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
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
|
/* NSC -- new Scala compiler
* Copyright 2005-2011 LAMP/EPFL
* @author
*/
package scala.tools.nsc
package transform
import symtab._
import Flags._
import util.TreeSet
import scala.collection.{ mutable, immutable }
import scala.collection.mutable.LinkedHashMap
abstract class LambdaLift extends InfoTransform {
import global._
import definitions._
/** the following two members override abstract members in Transform */
val phaseName: String = "lambdalift"
/** Converts types of captured variables to *Ref types.
*/
def boxIfCaptured(sym: Symbol, tpe: Type, erasedTypes: Boolean) =
if (sym.isCapturedVariable) {
val symClass = tpe.typeSymbol
def refType(valueRef: Map[Symbol, Symbol], objectRefClass: Symbol) =
if (isValueClass(symClass) && symClass != UnitClass) valueRef(symClass).tpe
else if (erasedTypes) objectRefClass.tpe
else appliedType(objectRefClass.typeConstructor, List(tpe))
if (sym.hasAnnotation(VolatileAttr)) refType(volatileRefClass, VolatileObjectRefClass)
else refType(refClass, ObjectRefClass)
} else tpe
private val lifted = new TypeMap {
def apply(tp: Type): Type = tp match {
case TypeRef(NoPrefix, sym, Nil) if sym.isClass && !sym.isPackageClass =>
typeRef(apply(sym.owner.enclClass.thisType), sym, Nil)
case ClassInfoType(parents, decls, clazz) =>
val parents1 = parents mapConserve this
if (parents1 eq parents) tp
else ClassInfoType(parents1, decls, clazz)
case _ =>
mapOver(tp)
}
}
def transformInfo(sym: Symbol, tp: Type): Type =
boxIfCaptured(sym, lifted(tp), erasedTypes = true)
protected def newTransformer(unit: CompilationUnit): Transformer =
new LambdaLifter(unit)
class LambdaLifter(unit: CompilationUnit) extends explicitOuter.OuterPathTransformer(unit) {
/** A map storing free variables of functions and classes */
private val free = new LinkedHashMap[Symbol, SymSet]
/** A map storing the free variable proxies of functions and classes */
private val proxies = new LinkedHashMap[Symbol, List[Symbol]]
/** A hashtable storing calls between functions */
private val called = new LinkedHashMap[Symbol, SymSet]
/** The set of symbols that need to be renamed. */
private val renamable = newSymSet
// (trait, name) -> owner
private val localTraits = mutable.HashMap[(Symbol, Name), Symbol]()
// (owner, name) -> implClass
private val localImplClasses = mutable.HashMap[(Symbol, Name), Symbol]()
/** A flag to indicate whether new free variables have been found */
private var changedFreeVars: Boolean = _
/** Buffers for lifted out classes and methods */
private val liftedDefs = new LinkedHashMap[Symbol, List[Tree]]
/** True if we are transforming under a ReferenceToBoxed node */
private var isBoxedRef = false
private type SymSet = TreeSet[Symbol]
private def newSymSet = new TreeSet[Symbol](_ isLess _)
private def symSet(f: LinkedHashMap[Symbol, SymSet], sym: Symbol): SymSet =
f.getOrElseUpdate(sym, newSymSet)
private def isSameOwnerEnclosure(sym: Symbol) =
sym.owner.logicallyEnclosingMember == currentOwner.logicallyEnclosingMember
/** Mark symbol `sym` as being free in `enclosure`, unless `sym`
* is defined in `enclosure` or there is a class between `enclosure`s owner
* and the owner of `sym`.
* Return `true` if there is no class between `enclosure` and
* the owner of sym.
* pre: sym.isLocal, (enclosure.isMethod || enclosure.isClass)
*
* The idea of `markFree` is illustrated with an example:
*
* def f(x: int) = {
* class C {
* class D {
* val y = x
* }
* }
* }
*
* In this case `x` is free in the primary constructor of class `C`.
* but it is not free in `D`, because after lambda lift the code would be transformed
* as follows:
*
* def f(x$0: int) {
* class C(x$0: int) {
* val x$1 = x$0
* class D {
* val y = outer.x$1
* }
* }
* }
*/
private def markFree(sym: Symbol, enclosure: Symbol): Boolean = {
debuglog("mark free: " + sym + " of " + sym.owner + " marked free in " + enclosure)
if (enclosure == sym.owner.logicallyEnclosingMember) true
else if (enclosure.isPackageClass || !markFree(sym, enclosure.skipConstructor.owner.logicallyEnclosingMember)) false
else {
val ss = symSet(free, enclosure)
if (!ss(sym)) {
ss addEntry sym
renamable addEntry sym
atPhase(currentRun.picklerPhase) {
// The param symbol in the MethodType should not be renamed, only the symbol in scope. This way,
// parameter names for named arguments are not changed. Example: without cloning the MethodType,
// def closure(x: Int) = { () => x }
// would have the signature
// closure: (x$1: Int)() => Int
if (sym.isParameter && sym.owner.info.paramss.exists(_ contains sym))
sym.owner modifyInfo (_ cloneInfo sym.owner)
}
changedFreeVars = true
debuglog("" + sym + " is free in " + enclosure);
if (sym.isVariable) sym setFlag CAPTURED
}
!enclosure.isClass
}
}
private def markCalled(sym: Symbol, owner: Symbol) {
debuglog("mark called: " + sym + " of " + sym.owner + " is called by " + owner)
symSet(called, owner) addEntry sym
}
/** The traverse function */
private val freeVarTraverser = new Traverser {
override def traverse(tree: Tree) {
try { //debug
val sym = tree.symbol;
tree match {
case ClassDef(_, _, _, _) =>
liftedDefs(tree.symbol) = Nil
if (sym.isLocal) {
// Don't rename implementation classes independently of their interfaces. If
// the interface is to be renamed, then we will rename the implementation
// class at that time. You'd think we could call ".implClass" on the trait
// rather than collecting them in another map, but that seems to fail for
// exactly the traits being renamed here (i.e. defined in methods.)
//
// !!! - it makes no sense to have methods like "implClass" and
// "companionClass" which fail for an arbitrary subset of nesting
// arrangements, and then have separate methods which attempt to compensate
// for that failure. There should be exactly one method for any given
// entity which always gives the right answer.
if (sym.isImplClass)
localImplClasses((sym.owner, nme.interfaceName(sym.name))) = sym
else {
renamable addEntry sym
if (sym.isTrait)
localTraits((sym, sym.name)) = sym.owner
}
}
case DefDef(_, _, _, _, _, _) =>
if (sym.isLocal) {
renamable addEntry sym
sym setFlag (PrivateLocal | FINAL)
} else if (sym.isPrimaryConstructor) {
symSet(called, sym) addEntry sym.owner
}
case Ident(name) =>
if (sym == NoSymbol) {
assert(name == nme.WILDCARD)
} else if (sym.isLocal) {
val owner = currentOwner.logicallyEnclosingMember
if (sym.isTerm && !sym.isMethod) markFree(sym, owner)
else if (sym.isMethod) markCalled(sym, owner)
//symSet(called, owner) addEntry sym
}
case Select(_, _) =>
if (sym.isConstructor && sym.owner.isLocal)
markCalled(sym, currentOwner.logicallyEnclosingMember)
case _ =>
}
super.traverse(tree)
} catch {//debug
case ex: Throwable =>
Console.println("exception when traversing " + tree)
throw ex
}
}
}
/** Compute free variables map `fvs`.
* Also assign unique names to all
* value/variable/let that are free in some function or class, and to
* all class/function symbols that are owned by some function.
*/
private def computeFreeVars() {
freeVarTraverser.traverse(unit.body)
do {
changedFreeVars = false
for (caller <- called.keys ; callee <- called(caller) ; fvs <- free get callee ; fv <- fvs)
markFree(fv, caller)
} while (changedFreeVars)
def renameSym(sym: Symbol) {
val originalName = sym.name
val base = sym.name + nme.NAME_JOIN_STRING + (
if (sym.isAnonymousFunction && sym.owner.isMethod)
sym.owner.name + nme.NAME_JOIN_STRING
else ""
)
sym.name =
if (sym.name.isTypeName) unit.freshTypeName(base)
else unit.freshTermName(base)
debuglog("renaming in %s: %s => %s".format(sym.owner.fullLocationString, originalName, sym.name))
}
/** Rename a trait's interface and implementation class in coordinated fashion.
*/
def renameTrait(traitSym: Symbol, implSym: Symbol) {
val originalImplName = implSym.name
renameSym(traitSym)
implSym.name = nme.implClassName(traitSym.name)
debuglog("renaming impl class in step with %s: %s => %s".format(traitSym, originalImplName, implSym.name))
}
for (sym <- renamable) {
// If we renamed a trait from Foo to Foo$1, we must rename the implementation
// class from Foo$class to Foo$1$class. (Without special consideration it would
// become Foo$class$1 instead.) Since the symbols are being renamed out from
// under us, and there's no reliable link between trait symbol and impl symbol,
// we have maps from ((trait, name)) -> owner and ((owner, name)) -> impl.
localTraits remove ((sym, sym.name)) match {
case None => renameSym(sym)
case Some(owner) =>
localImplClasses remove ((owner, sym.name)) match {
case Some(implSym) => renameTrait(sym, implSym)
case _ => renameSym(sym) // pure interface, no impl class
}
}
}
atPhase(phase.next) {
for ((owner, freeValues) <- free.toList) {
val newFlags = SYNTHETIC | ( if (owner.isClass) PARAMACCESSOR | PrivateLocal else PARAM )
debuglog("free var proxy: %s, %s".format(owner.fullLocationString, freeValues.toList.mkString(", ")))
proxies(owner) =
for (fv <- freeValues.toList) yield {
val proxy = owner.newValue(fv.name, owner.pos, newFlags) setInfo fv.info
if (owner.isClass) owner.info.decls enter proxy
proxy
}
}
}
}
private def proxy(sym: Symbol) = {
def searchIn(enclosure: Symbol): Symbol = {
if (enclosure eq NoSymbol) throw new IllegalArgumentException("Could not find proxy for "+ sym.defString +" in "+ sym.ownerChain +" (currentOwner= "+ currentOwner +" )")
debuglog("searching for " + sym + "(" + sym.owner + ") in " + enclosure + " " + enclosure.logicallyEnclosingMember)
val ps = (proxies get enclosure.logicallyEnclosingMember).toList.flatten filter (_.name == sym.name)
if (ps.isEmpty) searchIn(enclosure.skipConstructor.owner)
else ps.head
}
debuglog("proxy " + sym + " in " + sym.owner + " from " + currentOwner.ownerChain.mkString(" -> ") +
" " + sym.owner.logicallyEnclosingMember)
if (isSameOwnerEnclosure(sym)) sym
else searchIn(currentOwner)
}
private def memberRef(sym: Symbol) = {
val clazz = sym.owner.enclClass
//Console.println("memberRef from "+currentClass+" to "+sym+" in "+clazz)
val qual = if (clazz == currentClass) gen.mkAttributedThis(clazz)
else {
sym resetFlag(LOCAL | PRIVATE)
if (clazz.isStaticOwner) gen.mkAttributedQualifier(clazz.thisType)
else outerPath(outerValue, currentClass.outerClass, clazz)
}
Select(qual, sym) setType sym.tpe
}
private def proxyRef(sym: Symbol) = {
val psym = proxy(sym)
if (psym.isLocal) gen.mkAttributedIdent(psym) else memberRef(psym)
}
private def addFreeArgs(pos: Position, sym: Symbol, args: List[Tree]) = {
free get sym match {
case Some(fvs) => args ++ (fvs.toList map (fv => atPos(pos)(proxyRef(fv))))
case _ => args
}
}
private def addFreeParams(tree: Tree, sym: Symbol): Tree = proxies.get(sym) match {
case Some(ps) =>
val freeParams = ps map (p => ValDef(p) setPos tree.pos setType NoType)
tree match {
case DefDef(_, _, _, vparams :: _, _, _) =>
val addParams = cloneSymbols(ps).map(_.setFlag(PARAM))
sym.updateInfo(
lifted(MethodType(sym.info.params ::: addParams, sym.info.resultType)))
copyDefDef(tree)(vparamss = List(vparams ++ freeParams))
case ClassDef(mods, name, tparams, impl) =>
// Disabled attempt to to add getters to freeParams
// this does not work yet. Problem is that local symbols need local names
// and references to local symbols need to be transformed into
// method calls to setters.
// def paramGetter(param: Symbol): Tree = {
// val getter = param.newGetter setFlag TRANS_FLAG resetFlag PARAMACCESSOR // mark because we have to add them to interface
// sym.info.decls.enter(getter)
// val rhs = Select(gen.mkAttributedThis(sym), param) setType param.tpe
// DefDef(getter, rhs) setPos tree.pos setType NoType
// }
// val newDefs = if (sym.isTrait) freeParams ::: (ps map paramGetter) else freeParams
treeCopy.ClassDef(tree, mods, name, tparams, deriveTemplate(impl)(_ ::: freeParams))
}
case None =>
tree
}
/* Something like this will be necessary to eliminate the implementation
* restiction from paramGetter above:
* We need to pass getters to the interface of an implementation class.
private def fixTraitGetters(lifted: List[Tree]): List[Tree] =
for (stat <- lifted) yield stat match {
case ClassDef(mods, name, tparams, templ @ Template(parents, self, body))
if stat.symbol.isTrait && !stat.symbol.isImplClass =>
val iface = stat.symbol
lifted.find(l => l.symbol.isImplClass && l.symbol.toInterface == iface) match {
case Some(implDef) =>
val impl = implDef.symbol
val implGetters = impl.info.decls.toList filter (_ hasFlag TRANS_FLAG)
if (implGetters.nonEmpty) {
val ifaceGetters = implGetters map { ig =>
ig resetFlag TRANS_FLAG
val getter = ig cloneSymbol iface setFlag DEFERRED
iface.info.decls enter getter
getter
}
val ifaceGetterDefs = ifaceGetters map (DefDef(_, EmptyTree) setType NoType)
treeCopy.ClassDef(
stat, mods, name, tparams,
treeCopy.Template(templ, parents, self, body ::: ifaceGetterDefs))
} else
stat
case None =>
stat
}
case _ =>
stat
}
*/
private def liftDef(tree: Tree): Tree = {
val sym = tree.symbol
val oldOwner = sym.owner
if (sym.owner.isAuxiliaryConstructor && sym.isMethod) // # bug 1909
sym setFlag STATIC
sym.owner = sym.owner.enclClass
if (sym.isClass) sym.owner = sym.owner.toInterface
if (sym.isMethod) sym setFlag LIFTED
liftedDefs(sym.owner) ::= tree
sym.owner.info.decls enterUnique sym
debuglog("lifted: " + sym + " from " + oldOwner + " to " + sym.owner)
EmptyTree
}
private def postTransform(tree: Tree, isBoxedRef: Boolean = false): Tree = {
val sym = tree.symbol
tree match {
case ClassDef(_, _, _, _) =>
val tree1 = addFreeParams(tree, sym)
if (sym.isLocal) liftDef(tree1) else tree1
case DefDef(_, _, _, _, _, _) =>
val tree1 = addFreeParams(tree, sym)
if (sym.isLocal) liftDef(tree1) else tree1
case ValDef(mods, name, tpt, rhs) =>
if (sym.isCapturedVariable) {
val tpt1 = TypeTree(sym.tpe) setPos tpt.pos
/* Creating a constructor argument if one isn't present. */
val constructorArg = rhs match {
case EmptyTree =>
sym.primaryConstructor.info.paramTypes match {
case List(tp) => gen.mkZero(tp)
case _ =>
log("Couldn't determine how to properly construct " + sym)
rhs
}
case arg => arg
}
/** Wrap expr argument in new *Ref(..) constructor, but make
* sure that Try expressions stay at toplevel.
*/
def refConstr(expr: Tree): Tree = expr match {
case Try(block, catches, finalizer) =>
Try(refConstr(block), catches map refConstrCase, finalizer)
case _ =>
New(sym, expr)
}
def refConstrCase(cdef: CaseDef): CaseDef =
CaseDef(cdef.pat, cdef.guard, refConstr(cdef.body))
treeCopy.ValDef(tree, mods, name, tpt1, typer.typedPos(rhs.pos) {
refConstr(constructorArg)
})
} else tree
case Return(Block(stats, value)) =>
Block(stats, treeCopy.Return(tree, value)) setType tree.tpe setPos tree.pos
case Return(expr) =>
assert(sym == currentMethod, sym)
tree
case Apply(fn, args) =>
treeCopy.Apply(tree, fn, addFreeArgs(tree.pos, sym, args))
case Assign(Apply(TypeApply(sel @ Select(qual, _), _), List()), rhs) =>
// eliminate casts introduced by selecting a captured variable field
// on the lhs of an assignment.
assert(sel.symbol == Object_asInstanceOf)
treeCopy.Assign(tree, qual, rhs)
case Ident(name) =>
val tree1 =
if (sym != NoSymbol && sym.isTerm && !sym.isLabel)
if (sym.isMethod)
atPos(tree.pos)(memberRef(sym))
else if (sym.isLocal && !isSameOwnerEnclosure(sym))
atPos(tree.pos)(proxyRef(sym))
else tree
else tree
if (sym.isCapturedVariable && !isBoxedRef)
atPos(tree.pos) {
val tp = tree.tpe
val elemTree = typer typed Select(tree1 setType sym.tpe, nme.elem)
if (elemTree.tpe.typeSymbol != tp.typeSymbol) gen.mkAttributedCast(elemTree, tp) else elemTree
}
else tree1
case Block(stats, expr0) =>
val (lzyVals, rest) = stats partition {
case stat: ValDef => stat.symbol.isLazy || stat.symbol.isModuleVar
case _ => false
}
if (lzyVals.isEmpty) tree
else treeCopy.Block(tree, lzyVals ::: rest, expr0)
case _ =>
tree
}
}
private def preTransform(tree: Tree) = super.transform(tree) setType lifted(tree.tpe)
override def transform(tree: Tree): Tree = tree match {
case ReferenceToBoxed(idt) =>
postTransform(preTransform(idt), isBoxedRef = true)
case _ =>
postTransform(preTransform(tree))
}
/** Transform statements and add lifted definitions to them. */
override def transformStats(stats: List[Tree], exprOwner: Symbol): List[Tree] = {
def addLifted(stat: Tree): Tree = stat match {
case ClassDef(mods, name, tparams, impl) =>
val lifted = liftedDefs get stat.symbol match {
case Some(xs) => xs reverseMap addLifted
case _ => log("unexpectedly no lifted defs for " + stat.symbol) ; Nil
}
try treeCopy.ClassDef(stat, mods, name, tparams, deriveTemplate(impl)(_ ::: lifted))
finally liftedDefs -= stat.symbol
case DefDef(_, _, _, _, _, Block(Nil, expr)) if !stat.symbol.isConstructor =>
deriveDefDef(stat)(_ => expr)
case _ =>
stat
}
super.transformStats(stats, exprOwner) map addLifted
}
override def transformUnit(unit: CompilationUnit) {
computeFreeVars
atPhase(phase.next)(super.transformUnit(unit))
assert(liftedDefs.isEmpty, liftedDefs.keys mkString ", ")
}
} // class LambdaLifter
}
|