Find implicitNotFoundMessage on types

Fixes #11797

Author: odersky

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

@@ -375,17 +375,30 @@ class ImplicitSearchError(
    *  def foo(implicit foo: Foo): Any = ???
    */
   private def userDefinedImplicitNotFoundTypeMessage: Option[String] =
-    pt.baseClasses.iterator
-      // Don't inherit "No implicit view available..." message if subtypes of Function1 are not treated as implicit conversions anymore
-      .filter(sym => Feature.migrateTo3 || sym != defn.Function1)
-      .map(userDefinedImplicitNotFoundTypeMessage(_))
-      .find(_.isDefined).flatten
-
-  private def userDefinedImplicitNotFoundTypeMessage(classSym: ClassSymbol): Option[String] =
-    userDefinedMsg(classSym, defn.ImplicitNotFoundAnnot).map { rawMsg =>
-      val substituteType = (_: Type).asSeenFrom(pt, classSym)
-      formatAnnotationMessage(rawMsg, classSym, substituteType)
-    }
+    def recur(tp: Type): Option[String] = tp match
+      case tp: TypeRef =>
+        val sym = tp.symbol
+        userDefinedImplicitNotFoundTypeMessage(sym).orElse(recur(tp.info))
+      case tp: ClassInfo =>
+        tp.baseClasses.iterator
+          .map(userDefinedImplicitNotFoundTypeMessage)
+          .find(_.isDefined).flatten
+      case tp: TypeProxy =>
+        recur(tp.underlying)
+      case tp: AndType =>
+        recur(tp.tp1).orElse(recur(tp.tp2))
+      case _ =>
+        None
+    recur(pt)
+
+  private def userDefinedImplicitNotFoundTypeMessage(sym: Symbol): Option[String] =
+    for
+      rawMsg <- userDefinedMsg(sym, defn.ImplicitNotFoundAnnot)
+      if Feature.migrateTo3 || sym != defn.Function1
+        // Don't inherit "No implicit view available..." message if subtypes of Function1 are not treated as implicit conversions anymore
+    yield
+      val substituteType = (_: Type).asSeenFrom(pt, sym)
+      formatAnnotationMessage(rawMsg, sym, substituteType)
 
   private def hiddenImplicitsAddendum: String =
     def hiddenImplicitNote(s: SearchSuccess) =

tests/neg/i11797.check

@@ -0,0 +1,4 @@
+-- Error: tests/neg/i11797.scala:6:17 ----------------------------------------------------------------------------------
+6 |  summon[Foo.Bar]     // error
+  |                 ^
+  |                 Oops

tests/neg/i11797.scala

@@ -0,0 +1,6 @@
+object Foo:
+  @annotation.implicitNotFound("Oops")
+  type Bar
+
+@main def run(): Unit =
+  summon[Foo.Bar]     // error