address review

Author: Jasper-M

compiler/src/dotty/tools/dotc/typer/Implicits.scala

@@ -716,14 +716,16 @@ trait Implicits { self: Typer =>
         )
         val userDefined = maybeAnnot.flatMap { case (annot, alt) =>
           val params = alt.ref.underlying match {
-            case lambda: TypeLambda => lambda.typeParams.map(_.paramName.unexpandedName.toString)
-            case _                  => Nil
+            case p: PolyType => p.paramNames.map(_.toString)
+            case _           => Nil
           }
+          def resolveTypes(targs: List[Tree])(implicit ctx: Context) =
+            targs.map(a => fullyDefinedType(a.tpe, "type argument", a.pos))
           val args = alt.tree match {
-            case TypeApply(_, targs) if params.nonEmpty =>
-              def resolveTypes(targs: List[tpd.Tree])(implicit ctx: Context) =
-                targs.map(a => fullyDefinedType(a.tpe, "type parameter", a.pos))
+            case TypeApply(_, targs) =>
               resolveTypes(targs)(ctx.fresh.setTyperState(alt.tstate))
+            case Block(List(DefDef(_, _, _, _, Apply(TypeApply(_, targs), _))), _) =>
+              resolveTypes(targs.asInstanceOf[List[Tree]])(ctx.fresh.setTyperState(alt.tstate))
             case _ =>
               Nil
           }

compiler/test/dotty/tools/dotc/reporting/ErrorMessagesTests.scala

@@ -1385,4 +1385,27 @@ class ErrorMessagesTests extends ErrorMessagesTest {
 
       assertEquals(m.msg, "Could not prove Int =!= Int")
     }
+
+  @Test def userDefinedImplicitAmbiguous4 =
+    checkMessagesAfter("frontend") {
+      """
+        |class C {
+        |  @annotation.implicitAmbiguous("msg A=${A}")
+        |  implicit def f[A](x: Int): String = "f was here"
+        |  implicit def g(x: Int): String = "f was here"
+        |  def test: Unit = {
+        |    implicitly[Int => String]
+        |  }
+        |}
+
+      """.stripMargin
+    }.expect { (itcx, messages) =>
+      import diagnostic.NoExplanation
+      implicit val ctx: Context = itcx
+
+      assertMessageCount(1, messages)
+      val (m: NoExplanation) :: Nil = messages
+
+      assertEquals(m.msg, "msg A=Any")
+    }
 }