alvinalexander.com | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Scala example source code file (TreeInfo.scala)

This example Scala source code file (TreeInfo.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Scala tags/keywords

boolean, boolean, casedef, defdef, emptytree, emptytree, list, list, nil, select, tree, tree, typedef, valdef

The Scala TreeInfo.scala source code

/* NSC -- new Scala compiler
 * Copyright 2005-2011 LAMP/EPFL
 * @author  Martin Odersky
 */

package scala.tools.nsc
package ast

import symtab.Flags._
import symtab.SymbolTable
import util.HashSet

/** This class ...
 *
 *  @author Martin Odersky
 *  @version 1.0
 */
abstract class TreeInfo {
  val trees: SymbolTable
  import trees._
  import definitions.ThrowableClass

  def isOwnerDefinition(tree: Tree): Boolean = tree match {
    case PackageDef(_, _)
       | ClassDef(_, _, _, _)
       | ModuleDef(_, _, _)
       | DefDef(_, _, _, _, _, _)
       | Import(_, _) => true
    case _ => false
  }

  def isDefinition(tree: Tree): Boolean = tree.isDef

  def isDeclaration(tree: Tree): Boolean = tree match {
    case DefDef(_, _, _, _, _, EmptyTree)
       | ValDef(_, _, _, EmptyTree)
       | TypeDef(_, _, _, _) => true
    case _ => false
  }

  /** Is tree legal as a member definition of an interface?
   */
  def isInterfaceMember(tree: Tree): Boolean = tree match {
    case EmptyTree                     => true
    case Import(_, _)                  => true
    case TypeDef(_, _, _, _)           => true
    case DefDef(mods, _, _, _, _, __)  => mods.isDeferred
    case ValDef(mods, _, _, _)         => mods.isDeferred
    case DocDef(_, definition)         => isInterfaceMember(definition)
    case _ => false
  }

  /** Is tree a pure (i.e. non-side-effecting) definition?
   */
  def isPureDef(tree: Tree): Boolean = tree match {
    case EmptyTree
       | ClassDef(_, _, _, _)
       | TypeDef(_, _, _, _)
       | Import(_, _)
       | DefDef(_, _, _, _, _, _) =>
      true
    case ValDef(mods, _, _, rhs) =>
      !mods.isMutable && isPureExpr(rhs)
    case DocDef(_, definition) =>
      isPureDef(definition)
    case _ =>
      false
  }

  /** Is tree a stable and pure expression?
   */
  def isPureExpr(tree: Tree): Boolean = tree match {
    case EmptyTree
       | This(_)
       | Super(_, _)
       | Literal(_) =>
      true
    case Ident(_) =>
      tree.symbol.isStable
    case Select(qual, _) =>
      tree.symbol.isStable && isPureExpr(qual)
    case TypeApply(fn, _) =>
      isPureExpr(fn)
    case Apply(fn, List()) =>
      /* Note: After uncurry, field accesses are represented as Apply(getter, Nil),
       * so an Apply can also be pure.
       * However, before typing, applications of nullary functional values are also
       * Apply(function, Nil) trees. To prevent them from being treated as pure,
       * we check that the callee is a method. */
      fn.symbol.isMethod && !fn.symbol.isLazy && isPureExpr(fn)
    case Typed(expr, _) =>
      isPureExpr(expr)
    case Block(stats, expr) =>
      (stats forall isPureDef) && isPureExpr(expr)
    case _ =>
      false
  }

  def mayBeVarGetter(sym: Symbol): Boolean = sym.info match {
    case NullaryMethodType(_)              => sym.owner.isClass && !sym.isStable
    case PolyType(_, NullaryMethodType(_)) => sym.owner.isClass && !sym.isStable
    case mt @ MethodType(_, _)             => mt.isImplicit && sym.owner.isClass && !sym.isStable
    case _                                 => false
  }

  def isVariableOrGetter(tree: Tree) = {
    def sym       = tree.symbol
    def isVar     = sym.isVariable
    def isGetter  = mayBeVarGetter(sym) && sym.owner.info.member(nme.getterToSetter(sym.name)) != NoSymbol
    
    tree match {
      case Ident(_)         => isVar
      case Select(_, _)     => isVar || isGetter
      case _                =>
        methPart(tree) match {
          case Select(qual, nme.apply)  => qual.tpe.member(nme.update) != NoSymbol
          case _                        => false
        }
    }
  }

  /** Is tree a self constructor call?
   */
  def isSelfConstrCall(tree: Tree): Boolean = methPart(tree) match {
    case Ident(nme.CONSTRUCTOR) 
       | Select(This(_), nme.CONSTRUCTOR) => true
    case _ => false
  }

  def isSuperConstrCall(tree: Tree): Boolean = methPart(tree) match {
    case Select(Super(_, _), nme.CONSTRUCTOR) => true
    case _ => false
  }

  def isSelfOrSuperConstrCall(tree: Tree) =
    isSelfConstrCall(tree) || isSuperConstrCall(tree)

  /** Is tree a variable pattern */
  def isVarPattern(pat: Tree): Boolean = pat match {
    case _: BackQuotedIdent => false
    case x: Ident           => isVariableName(x.name)
    case _                  => false
  }

  /** The first constructor definitions in `stats' */
  def firstConstructor(stats: List[Tree]): Tree = stats find {
    case x: DefDef  => nme.isConstructorName(x.name)
    case _          => false
  } getOrElse EmptyTree
  
  /** The arguments to the first constructor in `stats'. */
  def firstConstructorArgs(stats: List[Tree]): List[Tree] = firstConstructor(stats) match {
    case DefDef(_, _, _, args :: _, _, _) => args
    case _                                => Nil
  }

  /** The value definitions marked PRESUPER in this statement sequence */
  def preSuperFields(stats: List[Tree]): List[ValDef] = 
    stats collect { case vd: ValDef if isEarlyValDef(vd) => vd }

  def isEarlyDef(tree: Tree) = tree match {
    case TypeDef(mods, _, _, _) => mods hasFlag PRESUPER
    case ValDef(mods, _, _, _) => mods hasFlag PRESUPER
    case _ => false
  }

  def isEarlyValDef(tree: Tree) = tree match {
    case ValDef(mods, _, _, _) => mods hasFlag PRESUPER
    case _ => false
  }

  def isEarlyTypeDef(tree: Tree) = tree match {
    case TypeDef(mods, _, _, _) => mods hasFlag PRESUPER
    case _ => false
  }

  /** Is tpt of the form T* ? */
  def isRepeatedParamType(tpt: Tree) = tpt match {
    case TypeTree()                                                          => definitions.isRepeatedParamType(tpt.tpe)
    case AppliedTypeTree(Select(_, tpnme.REPEATED_PARAM_CLASS_NAME), _)      => true
    case AppliedTypeTree(Select(_, tpnme.JAVA_REPEATED_PARAM_CLASS_NAME), _) => true
    case _                                                                   => false
  }
  /** The parameter ValDefs from a def of the form T*. */
  def repeatedParams(tree: Tree): List[ValDef] = tree match {
    case DefDef(_, _, _, vparamss, _, _)  => vparamss.flatten filter (vd => isRepeatedParamType(vd.tpt))
    case _                                => Nil
  }

  /** Is tpt a by-name parameter type? */
  def isByNameParamType(tpt: Tree) = tpt match {
    case TypeTree()                                                 => definitions.isByNameParamType(tpt.tpe)
    case AppliedTypeTree(Select(_, tpnme.BYNAME_PARAM_CLASS_NAME), _) => true
    case _                                                          => false
  }

  /** Is name a left-associative operator? */
  def isLeftAssoc(operator: Name) = operator.nonEmpty && (operator.endChar != ':')

  private val reserved = Set[Name](nme.false_, nme.true_, nme.null_)

  /** Is name a variable name? */
  def isVariableName(name: Name): Boolean = {
    val first = name(0)
    ((first.isLower && first.isLetter) || first == '_') && !reserved(name)
  }

  /** Is tree a this node which belongs to `enclClass'? */
  def isSelf(tree: Tree, enclClass: Symbol): Boolean = tree match {
    case This(_) => tree.symbol == enclClass
    case _ => false
  }

  /** can this type be a type pattern */
  def mayBeTypePat(tree: Tree): Boolean = tree match {
    case CompoundTypeTree(Template(tps, _, Nil)) => tps exists mayBeTypePat
    case Annotated(_, tp)                        => mayBeTypePat(tp)
    case AppliedTypeTree(constr, args)           => mayBeTypePat(constr) || args.exists(_.isInstanceOf[Bind])
    case SelectFromTypeTree(tp, _)               => mayBeTypePat(tp)
    case _                                       => false
  }

  /** Is this argument node of the form <expr> : _* ?
   */
  def isWildcardStarArg(tree: Tree): Boolean = tree match {
    case Typed(_, Ident(tpnme.WILDCARD_STAR)) => true
    case _                                  => false
  }
  def isWildcardStarArgList(trees: List[Tree]) =
    trees.nonEmpty && isWildcardStarArg(trees.last)
  
  /** Is the argument a (possibly bound) _ arg?
   */
  def isWildcardArg(tree: Tree): Boolean = unbind(tree) match {
    case Ident(nme.WILDCARD) => true
    case _                   => false
  }

  /** Is this pattern node a catch-all (wildcard or variable) pattern? */
  def isDefaultCase(cdef: CaseDef) = cdef match {
    case CaseDef(pat, EmptyTree, _) => isWildcardArg(pat)
    case _                          => false
  }
  
  /** Does this CaseDef catch Throwable? */
  def catchesThrowable(cdef: CaseDef) = catchesAllOf(cdef, ThrowableClass.tpe)
  
  /** Does this CaseDef catch everything of a certain Type? */
  def catchesAllOf(cdef: CaseDef, threshold: Type) =
    isDefaultCase(cdef) || (cdef.guard.isEmpty && (unbind(cdef.pat) match {
      case Typed(Ident(nme.WILDCARD), tpt)  => (tpt.tpe != null) && (threshold <:< tpt.tpe)
      case _                                => false
    }))

  /** Is this pattern node a catch-all or type-test pattern? */
  def isCatchCase(cdef: CaseDef) = cdef match {
    case CaseDef(Typed(Ident(nme.WILDCARD), tpt), EmptyTree, _) => 
      isSimpleThrowable(tpt.tpe)
    case CaseDef(Bind(_, Typed(Ident(nme.WILDCARD), tpt)), EmptyTree, _) => 
      isSimpleThrowable(tpt.tpe)
    case _ => 
      isDefaultCase(cdef)
  }

  private def isSimpleThrowable(tp: Type): Boolean = tp match {
    case TypeRef(pre, sym, args) =>
      (pre == NoPrefix || pre.widen.typeSymbol.isStatic) &&
      (sym isNonBottomSubClass ThrowableClass) &&  /* bq */ !sym.isTrait
    case _ =>
      false
  }

  /* If we have run-time types, and these are used for pattern matching, 
     we should replace this  by something like:

      tp match {
        case TypeRef(pre, sym, args) =>
          args.isEmpty && (sym.owner.isPackageClass || isSimple(pre))
        case NoPrefix =>
          true
        case _ =>
          false
      }
*/

  /** Is this pattern node a sequence-valued pattern? */
  def isSequenceValued(tree: Tree): Boolean = unbind(tree) match {
    case Alternative(ts)            => ts exists isSequenceValued
    case ArrayValue(_, _) | Star(_) => true
    case _                          => false
  }
  
  /** The underlying pattern ignoring any bindings */
  def unbind(x: Tree): Tree = x match {
    case Bind(_, y) => unbind(y)
    case y          => y
  }
  
  /** Is this tree a Star(_) after removing bindings? */
  def isStar(x: Tree) = unbind(x) match { 
    case Star(_)  => true
    case _        => false
  }

  /** The method part of an application node
   */
  def methPart(tree: Tree): Tree = tree match {
    case Apply(fn, _)           => methPart(fn)
    case TypeApply(fn, _)       => methPart(fn)
    case AppliedTypeTree(fn, _) => methPart(fn)
    case _                      => tree
  }

  def firstArgument(tree: Tree): Tree = tree match {
    case Apply(fn, args) => 
      val f = firstArgument(fn)
      if (f == EmptyTree && !args.isEmpty) args.head else f
    case _ =>
      EmptyTree
  }

  /** Top-level definition sequence contains a leading import of
   *  <code>Predef or scala.Predef.
   */
  def containsLeadingPredefImport(defs: List[Tree]): Boolean = defs match {
    case List(PackageDef(_, defs1)) => 
      containsLeadingPredefImport(defs1)
    case Import(Ident(nme.Predef), _) :: _ =>
      true
    case Import(Select(Ident(nme.scala_), nme.Predef), _) :: _ =>
      true
    case Import(_, _) :: defs1 =>
      containsLeadingPredefImport(defs1)
    case _ =>
      false
  }

  /** Compilation unit is class or object 'name' in package 'scala'
   */
  def isUnitInScala(tree: Tree, name: Name) = tree match {
    case PackageDef(Ident(nme.scala_), defs) => isImplDef(defs, name)
    case _ => false
  }

  private def isImplDef(trees: List[Tree], name: Name): Boolean = trees match {
    case Import(_, _) :: xs => isImplDef(xs, name)
    case DocDef(_, tree1) :: Nil => isImplDef(List(tree1), name)
    case Annotated(_, tree1) :: Nil => isImplDef(List(tree1), name)
    case ModuleDef(_, `name`, _) :: Nil => true
    case ClassDef(_, `name`, _, _) :: Nil => true
    case _ => false
  }

  def isAbsTypeDef(tree: Tree) = tree match {
    case TypeDef(_, _, _, TypeBoundsTree(_, _)) => true
    case TypeDef(_, _, _, rhs) => rhs.tpe.isInstanceOf[TypeBounds]
    case _ => false
  }

  def isAliasTypeDef(tree: Tree) = tree match {
    case TypeDef(_, _, _, _) => !isAbsTypeDef(tree)
    case _ => false
  }
  
  /** Some handy extractors for spotting trees through the
   *  the haze of irrelevant braces: i.e. Block(Nil, SomeTree)
   *  should not keep us from seeing SomeTree.
   */
  abstract class SeeThroughBlocks[T] {
    protected def unapplyImpl(x: Tree): T
    def unapply(x: Tree): T = x match {
      case Block(Nil, expr)         => unapply(expr)
      case _                        => unapplyImpl(x)
    }
  }
  object IsTrue extends SeeThroughBlocks[Boolean] {
    protected def unapplyImpl(x: Tree): Boolean = x match {
      case Literal(Constant(true)) => true
      case _                       => false
    }
  }
  object IsFalse extends SeeThroughBlocks[Boolean] {
    protected def unapplyImpl(x: Tree): Boolean = x match {
      case Literal(Constant(false)) => true
      case _                        => false
    }
  }
  object IsIf extends SeeThroughBlocks[Option[(Tree, Tree, Tree)]] {
    protected def unapplyImpl(x: Tree) = x match {
      case If(cond, thenp, elsep) => Some(cond, thenp, elsep)
      case _                      => None
    }
  }
}

Other Scala examples (source code examples)

Here is a short list of links related to this Scala TreeInfo.scala source code file:

... this post is sponsored by my books ...

#1 New Release!

FP Best Seller

 

new blog posts

 

Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.