Address review comments

Author: odersky

compiler/src/dotty/tools/dotc/transform/ElimErasedValueType.scala

@@ -96,11 +96,10 @@ class ElimErasedValueType extends MiniPhase with InfoTransformer { thisPhase =>
         (sym1.owner.derivesFrom(defn.PolyFunctionClass) ||
          sym2.owner.derivesFrom(defn.PolyFunctionClass))
 
-      if (sym1.name != sym2.name && 
-          !(sym1.name.is(SuperAccessorName) && sym2.name.is(SuperAccessorName))
-            // super-accessors start as private, and their expanded name can clash after
-            // erasure. TODO: Verify that this is OK.
-          ||
+      // super-accessors start as private, and their expanded name can clash after
+      // erasure. TODO: Verify that this is OK.
+      def bothSuperAccessors = sym1.name.is(SuperAccessorName) && sym2.name.is(SuperAccessorName)
+      if (sym1.name != sym2.name && !bothSuperAccessors ||
           !info1.matchesLoosely(info2) && !bothPolyApply)
         ctx.error(DoubleDefinition(sym1, sym2, root), root.sourcePos)
     }

compiler/test/dotty/tools/dotc/CompilationTests.scala

@@ -181,7 +181,7 @@ class CompilationTests extends ParallelTesting {
         defaultOptions),
       compileFile("tests/neg-custom-args/i6300.scala", allowDeepSubtypes),
       compileFile("tests/neg-custom-args/infix.scala", defaultOptions.and("-strict", "-deprecation", "-Xfatal-warnings")),
-      compileFile("tests/neg-custom-args/alpha.scala", defaultOptions.and("-strict", "-deprecation", "-Xfatal-warnings"))
+      compileFile("tests/neg-custom-args/missing-alpha.scala", defaultOptions.and("-strict", "-deprecation", "-Xfatal-warnings"))
     ).checkExpectedErrors()
   }
 

tests/neg-custom-args/alpha.scala renamed to tests/neg-custom-args/missing-alpha.scala

@@ -0,0 +1,6 @@
+// Java
+public class B_1 extends A_1 {
+  public int bar() {
+    return 2;
+  }
+}

tests/neg/alpha-override/B_1.java

@@ -0,0 +1,4 @@
+import annotation.alpha
+class C extends B_1 {   // error: Name clash between defined and inherited member
+  @alpha("bar") override def foo(): Int = 3
+}

tests/neg/alpha-override/C_2.scala

@@ -0,0 +1,7 @@
+import annotation.alpha
+class D extends B_1 {
+  @alpha("bar") def foo(): Int = 3   // error: needs override
+}
+class E extends B_1 {
+  @alpha("baz") override def bar(): Int = 3 // error: cannot have an @alpha annotation since external names would be different
+}

tests/neg/alpha-override/D_3.scala

@@ -0,0 +1,5 @@
+// Scala
+import annotation.alpha
+class A_1 {
+  @alpha("bar") def foo(): Int = 1
+}

tests/pos/alpha-override/A_1.scala

@@ -0,0 +1,7 @@
+// Java
+public class B_2 extends A_1 {
+  @Override
+  public int bar() {
+    return 2;
+  }
+}

tests/pos/alpha-override/B_2.java

@@ -5,5 +5,4 @@ object Test {
   def foo() = 1
 
   @alpha("bar") def foo(x: Int) = 2
-
-}
+}

tests/pos/alpha.scala

@@ -0,0 +1,8 @@
+import annotation.alpha
+
+object Test extends App {
+  def foo(x: Any): Int = 1
+  @alpha("bar") def foo[A <: AnyRef](x: A) = 2
+
+  assert(foo("a") == 2)
+}