5 files changed, 63 insertions, 1 deletions
diff --git a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
index 8f32f0e653..a74470a9cd 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
@@ -1399,11 +1399,12 @@ trait Implicits {
         val failstart = if (Statistics.canEnable) Statistics.startTimer(oftypeFailNanos) else null
         val succstart = if (Statistics.canEnable) Statistics.startTimer(oftypeSucceedNanos) else null
 
+        val wasAmbigious = result.isAmbiguousFailure // SI-6667, never search companions after an ambiguous error in in-scope implicits
         result = materializeImplicit(pt)
 
         // `materializeImplicit` does some preprocessing for `pt`
         // is it only meant for manifests/tags or we need to do the same for `implicitsOfExpectedType`?
-        if (result.isFailure) result = searchImplicit(implicitsOfExpectedType, false)
+        if (result.isFailure && !wasAmbigious) result = searchImplicit(implicitsOfExpectedType, false)
 
         if (result.isFailure) {
           context.updateBuffer(previousErrs)
diff --git a/test/files/neg/t6667.check b/test/files/neg/t6667.check
new file mode 100644
index 0000000000..43313fa4fe
--- /dev/null
+++ b/test/files/neg/t6667.check
@@ -0,0 +1,13 @@
+t6667.scala:8: error: ambiguous implicit values:
+ both value inScope1 in object Test of type => C
+ and value inScope2 in object Test of type => C
+ match expected type C
+  implicitly[C]: Unit // C.companion was used; whereas the ambiguity should abort the implicit search.
+            ^
+t6667.scala:9: error: ambiguous implicit values:
+ both value inScope1 in object Test of type => C
+ and value inScope2 in object Test of type => C
+ match expected type C
+  implicitly[C]       // ambiguity reported, rather than falling back to C.companion
+            ^
+two errors found
diff --git a/test/files/neg/t6667.scala b/test/files/neg/t6667.scala
new file mode 100644
index 0000000000..fb857ebd33
--- /dev/null
+++ b/test/files/neg/t6667.scala
@@ -0,0 +1,10 @@
+class C
+object C {
+  implicit def companion = new C
+}
+
+object Test {
+  implicit val inScope1, inScope2 = new C
+  implicitly[C]: Unit // C.companion was used; whereas the ambiguity should abort the implicit search.
+  implicitly[C]       // ambiguity reported, rather than falling back to C.companion
+}
diff --git a/test/files/neg/t6667b.check b/test/files/neg/t6667b.check
new file mode 100644
index 0000000000..99cea9a47c
--- /dev/null
+++ b/test/files/neg/t6667b.check
@@ -0,0 +1,13 @@
+t6667b.scala:16: error: ambiguous implicit values:
+ both value a in object Test of type => Test.Box
+ and value b of type Test.Box
+ match expected type Test.Box
+      new Test()
+      ^
+t6667b.scala:19: error: ambiguous implicit values:
+ both value a in object Test of type => Test.Box
+ and value b of type Test.Box
+ match expected type Test.Box
+    new Test()
+    ^
+two errors found
diff --git a/test/files/neg/t6667b.scala b/test/files/neg/t6667b.scala
new file mode 100644
index 0000000000..4e64e1af17
--- /dev/null
+++ b/test/files/neg/t6667b.scala
@@ -0,0 +1,25 @@
+object Test {
+  abstract class Box {
+    val value: Int
+  }
+
+  implicit val a: Box = new Box {
+    val value= 1
+  }
+
+  def main(args: Array[String]) {
+    implicit val b: Box= new Box {
+      val value= 2
+    }
+
+    new Object {
+      new Test()
+    }
+    // compare with:
+    new Test()
+  }
+}
+
+class Test()(implicit x: Test.Box) {
+  println(x.value)
+}