SI-6667 Abort after any ambiguous in-scope implicit

Rather than continuing on to a search of implicits
of the expected type.

Previously, the companion implicits were searched if the
the caller was running the implicit search in silent
mode, for example if searching for an implicit parameter
in an application which has an expected type.

After this commit, the behaviour is consistent, regardless
on silent/non-silent typing.

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)
+}