1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
|
/* 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);
}
}
}
|