fix GenApplyLensSyntax.value collision

example/src/test/scala/monocle/LensExample.scala

@@ -69,6 +69,16 @@ class LensMonoExample extends MonocleSuite {
   test("@Lenses is for case classes only") {
     illTyped( """@Lenses class C""", "Invalid annotation target: must be a case class")
   }
+
+  test("GenApplyLensOps has no collision with .value") {
+    case class MyString(s: String)
+    object MyString {
+      implicit class Ops(self: MyString) {
+        val value: String = self.s
+      }
+    }
+    MyString("a").value shouldEqual "a"
+  }
 }
 
 class LensPolyExample extends MonocleSuite {

macro/shared/src/main/scala/monocle/macros/syntax/GenApplyLensSyntax.scala

@@ -6,17 +6,24 @@ trait GenApplyLensSyntax {
   implicit def toGenApplyLensOps[S](value: S): GenApplyLensOps[S] = new GenApplyLensOps(value)
 }
 
-class GenApplyLensOps[A](val value: A) extends AnyVal {
+class GenApplyLensOps[A](private val value: A) extends AnyVal {
   def lens[C]( field: A => C ): ApplyLens[A,A,C,C] = macro GenApplyLensOpsImpl.lens_impl[A, C]
 }
 
 @macrocompat.bundle
 class GenApplyLensOpsImpl(val c: blackbox.Context){
   def lens_impl[A: c.WeakTypeTag, C](field: c.Expr[A => C]): c.Expr[ApplyLens[A,A,C,C]] = {
     import c.universe._
+
+    val subj = c.prefix.tree match {
+      case Apply(TypeApply(_, _), List(x)) => x
+      case t =>
+        c.abort(c.enclosingPosition, s"Invalid prefix tree ${show(t)}")
+    }
+
     c.Expr[ApplyLens[A,A,C,C]](q"""
       _root_.monocle.syntax.ApplyLens(
-        ${c.prefix.tree}.value,
+        $subj,
         _root_.monocle.macros.GenLens[${c.weakTypeOf[A]}](${field})
       )
     """)