Check that value classes are static

Author: odersky

src/dotty/tools/dotc/typer/RefChecks.scala

@@ -655,12 +655,14 @@ object RefChecks {
   }
 
   /** Verify classes extending AnyVal meet the requirements */
-  private def checkAnyValSubclass(clazz: Symbol)(implicit ctx: Context) =
+  private def checkDerivedValueClass(clazz: Symbol)(implicit ctx: Context) =
     if (isDerivedValueClass(clazz)) {
       if (clazz.is(Trait))
         ctx.error("Only classes (not traits) are allowed to extend AnyVal", clazz.pos)
-      else if (clazz.is(Abstract))
+      if (clazz.is(Abstract))
         ctx.error("`abstract' modifier cannot be used with value classes", clazz.pos)
+      if (!clazz.isStatic)
+        ctx.error("value class cannot be an inner class", clazz.pos)
     }
 
   type LevelAndIndex = immutable.Map[Symbol, (LevelInfo, Int)]
@@ -708,7 +710,7 @@ import RefChecks._
  *  - only one overloaded alternative defines default arguments
  *  - applyDynamic methods are not overloaded
  *  - all overrides conform to rules laid down by `checkAllOverrides`.
- *  - any value classes conform to rules laid down by `checkAnyValSubClass`.
+ *  - any value classes conform to rules laid down by `checkDerivedValueClass`.
  *  - this(...) constructor calls do not forward reference other definitions in their block (not even lazy vals).
  *  - no forward reference in a local block jumps over a non-lazy val definition.
  *  - a class and its companion object do not both define a class or module with the same name.
@@ -778,7 +780,7 @@ class RefChecks extends MiniPhase { thisTransformer =>
       checkParents(cls)
       checkCompanionNameClashes(cls)
       checkAllOverrides(cls)
-      checkAnyValSubclass(cls)
+      checkDerivedValueClass(cls)
       tree
     }
 

test/dotc/tests.scala

@@ -133,6 +133,8 @@ class tests extends CompilerTest {
   @Test def neg_i0248_inherit_refined = compileFile(negDir, "i0248-inherit-refined", xerrors = 4)
   @Test def neg_i0281 = compileFile(negDir, "i0281-null-primitive-conforms", xerrors = 3)
   @Test def neg_i583 = compileFile(negDir, "i0583-skolemize", xerrors = 2)
+  @Test def neg_finalSealed = compileFile(negDir, "final-sealed", xerrors = 2)
+  @Test def neg_i705 = compileFile(negDir, "i705-inner-value-class", xerrors = 3)
   @Test def neg_moduleSubtyping = compileFile(negDir, "moduleSubtyping", xerrors = 4)
   @Test def neg_escapingRefs = compileFile(negDir, "escapingRefs", xerrors = 2)
   @Test def neg_instantiateAbstract = compileFile(negDir, "instantiateAbstract", xerrors = 8)

tests/neg/i705-inner-value-class.scala

@@ -0,0 +1,15 @@
+class Foo {
+  class B(val a: Int) extends AnyVal // error
+}
+
+object Test {
+  class B(val a: Int) extends AnyVal // ok
+  def f = {
+    class C(val a: Int) extends AnyVal // error
+    new C(1)
+  }
+  class B1(val b: Int) extends B(b)
+//  class D extends B( { class E(val a: Int) extends AnyVal; new E(1) } ) // error
+}
+
+