Avoid repeatedly evaluating the source if it's a complex expression

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

@@ -7,7 +7,9 @@ import scala.reflect.ClassTag
 
 package object quicklens {
 
-  extension [S, A](inline obj: S)
+  // #114: obj shouldn't be inline since we want to reference the parameter by-name, rather then embedding the whole
+  // expression whenever obj is used; this is especially important for chained .modify invocations
+  extension [S, A](obj: S)
     /** Create an object allowing modifying the given (deeply nested) field accessible in a `case class` hierarchy via
       * `path` on the given `obj`.
       *

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

@@ -0,0 +1,27 @@
+package com.softwaremill.quicklens.test
+
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+
+class CompileTimeTest extends AnyFlatSpec with Matchers {
+  // #114
+  it should "not compile for too long in case of chained modify invocations" in {
+    val start = System.currentTimeMillis()
+    assertDoesNotCompile("""
+      case class B(a1: Double, a2: Double, a3: Double, a4: Double, a5: Double)
+      case class C(b: B)
+
+      import com.softwaremill.quicklens.*
+
+      val c = C(B(1, 1, 1, 1, 1))
+      c
+        .modify(_.b.a1).setTo(0)
+        .modify(_.b.a2).setTo(0)
+        .modify(_.b.a3).setTo(0)
+        .modify(_.b.a4).setTo(0)
+        .modify(_.b.a5).setTo(0)
+  """)
+    val end = System.currentTimeMillis()
+    (end - start) shouldBe <=(5000L) // that's a lot anyway
+  }
+}

quicklens/src/test/scala/com/softwaremill/quicklens/RepeatedModifyTest.scala

@@ -0,0 +1,43 @@
+package com.softwaremill.quicklens
+
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+
+class RepeatedModifyTest extends AnyFlatSpec with Matchers {
+  import RepeatedModifyTest._
+
+  it should "properly handle repeated modify invocations for different fields" in {
+    val c = C(B(1, 1, 1, 1, 1))
+    c
+      .modify(_.b.a1)
+      .setTo(0.0d)
+      .modify(_.b.a2)
+      .setTo(0.0d)
+      .modify(_.b.a3)
+      .setTo(0.0d)
+      .modify(_.b.a4)
+      .setTo(0.0d)
+      .modify(_.b.a5)
+      .setTo(0.0d) shouldBe C(B(0, 0, 0, 0, 0))
+  }
+
+  it should "properly handle repeated modify invocations for the same field" in {
+    val c = C(B(1, 1, 1, 1, 1))
+    c
+      .modify(_.b.a1)
+      .setTo(0.0d)
+      .modify(_.b.a1)
+      .setTo(1.0d)
+      .modify(_.b.a1)
+      .setTo(2.0d)
+      .modify(_.b.a1)
+      .setTo(3.0d)
+      .modify(_.b.a1)
+      .setTo(4.0d) shouldBe C(B(4, 1, 1, 1, 1))
+  }
+}
+
+object RepeatedModifyTest {
+  case class B(a1: Double, a2: Double, a3: Double, a4: Double, a5: Double)
+  case class C(b: B)
+}