Merge pull request #179 from smarter/fix/namedtype-subtyping

Fix isSubType(A#X, B#X) not checking if A <: B

Author: odersky

src/dotty/tools/dotc/core/TypeComparer.scala

@@ -476,6 +476,7 @@ class TypeComparer(initctx: Context) extends DotClass {
                      ||    sym1.isClass
                         && pre2.classSymbol.exists
                         && pre2.abstractTypeMembers.isEmpty
+                        && isSubType(pre1, pre2)
                      )
                    }
                 )

test/dotc/tests.scala

@@ -87,6 +87,7 @@ class tests extends CompilerTest {
   @Test def neg_t1843 = compileFile(negDir, "t1843", xerrors = 1)
   @Test def neg_t1843_variances = compileFile(negDir, "t1843-variances", xerrors = 1)
   @Test def neg_t2994 = compileFile(negDir, "t2994", xerrors = 2)
+  @Test def neg_subtyping = compileFile(negDir, "subtyping", xerrors = 1)
   @Test def neg_variances = compileFile(negDir, "variances", xerrors = 2)
 
   @Test def dotc = compileDir(dotcDir + "tools/dotc", twice)

tests/neg/subtyping.scala

@@ -0,0 +1,13 @@
+class B {
+  class X
+}
+class A extends B
+
+object Test {
+  def foo(a: A#X): Unit = {
+    return;
+  }
+  def test(): Unit = {
+    foo(??? : B#X);
+  }
+}