Merge pull request #155 from dotty-staging/tailrecTC

Tailrec tc

Author: DarkDimius

src/dotty/tools/dotc/ast/Trees.scala

@@ -1109,36 +1109,20 @@ object Trees {
           cpy.Apply(tree, transform(fun), transform(args))
         case TypeApply(fun, args) =>
           cpy.TypeApply(tree, transform(fun), transform(args))
-        case Literal(const) =>
-          tree
         case New(tpt) =>
           cpy.New(tree, transform(tpt))
-        case Pair(left, right) =>
-          cpy.Pair(tree, transform(left), transform(right))
         case Typed(expr, tpt) =>
           cpy.Typed(tree, transform(expr), transform(tpt))
         case NamedArg(name, arg) =>
           cpy.NamedArg(tree, name, transform(arg))
         case Assign(lhs, rhs) =>
           cpy.Assign(tree, transform(lhs), transform(rhs))
-        case Block(stats, expr) =>
-          cpy.Block(tree, transformStats(stats), transform(expr))
-        case If(cond, thenp, elsep) =>
-          cpy.If(tree, transform(cond), transform(thenp), transform(elsep))
         case Closure(env, meth, tpt) =>
           cpy.Closure(tree, transform(env), transform(meth), transform(tpt))
-        case Match(selector, cases) =>
-          cpy.Match(tree, transform(selector), transformSub(cases))
-        case CaseDef(pat, guard, body) =>
-          cpy.CaseDef(tree, transform(pat), transform(guard), transform(body))
         case Return(expr, from) =>
           cpy.Return(tree, transform(expr), transformSub(from))
-        case Try(block, handler, finalizer) =>
-          cpy.Try(tree, transform(block), transform(handler), transform(finalizer))
         case Throw(expr) =>
           cpy.Throw(tree, transform(expr))
-        case SeqLiteral(elems) =>
-          cpy.SeqLiteral(tree, transform(elems))
         case TypeTree(original) =>
           tree
         case SingletonTypeTree(ref) =>
@@ -1177,12 +1161,29 @@ object Trees {
           cpy.Import(tree, transform(expr), selectors)
         case PackageDef(pid, stats) =>
           cpy.PackageDef(tree, transformSub(pid), transformStats(stats))
-        case Annotated(annot, arg) =>
-          cpy.Annotated(tree, transform(annot), transform(arg))
         case Thicket(trees) =>
           val trees1 = transform(trees)
           if (trees1 eq trees) tree else Thicket(trees1)
+        case Literal(const) =>
+          tree
+        case Pair(left, right) =>
+          cpy.Pair(tree, transform(left), transform(right))
+        case Block(stats, expr) =>
+          cpy.Block(tree, transformStats(stats), transform(expr))
+        case If(cond, thenp, elsep) =>
+          cpy.If(tree, transform(cond), transform(thenp), transform(elsep))
+        case Match(selector, cases) =>
+          cpy.Match(tree, transform(selector), transformSub(cases))
+        case CaseDef(pat, guard, body) =>
+          cpy.CaseDef(tree, transform(pat), transform(guard), transform(body))
+        case Try(block, handler, finalizer) =>
+          cpy.Try(tree, transform(block), transform(handler), transform(finalizer))
+        case SeqLiteral(elems) =>
+          cpy.SeqLiteral(tree, transform(elems))
+        case Annotated(annot, arg) =>
+          cpy.Annotated(tree, transform(annot), transform(arg))
       }
+
       def transformStats(trees: List[Tree])(implicit ctx: Context): List[Tree] =
         transform(trees)
       def transform(trees: List[Tree])(implicit ctx: Context): List[Tree] =

src/dotty/tools/dotc/ast/tpd.scala

@@ -3,12 +3,15 @@ package dotc
 package ast
 
 import core._
+import dotty.tools.dotc.transform.TypeUtils
 import util.Positions._, Types._, Contexts._, Constants._, Names._, Flags._
 import SymDenotations._, Symbols._, StdNames._, Annotations._, Trees._, Symbols._
 import CheckTrees._, Denotations._, Decorators._
 import config.Printers._
 import typer.ErrorReporting._
 
+import scala.annotation.tailrec
+
 /** Some creators for typed trees */
 object tpd extends Trees.Instance[Type] with TypedTreeInfo {
 
@@ -413,6 +416,68 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
     def tpes: List[Type] = xs map (_.tpe)
   }
 
+  /** RetypingTreeMap is a TreeMap that is able to propagate type changes.
+   *
+   *   This is required when types can change during transformation,
+   *   for example if `Block(stats, expr)` is being transformed
+   *   and type of `expr` changes from `TypeRef(prefix, name)` to  `TypeRef(newPrefix, name)` with different prefix, t
+   *   type of enclosing Block should also change, otherwise the whole tree would not be type-correct anymore.
+   *   see `propagateType` methods for propagation rulles.
+   *
+   *   TreeMap does not include such logic as it assumes that types of threes do not change during transformation.
+   */
+  class RetypingTreeMap extends TreeMap {
+
+    override def transform(tree: Tree)(implicit ctx: Context): Tree = tree match {
+      case tree@Select(qualifier, name) =>
+        val tree1 = cpy.Select(tree, transform(qualifier), name)
+        propagateType(tree, tree1)
+      case tree@Pair(left, right) =>
+        val left1 = transform(left)
+        val right1 = transform(right)
+        val tree1 = cpy.Pair(tree, left1, right1)
+        propagateType(tree, tree1)
+      case tree@Block(stats, expr) =>
+        val stats1 = transform(stats)
+        val expr1 = transform(expr)
+        val tree1 = cpy.Block(tree, stats1, expr1)
+        propagateType(tree, tree1)
+      case tree@If(cond, thenp, elsep) =>
+        val cond1 = transform(cond)
+        val thenp1 = transform(thenp)
+        val elsep1 = transform(elsep)
+        val tree1 = cpy.If(tree, cond1, thenp1, elsep1)
+        propagateType(tree, tree1)
+      case tree@Match(selector, cases) =>
+        val selector1 = transform(selector)
+        val cases1 = transformSub(cases)
+        val tree1 = cpy.Match(tree, selector1, cases1)
+        propagateType(tree, tree1)
+      case tree@CaseDef(pat, guard, body) =>
+        val pat1 = transform(pat)
+        val guard1 = transform(guard)
+        val body1 = transform(body)
+        val tree1 = cpy.CaseDef(tree, pat1, guard1, body1)
+        propagateType(tree, tree1)
+      case tree@Try(block, handler, finalizer) =>
+        val expr1 = transform(block)
+        val handler1 = transform(handler)
+        val finalizer1 = transform(finalizer)
+        val tree1 = cpy.Try(tree, expr1, handler1, finalizer1)
+        propagateType(tree, tree1)
+      case tree@SeqLiteral(elems) =>
+        val elems1 = transform(elems)
+        val tree1 = cpy.SeqLiteral(tree, elems1)
+        propagateType(tree, tree1)
+      case tree@Annotated(annot, arg) =>
+        val annot1 = transform(annot)
+        val arg1 = transform(arg)
+        val tree1 = cpy.Annotated(tree, annot1, arg1)
+        propagateType(tree, tree1)
+      case _ => super.transform(tree)
+    }
+  }
+
   /** A map that applies three functions together to a tree and makes sure
    *  they are coordinated so that the result is well-typed. The functions are
    *  @param  typeMap  A function from Type to type that gets applied to the
@@ -425,7 +490,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
   final class TreeTypeMap(
       val typeMap: Type => Type = IdentityTypeMap,
       val ownerMap: Symbol => Symbol = identity _,
-      val treeMap: Tree => Tree = identity _)(implicit ctx: Context) extends TreeMap {
+      val treeMap: Tree => Tree = identity _)(implicit ctx: Context) extends RetypingTreeMap {
 
     override def transform(tree: tpd.Tree)(implicit ctx: Context): tpd.Tree = {
       val tree1 = treeMap(tree)
@@ -436,10 +501,16 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
           cpy.DefDef(ddef, mods, name, tparams1, vparamss1, tmap2.transform(tpt), tmap2.transform(rhs))
         case blk @ Block(stats, expr) =>
           val (tmap1, stats1) = transformDefs(stats)
-          cpy.Block(blk, stats1, tmap1.transform(expr))
+          val expr1 = tmap1.transform(expr)
+          val tree1 = cpy.Block(blk, stats1, expr1)
+          propagateType(blk, tree1)
         case cdef @ CaseDef(pat, guard, rhs) =>
           val tmap = withMappedSyms(patVars(pat))
-          cpy.CaseDef(cdef, tmap.transform(pat), tmap.transform(guard), tmap.transform(rhs))
+          val pat1 = tmap.transform(pat)
+          val guard1 = tmap.transform(guard)
+          val rhs1 = tmap.transform(rhs)
+          val tree1 = cpy.CaseDef(tree, pat1, guard1, rhs1)
+          propagateType(cdef, tree1)
         case tree1 =>
           super.transform(tree1)
       }
@@ -501,6 +572,56 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
     acc(Nil, tree)
   }
 
+  def propagateType(origTree: Pair, newTree: Pair)(implicit ctx: Context) = {
+    if ((newTree eq origTree) ||
+      ((newTree.left.tpe eq origTree.left.tpe) && (newTree.right.tpe eq origTree.right.tpe))) newTree
+    else ta.assignType(newTree, newTree.left, newTree.right)
+  }
+
+  def propagateType(origTree: Block, newTree: Block)(implicit ctx: Context) = {
+    if ((newTree eq origTree) || (newTree.expr.tpe eq origTree.expr.tpe)) newTree
+    else ta.assignType(newTree, newTree.stats, newTree.expr)
+  }
+
+  def propagateType(origTree: If, newTree: If)(implicit ctx: Context) = {
+    if ((newTree eq origTree) ||
+      ((newTree.thenp.tpe eq origTree.thenp.tpe) && (newTree.elsep.tpe eq origTree.elsep.tpe))) newTree
+    else ta.assignType(newTree, newTree.thenp, newTree.elsep)
+  }
+
+  def propagateType(origTree: Match, newTree: Match)(implicit ctx: Context) = {
+    if ((newTree eq origTree) || sameTypes(newTree.cases, origTree.cases)) newTree
+    else ta.assignType(newTree, newTree.cases)
+  }
+
+  def propagateType(origTree: CaseDef, newTree: CaseDef)(implicit ctx: Context) = {
+    if ((newTree eq newTree) || (newTree.body.tpe eq origTree.body.tpe)) newTree
+    else ta.assignType(newTree, newTree.body)
+  }
+
+  def propagateType(origTree: Try, newTree: Try)(implicit ctx: Context) = {
+    if ((newTree eq origTree) ||
+      ((newTree.expr.tpe eq origTree.expr.tpe) && (newTree.handler.tpe eq origTree.handler.tpe))) newTree
+    else ta.assignType(newTree, newTree.expr, newTree.handler)
+  }
+
+  def propagateType(origTree: SeqLiteral, newTree: SeqLiteral)(implicit ctx: Context) = {
+    if ((newTree eq origTree) || sameTypes(newTree.elems, origTree.elems)) newTree
+    else ta.assignType(newTree, newTree.elems)
+  }
+
+  def propagateType(origTree: Annotated, newTree: Annotated)(implicit ctx: Context) = {
+    if ((newTree eq origTree) || ((newTree.arg.tpe eq origTree.arg.tpe) && (newTree.annot eq origTree.annot))) newTree
+    else ta.assignType(newTree, newTree.annot, newTree.arg)
+  }
+
+  def propagateType(origTree: Select, newTree: Select)(implicit ctx: Context) = {
+    if ((origTree eq newTree) || (origTree.qualifier.tpe eq newTree.qualifier.tpe)) newTree
+    else newTree.tpe match {
+      case tpe: NamedType => newTree.withType(tpe.derivedSelect(newTree.qualifier.tpe))
+      case _ => newTree
+    }
+  }
   // convert a numeric with a toXXX method
   def primitiveConversion(tree: Tree, numericCls: Symbol)(implicit ctx: Context): Tree = {
     val mname      = ("to" + numericCls.name).toTermName
@@ -515,6 +636,13 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
     }
   }
 
+  @tailrec
+  def sameTypes(trees: List[tpd.Tree], trees1: List[tpd.Tree]): Boolean = {
+    if (trees.isEmpty) trees.isEmpty
+    else if (trees1.isEmpty) trees.isEmpty
+    else (trees.head.tpe eq trees1.head.tpe) && sameTypes(trees.tail, trees1.tail)
+  }
+
   def evalOnce(tree: Tree)(within: Tree => Tree)(implicit ctx: Context) = {
     if (isIdempotentExpr(tree)) within(tree)
     else {

src/dotty/tools/dotc/core/Substituters.scala

@@ -89,6 +89,40 @@ trait Substituters { this: Context =>
     }
   }
 
+  final def substDealias(tp: Type, from: List[Symbol], to: List[Type], theMap: SubstDealiasMap): Type = {
+    tp match {
+      case tp: NamedType =>
+        val sym = tp.symbol
+        var fs = from
+        var ts = to
+        while (fs.nonEmpty) {
+          if (fs.head eq sym) return ts.head
+          fs = fs.tail
+          ts = ts.tail
+        }
+        if (sym.isStatic && !existsStatic(from)) tp
+        else {
+          val prefix1 = substDealias(tp.prefix, from, to, theMap)
+          if (prefix1 ne tp.prefix) tp.derivedSelect(prefix1)
+          else if (sym.isAliasType) {
+            val hi = sym.info.bounds.hi
+            val hi1 = substDealias(hi, from, to, theMap)
+            if (hi1 eq hi) tp else hi1
+          }
+          else tp
+        }
+      case _: ThisType | _: BoundType | NoPrefix =>
+        tp
+      case tp: RefinedType =>
+        tp.derivedRefinedType(substDealias(tp.parent, from, to, theMap), tp.refinedName, substDealias(tp.refinedInfo, from, to, theMap))
+      case tp: TypeBounds if tp.lo eq tp.hi =>
+        tp.derivedTypeAlias(substDealias(tp.lo, from, to, theMap))
+      case _ =>
+        (if (theMap != null) theMap else new SubstDealiasMap(from, to))
+          .mapOver(tp)
+    }
+  }
+
   final def substSym(tp: Type, from: List[Symbol], to: List[Symbol], theMap: SubstSymMap): Type =
     tp match {
       case tp: NamedType =>
@@ -205,11 +239,11 @@ trait Substituters { this: Context =>
   final class SubstMap(from: List[Symbol], to: List[Type]) extends DeepTypeMap {
     def apply(tp: Type): Type = subst(tp, from, to, this)
   }
-/* not needed yet
-  final class SubstDealiasMap(from: List[Symbol], to: List[Type]) extends SubstMap(from, to) {
-    override def apply(tp: Type): Type = subst(tp.dealias, from, to, this)
+
+  final class SubstDealiasMap(from: List[Symbol], to: List[Type]) extends DeepTypeMap {
+    override def apply(tp: Type): Type = substDealias(tp, from, to, this)
   }
-*/
+
   final class SubstSymMap(from: List[Symbol], to: List[Symbol]) extends DeepTypeMap {
     def apply(tp: Type): Type = substSym(tp, from, to, this)
   }

src/dotty/tools/dotc/core/Types.scala

@@ -818,10 +818,17 @@ object Types {
         }
       }
 
-/* Not needed yet:
+    /** Same as `subst` but follows aliases as a fallback. When faced with a reference
+     *  to an alias type, where normal substiution does not yield a new type, the
+     *  substitution is instead applied to the alias. If that yields a new type,
+     *  this type is returned, outherwise the original type (not the alias) is returned.
+     *  A use case for this method is if one wants to substitute the type parameters
+     *  of a class and also wants to substitute any parameter accessors that alias
+     *  the type parameters.
+     */
     final def substDealias(from: List[Symbol], to: List[Type])(implicit ctx: Context): Type =
-      new ctx.SubstDealiasMap(from, to).apply(this)
-*/
+      ctx.substDealias(this, from, to, null)
+
     /** Substitute all types of the form `PolyParam(from, N)` by
      *  `PolyParam(to, N)`.
      */

src/dotty/tools/dotc/transform/FullParameterization.scala

@@ -104,7 +104,7 @@ trait FullParameterization {
     /** Replace class type parameters by the added type parameters of the polytype `pt` */
     def mapClassParams(tp: Type, pt: PolyType): Type = {
       val classParamsRange = (mtparamCount until mtparamCount + ctparams.length).toList
-      tp.subst(clazz.typeParams, classParamsRange map (PolyParam(pt, _)))
+      tp.substDealias(clazz.typeParams, classParamsRange map (PolyParam(pt, _)))
     }
 
     /** The bounds for the added type paraneters of the polytype `pt` */
@@ -142,7 +142,7 @@ trait FullParameterization {
    *  followed by the class parameters of its enclosing class.
    */
   private def allInstanceTypeParams(originalDef: DefDef)(implicit ctx: Context): List[Symbol] =
-    originalDef.tparams.map(_.symbol) ::: originalDef.symbol.owner.typeParams
+    originalDef.tparams.map(_.symbol) ::: originalDef.symbol.enclosingClass.typeParams
 
   /** Given an instance method definition `originalDef`, return a
    *  fully parameterized method definition derived from `originalDef`, which
@@ -152,7 +152,7 @@ trait FullParameterization {
   def fullyParameterizedDef(derived: TermSymbol, originalDef: DefDef)(implicit ctx: Context): Tree =
     polyDefDef(derived, trefs => vrefss => {
       val origMeth = originalDef.symbol
-      val origClass = origMeth.owner.asClass
+      val origClass = origMeth.enclosingClass.asClass
       val origTParams = allInstanceTypeParams(originalDef)
       val origVParams = originalDef.vparamss.flatten map (_.symbol)
       val thisRef :: argRefs = vrefss.flatten
@@ -201,7 +201,7 @@ trait FullParameterization {
 
       new TreeTypeMap(
         typeMap = rewireType(_)
-          .subst(origTParams, trefs)
+          .substDealias(origTParams, trefs)
           .subst(origVParams, argRefs.map(_.tpe))
           .substThisUnlessStatic(origClass, thisRef.tpe),
         ownerMap = (sym => if (sym eq origMeth) derived else sym),
@@ -219,7 +219,7 @@ trait FullParameterization {
   def forwarder(derived: TermSymbol, originalDef: DefDef)(implicit ctx: Context): Tree =
     ref(derived.termRef)
       .appliedToTypes(allInstanceTypeParams(originalDef).map(_.typeRef))
-      .appliedTo(This(originalDef.symbol.owner.asClass))
+      .appliedTo(This(originalDef.symbol.enclosingClass.asClass))
       .appliedToArgss(originalDef.vparamss.nestedMap(vparam => ref(vparam.symbol)))
       .withPos(originalDef.rhs.pos)
 }

src/dotty/tools/dotc/transform/LazyVals.scala

@@ -144,7 +144,7 @@ class LazyValTranformContext {
       *     flag = true
       *     target
       *     }
-      *   }`
+      *   }
       */
 
     def mkNonThreadSafeDef(target: Symbol, flag: Symbol, rhs: Tree)(implicit ctx: Context) = {