From 9ccfa5ce0bd02c66571c10a87c0ceab1096878af Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20=C5=A0pan=C4=9Bl?=
 <OndrejSpanel@users.noreply.github.com>
Date: Sun, 1 Dec 2024 17:20:48 +0100
Subject: [PATCH] Add test for #258, improve error message

---
 .../softwaremill/quicklens/QuicklensMacros.scala    | 10 ++++++++--
 .../quicklens/test/ExplicitCopyTest.scala           | 13 +++++++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/quicklens/src/main/scala-3/com/softwaremill/quicklens/QuicklensMacros.scala b/quicklens/src/main/scala-3/com/softwaremill/quicklens/QuicklensMacros.scala
index 20e640e..b79462a 100644
--- a/quicklens/src/main/scala-3/com/softwaremill/quicklens/QuicklensMacros.scala
+++ b/quicklens/src/main/scala-3/com/softwaremill/quicklens/QuicklensMacros.scala
@@ -58,6 +58,9 @@ object QuicklensMacros {
     def noSuchMember(tpeStr: String, name: String) =
       s"$tpeStr has no member named $name"
 
+    def noSuitableMember(tpeStr: String, name: String, argNames: Iterable[String]) =
+      s"$tpeStr has no member $name with parameters ${argNames.mkString("(", ", ", ")")}"
+
     def multipleMatchingMethods(tpeStr: String, name: String, syms: Seq[Symbol]) =
       val symsStr = syms.map(s => s" - $s: ${s.termRef.dealias.widen.show}").mkString("\n", "\n", "")
       s"Multiple methods named $name found in $tpeStr: $symsStr"
@@ -181,13 +184,16 @@ object QuicklensMacros {
 
     def methodSymbolByNameAndArgsOrError(sym: Symbol, name: String, argsMap: Map[String, Term]): Symbol = {
       val argNames = argsMap.keys
-      sym.methodMember(name).filter{ msym =>
+      val allCopyMembers = sym.methodMember(name)
+      allCopyMembers.filter{ msym =>
         // for copy, we filter out the methods that don't have the desired parameter names
         val paramNames = msym.paramSymss.flatten.filter(_.isTerm).map(_.name)
         argNames.forall(paramNames.contains)
       } match
         case List(m) => m
-        case Nil     => report.errorAndAbort(noSuchMember(sym.name, name))
+        case Nil     =>
+          if allCopyMembers.isEmpty then report.errorAndAbort(noSuchMember(sym.name, name))
+          else report.errorAndAbort(noSuitableMember(sym.name, name, argNames))
         case lst @ (m :: _)     =>
           // if we have multiple matching copy methods, pick the synthetic one, if it exists, otherwise, pick any method
           val syntheticCopies = lst.filter(_.flags.is(Flags.Synthetic))
diff --git a/quicklens/src/test/scala-3/com/softwaremill/quicklens/test/ExplicitCopyTest.scala b/quicklens/src/test/scala-3/com/softwaremill/quicklens/test/ExplicitCopyTest.scala
index f1ecce1..46ba044 100644
--- a/quicklens/src/test/scala-3/com/softwaremill/quicklens/test/ExplicitCopyTest.scala
+++ b/quicklens/src/test/scala-3/com/softwaremill/quicklens/test/ExplicitCopyTest.scala
@@ -77,6 +77,19 @@ class ExplicitCopyTest extends AnyFlatSpec with Matchers {
     accessed shouldEqual 0
   }
 
+  it should "not compile when modifying a field which is not present as a copy parameter" in {
+    """
+    case class Content(x: String)
+
+    class A(val c: Content) {
+      def copy(x: String = c.x): A = new A(Content(x))
+    }
+
+    val a = new A(Content("A"))
+    val am = a.modify(_.c).setTo(Content("B"))
+    """ shouldNot compile
+  }
+
   // TODO: Would be nice to be able to handle this case. Based on the types, it
   // is obvious, that the explicit copy should be picked, but I'm not sure if we
   // can get that information