Closes SI-5354.

The reason why the test case compiled without error is pretty  devious: When checking the `Foo.x' implicit, a CyclicReference error occurs which causes the alternative to be discarded. Why a CylicReference? Because the inferencer tries to decide whether the owner of `z` is a subclass of the owner od `x`. To do this, it computed the info of the owner of `z1`, which is not complete because no result type for `f1` was given. Hence a CyclicReference error.

The fix is twofold: (1) We make isNonBottomSubClass smarter so that it always returns false if the symbol in question is not a type; hence the info need not be computed. (2) It's dubious to swallow CyclicReference errors anywhere, but I deemed it too risky to propagate them. But at least the CyclicReference is now logged if -Ylog-implicit is true. This hopefully spares future maintainers the same detective work I had to go through when digging this out.

2 files changed, 22 insertions, 0 deletions

diff --git a/test/files/neg/t5354.check b/test/files/neg/t5354.check
new file mode 100644
index 0000000000..e47cecb5fe
--- /dev/null
+++ b/test/files/neg/t5354.check
@@ -0,0 +1,7 @@
+t5354.scala:9: error: ambiguous implicit values:
+ both method x123 in package foo of type => foo.Bippy
+ and method z of type => foo.Bippy
+ match expected type foo.Bippy
+      implicitly[Bippy]
+                ^
+one error found
diff --git a/test/files/neg/t5354.scala b/test/files/neg/t5354.scala
new file mode 100644
index 0000000000..99b5650155
--- /dev/null
+++ b/test/files/neg/t5354.scala
@@ -0,0 +1,15 @@
+package object foo {
+  implicit def x123: Bippy = new Bippy("x")
+}
+package foo {
+  class Bippy(override val toString: String){ }
+  class Dingus {
+    def f1 = {
+      implicit def z: Bippy = new Bippy("z")
+      implicitly[Bippy]
+    }
+  }
+  object Test extends App {
+    println(new Dingus().f1)
+  }
+}