Merge pull request #6431 from milessabin/topic/dep-match

Check for symbol existence when working with GADT bounds in TypeComparer

Author: milessabin

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

@@ -2158,17 +2158,17 @@ class TrackingTypeComparer(initctx: Context) extends TypeComparer(initctx) {
   }
 
   override def gadtBounds(sym: Symbol)(implicit ctx: Context): TypeBounds = {
-    footprint += sym.typeRef
+    if (sym.exists) footprint += sym.typeRef
     super.gadtBounds(sym)
   }
 
   override def gadtAddLowerBound(sym: Symbol, b: Type): Boolean = {
-    footprint += sym.typeRef
+    if (sym.exists) footprint += sym.typeRef
     super.gadtAddLowerBound(sym, b)
   }
 
   override def gadtAddUpperBound(sym: Symbol, b: Type): Boolean = {
-    footprint += sym.typeRef
+    if (sym.exists) footprint += sym.typeRef
     super.gadtAddUpperBound(sym, b)
   }
 

tests/pos/dep-match.scala

@@ -0,0 +1,9 @@
+object Test {
+  type Foo = Int { type U }
+  type Bar[T] = T match {
+    case Unit => Unit
+  }
+  inline def baz(foo: Foo): Unit = {
+    val v: Bar[foo.U] = ???
+  }
+}