1 files changed, 35 insertions, 0 deletions
diff --git a/test/junit/scala/reflect/internal/TypesTest.scala b/test/junit/scala/reflect/internal/TypesTest.scala
new file mode 100644
index 0000000000..95194ef0a4
--- /dev/null
+++ b/test/junit/scala/reflect/internal/TypesTest.scala
@@ -0,0 +1,35 @@
+package scala.reflect.internal
+
+import org.junit.Assert._
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+import scala.tools.nsc.symtab.SymbolTableForUnitTesting
+
+@RunWith(classOf[JUnit4])
+class TypesTest {
+
+  object symbolTable extends SymbolTableForUnitTesting
+  import symbolTable._, definitions._
+
+  @Test
+  def testRefinedTypeSI8611(): Unit = {
+    def stringNarrowed = StringTpe.narrow
+    assert(stringNarrowed != stringNarrowed)
+    assert(!(stringNarrowed =:= stringNarrowed))
+
+    def boolWithString = refinedType(BooleanTpe :: StringTpe :: Nil, NoSymbol)
+    assert(boolWithString != boolWithString)
+    assert(boolWithString =:= boolWithString)
+
+    val boolWithString1 = boolWithString
+    val boolWithString1narrow1 = boolWithString1.narrow
+    val boolWithString1narrow2 = boolWithString1.narrow
+    // Two narrowings of the same refinement end up =:=. This was the root
+    // cause of SI-8611. See `narrowUniquely` in `Logic` for the workaround.
+    assert(boolWithString1narrow1 =:= boolWithString1narrow2)
+    val uniquelyNarrowed1 = refinedType(boolWithString1narrow1 :: Nil, NoSymbol)
+    val uniquelyNarrowed2 = refinedType(boolWithString1narrow2 :: Nil, NoSymbol)
+    assert(uniquelyNarrowed1 =:= uniquelyNarrowed2)
+  }
+}