Merge pull request #826 from lrytz/t5907

SI-5907, SI-5009 case-class copy defaults only for first param list

2 files changed, 66 insertions, 50 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Namers.scala b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
index decd18b599..6428173577 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Namers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
@@ -502,32 +502,29 @@ trait Namers extends MethodSynthesis {
       noDuplicates(selectors map (_.rename), AppearsTwice)
     }
 
-    def enterCopyMethodOrGetter(tree: Tree, tparams: List[TypeDef]): Symbol = {
-      val sym          = tree.symbol
-      val lazyType     = completerOf(tree, tparams)
-      def completeCopyFirst = sym.isSynthetic && (!sym.hasDefault || sym.owner.info.member(nme.copy).isSynthetic)
-      def completeCopyMethod(clazz: Symbol) {
-        // the 'copy' method of case classes needs a special type completer to make
-        // bug0054.scala (and others) work. the copy method has to take exactly the same
-        // parameter types as the primary constructor.
+    def enterCopyMethod(copyDefDef: Tree, tparams: List[TypeDef]): Symbol = {
+      val sym      = copyDefDef.symbol
+      val lazyType = completerOf(copyDefDef, tparams)
+
+      /** Assign the types of the class parameters to the parameters of the
+       *  copy method. See comment in `Unapplies.caseClassCopyMeth` */
+      def assignParamTypes() {
+        val clazz = sym.owner
         val constructorType = clazz.primaryConstructor.tpe
-        val subst           = new SubstSymMap(clazz.typeParams, tparams map (_.symbol))
-        val vparamss        = tree match { case x: DefDef => x.vparamss ; case _ => Nil }
-        val cparamss        = constructorType.paramss
-
-        map2(vparamss, cparamss)((vparams, cparams) =>
-          map2(vparams, cparams)((param, cparam) =>
-            // need to clone the type cparam.tpe???
-            // problem is: we don't have the new owner yet (the new param symbol)
-            param.tpt setType subst(cparam.tpe)
+        val subst = new SubstSymMap(clazz.typeParams, tparams map (_.symbol))
+        val classParamss = constructorType.paramss
+        val DefDef(_, _, _, copyParamss, _, _) = copyDefDef
+
+        map2(copyParamss, classParamss)((copyParams, classParams) =>
+          map2(copyParams, classParams)((copyP, classP) =>
+            copyP.tpt setType subst(classP.tpe)
           )
         )
       }
-      sym setInfo {
-        mkTypeCompleter(tree) { copySym =>
-          if (completeCopyFirst)
-            completeCopyMethod(copySym.owner)
 
+      sym setInfo {
+        mkTypeCompleter(copyDefDef) { sym =>
+          assignParamTypes()
           lazyType complete sym
         }
       }
@@ -604,8 +601,8 @@ trait Namers extends MethodSynthesis {
         val bridgeFlag = if (mods hasAnnotationNamed tpnme.bridgeAnnot) BRIDGE else 0
         val sym = assignAndEnterSymbol(tree) setFlag bridgeFlag
 
-        if (name == nme.copy || tree.symbol.name.startsWith(nme.copy + nme.DEFAULT_GETTER_STRING))
-          enterCopyMethodOrGetter(tree, tparams)
+        if (name == nme.copy && sym.isSynthetic)
+          enterCopyMethod(tree, tparams)
         else
           sym setInfo completerOf(tree, tparams)
     }
diff --git a/src/compiler/scala/tools/nsc/typechecker/Unapplies.scala b/src/compiler/scala/tools/nsc/typechecker/Unapplies.scala
index 4c20d14406..1b89f3db44 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Unapplies.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Unapplies.scala
@@ -197,42 +197,61 @@ trait Unapplies extends ast.TreeDSL
     )
   }
 
+  /**
+   * Generates copy methods for case classes. Copy only has defaults on the first
+   * parameter list, as of SI-5009.
+   *
+   * The parameter types of the copy method need to be exactly the same as the parameter
+   * types of the primary constructor. Just copying the TypeTree is not enough: a type `C`
+   * might refer to something else *inside* the class (i.e. as parameter type of `copy`)
+   * than *outside* the class (i.e. in the class parameter list).
+   *
+   * One such example is t0054.scala:
+   *   class A {
+   *     case class B(x: C) extends A { def copy(x: C = x) = ... }
+   *     class C {}      ^                          ^
+   *   }                (1)                        (2)
+   *
+   * The reference (1) to C is `A.this.C`. The reference (2) is `B.this.C` - not the same.
+   *
+   * This is fixed with a hack currently. `Unapplies.caseClassCopyMeth`, which creates the
+   * copy method, uses empty `TypeTree()` nodes for parameter types.
+   *
+   * In `Namers.enterDefDef`, the copy method gets a special type completer (`enterCopyMethod`).
+   * Before computing the body type of `copy`, the class parameter types are assigned the copy
+   * method parameters.
+   *
+   * This attachment class stores the copy method parameter ValDefs as an attachment in the
+   * ClassDef of the case class.
+   */
   def caseClassCopyMeth(cdef: ClassDef): Option[DefDef] = {
     def isDisallowed(vd: ValDef) = isRepeatedParamType(vd.tpt) || isByNameParamType(vd.tpt)
-    val cparamss  = constrParamss(cdef)
-    val flat      = cparamss.flatten
+    val classParamss  = constrParamss(cdef)
 
-    if (cdef.symbol.hasAbstractFlag || (flat exists isDisallowed)) None
+    if (cdef.symbol.hasAbstractFlag || mexists(classParamss)(isDisallowed)) None
     else {
+      def makeCopyParam(vd: ValDef, putDefault: Boolean) = {
+        val rhs = if (putDefault) toIdent(vd) else EmptyTree
+        val flags = PARAM | (vd.mods.flags & IMPLICIT) | (if (putDefault) DEFAULTPARAM else 0)
+        // empty tpt: see comment above
+        val tpt = atPos(vd.pos.focus)(TypeTree() setOriginal vd.tpt)
+        treeCopy.ValDef(vd, Modifiers(flags), vd.name, tpt, rhs)
+      }
+
       val tparams = cdef.tparams map copyUntypedInvariant
-      // the parameter types have to be exactly the same as the constructor's parameter types; so it's
-      // not good enough to just duplicated the (untyped) tpt tree; the parameter types are removed here
-      // and re-added in ``finishWith'' in the namer.
-      def paramWithDefault(vd: ValDef) =
-        treeCopy.ValDef(vd, vd.mods | DEFAULTPARAM, vd.name, atPos(vd.pos.focus)(TypeTree() setOriginal vd.tpt), toIdent(vd))
-        
-      val (copyParamss, funParamss) = cparamss match {
-        case Nil => (Nil, Nil)
+      val paramss = classParamss match {
+        case Nil => Nil
         case ps :: pss =>
-          (List(ps.map(paramWithDefault)), mmap(pss)(p => copyUntyped[ValDef](p).copy(rhs = EmptyTree)))
+          ps.map(makeCopyParam(_, putDefault = true)) :: mmap(pss)(makeCopyParam(_, putDefault = false))
       }
 
       val classTpe = classType(cdef, tparams)
-      val bodyTpe = funParamss.foldRight(classTpe)((params, restp) => gen.scalaFunctionConstr(params.map(_.tpt), restp))
-
-      val argss = copyParamss match {
-        case Nil     => Nil
-        case ps :: _ => mmap(ps :: funParamss)(toIdent)
-      }
-      def mkFunction(vparams: List[ValDef], body: Tree) = Function(vparams, body)
-      val body = funParamss.foldRight(New(classTpe, argss): Tree)(mkFunction)
-      // [Eugene++] no longer compiles after I moved the `Function` case class into scala.reflect.internal
-      // val body = funParamss.foldRight(New(classTpe, argss): Tree)(Function)
-
-      Some(atPos(cdef.pos.focus)(
-        DefDef(Modifiers(SYNTHETIC), nme.copy, tparams, copyParamss, bodyTpe,
-          body)
-      ))
+      val argss = mmap(paramss)(toIdent)
+      val body: Tree = New(classTpe, argss)
+      val copyDefDef = atPos(cdef.pos.focus)(
+        DefDef(Modifiers(SYNTHETIC), nme.copy, tparams, paramss, TypeTree(), body)
+      )
+      Some(copyDefDef)
     }
   }
 }