Make compilable with -Xcheck-macros

build.sbt

@@ -14,7 +14,14 @@ excludeLintKeys in Global ++= Set(ideSkipProject)
 val commonSettings = commonSmlBuildSettings ++ ossPublishSettings ++ Seq(
   organization := "com.softwaremill.quicklens",
   updateDocs := UpdateVersionInDocs(sLog.value, organization.value, version.value, List(file("README.md"))),
-  scalacOptions ++= Seq("-deprecation", "-feature", "-unchecked"), // useful for debugging macros: "-Ycheck:all", "-Xcheck-macros"
+  scalacOptions ++= Seq("-deprecation", "-feature", "-unchecked"),
+  scalacOptions ++= {
+    val sv = (Compile / scalaVersion).value
+    CrossVersion.partialVersion(sv) match {
+      case Some((3, _))  => List("-Xcheck-macros")
+      case _             => Nil
+    }
+  },
   ideSkipProject := (scalaVersion.value != scalaIdeaVersion)
 )
 

quicklens/src/main/scala-3/com/softwaremill/quicklens/QuicklensMacros.scala

@@ -157,6 +157,8 @@ object QuicklensMacros {
       def poorMansLUB: TypeRepr = tpe match {
         case AndType(l, r) if l <:< r => l
         case AndType(l, r) if r <:< l => r
+        case AndType(_, _) =>
+          report.errorAndAbort(s"Implementation limitation: Cannot modify an & type with unrelated types.")
         case _                        => tpe
       }
 
@@ -176,6 +178,10 @@ object QuicklensMacros {
     extension (term: Term)
       def appliedToIfNeeded(args: List[Term]): Term =
         if args.isEmpty then term else term.appliedToArgs(args)
+      def appliedToTypesIfNeeded(args: List[TypeRepr]): Term =
+        if term.symbol.paramSymss.headOption.toList.flatten.filter(_.isType).nonEmpty then
+          term.appliedToTypes(args)
+        else term
 
     def symbolAccessorByNameOrError(obj: Term, name: String): Term = {
       val objTpe = obj.tpe.widenAll
@@ -251,7 +257,7 @@ object QuicklensMacros {
           val methodSymbol = methodSymbolByNameOrError(objSymbol, copy.name + "$default$" + i.toString)
           // default values in extension methods take the extension receiver as the first parameter
           val defaultMethodArgs = argsMap.dropRight(1).flatMap(_.values)
-          obj.select(methodSymbol).appliedToIfNeeded(defaultMethodArgs)
+          obj.select(methodSymbol).appliedToTypesIfNeeded(typeParams).appliedToIfNeeded(defaultMethodArgs)
         n -> v.getOrElse(defaultMethod)
       }.toMap
 

quicklens/src/test/scala-3/com/softwaremill/quicklens/test/ModifyAndTypeTest.scala

@@ -9,6 +9,7 @@ object ModifyAndTypeTest {
   case class A(a: Int) extends B
   trait B {
     def a: Int
+    def b: Int = 0
   }
 
   case class A1(a: Int)
@@ -26,6 +27,7 @@ class ModifyAndTypeTest extends AnyFlatSpec with Matchers {
 
     val modified = ab.modify(_.a).setTo(1)
 
+    modified.b shouldBe 0
     modified.a shouldBe 1
   }
 
@@ -34,22 +36,7 @@ class ModifyAndTypeTest extends AnyFlatSpec with Matchers {
 
     val modified = ab.modify(_.a).setTo(1)
 
-    modified.a shouldBe 1
-  }
-
-  it should "modify an & type object 2" in {
-    val ab: B & A1 = new A1(0) with B
-
-    val modified = ab.modify(_.a).setTo(1)
-
-    modified.a shouldBe 1
-  }
-
-  it should "modify an & type object 3" in {
-    val ab: A1 & B = new A1(0) with B
-
-    val modified = ab.modify(_.a).setTo(1)
-
+    modified.b shouldBe 0
     modified.a shouldBe 1
   }