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/* NSC -- new scala compiler
* Copyright 2005 LAMP/EPFL
* @author buraq
*/
// $Id$
package scala.tools.nsc.matching;
/** Translation of pattern matching
*/
abstract class TransMatcher extends transform.Transform
with PatternNodes
with CodeFactory
with PatternMatchers
with SequenceMatchers
with AlgebraicMatchers
with MatcherLabels
with BerrySethis
with DetWordAutoms
with NondetWordAutoms
with Autom2
with WordAutoms
with LeftTracers
with RightTracers {
import global._;
import definitions._;
import posAssigner.atPos;
val phaseName = "transmatcher";
protected def newTransformer(unit: global.CompilationUnit): global.Transformer = {
cunit = unit;
new TransMatch
}
/** container. classes AlgebraicMatcher and SequenceMatcher get input and
* store their results in here. resembles the 'Memento' design pattern,
* could also be named 'Liaison'
*/
abstract class PartialMatcher {
/** owner of the code we create (input)
*/
val owner: Symbol;
/** the selector value (input)
*/
val selector:Tree;
/** tree representing the matcher (output)
*/
var tree: Tree = _ ;
def pos: int = selector.pos;
//assert( owner != null ) : "owner is null";
//assert owner != Symbol.NONE ;
//this.owner = owner;
//assert root != null;
//assert root.type != null;
//this.selector = root;
//assert this.resultType != Type.NoType;
//this.resultType = resultType;
//this.pos = root.pos; // for convenience only
}
var cunit: CompilationUnit = _;
def fresh = cunit.fresh ;
var owner: Symbol = _;
def containsBinding(pat: Tree): Boolean = {
var generatedVars = false;
def handleVariableSymbol(sym: Symbol): Unit =
if (sym.name.toString().indexOf("$") == -1) {
generatedVars = true; // .add(sym);
}
def isVariableName(name: Name): Boolean =
( treeInfo.isVariableName(name) ) && ( name != nme.USCOREkw ) ;
def isVariableSymbol(sym: Symbol): Boolean =
( sym != null )&&( !sym.isPrimaryConstructor );
def traverse(tree: Tree): Unit = {
tree match {
case x @ Ident(name) =>
if(x.symbol != definitions.PatternWildcard)
error("shouldn't happen?!");
case Bind(name, subtree) =>
var sym: Symbol = _;
if (isVariableName(name)
&& isVariableSymbol( {sym = tree.symbol; tree.symbol} ))
handleVariableSymbol(sym);
traverse( subtree );
// congruence
case Apply(fun, args) => args foreach traverse;
case Sequence(trees) => trees foreach traverse
case Star(arg) => traverse(arg)
case Typed(expr, tpe) => traverse(expr); // needed??
case _ : Select |
_ : Alternative |
_ : Select |
_ : Literal => ; // no variables
case _ =>
error("unknown pattern node:" + tree + " = " + tree.getClass());
}
}
traverse(pat);
generatedVars;
}
class TransMatch extends Transformer {
def isRegular(pat:Tree): Boolean = pat match {
case Alternative(trees) =>
trees exists { isRegular }
case Star(_) => true;
case Ident(_) => false
case Bind( n, pat1 ) => isRegular( pat1 )
case Sequence( trees ) =>
( trees.length == 0 ) || (trees exists { isRegular });
case Apply( fn, List(Sequence(List()))) =>
false;
case Apply( fn, trees ) =>
( trees exists { isRegular })
// && !((trees.length == 1) && TreeInfo.isEmptySequence( trees( 0 )))
case Literal(_) => false;
case Select(_,_) => false;
case Typed(_,_) => false;
}
/** a casedef with sequence subpatterns like
*
* case ..x @ ().. => body
*
* should be replaced straight away with
*
* case .. () .. => val x = Nil; body
*/
def removeNilVariables( cd: CaseDef ): CaseDef = {
var nilVars:List[Symbol] = Nil;
def remove(pat: Tree): Tree = pat match {
case Alternative( _ ) => pat /* no bind/var allowed! */
case Star( _ ) => pat /* no bind/var allowed! */
case Bind( id, empt @ Sequence(List())) =>
nilVars = pat.symbol /*id.symbol()*/ :: nilVars;
empt
case Bind( id, pat ) =>
copy.Bind( pat, id, remove(pat) );
case Sequence( trees ) =>
copy.Sequence( pat, trees map remove )
case Apply( fn, args ) =>
copy.Apply( pat, fn, args map remove )
case Ident(_) => pat
case Literal(_) => pat
case Select(_,_) => pat
case Typed(_,_) => pat
case _ => scala.Predef.error("unknown node"+pat.getClass());
}
cd match {
case CaseDef(pat, guard, body) =>
val npat = remove(pat);
val nbody = {
if(nilVars.isEmpty)
body
else
atPos(body.pos)(
Block(nilVars map {
x => ValDef(x, Ident(definitions.NilModule))
}, body)
)
}
copy.CaseDef(cd, npat, guard, nbody)
}
}
def handle(sel:Tree, cases:List[CaseDef]): Tree = {
// 1. is there a regular pattern?
val containsReg = cases.exists { x => isRegular(x.pat) };
// @todo: remove unused variables
if(containsReg) {
// 2. replace nilVariables
//@todo: bring over AlgebraicMatcher
val ncases = cases.map { removeNilVariables };
val matcher = new PartialMatcher {
val global: TransMatcher.this.global.type = TransMatcher.this.global;
val owner = currentOwner;
val selector = sel ;
}
TransMatcher.this.owner = currentOwner; // @todo: remove from partial matcher
//new AlgebraicMatcher() {
// val tm: TransMatcher.this.type = TransMatcher.this;
//}.construct( matcher, ncases );
//matcher.tree
null
} else {
val pm = new PatternMatcher();
pm.initialize(sel, currentOwner, true );
pm.construct( cases );
//if (global.log()) {
// global.log("internal pattern matching structure");
// pm.print();
//}
pm.toTree();
}
}
override def transform(tree: Tree): Tree = tree match {
case Match(selector, cases) =>
val ts = cases map { transform };
handle(transform(selector), ts.asInstanceOf[List[CaseDef]]);
case _ =>
super.transform(tree);
}
}
}
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