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author | Martin Odersky <odersky@gmail.com> | 2015-03-04 14:39:13 +0100 |
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committer | Dmitry Petrashko <dmitry.petrashko@gmail.com> | 2015-03-18 11:14:14 +0100 |
commit | a4b2a67fa5d58f7dbd34b8876e8a87e309524e22 (patch) | |
tree | 66c721ac1d151b0c3b640dffb56f647ebf727f4f /src/dotty/tools/dotc/core/TypeErasure.scala | |
parent | 96fbd7bfe252026f59d1f5e8aa33f2d8fae65769 (diff) | |
download | dotty-a4b2a67fa5d58f7dbd34b8876e8a87e309524e22.tar.gz dotty-a4b2a67fa5d58f7dbd34b8876e8a87e309524e22.tar.bz2 dotty-a4b2a67fa5d58f7dbd34b8876e8a87e309524e22.zip |
Changes to Tasty format
Use fewer length fields in type encodings.
- create new category of tags that take exactly one argument tree.
- avoid using length where a tag fits in one of theopther categories.
Diffstat (limited to 'src/dotty/tools/dotc/core/TypeErasure.scala')
-rw-r--r-- | src/dotty/tools/dotc/core/TypeErasure.scala | 418 |
1 files changed, 418 insertions, 0 deletions
diff --git a/src/dotty/tools/dotc/core/TypeErasure.scala b/src/dotty/tools/dotc/core/TypeErasure.scala new file mode 100644 index 000000000..a45e29287 --- /dev/null +++ b/src/dotty/tools/dotc/core/TypeErasure.scala @@ -0,0 +1,418 @@ +package dotty.tools +package dotc +package core + +import Symbols._, Types._, Contexts._, Flags._, Names._, StdNames._, Decorators._, Flags.JavaDefined +import dotc.transform.ExplicitOuter._ +import typer.Mode +import util.DotClass + +/** Erased types are: + * + * TypeRef(prefix is ignored, denot is ClassDenotation) + * TermRef(prefix is ignored, denot is SymDenotation) + * JavaArrayType + * AnnotatedType + * MethodType + * ThisType + * SuperType + * ClassInfo (NoPrefix, ...) + * NoType + * NoPrefix + * WildcardType + * ErrorType + * + * only for isInstanceOf, asInstanceOf: PolyType, PolyParam, TypeBounds + * + */ +object TypeErasure { + + /** A predicate that tests whether a type is a legal erased type. Only asInstanceOf and + * isInstanceOf may have types that do not satisfy the predicate. + */ + def isErasedType(tp: Type)(implicit ctx: Context): Boolean = tp match { + case tp: TypeRef => + tp.symbol.isClass && tp.symbol != defn.AnyClass + case _: TermRef => + true + case JavaArrayType(elem) => + isErasedType(elem) + case AnnotatedType(_, tp) => + isErasedType(tp) + case ThisType(tref) => + isErasedType(tref) + case tp: MethodType => + tp.paramTypes.forall(isErasedType) && isErasedType(tp.resultType) + case tp @ ClassInfo(pre, _, parents, decls, _) => + isErasedType(pre) && parents.forall(isErasedType) //&& decls.forall(sym => isErasedType(sym.info)) && isErasedType(tp.selfType) + case NoType | NoPrefix | WildcardType | ErrorType | SuperType(_, _) => + true + case _ => + false + } + + case class ErasedValueType(cls: ClassSymbol, underlying: Type) extends CachedGroundType { + override def computeHash = doHash(cls, underlying) + } + + private def erasureIdx(isJava: Boolean, isSemi: Boolean, isConstructor: Boolean, wildcardOK: Boolean) = + (if (isJava) 1 else 0) + + (if (isSemi) 2 else 0) + + (if (isConstructor) 4 else 0) + + (if (wildcardOK) 8 else 0) + + private val erasures = new Array[TypeErasure](16) + + for { + isJava <- List(false, true) + isSemi <- List(false, true) + isConstructor <- List(false, true) + wildcardOK <- List(false, true) + } erasures(erasureIdx(isJava, isSemi, isConstructor, wildcardOK)) = + new TypeErasure(isJava, isSemi, isConstructor, wildcardOK) + + /** Produces an erasure function. + * @param isJava Arguments should be treated the way Java does it + * @param isSemi Value classes are mapped in an intermediate step to + * ErasedValueClass types, instead of going directly to + * the erasure of the underlying type. + * @param isConstructor Argument forms part of the type of a constructor + * @param wildcardOK Wildcards are acceptable (true when using the erasure + * for computing a signature name). + */ + private def erasureFn(isJava: Boolean, isSemi: Boolean, isConstructor: Boolean, wildcardOK: Boolean): TypeErasure = + erasures(erasureIdx(isJava, isSemi, isConstructor, wildcardOK)) + + private val scalaErasureFn = erasureFn(isJava = false, isSemi = false, isConstructor = false, wildcardOK = false) + private val scalaSigFn = erasureFn(isJava = false, isSemi = false, isConstructor = false, wildcardOK = true) + private val javaSigFn = erasureFn(isJava = true, isSemi = false, isConstructor = false, wildcardOK = true) + private val semiErasureFn = erasureFn(isJava = false, isSemi = true, isConstructor = false, wildcardOK = false) + + /** The current context with a phase no later than erasure */ + private def erasureCtx(implicit ctx: Context) = + if (ctx.erasedTypes) ctx.withPhase(ctx.erasurePhase).addMode(Mode.FutureDefsOK) else ctx + + def erasure(tp: Type)(implicit ctx: Context): Type = scalaErasureFn(tp)(erasureCtx) + def semiErasure(tp: Type)(implicit ctx: Context): Type = semiErasureFn(tp)(erasureCtx) + def sigName(tp: Type, isJava: Boolean)(implicit ctx: Context): TypeName = { + val seqClass = if(isJava) defn.ArrayClass else defn.SeqClass + val normTp = + if (tp.isRepeatedParam) tp.translateParameterized(defn.RepeatedParamClass, seqClass) + else tp + (if (isJava) javaSigFn else scalaSigFn).sigName(normTp)(erasureCtx) + } + + /** The erasure of a top-level reference. Differs from normal erasure in that + * TermRefs are kept instead of being widened away. + */ + def erasedRef(tp: Type)(implicit ctx: Context): Type = tp match { + case tp: TermRef => + assert(tp.symbol.exists, tp) + val tp1 = ctx.makePackageObjPrefixExplicit(tp) + if (tp1 ne tp) erasedRef(tp1) + else TermRef(erasedRef(tp.prefix), tp.symbol.asTerm) + case tp: ThisType => + tp + case tp => + erasure(tp) + } + + /** The erasure of a symbol's info. This is different of `erasure` in the way `ExprType`s are + * treated. `eraseInfo` maps them them to nullary method types, whereas `erasure` maps them + * to `Function0`. + */ + def eraseInfo(tp: Type, sym: Symbol)(implicit ctx: Context): Type = + scalaErasureFn.eraseInfo(tp, sym)(erasureCtx) + + /** The erasure of a function result type. Differs from normal erasure in that + * Unit is kept instead of being mapped to BoxedUnit. + */ + def eraseResult(tp: Type)(implicit ctx: Context): Type = + scalaErasureFn.eraseResult(tp)(erasureCtx) + + /** The symbol's erased info. This is the type's erasure, except for the following symbols: + * + * - For $asInstanceOf : [T]T + * - For $isInstanceOf : [T]Boolean + * - For all abstract types : = ? + * - For all other symbols : the semi-erasure of their types, with + * isJava, isConstructor set according to symbol. + */ + def transformInfo(sym: Symbol, tp: Type)(implicit ctx: Context): Type = { + val erase = erasureFn(sym is JavaDefined, isSemi = true, sym.isConstructor, wildcardOK = false) + + def eraseParamBounds(tp: PolyType): Type = + tp.derivedPolyType( + tp.paramNames, tp.paramNames map (Function.const(TypeBounds.upper(defn.ObjectType))), tp.resultType) + + if (defn.isPolymorphicAfterErasure(sym)) eraseParamBounds(sym.info.asInstanceOf[PolyType]) + else if (sym.isAbstractType) TypeAlias(WildcardType) + else if (sym.isConstructor) outer.addParam(sym.owner.asClass, erase(tp)(erasureCtx)) + else eraseInfo(tp, sym)(erasureCtx) match { + case einfo: MethodType if sym.isGetter && einfo.resultType.isRef(defn.UnitClass) => + defn.BoxedUnitClass.typeRef + case einfo => + einfo + } + } + + /** Is `tp` an abstract type or polymorphic type parameter that has `Any` + * as upper bound and that is not Java defined? Arrays of such types are + * erased to `Object` instead of `ObjectArray`. + */ + def isUnboundedGeneric(tp: Type)(implicit ctx: Context): Boolean = tp.dealias match { + case tp: TypeRef => + !tp.symbol.isClass && + !tp.derivesFrom(defn.ObjectClass) && + !tp.symbol.is(JavaDefined) + case tp: PolyParam => + !tp.derivesFrom(defn.ObjectClass) && + !tp.binder.resultType.isInstanceOf[JavaMethodType] + case tp: TypeProxy => isUnboundedGeneric(tp.underlying) + case tp: AndType => isUnboundedGeneric(tp.tp1) || isUnboundedGeneric(tp.tp2) + case tp: OrType => isUnboundedGeneric(tp.tp1) && isUnboundedGeneric(tp.tp2) + case _ => false + } + + + /** The erased least upper bound is computed as follows + * - if both argument are arrays, an array of the lub of the element types + * - if one argument is an array, Object + * - otherwise a common superclass or trait S of the argument classes, with the + * following two properties: + * S is minimal: no other common superclass or trait derives from S] + * S is last : in the linearization of the first argument type `tp1` + * there are no minimal common superclasses or traits that + * come after S. + * (the reason to pick last is that we prefer classes over traits that way). + */ + def erasedLub(tp1: Type, tp2: Type)(implicit ctx: Context): Type = tp1 match { + case JavaArrayType(elem1) => + tp2 match { + case JavaArrayType(elem2) => JavaArrayType(erasedLub(elem1, elem2)) + case _ => defn.ObjectType + } + case _ => + tp2 match { + case JavaArrayType(_) => defn.ObjectType + case _ => + val cls2 = tp2.classSymbol + def loop(bcs: List[ClassSymbol], bestSoFar: ClassSymbol): ClassSymbol = bcs match { + case bc :: bcs1 => + if (cls2.derivesFrom(bc)) + if (!bc.is(Trait) && bc != defn.AnyClass) bc + else loop(bcs1, if (bestSoFar.derivesFrom(bc)) bestSoFar else bc) + else + loop(bcs1, bestSoFar) + case nil => + bestSoFar + } + loop(tp1.baseClasses, defn.ObjectClass).typeRef + } + } + + /** The erased greatest lower bound picks one of the two argument types. It prefers, in this order: + * - arrays over non-arrays + * - subtypes over supertypes, unless isJava is set + * - real classes over traits + */ + def erasedGlb(tp1: Type, tp2: Type, isJava: Boolean)(implicit ctx: Context): Type = tp1 match { + case JavaArrayType(elem1) => + tp2 match { + case JavaArrayType(elem2) => JavaArrayType(erasedGlb(elem1, elem2, isJava)) + case _ => tp1 + } + case _ => + tp2 match { + case JavaArrayType(_) => tp2 + case _ => + val tsym1 = tp1.typeSymbol + val tsym2 = tp2.typeSymbol + if (!tsym2.exists) tp1 + else if (!tsym1.exists) tp2 + else if (!isJava && tsym1.derivesFrom(tsym2)) tp1 + else if (!isJava && tsym2.derivesFrom(tsym1)) tp2 + else if (tp1.typeSymbol.isRealClass) tp1 + else if (tp2.typeSymbol.isRealClass) tp2 + else tp1 + } + } +} +import TypeErasure._ + +/** + * This is used as the Scala erasure during the erasure phase itself + * It differs from normal erasure in that value classes are erased to ErasedValueTypes which + * are then later converted to the underlying parameter type in phase posterasure. + * + */ +class TypeErasure(isJava: Boolean, isSemi: Boolean, isConstructor: Boolean, wildcardOK: Boolean) extends DotClass { + + /** The erasure |T| of a type T. This is: + * + * - For a refined type scala.Array+[T]: + * - if T is Nothing or Null, []Object + * - otherwise, if T <: Object, []|T| + * - otherwise, if T is a type paramter coming from Java, []Object + * - otherwise, Object + * - For a term ref p.x, the type <noprefix> # x. + * - For a typeref scala.Any, scala.AnyVal or scala.Singleton: |java.lang.Object| + * - For a typeref scala.Unit, |scala.runtime.BoxedUnit|. + * - For a typeref P.C where C refers to a class, <noprefix> # C. + * - For a typeref P.C where C refers to an alias type, the erasure of C's alias. + * - For a typeref P.C where C refers to an abstract type, the erasure of C's upper bound. + * - For a this-type C.this, the type itself. + * - For all other type proxies: The erasure of the underlying type. + * - For T1 & T2, the erased glb of |T1| and |T2| (see erasedGlb) + * - For T1 | T2, the first base class in the linearization of T which is also a base class of T2 + * - For => T, ()T + * - For a method type (Fs)scala.Unit, (|Fs|)scala.Unit. + * - For any other uncurried method type (Fs)T, (|Fs|)|T|. + * - For a curried method type (Fs1)(Fs2)T, (|Fs1|,Es2)ET where (Es2)ET = |(Fs2)T|. + * - For a polymorphic type [Ts](Ps)T, |(Ps)T| + * _ For a polymorphic type [Ts]T where T is not a method type, ()|T| + * - 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 NoType or NoPrefix, the type itself. + * - For any other type, exception. + */ + private def apply(tp: Type)(implicit ctx: Context): Type = tp match { + case tp: TypeRef => + val sym = tp.symbol + if (!sym.isClass) this(tp.info) + else if (sym.isDerivedValueClass) eraseDerivedValueClassRef(tp) + else eraseNormalClassRef(tp) + case tp: RefinedType => + val parent = tp.parent + if (parent isRef defn.ArrayClass) eraseArray(tp) + else this(parent) + case tp: TermRef => + this(tp.widen) + case tp: ThisType => + this(tp.cls.typeRef) + case SuperType(thistpe, supertpe) => + SuperType(this(thistpe), this(supertpe)) + case ExprType(rt) => + defn.FunctionClass(0).typeRef + case tp: TypeProxy => + this(tp.underlying) + case AndType(tp1, tp2) => + erasedGlb(this(tp1), this(tp2), isJava) + case OrType(tp1, tp2) => + ctx.typeComparer.orType(this(tp1), this(tp2), erased = true) + case tp: MethodType => + val paramErasure = erasureFn(tp.isJava, isSemi, isConstructor, wildcardOK)(_) + val formals = tp.paramTypes.mapConserve(paramErasure) + eraseResult(tp.resultType) match { + case rt: MethodType => + tp.derivedMethodType(tp.paramNames ++ rt.paramNames, formals ++ rt.paramTypes, rt.resultType) + case rt => + tp.derivedMethodType(tp.paramNames, formals, rt) + } + case tp: PolyType => + this(tp.resultType) match { + case rt: MethodType => rt + case rt => MethodType(Nil, Nil, rt) + } + case tp @ ClassInfo(pre, cls, classParents, decls, _) => + if (cls is Package) tp + else { + def eraseTypeRef(p: TypeRef) = this(p).asInstanceOf[TypeRef] + val parents: List[TypeRef] = + if ((cls eq defn.ObjectClass) || cls.isPrimitiveValueClass) Nil + else classParents.mapConserve(eraseTypeRef) match { + case tr :: trs1 => + assert(!tr.classSymbol.is(Trait), cls) + val tr1 = if (cls is Trait) defn.ObjectClass.typeRef else tr + tr1 :: trs1.filterNot(_ isRef defn.ObjectClass) + case nil => nil + } + val erasedDecls = decls.filteredScope(d => !d.isType || d.isClass) + tp.derivedClassInfo(NoPrefix, parents, erasedDecls, erasedRef(tp.selfType)) + // can't replace selftype by NoType because this would lose the sourceModule link + } + case NoType | NoPrefix | ErrorType | JavaArrayType(_) => + tp + case tp: WildcardType if wildcardOK => + tp + } + + private def eraseArray(tp: RefinedType)(implicit ctx: Context) = { + val defn.ArrayType(elemtp) = tp + if (elemtp derivesFrom defn.NullClass) JavaArrayType(defn.ObjectType) + else if (isUnboundedGeneric(elemtp)) defn.ObjectType + else JavaArrayType(this(elemtp)) + } + + def eraseInfo(tp: Type, sym: Symbol)(implicit ctx: Context) = tp match { + case ExprType(rt) => + if (sym is Param) apply(tp) + // Note that params with ExprTypes are eliminated by ElimByName, + // but potentially re-introduced by ResolveSuper, when we add + // forwarders to mixin methods. + // See doc comment for ElimByName for speculation how we could improve this. + else MethodType(Nil, Nil, eraseResult(rt)) + case tp => erasure(tp) + } + + private def eraseDerivedValueClassRef(tref: TypeRef)(implicit ctx: Context): Type = + unsupported("eraseDerivedValueClass") + + private def eraseNormalClassRef(tref: TypeRef)(implicit ctx: Context): Type = { + val cls = tref.symbol.asClass + (if (cls.owner is Package) normalizeClass(cls) else cls).typeRef + } + + private def eraseResult(tp: Type)(implicit ctx: Context): Type = tp match { + case tp: TypeRef => + val sym = tp.typeSymbol + if (sym eq defn.UnitClass) sym.typeRef + else if (sym.isDerivedValueClass) eraseNormalClassRef(tp) + else this(tp) + case RefinedType(parent, _) if !(parent isRef defn.ArrayClass) => + eraseResult(parent) + case _ => + this(tp) + } + + private def normalizeClass(cls: ClassSymbol)(implicit ctx: Context): ClassSymbol = { + if (cls.owner == defn.ScalaPackageClass) { + if (cls == defn.AnyClass || cls == defn.AnyValClass || cls == defn.SingletonClass) + return defn.ObjectClass + if (cls == defn.UnitClass) + return defn.BoxedUnitClass + } + cls + } + + /** The name of the type as it is used in `Signature`s. + * Need to ensure correspondence with erasure! + */ + private def sigName(tp: Type)(implicit ctx: Context): TypeName = tp match { + case tp: TypeRef => + val sym = tp.symbol + if (!sym.isClass) sigName(tp.info) + else if (sym.isDerivedValueClass) sigName(eraseDerivedValueClassRef(tp)) + else normalizeClass(sym.asClass).fullName.asTypeName + case defn.ArrayType(elem) => + sigName(this(tp)) + case JavaArrayType(elem) => + sigName(elem) ++ "[]" + case tp: TermRef => + sigName(tp.widen) + case ExprType(rt) => + sigName(defn.FunctionType(Nil, rt)) + case tp: TypeProxy => + sigName(tp.underlying) + case ErrorType | WildcardType => + tpnme.WILDCARD + case tp: WildcardType => + sigName(tp.optBounds) + case _ => + val erased = this(tp) + assert(erased ne tp, tp) + sigName(erased) + } +} |