Improve automatic type id generation, fixes #685

derivation/src/main/scala/io/bullet/borer/derivation/Deriver.scala

@@ -138,13 +138,7 @@ abstract private[derivation] class Deriver[F[_]: Type, T: Type, Q <: Quotes](usi
   }
 
   case class AdtTypeNode(tpe: TypeRepr, subs: List[AdtTypeNode]) extends WithAnnotations {
-    @threadUnsafe lazy val name: String = {
-      var s = tpe.show
-      s = s.substring(s.lastIndexOf('.') + 1)
-      s.indexOf('[') match
-        case -1 => s
-        case x  => s.substring(0, x)
-    }
+    @threadUnsafe lazy val name: String = if (tpe.isSingleton) tpe.termSymbol.name else tpe.typeSymbol.name
     def annotations: List[Term]                       = tpe.typeSymbol.annotations
     def containedIn(list: List[AdtTypeNode]): Boolean = list.exists(_ eq this)
     def isEnum: Boolean                               = isRoot && tpe.typeSymbol.flags.is(Flags.Enum)

derivation/src/test/scala/io/bullet/borer/derivation/Issue685.scala

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2019-2023 Mathias Doenitz
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+package io.bullet.borer.derivation
+
+// compile-time only
+object Issue685:
+  import io.bullet.borer.*
+  import io.bullet.borer.derivation.MapBasedCodecs.*
+
+  sealed trait Bar:
+    def toEither: Either[Int, String] =
+      this match
+        case Bar.IntBar(int) => Left(int)
+        case Bar.StrBar(str) => Right(str)
+
+  object Bar:
+    case class IntBar(int: Int) extends Bar
+    case class StrBar(str: String) extends Bar
+    given Encoder[Bar] = Encoder.ForEither.default[Int, String].contramap[Bar](_.toEither)
+
+  sealed trait Foo
+  object Foo:
+    case class Foo1[B <: Bar](b1: B) extends Foo
+    case class Foo2[B <: Bar](b2: B) extends Foo
+
+    given Encoder[Foo] = {
+      given Encoder[Foo1[Bar]] = deriveEncoder
+      given Encoder[Foo2[Bar]] = deriveEncoder
+      deriveEncoder
+    }