID) {
+    val msg = hl"""value classes may not define non-parameter field"""
+    val kind = "Syntax"
+    val explanation = ""
+  }
+
+  case class ValueClassesMayNotDefineASecondaryConstructor(valueClass: Symbol, constructor: Symbol)(implicit ctx: Context)
+    extends Message(ValueClassesMayNotDefineASecondaryConstructorID) {
+    val msg = hl"""value classes may not define a secondary constructor"""
+    val kind = "Syntax"
+    val explanation = ""
+  }
+
+  case class ValueClassesMayNotContainInitalization(valueClass: Symbol)(implicit ctx: Context)
+    extends Message(ValueClassesMayNotContainInitalizationID) {
+    val msg = hl"""value classes may not contain initialization statements"""
+    val kind = "Syntax"
+    val explanation = ""
+  }
+
+  case class ValueClassesMayNotBeAbstract(valueClass: Symbol)(implicit ctx: Context)
+    extends Message(ValueClassesMayNotBeAbstractID) {
+    val msg = hl"""value classes may not be ${"abstract"}"""
+    val kind = "Syntax"
+    val explanation = ""
+  }
+
+  case class ValueClassesMayNotBeContainted(valueClass: Symbol)(implicit ctx: Context)
+    extends Message(ValueClassesMayNotBeContaintedID) {
+    private val localOrMember = if (valueClass.owner.isTerm) "local class" else "member of another class"
+    val msg = s"""value classes may not be a $localOrMember"""
+    val kind = "Syntax"
+    val explanation = ""
+  }
+
+  case class ValueClassesMayNotWrapItself(valueClass: Symbol)(implicit ctx: Context)
+    extends Message(ValueClassesMayNotWrapItselfID) {
+    val msg = """a value class may not wrap itself"""
+    val kind = "Syntax"
+    val explanation = ""
+  }
+
+  case class ValueClassParameterMayNotBeAVar(valueClass: Symbol, param: Symbol)(implicit ctx: Context)
+    extends Message(ValueClassParameterMayNotBeAVarID) {
+    val msg = hl"""a value class parameter may not be a ${"var"}"""
+    val kind = "Syntax"
+    val explanation =
+      hl"""A value class must have exactly one ${"val"} parameter.
+          |"""
+  }
+
+  case class ValueClassNeedsExactlyOneValParam(valueClass: Symbol)(implicit ctx: Context)
+    extends Message(ValueClassNeedsExactlyOneValParamID) {
+    val msg = hl"""value class needs to have exactly one ${"val"} parameter"""
+    val kind = "Syntax"
+    val explanation = ""
+  }
 
 }

compiler/src/dotty/tools/dotc/typer/Checking.scala

@@ -439,35 +439,35 @@ object Checking {
   def checkDerivedValueClass(clazz: Symbol, stats: List[Tree])(implicit ctx: Context) = {
     def checkValueClassMember(stat: Tree) = stat match {
       case _: TypeDef if stat.symbol.isClass =>
-        ctx.error(s"value class may not define an inner class", stat.pos)
+        ctx.error(ValueClassesMayNotDefineInner(clazz, stat.symbol), stat.pos)
       case _: ValDef if !stat.symbol.is(ParamAccessor) =>
-        ctx.error(s"value class may not define non-parameter field", stat.pos)
-      case d: DefDef if d.symbol.isConstructor =>
-        ctx.error(s"value class may not define secondary constructor", stat.pos)
+        ctx.error(ValueClassesMayNotDefineNonParameterField(clazz, stat.symbol), stat.pos)
+      case _: DefDef if stat.symbol.isConstructor =>
+        ctx.error(ValueClassesMayNotDefineASecondaryConstructor(clazz, stat.symbol), stat.pos)
       case _: MemberDef | _: Import | EmptyTree =>
       // ok
       case _ =>
-        ctx.error(s"value class may not contain initialization statements", stat.pos)
+        ctx.error(ValueClassesMayNotContainInitalization(clazz), stat.pos)
     }
     if (isDerivedValueClass(clazz)) {
       if (clazz.is(Trait))
         ctx.error(CannotExtendAnyVal(clazz), clazz.pos)
       if (clazz.is(Abstract))
-        ctx.error("`abstract' modifier cannot be used with value classes", clazz.pos)
+        ctx.error(ValueClassesMayNotBeAbstract(clazz), clazz.pos)
       if (!clazz.isStatic)
-        ctx.error(s"value class may not be a ${if (clazz.owner.isTerm) "local class" else "member of another class"}", clazz.pos)
+        ctx.error(ValueClassesMayNotBeContainted(clazz), clazz.pos)
       if (isCyclic(clazz.asClass))
-        ctx.error("value class cannot wrap itself", clazz.pos)
+        ctx.error(ValueClassesMayNotWrapItself(clazz), clazz.pos)
       else {
         val clParamAccessors = clazz.asClass.paramAccessors.filter(_.isTerm)
         clParamAccessors match {
           case List(param) =>
             if (param.is(Mutable))
-              ctx.error("value class parameter must not be a var", param.pos)
+              ctx.error(ValueClassParameterMayNotBeAVar(clazz, param), param.pos)
             if (param.info.isPhantom)
               ctx.error("value class parameter must not be phantom", param.pos)
           case _ =>
-            ctx.error("value class needs to have exactly one val parameter", clazz.pos)
+            ctx.error(ValueClassNeedsExactlyOneValParam(clazz), clazz.pos)
         }
       }
       stats.foreach(checkValueClassMember)

compiler/test/dotty/tools/dotc/reporting/ErrorMessagesTests.scala

@@ -689,5 +689,111 @@ class ErrorMessagesTests extends ErrorMessagesTest {
         assertEquals("class A", cls.show)
       }
 
+  @Test def valueClassesMayNotDefineInner =
+    checkMessagesAfter("refchecks") {
+      """class MyValue(i: Int) extends AnyVal {
+        |  class Inner
+        |}
+        |""".stripMargin
+    }
+      .expect { (ictx, messages) =>
+        implicit val ctx: Context = ictx
+        assertMessageCount(1, messages)
+        val ValueClassesMayNotDefineInner(valueClass, inner) :: Nil = messages
+        assertEquals("class MyValue", valueClass.show)
+        assertEquals("class Inner", inner.show)
+      }
+
+  @Test def valueClassesMayNotDefineNonParameterField =
+    checkMessagesAfter("refchecks") {
+      """class MyValue(i: Int) extends AnyVal {
+        |  val illegal: Int
+        |}
+        |""".stripMargin
+    }
+      .expect { (ictx, messages) =>
+        implicit val ctx: Context = ictx
+        assertMessageCount(1, messages)
+        val ValueClassesMayNotDefineNonParameterField(valueClass, field) :: Nil = messages
+        assertEquals("class MyValue", valueClass.show)
+        assertEquals("value illegal", field.show)
+      }
+
+  @Test def valueClassesMayNotDefineASecondaryConstructor =
+    checkMessagesAfter("refchecks") {
+      """class MyValue(i: Int) extends AnyVal {
+        |  def this() = this(2)
+        |}
+        |""".stripMargin
+    }
+      .expect { (ictx, messages) =>
+        implicit val ctx: Context = ictx
+        assertMessageCount(1, messages)
+        val ValueClassesMayNotDefineASecondaryConstructor(valueClass, constuctor) :: Nil = messages
+        assertEquals("class MyValue", valueClass.show)
+        assertEquals("constructor MyValue", constuctor.show)
+      }
+
+  @Test def valueClassesMayNotContainInitalization =
+    checkMessagesAfter("refchecks") {
+      """class MyValue(i: Int) extends AnyVal {
+        |  println("Hallo?")
+        |}
+        |""".stripMargin
+    }
+      .expect { (ictx, messages) =>
+        implicit val ctx: Context = ictx
+        assertMessageCount(1, messages)
+        val ValueClassesMayNotContainInitalization(valueClass) :: Nil = messages
+        assertEquals("class MyValue", valueClass.show)
+      }
+
+  @Test def valueClassesMayNotBeContained =
+    checkMessagesAfter("refchecks") {
+      """class Outer {
+        |  class MyValue(i: Int) extends AnyVal
+        |}
+        |""".stripMargin
+    }
+      .expect { (ictx, messages) =>
+        implicit val ctx: Context = ictx
+        assertMessageCount(1, messages)
+        val ValueClassesMayNotBeContainted(valueClass) :: Nil = messages
+        assertEquals("class MyValue", valueClass.show)
+      }
+
+  @Test def valueClassesMayNotWrapItself =
+    checkMessagesAfter("refchecks") {
+      """class MyValue(i: MyValue) extends AnyVal"""
+    }
+      .expect { (ictx, messages) =>
+        implicit val ctx: Context = ictx
+        assertMessageCount(1, messages)
+        val ValueClassesMayNotWrapItself(valueClass) :: Nil = messages
+        assertEquals("class MyValue", valueClass.show)
+      }
+
+  @Test @Ignore def valueClassParameterMayNotBeVar =
+    checkMessagesAfter("refchecks") {
+      """class MyValue(var i: Int) extends AnyVal"""
+    }
+      .expect { (ictx, messages) =>
+        implicit val ctx: Context = ictx
+        assertMessageCount(1, messages)
+        val ValueClassParameterMayNotBeAVar(valueClass, param) :: Nil = messages
+        assertEquals("class MyValue", valueClass.show)
+        assertEquals("variable i", param.show)
+      }
+
+  @Test def valueClassNeedsExactlyOneVal =
+    checkMessagesAfter("refchecks") {
+      """class MyValue(var i: Int, j: Int) extends AnyVal"""
+    }
+      .expect { (ictx, messages) =>
+        implicit val ctx: Context = ictx
+        assertMessageCount(1, messages)
+        val ValueClassNeedsExactlyOneValParam(valueClass) :: Nil = messages
+        assertEquals("class MyValue", valueClass.show)
+      }
 
 }