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
507
508
509
510
511
512
513
514
515
516
517
518
|
/* NSC -- new scala compiler
* Copyright 2005 LAMP/EPFL
* @author
*/
// $Id$
package scala.tools.nsc.transform;
import collection.mutable.HashMap;
import symtab._;
import Flags._;
import scala.tools.util.Position;
import util.ListBuffer;
abstract class Erasure extends AddInterfaces with typechecker.Analyzer {
import global._; // the global environment
import definitions._; // standard classes and methods
import typer.{typed}; // methods to type trees
import posAssigner.atPos; // for filling in tree positions
val phaseName: String = "erasure";
def newTransformer(unit: CompilationUnit): Transformer = new ErasureTransformer(unit);
// -------- erasure on types --------------------------------------------------------
/** The erasure |T| of a type T. This is:
* - For a constant type, itself.
* - For a type-bounds structure, the erasure of its upper bound.
* - For every other singleton type, the erasure of its supertype.
* - For a typeref scala.Array[T] where T is an abstract type, scala.runtime.BoxedArray.
* - For a typeref scala.Array[T] where T is not an abstract type, scala.Array[|T|].
* - For a typeref scala.Any or scala.AnyVal, java.lang.Object.
* - For a typeref scala.Unit, scala.runtime.BoxedUnit.
* - For a typeref P.C[Ts] where C refers to a class, |P|.C.
* - For a typeref P.C[Ts] where C refers to an alias type, the erasure of C's alias.
* - For a typeref P.C[Ts] where C refers to an abstract type, the erasure of C's upper bound.
* - For a non-empty type intersection (possibly with refinement), the erasure of its first parent.
* - For an empty type intersection, java.lang.Object
* - For a method type (Fs)scala.Unit, (|Fs|)scala#Unit.
* - For any other method type (Fs)Y, (|Fs|)|T|.
* - For a polymorphic type, the erasure of its result type
* - For the class info type of java.lang.Object, the same type without any parents
* - For a class info type of a value class, the same type without any parents
* - For any other class info type with parents Ps, the same type with parents |Ps|, but
* with duplicate references of Object removed.
* - for all other types, the type itself (with any sub-components erased)
*/
private val erasure = new TypeMap {
def apply(tp: Type): Type = tp match {
case ConstantType(_) =>
tp
case st: SubType =>
apply(st.supertype)
case TypeRef(pre, sym, args) =>
if (sym == ArrayClass)
args.head match {
case TypeRef(_, tvar, _) if (tvar.isAbstractType) => erasedTypeRef(BoxedArrayClass)
case _ => typeRef(apply(pre), sym, args map this)
}
else if (sym == AnyClass || sym == AnyValClass) erasedTypeRef(ObjectClass)
else if (sym == UnitClass) erasedTypeRef(BoxedUnitClass)
else if (sym.isClass) typeRef(apply(pre), sym, List())
else apply(sym.info)
case PolyType(tparams, restpe) =>
apply(restpe)
case MethodType(formals, restpe) =>
MethodType(
formals map apply,
if (restpe.symbol == UnitClass) erasedTypeRef(UnitClass) else apply(restpe));
case RefinedType(parents, decls) =>
if (parents.isEmpty) erasedTypeRef(ObjectClass)
else apply(parents.head)
case ClassInfoType(parents, decls, clazz) =>
ClassInfoType(
if ((clazz == ObjectClass) || (isValueClass(clazz))) List()
else if (clazz == ArrayClass) List(erasedTypeRef(ObjectClass))
else removeDoubleObject(parents map this),
decls, clazz)
case _ =>
mapOver(tp)
}
}
/** Type reference after erasure */
def erasedTypeRef(sym: Symbol): Type = typeRef(erasure(sym.owner.tpe), sym, List());
/** Remove duplicate references to class Object in a list of parent classes
* todo: needed?
*/
private def removeDoubleObject(tps: List[Type]): List[Type] = tps match {
case List() => List()
case tp :: tps1 =>
if (tp.symbol == ObjectClass) tp :: tps1.filter(.symbol.!=(ObjectClass))
else tp :: removeDoubleObject(tps1)
}
/** The symbol's erased info. This is the type's erasure, except for the following symbols
* - For $asInstanceOf : [T]T
* - For $isInstanceOf : [T]scala#Boolean
* - For class Array : [T]C where C is the erased classinfo of the Array class
* - For Array[T].<init> : {scala#Int)Array[T]
* - For a type parameter : A type bounds type consisting of the erasures of its bounds.
*/
def transformInfo(sym: Symbol, tp: Type): Type =
if (sym == Object_asInstanceOf)
sym.info
else if (sym == Object_isInstanceOf || sym == ArrayClass)
PolyType(sym.info.typeParams, erasure(sym.info.resultType))
else if (sym.isAbstractType)
TypeBounds(WildcardType, WildcardType)
else if (sym.isTerm && sym.owner == ArrayClass) {
if (sym.isClassConstructor)
tp match {
case MethodType(formals, TypeRef(pre, sym, args)) =>
MethodType(formals map erasure, typeRef(erasure(pre), sym, args))
}
else if (sym.name == nme.apply)
tp
else if (sym.name == nme.update)
tp match {
case MethodType(List(index, tvar), restpe) =>
MethodType(List(erasure(index), tvar), erasure(restpe))
}
else erasure(tp)
} else
transformTraitInfo(erasure(tp));
// -------- boxing/unboxing --------------------------------------------------------
override def newTyper(context: Context) = new Eraser(context);
/** The modifier typer which retypes with erased types. */
class Eraser(context: Context) extends Typer(context) {
/** Box `tree' of unboxed type */
private def box(tree: Tree): Tree =
typed {
atPos(tree.pos) {
val sym = tree.tpe.symbol;
if (sym == UnitClass) {
if (treeInfo.isPureExpr(tree)) gen.mkRef(BoxedUnit_UNIT)
else Block(List(tree), gen.mkRef(BoxedUnit_UNIT))
} else if (sym == ArrayClass) {
val elemClass = tree.tpe.typeArgs.head.symbol;
val boxedClass = if (isValueClass(elemClass)) boxedArrayClass(elemClass)
else BoxedObjectArrayClass;
Apply(Select(New(TypeTree(boxedClass.tpe)), nme.CONSTRUCTOR), List(tree))
} else {
val boxedModule = boxedClass(tree.tpe.symbol).linkedModule;
Apply(Select(gen.mkRef(boxedModule), nme.box), List(tree))
}
}
}
/** Unbox `tree' of boxed type to expected type `pt' */
private def unbox(tree: Tree, pt: Type): Tree =
typed {
atPos(tree.pos) {
if (pt.symbol == UnitClass) {
Literal(())
} else if (pt.symbol == BooleanClass) {
val tree1 = adaptToType(tree, boxedClass(BooleanClass).tpe);
Apply(Select(tree1, "booleanValue"), List())
} else if (pt.symbol == ArrayClass) {
val tree1 = adaptToType(tree, BoxedArrayClass.tpe);
val elemClass = pt.typeArgs.head.symbol;
val elemTag =
if (isValueClass(elemClass))
Apply(
Select(gen.mkRef(ScalaRunTimeModule), newTermName(elemClass.name.toString() + "Tag")),
List())
else Literal(signature(pt));
Apply(Select(tree1, "unbox"), List(elemTag))
} else {
val tree1 = adaptToType(tree, BoxedNumberClass.tpe);
val unboxedName = pt.symbol.name.toString();
val unboxOp =
String.valueOf((unboxedName.charAt(0) + ('a' - 'A')).asInstanceOf[char]) +
unboxedName.substring(1) + "Value";
Apply(Select(tree1, unboxOp), List())
}
}
}
/** Is symbol a member of unboxed arrays (which will be expanded directly later)? */
private def isUnboxedArrayMember(sym: Symbol) =
sym.name == nme.apply || sym.name == nme.length || sym.name == nme.update ||
sym.owner == ObjectClass;
/** Is symbol a member of a boxed value class (which will not be expanded later)? */
def isBoxedValueMember(sym: Symbol) =
(sym.name == nme.equals_ || sym.name == nme.hashCode_ || sym.name == nme.toString_ ||
(sym.name == nme.EQ || sym.name == nme.NE) && sym.info.paramTypes.head.symbol == ObjectClass ||
sym == Object_isInstanceOf || sym == Object_asInstanceOf);
/** Adapt `tree' to expected type `pt' */
private def adaptToType(tree: Tree, pt: Type): Tree = {
//if (settings.debug.value && pt != WildcardType) log("adapting " + tree + ":" + tree.tpe + " to " + pt);//DEBUG
if (tree.tpe <:< pt)
tree
else if (isUnboxedClass(tree.tpe.symbol) && !isUnboxedClass(pt.symbol))
adaptToType(box(tree), pt)
else if (tree.tpe.isInstanceOf[MethodType] && tree.tpe.paramTypes.isEmpty) {
assert(tree.symbol.isStable);
adaptToType(Apply(tree, List()) setPos tree.pos setType tree.tpe.resultType, pt)
} else if (pt <:< tree.tpe)
gen.cast(tree, pt)
else if (isUnboxedClass(pt.symbol) && !isUnboxedClass(tree.tpe.symbol))
adaptToType(unbox(tree, pt), pt)
else
gen.cast(tree, pt)
}
// todo: remove after removing ==, != from value classes
private def corresponds(sym: Symbol, anyMember: Symbol): boolean =
sym == anyMember ||
sym != NoSymbol && isValueClass(sym.owner) && sym.name == anyMember.name && sym.tpe == anyMember.tpe;
/** Replace member references as follows:
* - `x == y' for `==' in class Any becomes `x equals y' with `equals' in class Object
* - `x != y' for `!=' in class Any becomes `!(x equals y)' with `equals' in class Object
* - `new BoxedArray.<init>(len)' becomes `new BoxedAnyArray.<init>(len): BoxedArray'
* (the widening typing is necessary so that subsequent member symbols stay the same)
* - `x.asInstanceOf[T]' and `x.asInstanceOf$erased[T]' become `x.$asInstanceOf[T]'
* - `x.isInstanceOf[T]' and `x.isInstanceOf$erased[T]' become `x.$isInstanceOf[T]'
* - `x.m' where `m' is some other member of Any becomes `x.m' where m is a member of class Object
* - `x.m' where `x' has unboxed value type `T' and `m' is not a directly
* translated member of `T' becomes T.box(x).m
* - `x.m' where `x' has type `Array[T]' and `m' is not a directly
* translated member of `Array' becomes new BoxedTArray.<init>(x).m
* - `x.m' where `x' is a reference type and `m' is a directly translated member of value type
* T becomes x.TValue().m
* - All forms of `x.m' where `x' is a boxed type and `m' is a member of an unboxed class
* become `x.m' where `m' is the corresponding member of the boxed class.
*/
private def adaptMember(tree: Tree): Tree = {
tree match {
case Apply(Select(New(tpt), name), args) if (tpt.tpe.symbol == BoxedArrayClass) =>
assert(name == nme.CONSTRUCTOR);
atPos(tree.pos) {
Typed(Apply(Select(New(TypeTree(BoxedAnyArrayClass.tpe)), name), args), tpt)
}
case Select(qual, name) if (name != nme.CONSTRUCTOR) =>
if (tree.symbol == Any_asInstanceOf || tree.symbol == Any_asInstanceOfErased)
adaptMember(atPos(tree.pos)(Select(qual, Object_asInstanceOf)))
else if (tree.symbol == Any_isInstanceOf || tree.symbol == Any_isInstanceOfErased)
adaptMember(atPos(tree.pos)(Select(qual, Object_isInstanceOf)))
else if (tree.symbol != NoSymbol && tree.symbol.owner == AnyClass)
adaptMember(atPos(tree.pos)(Select(qual, getMember(ObjectClass, name))))
else {
var qual1 = typedQualifier(qual);
if ((isValueClass(qual1.tpe.symbol) && isBoxedValueMember(tree.symbol)) ||
(qual1.tpe.symbol == ArrayClass && !isUnboxedArrayMember(tree.symbol))) {
qual1 = box(qual1);
} else if (!isValueClass(qual1.tpe.symbol) &&
tree.symbol != NoSymbol &&
isValueClass(tree.symbol.owner) &&
!isBoxedValueMember(tree.symbol)) {
qual1 = unbox(qual1, tree.symbol.owner.tpe)
}
if (tree.symbol != NoSymbol)
if (isUnboxedClass(tree.symbol.owner) && !isUnboxedClass(qual1.tpe.symbol))
tree.symbol = NoSymbol
else if (qual1.tpe.isInstanceOf[MethodType] && qual1.tpe.paramTypes.isEmpty) {
assert(qual1.symbol.isStable);
qual1 = Apply(qual1, List()) setPos qual1.pos setType qual1.tpe.resultType;
} else if (!(qual1.isInstanceOf[Super] || (qual1.tpe.symbol isSubClass tree.symbol.owner)))
qual1 = gen.cast(qual1, tree.symbol.owner.tpe);
copy.Select(tree, qual1, name)
}
case _ =>
tree
}
}
/** A replacement for the standard typer's `adapt' method */
override protected def adapt(tree: Tree, mode: int, pt: Type): Tree = adaptToType(tree, pt);
/** A replacement for the standard typer's `typed1' method */
override protected def typed1(tree: Tree, mode: int, pt: Type): Tree = {
val tree1 = super.typed1(adaptMember(tree), mode, pt);
tree1 match {
case If(cond, thenp, elsep) =>
val thenp1 = adaptToType(thenp, tree1.tpe);
val elsep1 = if (elsep.isEmpty) elsep else adaptToType(elsep, tree1.tpe);
copy.If(tree1, cond, thenp1, elsep1);
case Match(selector, cases) =>
val cases1 = cases map {
case cdef @ CaseDef(pat, guard, body) =>
val body1 = adaptToType(body, tree1.tpe);
copy.CaseDef(cdef, pat, guard, body1) setType body1.tpe
}
copy.Match(tree1, selector, cases1)
// todo: do same for try
case _ =>
tree1
}
}
}
/** The erasure transformer */
class ErasureTransformer(unit: CompilationUnit) extends Transformer {
/** Emit an error if there is a double definition. This can happen in the following
* circumstances:
* - A template defines two members with the same name and erased type.
* - A template defines and inherits two members `m' with different types,
* but their erased types are the same.
* - A template inherits two members `m' with different types,
* but their erased types are the same.
*/
private def checkNoDoubleDefs(root: Symbol): unit = {
def doubleDefError(sym1: Symbol, sym2: Symbol) = {
val tpe1 = atPhase(currentRun.refchecksPhase.next)(root.tpe.memberType(sym1));
val tpe2 = atPhase(currentRun.refchecksPhase.next)(root.tpe.memberType(sym2));
unit.error(
if (sym1.owner == root) sym1.pos else root.pos,
(if (sym1.owner == sym2.owner) "double definition:\n"
else if (sym1.owner == root) "name clash between defined and inherited member:\n"
else "name clash between inherited members:\n") +
sym1 + ":" + tpe1 +
(if (sym1.owner == root) "" else sym1.locationString) + " and\n" +
sym2 + ":" + tpe2 +
(if (sym2.owner == root) " at line " + Position.line(sym2.pos) else sym2.locationString) +
"\nhave same type" +
(if (tpe1 =:= tpe2) "" else " after erasure: " + atPhase(phase.next)(sym1.tpe)))
}
val decls = root.info.decls;
var e = decls.elems;
while (e != null) {
if (e.sym.isTerm && !e.sym.isConstructor) {
var e1 = decls.lookupNextEntry(e);
while (e1 != null) {
if (atPhase(phase.next)(e1.sym.info =:= e.sym.info)) doubleDefError(e.sym, e1.sym);
e1 = decls.lookupNextEntry(e1)
}
}
e = e.next
}
val opc = new overridingPairs.Cursor(root) {
override def exclude(sym: Symbol): boolean =
!sym.isTerm || (sym hasFlag (PRIVATE | BRIDGE)) || super.exclude(sym);
override def matches(sym1: Symbol, sym2: Symbol): boolean =
atPhase(phase.next)(sym1.tpe =:= sym2.tpe)
}
while (opc.hasNext) {
if (!atPhase(currentRun.refchecksPhase.next)(
root.thisType.memberType(opc.overriding) matches
root.thisType.memberType(opc.overridden))) {
if (settings.debug.value) log("" + opc.overriding.locationString + " " + opc.overriding.infosString + opc.overridden.locationString + " " + opc.overridden.infosString);
doubleDefError(opc.overriding, opc.overridden)
}
opc.next
}
}
/*
for (val bc <- root.info.baseClasses.tail; val other <- bc.info.decls.toList) {
if (other.isTerm && !other.isConstructor && !(other hasFlag (PRIVATE | BRIDGE))) {
for (val member <- root.info.nonPrivateMember(other.name).alternatives) {
if (member != other &&
!(member hasFlag BRIDGE) &&
atPhase(phase.next)(member.tpe =:= other.tpe) &&
!atPhase(refchecksPhase.next)(
root.thisType.memberType(member) matches root.thisType.memberType(other))) {
if (settings.debug.value) log("" + member.locationString + " " + member.infosString + other.locationString + " " + other.infosString);
doubleDefError(member, other)
}
}
}
}
*/
/** Add bridge definitions to a template. This means:
* If there is a concrete member `m' which overrides a member in a base class of the template,
* and the erased types of the two members differ,
* and the two members are not inherited or defined by some parent class of the template,
* then a bridge from the overridden member `m1' to the member `m0' is added.
* The bridge has the erased type of `m1' and forwards to `m0'.
* No bridge is added if there is already a bridge to `m0' with the erased type of `m1'
* in the template.
*/
private def bridgeDefs(owner: Symbol): List[Tree] = {
val site = owner.thisType;
val bridgesScope = new Scope();
val bridgeTarget = new HashMap[Symbol, Symbol];
var bridges: List[Tree] = List();
val opc = atPhase(phase.prev) { // to avoid DEFERRED flags for interfaces
new overridingPairs.Cursor(owner) {
override def parents: List[Type] = List(owner.info.parents.head);
override def exclude(sym: Symbol): boolean =
!sym.isMethod || (sym hasFlag (PRIVATE | BRIDGE)) || super.exclude(sym);
}
}
while (opc.hasNext) {
val member = opc.overriding;
val other = opc.overridden;
if (!(member hasFlag DEFERRED)) {
/*
for (val bc <- site.baseClasses.tail; val other <- bc.info.decls.toList) {
if (other.isMethod && !other.isConstructor) {
for (val member <- site.nonPrivateMember(other.name).alternatives) {
if (member != other &&
!(member hasFlag DEFERRED) &&
(site.memberType(member) matches site.memberType(other)) &&
!(site.parents exists (p =>
(p.symbol isSubClass member.owner) && (p.symbol isSubClass other.owner)))) {
*/
val otpe = erasure(other.tpe);
if (!(otpe =:= erasure(member.tpe))) {
var e = bridgesScope.lookupEntry(member.name);
while (e != null && !((e.sym.tpe =:= otpe) && (bridgeTarget(e.sym) == member)))
e = bridgesScope.lookupNextEntry(e);
if (e == null) {
val bridge = other.cloneSymbolImpl(owner)
setPos(owner.pos)
setFlag (member.flags | BRIDGE)
resetFlag ACCESSOR
setInfo otpe;
bridgeTarget(bridge) = member;
bridgesScope enter bridge;
bridges =
atPhase(phase.next) {
atPos(bridge.pos) {
val bridgeDef =
DefDef(bridge, vparamss =>
member.tpe match {
case MethodType(List(), ConstantType(c)) => Literal(c)
case _ =>
((Select(This(owner), member): Tree) /: vparamss)
((fun, vparams) => Apply(fun, vparams map Ident))
});
if (settings.debug.value)
log("generating bridge from " + other + ":" + otpe + other.locationString + " to " + member + ":" + erasure(member.tpe) + member.locationString + " =\n " + bridgeDef);
bridgeDef
}
} :: bridges;
}
}
/*
}
}
*/
}
opc.next
}
bridges
}
def addBridges(stats: List[Tree], base: Symbol): List[Tree] =
if (base.isTrait) stats
else {
val bridges = bridgeDefs(base);
if (bridges.isEmpty) stats else stats ::: bridges
}
/** Transform tree at phase `erasure' before retyping it. This entails the following:
* - Remove all type parameters in class and method definitions.
* - Remove all abstract and alias type definitions.
* - Remove all type applications other than those involving a type test or cast.
* - Remove all empty trees in statements and definitions in a PackageDef.
* - Check that there are no double definitions in a template.
* - Add bridge definitions to a template.
* - Replace all types in type nodes and the EmptyTree object by their erasure.
* Type nodes of type Unit representing result types of methods are left alone.
* - Reset all other type attributes to `null, thus enforcing a retyping.
*/
private val preTransformer = new Transformer {
override def transform(tree: Tree): Tree = {
if (tree.symbol == ArrayClass) return tree;
val tree1 = tree match {
case ClassDef(mods, name, tparams, tpt, impl) =>
copy.ClassDef(tree, mods, name, List(), tpt, impl)
case DefDef(mods, name, tparams, vparamss, tpt, rhs) =>
copy.DefDef(tree, mods, name, List(), vparamss, tpt, rhs)
case AbsTypeDef(_, _, _, _) =>
EmptyTree
case AliasTypeDef(_, _, _, _) =>
EmptyTree
case TypeApply(fun, args) if (fun.symbol.owner != AnyClass) =>
// leave type tests/type casts, remove all other type applications
fun
case Template(parents, body) =>
assert(!currentOwner.isImplClass);
//System.out.println("checking no dble defs " + tree);//DEBUG
checkNoDoubleDefs(tree.symbol.owner);
copy.Template(tree, parents, addBridges(body, currentOwner));
case _ =>
tree
}
tree1 match {
case EmptyTree | TypeTree() =>
tree1 setType erasure(tree1.tpe)
case DefDef(mods, name, tparams, vparamss, tpt, rhs) =>
val result = super.transform(tree1) setType null;
tpt.tpe = erasure(tree.symbol.tpe).resultType;
result
case _ =>
super.transform(tree1) setType null
}
}
}
/** The main transform function: Pretransfom the tree, and then
* re-type it at phase erasure.next.
*/
override def transform(tree: Tree): Tree = {
val tree1 = preTransformer.transform(tree);
atPhase(phase.next) {
val tree2 = traitTransformer.transform(tree1);
if (settings.debug.value) log("tree after addinterfaces: \n" + tree2);
newTyper(startContext).typed(tree2)
}
}
}
}
|