3 files changed, 123 insertions, 0 deletions
diff --git a/test/files/neg/t7834neg.check b/test/files/neg/t7834neg.check
new file mode 100644
index 0000000000..569df4b8ce
--- /dev/null
+++ b/test/files/neg/t7834neg.check
@@ -0,0 +1,41 @@
+t7834neg.scala:48: error: type mismatch;
+ found   : C.super.q.type (with underlying type M2)
+ required: C.super.q.type
+  x1 = x2  // fail
+       ^
+t7834neg.scala:50: error: type mismatch;
+ found   : C.super.q.type (with underlying type M1)
+ required: C.super.q.type
+  x2 = x1  // fail
+       ^
+t7834neg.scala:53: error: type mismatch;
+ found   : C.super.q.type (with underlying type M1)
+ required: C.this.q.type
+  x3 = x1  // fail
+       ^
+t7834neg.scala:54: error: type mismatch;
+ found   : C.super.q.type (with underlying type M2)
+ required: C.this.q.type
+  x3 = x2  // fail
+       ^
+t7834neg.scala:69: error: type mismatch;
+ found   : C.super.q.type (with underlying type M2)
+ required: C.super.q.type
+  x1 = super[S2].q  // fail
+                 ^
+t7834neg.scala:71: error: type mismatch;
+ found   : C.super.q.type (with underlying type M1)
+ required: C.super.q.type
+  x2 = super[S1].q  // fail
+                 ^
+t7834neg.scala:74: error: type mismatch;
+ found   : C.super.q.type (with underlying type M1)
+ required: C.this.q.type
+  x3 = super[S1].q  // fail
+                 ^
+t7834neg.scala:75: error: type mismatch;
+ found   : C.super.q.type (with underlying type M2)
+ required: C.this.q.type
+  x3 = super[S2].q  // fail
+                 ^
+8 errors found
diff --git a/test/files/neg/t7834neg.scala b/test/files/neg/t7834neg.scala
new file mode 100644
index 0000000000..d35a84eadd
--- /dev/null
+++ b/test/files/neg/t7834neg.scala
@@ -0,0 +1,76 @@
+class M1
+class M2 extends M1
+class M3 extends M2
+
+trait S1 { val q = new M1 ; val q1: q.type = q }
+trait S2 { val q = new M2 ; val q2: q.type = q }
+
+class B extends S1 with S2 {
+  override val q = new M3
+  val q3: q.type = q
+
+  var x1: B.super[S1].q1.type = null
+  var x2: B.super[S2].q2.type = null
+  var x3: B.this.q3.type      = null
+
+  x1 = x1
+  x1 = x2
+  x1 = x3
+  x2 = x1
+  x2 = x2
+  x2 = x3
+  x3 = x1
+  x3 = x2
+  x3 = x3
+
+  x1 = q1
+  x1 = q2
+  x1 = q3
+  x2 = q1
+  x2 = q2
+  x2 = q3
+  x3 = q1
+  x3 = q2
+  x3 = x3
+}
+
+class C extends S1 with S2 {
+  override val q = new M3
+  val q3: q.type = q
+
+  // x1's type and x2's type are incompatible
+  // x3's is assignable to x1 or x2, but not vice versa
+  var x1: C.super[S1].q.type = null
+  var x2: C.super[S2].q.type = null
+  var x3: C.this.q.type      = null
+
+  x1 = x1
+  x1 = x2  // fail
+  x1 = x3
+  x2 = x1  // fail
+  x2 = x2
+  x2 = x3
+  x3 = x1  // fail
+  x3 = x2  // fail
+  x3 = x3
+
+  x1 = q1
+  x1 = q2
+  x1 = q3
+  x2 = q1
+  x2 = q2
+  x2 = q3
+  x3 = q1
+  x3 = q2
+  x3 = x3
+
+  x1 = q
+  x1 = super[S1].q
+  x1 = super[S2].q  // fail
+  x2 = q
+  x2 = super[S1].q  // fail
+  x2 = super[S2].q
+  x3 = q
+  x3 = super[S1].q  // fail
+  x3 = super[S2].q  // fail
+}
diff --git a/test/files/pos/t7834.scala b/test/files/pos/t7834.scala
new file mode 100644
index 0000000000..fc9a0aa09d
--- /dev/null
+++ b/test/files/pos/t7834.scala
@@ -0,0 +1,6 @@
+class S { val q = "" }
+
+class B extends S {
+  val x1: B.super.q.type = q
+  val x2: B.this.q.type  = q
+}