Merge pull request #1448 from dotty-staging/fix/object-subtyping

Fix #1447: Make X$ <:< X.type when X is an object

2 files changed, 17 insertions, 1 deletions

diff --git a/src/dotty/tools/dotc/core/TypeComparer.scala b/src/dotty/tools/dotc/core/TypeComparer.scala
index 18eb424bc..d6ada7244 100644
--- a/src/dotty/tools/dotc/core/TypeComparer.scala
+++ b/src/dotty/tools/dotc/core/TypeComparer.scala
@@ -165,7 +165,13 @@ class TypeComparer(initctx: Context) extends DotClass with ConstraintHandling {
                     // However the original judgment should be true.
                 case _ =>
               }
-              val sym1 = tp1.symbol
+              val sym1 =
+                if (tp1.symbol.is(ModuleClass) && tp2.symbol.is(ModuleVal))
+                  // For convenience we want X$ <:< X.type
+                  // This is safe because X$ self-type is X.type
+                  tp1.symbol.companionModule
+                else
+                  tp1.symbol
               if ((sym1 ne NoSymbol) && (sym1 eq tp2.symbol))
                 ctx.erasedTypes ||
                 sym1.isStaticOwner ||
diff --git a/tests/pos/i1447.scala b/tests/pos/i1447.scala
new file mode 100644
index 000000000..661fc3917
--- /dev/null
+++ b/tests/pos/i1447.scala
@@ -0,0 +1,10 @@
+case object X
+
+object Test {
+  val Alias = X
+
+  val x: X.type = Alias
+
+  type Alias = X.type
+  val a: Alias = Alias
+}