Fleshed out tree handling

1 files changed, 352 insertions, 29 deletions

diff --git a/src/dotty/tools/dotc/core/Trees.scala b/src/dotty/tools/dotc/core/Trees.scala
index 3a0c4efad..ccc20ab97 100644
--- a/src/dotty/tools/dotc/core/Trees.scala
+++ b/src/dotty/tools/dotc/core/Trees.scala
@@ -1,11 +1,14 @@
 package dotty.tools.dotc.core
 
 import Types._, Names._, Flags._, Positions._, Contexts._, Constants._, SymDenotations._, Symbols._
+import Denotations._
 
 object Trees {
 
-  abstract class Modifiers {
+  abstract class Modifiers[T] {
     val flags: FlagSet
+    val privateWithin: Name
+    val annotations: List[Tree[T]]
   }
 
   /** Trees take a parameter indicating what the type of their `tpe` field
@@ -27,74 +30,394 @@ object Trees {
    *   - Type checking an untyped tree will remove all embedded `TypedSplice`
    *     nodes.
    */
-  abstract class Tree[T] {
+  abstract class Tree[T] extends DotClass {
     def pos: Position
 
-    private var _tpe: T = _
+    type ThisTree[T] <: Tree[T]
+
+    protected var _tpe: T = _
 
     def tpe: T = {
       if (_tpe == null) throw new UnAssignedTypeException(this)
       _tpe
     }
 
-    def withType(tpe: Type): Tree[Type] = {
+    def withType(tpe: Type): ThisTree[Type] = {
       val tree =
         (if (_tpe == null ||
             (_tpe.asInstanceOf[AnyRef] eq tpe.asInstanceOf[AnyRef])) this
-         else clone).asInstanceOf[Tree[Type]]
+         else clone).asInstanceOf[TypedTree]
       tree._tpe = tpe
-      tree
+      tree.asInstanceOf[ThisTree[Type]]
     }
 
+    def denot(implicit ctx: Context): Denotation = NoDenotation
+    def symbol(implicit ctx: Context): Symbol = NoSymbol
+
+    def isType: Boolean = false
+    def isTerm: Boolean = false
+    def isDef: Boolean = false
+
     def withPosition(pos: Position) = ???
   }
 
-  case class Ident[T] (name: Name)(implicit val pos: Position) extends Tree[T]
+  class UnAssignedTypeException[T](tree: Tree[T]) extends RuntimeException {
+    override def getMessage: String = s"type of $tree is not assigned"
+  }
 
-  case class Select[T](qualifier: Tree[T], name: Name)(implicit val pos: Position) extends Tree[T]
+  type TypedTree = Tree[Type]
+  type UntypedTree = Tree[Nothing]
 
-  case class Apply[T](fun: Tree[T], args: List[Tree[T]])(implicit val pos: Position) extends Tree[T]
+// ------ Categories of trees -----------------------------------
 
-  case class Pair[T](left: Tree[T], right: Tree[T])(implicit val pos: Position) extends Tree[T]
+  /** Tree is definitely a type. Note that some trees
+   *  have isType = true without being TypTrees (e.g. Ident, AnnotatedTree)
+   */
+  trait TypTree[T] extends Tree[T] {
+    type ThisTree[T] <: TypTree[T]
+    override def isType = true
+  }
 
-  case class ValDef[T](mods: Modifiers, name: Name, rtpe: Tree[T], rhs: Tree[T])(implicit val pos: Position) extends Tree[T]
+  /** Tree is definitely a term. Note that some trees
+   *  have isType = true without being TypTrees (e.g. Ident, AnnotatedTree)
+   */
+  trait TermTree[T] extends Tree[T] {
+    type ThisTree[T] <: TermTree[T]
+    override def isTerm = true
+  }
 
-  case class TypeDef[T](mods: Modifiers, name: Name, rhs: Tree[T])(implicit val pos: Position) extends Tree[T]
+  /** Tree's symbol can be derived from its type */
+  abstract class SymTree[T] extends Tree[T] {
+    type ThisTree[T] <: SymTree[T]
+    override def denot(implicit ctx: Context) = tpe match {
+      case tpe: NamedType => tpe.denot
+      case _ => NoDenotation
+    }
+    override def symbol(implicit ctx: Context): Symbol = tpe match {
+      case tpe: Type => if (isType) tpe.typeSymbol else tpe.termSymbol
+      case _ => NoSymbol
+    }
+  }
 
-  case class DefDef[T](mods: Modifiers, name: Name, tparams: List[TypeDef[T]], vparamss: List[List[ValDef[T]]], rtpe: Tree[T], rhs: Tree[T])(implicit val pos: Position) extends Tree[T]
+  /** Tree's symbol/isType/isTerm properties come from a subtree identifier
+   *  by `forwardTo`.
+   */
+  abstract class ProxyTree[T] extends Tree[T] {
+    type ThisTree[T] <: ProxyTree[T]
+    def forwardTo: Tree[T]
+    override def denot(implicit ctx: Context): Denotation = forwardTo.denot
+    override def symbol(implicit ctx: Context): Symbol = forwardTo.symbol
+    override def isTerm = forwardTo.isTerm
+    override def isType = forwardTo.isType
+  }
 
-  case class TypeTree[T](original: Tree[T] = EmptyTree[T])(implicit val pos: Position) extends Tree[T]
+  /** Tree has a name */
+  abstract class NameTree[T] extends SymTree[T] {
+    type ThisTree[T] <: NameTree[T]
+    def name: Name
+  }
 
-  case class EmptyTree[T]() extends Tree[T] {
-    val pos = NoPosition
+  /** Tree refers by name to a denotation */
+  abstract class RefTree[T] extends NameTree[T] {
+    type ThisTree[T] <: RefTree[T]
+    def qualifier: Tree[T]
+    override def isType = name.isTypeName
+    override def isTerm = name.isTermName
+  }
+
+  abstract class DefTree[T] extends NameTree[T] {
+    type ThisTree[T] <: DefTree[T]
+    override def isDef = true
+  }
+
+// ----------- Tree case classes ------------------------------------
+
+  /** name */
+  case class Ident[T] (name: Name)(implicit val pos: Position)
+    extends RefTree[T] {
+    type ThisTree[T] = Ident[T]
+    def qualifier: Tree[T] = EmptyTree[T]
+  }
+
+  /** qualifier.name */
+  case class Select[T](qualifier: Tree[T], name: Name)(implicit val pos: Position)
+    extends RefTree[T] {
+    type ThisTree[T] = Select[T]
+  }
+
+  /** qual.this */
+  case class This[T](qual: TypeName)(implicit val pos: Position)
+    extends SymTree[T] with TermTree[T] {
+    type ThisTree[T] = This[T]
+  }
+
+  /** C.super[mix], where qual = C.this */
+  case class Super[T](qual: Tree[T], mix: TypeName)(implicit val pos: Position)
+    extends ProxyTree[T] with TermTree[T] {
+    type ThisTree[T] = Super[T]
+    def forwardTo = qual
+  }
+
+  abstract class GenericApply[T] extends ProxyTree[T] with TermTree[T] {
+    type ThisTree[T] <: GenericApply[T]
+    val fun: Tree[T]
+    val args: List[Tree[T]]
+    def forwardTo = fun
+  }
+
+  /** fun(args) */
+  case class Apply[T](fun: Tree[T], args: List[Tree[T]])(implicit val pos: Position)
+    extends GenericApply[T] {
+    type ThisTree[T] = Apply[T]
+  }
+
+  /** fun[args] */
+  case class TypeApply[T](fun: Tree[T], args: List[Tree[T]])(implicit val pos: Position)
+    extends GenericApply[T] {
+    type ThisTree[T] = TypeApply[T]
+  }
+
+  /** const */
+  case class Literal[T](const: Constant)(implicit val pos: Position)
+    extends TermTree[T] {
+    type ThisTree[T] = Literal[T]
+  }
+
+  /** new tpt, but no constructor call */
+  case class New[T](tpt: Tree[T])(implicit val pos: Position)
+    extends TermTree[T] {
+    type ThisTree[T] = New[T]
+  }
+
+  /** (left, right) */
+  case class Pair[T](left: Tree[T], right: Tree[T])(implicit val pos: Position)
+    extends TermTree[T] {
+    type ThisTree[T] = Pair[T]
+  }
+
+  /** expr : tpt */
+  case class Typed[T](expr: Tree[T], tpt: Tree[T])(implicit val pos: Position)
+    extends ProxyTree[T] with TermTree[T] {
+    type ThisTree[T] = Typed[T]
+    def forwardTo = expr
+  }
+
+  /** name = arg, in a parameter list */
+  case class NamedArg[T](name: Name, arg: Tree[T])(implicit val pos: Position)
+    extends TermTree[T] {
+    type ThisTree[T] = NamedArg[T]
+  }
+
+  /** name = arg, outside a parameter list */
+  case class Assign[T](name: Name, arg: Tree[T])(implicit val pos: Position)
+    extends TermTree[T] {
+    type ThisTree[T] = Assign[T]
+  }
+
+  /** (vparams) => body */
+  case class Function[T](vparams: List[ValDef[T]], body: Tree[T])(implicit val pos: Position)
+    extends SymTree[T] with TermTree[T] {
+    type ThisTree[T] = Function[T]
+  }
+
+  /** { stats; expr } */
+  case class Block[T](stats: List[Tree[T]], expr: Tree[T])(implicit val pos: Position)
+    extends TermTree[T] {
+    type ThisTree[T] = Block[T]
+  }
+
+  /** if cond then thenp else elsep */
+  case class If[T](cond: Tree[T], thenp: Tree[T], elsep: Tree[T])(implicit val pos: Position)
+    extends TermTree[T] {
+    type ThisTree[T] = If[T]
+  }
+
+  /** selector match { cases } */
+  case class Match[T](selector: Tree[T], cases: List[CaseDef[T]])(implicit val pos: Position)
+    extends TermTree[T] {
+    type ThisTree[T] = Match[T]
+  }
+
+  /** return expr
+   *  where `from` refers to the method from which the return takes place
+   *  After program transformations this is not necessarily the enclosing method, because
+   *  closures can intervene.
+   */
+  case class Return[T](expr: Tree[T], from: Ident[T])(implicit val pos: Position)
+    extends TermTree[T] {
+    type ThisTree[T] = Return[T]
+  }
+
+  /** try block catch { catches } */
+  case class Try[T](block: Tree[T], catches: List[CaseDef[T]], finalizer: Tree[T])(implicit val pos: Position)
+    extends TermTree[T] {
+    type ThisTree[T] = Try[T]
+  }
+
+  /** throw expr */
+  case class Throw[T](expr: Tree[T])(implicit val pos: Position)
+    extends TermTree[T] {
+    type ThisTree[T] = Throw[T]
+  }
+
+  /** Array[elemtpt](elems) */
+  case class ArrayValue[T](elemtpt: Tree[T], elems: List[Tree[T]])(implicit val pos: Position)
+    extends TermTree[T] {
+    type ThisTree[T] = ArrayValue[T]
+  }
+
+  /** A type tree that represents an existing or inferred type */
+  case class TypeTree[T](original: Tree[T] = EmptyTree[T])(implicit val pos: Position)
+    extends SymTree[T] with TypTree[T] {
+    type ThisTree[T] = TypeTree[T]
+  }
+
+  /** ref.type */
+  case class SingletonTypeTree[T](ref: Tree[T])(implicit val pos: Position)
+    extends SymTree[T] with TypTree[T] {
+    type ThisTree[T] = SingletonTypeTree[T]
+  }
+
+  /** qualifier # name */
+  case class SelectFromTypeTree[T](qualifier: Tree[T], name: TypeName)(implicit val pos: Position)
+    extends RefTree[T] with TypTree[T] {
+    type ThisTree[T] = SelectFromTypeTree[T]
+  }
+
+  /** left & right */
+  case class AndTypeTree[T](left: Tree[T], right: Tree[T])(implicit val pos: Position)
+    extends TypTree[T] {
+    type ThisTree[T] = AndTypeTree[T]
+  }
+
+  /** left | right */
+  case class OrTypeTree[T](left: Tree[T], right: Tree[T])(implicit val pos: Position)
+    extends TypTree[T] {
+    type ThisTree[T] = OrTypeTree[T]
+  }
+
+  /** tpt { refinements } */
+  case class RefineTypeTree[T](tpt: Tree[T], refinements: List[DefTree[T]])(implicit val pos: Position)
+    extends ProxyTree[T] with TypTree[T] {
+    type ThisTree[T] = RefineTypeTree[T]
+    def forwardTo = tpt
+  }
+
+  /** tpt[args] */
+  case class AppliedTypeTree[T](tpt: Tree[T], args: List[Tree[T]])(implicit val pos: Position)
+    extends ProxyTree[T] with TypTree[T] {
+    type ThisTree[T] = AppliedTypeTree[T]
+    def forwardTo = tpt
+  }
+
+  /** >: lo <: hi */
+  case class TypeBoundsTree[T](lo: Tree[T], hi: Tree[T])(implicit val pos: Position)
+     extends Tree[T] {
+    type ThisTree[T] = TypeBoundsTree[T]
+  }
+
+  /** name @ body */
+  case class Bind[T](name: Name, body: Tree[T])(implicit val pos: Position)
+    extends DefTree[T] {
+    type ThisTree[T] = Bind[T]
   }
 
-  case class Literal[T](const: Constant)(implicit val pos: Position) extends Tree[T]
+  /** case pat if guard => body */
+  case class CaseDef[T](pat: Tree[T], guard: Tree[T], body: Tree[T])(implicit val pos: Position)
+    extends Tree[T] {
+    type ThisTree[T] = CaseDef[T]
+  }
 
-  case class New[T](tpt: Tree[T])(implicit val pos: Position) extends Tree[T]
+  /** tree_1 | ... | tree_n */
+  case class Alternative[T](trees: List[Tree[T]])(implicit val pos: Position)
+    extends Tree[T] {
+    type ThisTree[T] = Alternative[T]
+  }
 
-  case class ArrayValue[T](elemtpt: Tree[T], elems: List[Tree[T]])(implicit val pos: Position) extends Tree[T]
+  /** fun(args) in a pattern, if fun is an extractor */
+  case class UnApply[T](fun: Tree[T], args: List[Tree[T]])(implicit val pos: Position)
+    extends Tree[T] {
+    type ThisTree[T] = UnApply[T]
+  }
 
-  case class NamedArg[T](name: Name, arg: Tree[T])(implicit val pos: Position) extends Tree[T]
+  /** mods val name: rtpe = rhs */
+  case class ValDef[T](mods: Modifiers[T], name: Name, rtpe: Tree[T], rhs: Tree[T])(implicit val pos: Position)
+    extends DefTree[T] {
+    type ThisTree[T] = ValDef[T]
+  }
+
+  /** mods def name[tparams](vparams_1)...(vparams_n): rtpe = rhs */
+  case class DefDef[T](mods: Modifiers[T], name: Name, tparams: List[TypeDef[T]], vparamss: List[List[ValDef[T]]], rtpe: Tree[T], rhs: Tree[T])(implicit val pos: Position)
+    extends DefTree[T] {
+    type ThisTree[T] = DefDef[T]
+  }
 
-  class ImplicitDefDef[T](mods: Modifiers, name: Name, tparams: List[TypeDef[T]], vparamss: List[List[ValDef[T]]], rtpe: Tree[T], rhs: Tree[T])
+  class ImplicitDefDef[T](mods: Modifiers[T], name: Name, tparams: List[TypeDef[T]], vparamss: List[List[ValDef[T]]], rtpe: Tree[T], rhs: Tree[T])
     (implicit pos: Position) extends DefDef[T](mods, name, tparams, vparamss, rtpe, rhs) {
-    override def copy[T](mods: Modifiers, name: Name, tparams: List[TypeDef[T]], vparamss: List[List[ValDef[T]]], rtpe: Tree[T], rhs: Tree[T])(implicit pos: Position) =
+    override def copy[T](mods: Modifiers[T], name: Name, tparams: List[TypeDef[T]], vparamss: List[List[ValDef[T]]], rtpe: Tree[T], rhs: Tree[T])(implicit pos: Position) =
       new ImplicitDefDef[T](mods, name, tparams, vparamss, rtpe, rhs)
   }
 
-  case class TypedSplice(tree: Tree[Type]) extends Tree[Nothing] {
-    def pos = tree.pos
+  /** mods type name = rhs   or
+   *  mods type name >: lo <: hi, if rhs = TypeBoundsTree(lo, hi) */
+  case class TypeDef[T](mods: Modifiers[T], name: Name, rhs: Tree[T])(implicit val pos: Position)
+    extends DefTree[T] {
+    type ThisTree[T] = TypeDef[T]
   }
 
-  implicit def embedTyped(tree: Tree[Type]): Tree[Nothing] = TypedSplice(tree)
+  /** extends parents { self => body } */
+  case class Template[T](parents: List[Tree[T]], self: ValDef[T], body: List[Tree[T]])(implicit val pos: Position)
+    extends SymTree[T] {
+    type ThisTree[T] = Template[T]
+  }
 
-  class UnAssignedTypeException[T](tree: Tree[T]) extends Exception {
-    override def getMessage: String = s"type of $tree is not assigned"
+  /** mods class name[tparams] impl */
+  case class ClassDef[T](mods: Modifiers[T], name: TypeName, tparams: List[TypeDef[T]], impl: Template[T])(implicit val pos: Position)
+    extends DefTree[T] {
+    type ThisTree[T] = ClassDef[T]
   }
 
-  type TypedTree = Tree[Type]
-  type UntypedTree = Tree[Nothing]
+  /** import expr.selectors
+   *  where a selector is either an untyped `Ident`, `name` or
+   *  an untyped `Pair` `name => rename`
+   */
+  case class Import[T](expr: Tree[T], selectors: List[UntypedTree])(implicit val pos: Position)
+    extends SymTree[T] {
+    type ThisTree[T] = Import[T]
+  }
+
+  /** package pid { stats } */
+  case class PackageDef[T](pid: RefTree[T], stats: List[Tree[T]])(implicit val pos: Position)
+    extends DefTree[T] {
+    type ThisTree[T] = PackageDef[T]
+    override def name = pid.name
+  }
+
+  /** arg @annot */
+  case class Annotated[T](annot: Tree[T], arg: Tree[T])(implicit val pos: Position)
+    extends ProxyTree[T] {
+    type ThisTree[T] = Annotated[T]
+    def forwardTo = arg
+  }
+
+  /** A missing tree */
+  case class EmptyTree[T]()
+    extends Tree[T] {
+    type ThisTree[T] = EmptyTree[T]
+    val pos = NoPosition
+  }
+
+// ----- Tree cases that exist in untyped form only ------------------
+
+  /** A typed subtree of an untyped tree needs to be wrapped in a TypedSlice */
+  case class TypedSplice(tree: TypedTree) extends UntypedTree {
+    def pos = tree.pos
+  }
+
+  /** mods object name impl */
+  case class ModuleDef(mods: Modifiers[Nothing], name: TermName, impl: Template[Nothing])(implicit val pos: Position)
+    extends DefTree[Nothing] {
+  }
 
   // this will probably to its own file at some point.
   class MakeTypedTree(implicit val ctx: Context) extends AnyVal {