Merge pull request #5291 from dotty-staging/add-regression-tests-#1593

Add regression tests for #1593

Author: nicolasstucki

tests/neg/isRef.scala

@@ -0,0 +1,13 @@
+trait Foo {
+  type A = (Any { type T = Int })
+  type B = (Any { type S = String })
+  def a: A
+  def b: B
+  def aandb: A & B = b // error: found: B, required: A & B
+}
+trait Foo2 {
+  type A[_]
+  type B[_]
+  def b: B[Int]
+  def aandb: A[Int] & B[Int] = b // error: found: B[Int], required: A[Int] & B[Int]
+}

tests/pos/isRef.scala

@@ -0,0 +1,12 @@
+trait Foo {
+  type A = (Any { type T = Int })
+  type B = (Any { type S = String })
+  def b: B
+  def aorb: A | B = b
+}
+trait Foo2 {
+  type A[_]
+  type B[_]
+  def b: B[Int]
+  def aorb: A[Int] | B[Int] = b
+}