/
Infer.scala
1760 lines (1612 loc) · 77 KB
/
Infer.scala
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/* NSC -- new Scala compiler
* Copyright 2005-2013 LAMP/EPFL
* @author Martin Odersky
*/
package scala.tools.nsc
package typechecker
import scala.collection.{ mutable, immutable }
import scala.collection.mutable.ListBuffer
import scala.util.control.ControlThrowable
import symtab.Flags._
import scala.annotation.tailrec
/** This trait ...
*
* @author Martin Odersky
* @version 1.0
*/
trait Infer extends Checkable {
self: Analyzer =>
import global._
import definitions._
import typer.printInference
import typeDebug.ptBlock
/* -- Type parameter inference utility functions --------------------------- */
private def assertNonCyclic(tvar: TypeVar) =
assert(tvar.constr.inst != tvar, tvar.origin)
/** The formal parameter types corresponding to <code>formals</code>.
* If <code>formals</code> has a repeated last parameter, a list of
* (nargs - params.length + 1) copies of its type is returned.
* By-name types are replaced with their underlying type.
*
* @param removeByName allows keeping ByName parameters. Used in NamesDefaults.
* @param removeRepeated allows keeping repeated parameter (if there's one argument). Used in NamesDefaults.
*/
def formalTypes(formals: List[Type], nargs: Int, removeByName: Boolean = true, removeRepeated: Boolean = true): List[Type] = {
val formals1 = if (removeByName) formals mapConserve {
case TypeRef(_, ByNameParamClass, List(arg)) => arg
case formal => formal
} else formals
if (isVarArgTypes(formals1) && (removeRepeated || formals.length != nargs)) {
val ft = formals1.last.dealiasWiden.typeArgs.head
formals1.init ::: (for (i <- List.range(formals1.length - 1, nargs)) yield ft)
} else formals1
}
/** Returns `(formals, formalsExpanded)` where `formalsExpanded` are the expected types
* for the `nbSubPats` sub-patterns of an extractor pattern, of which the corresponding
* unapply[Seq] call is assumed to have result type `resTp`.
*
* `formals` are the formal types before expanding a potential repeated parameter (must come last in `formals`, if at all)
*
* @param nbSubPats The number of arguments to the extractor pattern
* @param effectiveNbSubPats `nbSubPats`, unless there is one sub-pattern which, after unwrapping
* bind patterns, is a Tuple pattern, in which case it is the number of
* elements. Used to issue warnings about binding a `TupleN` to a single value.
* @throws TypeError when the unapply[Seq] definition is ill-typed
* @returns (null, null) when the expected number of sub-patterns cannot be satisfied by the given extractor
*
* This is the spec currently implemented -- TODO: update it.
*
* 8.1.8 ExtractorPatterns
*
* An extractor pattern x(p1, ..., pn) where n ≥ 0 is of the same syntactic form as a constructor pattern.
* However, instead of a case class, the stable identifier x denotes an object which has a member method named unapply or unapplySeq that matches the pattern.
*
* An `unapply` method with result type `R` in an object `x` matches the
* pattern `x(p_1, ..., p_n)` if it takes exactly one argument and, either:
* - `n = 0` and `R =:= Boolean`, or
* - `n = 1` and `R <:< Option[T]`, for some type `T`.
* The argument pattern `p1` is typed in turn with expected type `T`.
* - Or, `n > 1` and `R <:< Option[Product_n[T_1, ..., T_n]]`, for some
* types `T_1, ..., T_n`. The argument patterns `p_1, ..., p_n` are
* typed with expected types `T_1, ..., T_n`.
*
* An `unapplySeq` method in an object `x` matches the pattern `x(p_1, ..., p_n)`
* if it takes exactly one argument and its result type is of the form `Option[S]`,
* where either:
* - `S` is a subtype of `Seq[U]` for some element type `U`, (set `m = 0`)
* - or `S` is a `ProductX[T_1, ..., T_m]` and `T_m <: Seq[U]` (`m <= n`).
*
* The argument patterns `p_1, ..., p_n` are typed with expected types
* `T_1, ..., T_m, U, ..., U`. Here, `U` is repeated `n-m` times.
*
*/
def extractorFormalTypes(pos: Position, resTp: Type, nbSubPats: Int,
unappSym: Symbol, effectiveNbSubPats: Int): (List[Type], List[Type]) = {
val isUnapplySeq = unappSym.name == nme.unapplySeq
val booleanExtractor = resTp.typeSymbolDirect == BooleanClass
def seqToRepeatedChecked(tp: Type) = {
val toRepeated = seqToRepeated(tp)
if (tp eq toRepeated) throw new TypeError("(the last tuple-component of) the result type of an unapplySeq must be a Seq[_]")
else toRepeated
}
// empty list --> error, otherwise length == 1
lazy val optionArgs = resTp.baseType(OptionClass).typeArgs
// empty list --> not a ProductN, otherwise product element types
def productArgs = getProductArgs(optionArgs.head)
val formals =
// convert Seq[T] to the special repeated argument type
// so below we can use formalTypes to expand formals to correspond to the number of actuals
if (isUnapplySeq) {
if (optionArgs.nonEmpty)
productArgs match {
case Nil => List(seqToRepeatedChecked(optionArgs.head))
case normalTps :+ seqTp => normalTps :+ seqToRepeatedChecked(seqTp)
}
else throw new TypeError(s"result type $resTp of unapplySeq defined in ${unappSym.fullLocationString} does not conform to Option[_]")
} else {
if (booleanExtractor && nbSubPats == 0) Nil
else if (optionArgs.nonEmpty)
if (nbSubPats == 1) {
val productArity = productArgs.size
if (settings.lint.value && productArity > 1 && productArity != effectiveNbSubPats)
global.currentUnit.warning(pos,
s"extractor pattern binds a single value to a Product${productArity} of type ${optionArgs.head}")
optionArgs
}
// TODO: update spec to reflect we allow any ProductN, not just TupleN
else productArgs
else
throw new TypeError(s"result type $resTp of unapply defined in ${unappSym.fullLocationString} does not conform to Option[_] or Boolean")
}
// for unapplySeq, replace last vararg by as many instances as required by nbSubPats
val formalsExpanded =
if (isUnapplySeq && formals.nonEmpty) formalTypes(formals, nbSubPats)
else formals
if (formalsExpanded.lengthCompare(nbSubPats) != 0) (null, null)
else (formals, formalsExpanded)
}
def actualTypes(actuals: List[Type], nformals: Int): List[Type] =
if (nformals == 1 && !hasLength(actuals, 1))
List(if (actuals.isEmpty) UnitClass.tpe else tupleType(actuals))
else actuals
def actualArgs(pos: Position, actuals: List[Tree], nformals: Int): List[Tree] = {
val inRange = nformals == 1 && !hasLength(actuals, 1) && actuals.lengthCompare(MaxTupleArity) <= 0
if (inRange && !phase.erasedTypes) List(atPos(pos)(gen.mkTuple(actuals)))
else actuals
}
/** A fresh type variable with given type parameter as origin.
*
* @param tparam ...
* @return ...
*/
def freshVar(tparam: Symbol): TypeVar = TypeVar(tparam)
class NoInstance(msg: String) extends Throwable(msg) with ControlThrowable { }
private class DeferredNoInstance(getmsg: () => String) extends NoInstance("") {
override def getMessage(): String = getmsg()
}
private def ifNoInstance[T](f: String => T): PartialFunction[Throwable, T] = {
case x: NoInstance => f(x.getMessage)
}
/** Map every TypeVar to its constraint.inst field.
* throw a NoInstance exception if a NoType or WildcardType is encountered.
*/
object instantiate extends TypeMap {
private var excludedVars = immutable.Set[TypeVar]()
def apply(tp: Type): Type = tp match {
case WildcardType | BoundedWildcardType(_) | NoType =>
throw new NoInstance("undetermined type")
case tv @ TypeVar(origin, constr) if !tv.untouchable =>
if (constr.inst == NoType) {
throw new DeferredNoInstance(() =>
"no unique instantiation of type variable " + origin + " could be found")
} else if (excludedVars(tv)) {
throw new NoInstance("cyclic instantiation")
} else {
excludedVars += tv
val res = apply(constr.inst)
excludedVars -= tv
res
}
case _ =>
mapOver(tp)
}
}
/** Is type fully defined, i.e. no embedded anytypes or wildcards in it?
*
* @param tp ...
* @return ...
*/
private[typechecker] def isFullyDefined(tp: Type): Boolean = tp match {
case WildcardType | BoundedWildcardType(_) | NoType =>
false
case NoPrefix | ThisType(_) | ConstantType(_) =>
true
case TypeRef(pre, sym, args) =>
isFullyDefined(pre) && (args forall isFullyDefined)
case SingleType(pre, sym) =>
isFullyDefined(pre)
case RefinedType(ts, decls) =>
ts forall isFullyDefined
case TypeVar(origin, constr) if (constr.inst == NoType) =>
false
case _ =>
try {
instantiate(tp); true
} catch {
case ex: NoInstance => false
}
}
/** Solve constraint collected in types `tvars`.
*
* @param tvars All type variables to be instantiated.
* @param tparams The type parameters corresponding to `tvars`
* @param variances The variances of type parameters; need to reverse
* solution direction for all contravariant variables.
* @param upper When `true` search for max solution else min.
* @throws NoInstance
*/
def solvedTypes(tvars: List[TypeVar], tparams: List[Symbol],
variances: List[Int], upper: Boolean, depth: Int): List[Type] = {
if (tvars.nonEmpty)
printInference("[solve types] solving for " + tparams.map(_.name).mkString(", ") + " in " + tvars.mkString(", "))
if (!solve(tvars, tparams, variances, upper, depth)) {
// no panic, it's good enough to just guess a solution, we'll find out
// later whether it works. *ZAP* @M danger, Will Robinson! this means
// that you should never trust inferred type arguments!
//
// Need to call checkBounds on the args/typars or type1 on the tree
// for the expression that results from type inference see e.g., #2421:
// implicit search had been ignoring this caveat
// throw new DeferredNoInstance(() =>
// "no solution exists for constraints"+(tvars map boundsString))
}
for (tvar <- tvars ; if tvar.constr.inst == tvar) {
if (tvar.origin.typeSymbol.info eq ErrorType)
// this can happen if during solving a cyclic type parameter
// such as T <: T gets completed. See #360
tvar.constr.inst = ErrorType
else
abort(tvar.origin+" at "+tvar.origin.typeSymbol.owner)
}
tvars map instantiate
}
def skipImplicit(tp: Type) = tp match {
case mt: MethodType if mt.isImplicit => mt.resultType
case _ => tp
}
/** Automatically perform the following conversions on expression types:
* A method type becomes the corresponding function type.
* A nullary method type becomes its result type.
* Implicit parameters are skipped.
* This method seems to be performance critical.
*/
def normalize(tp: Type): Type = tp match {
case mt @ MethodType(params, restpe) if mt.isImplicit =>
normalize(restpe)
case mt @ MethodType(_, restpe) if !mt.isDependentMethodType =>
functionType(mt.paramTypes, normalize(restpe))
case NullaryMethodType(restpe) =>
normalize(restpe)
case ExistentialType(tparams, qtpe) =>
newExistentialType(tparams, normalize(qtpe))
case tp1 =>
tp1 // @MAT aliases already handled by subtyping
}
private lazy val stdErrorClass = rootMirror.RootClass.newErrorClass(tpnme.ERROR)
private lazy val stdErrorValue = stdErrorClass.newErrorValue(nme.ERROR)
/** The context-dependent inferencer part */
class Inferencer(context: Context) extends InferencerContextErrors with InferCheckable {
import InferErrorGen._
/* -- Error Messages --------------------------------------------------- */
def setError[T <: Tree](tree: T): T = {
debuglog("set error: "+ tree)
// this breaks -Ydebug pretty radically
// if (settings.debug.value) { // DEBUG
// println("set error: "+tree);
// throw new Error()
// }
def name = newTermName("<error: " + tree.symbol + ">")
def errorClass = if (context.reportErrors) context.owner.newErrorClass(name.toTypeName) else stdErrorClass
def errorValue = if (context.reportErrors) context.owner.newErrorValue(name) else stdErrorValue
def errorSym = if (tree.isType) errorClass else errorValue
if (tree.hasSymbol)
tree setSymbol errorSym
tree setType ErrorType
}
def getContext = context
def issue(err: AbsTypeError): Unit = context.issue(err)
def isPossiblyMissingArgs(found: Type, req: Type) = (
false
/** However it is that this condition is expected to imply
* "is possibly missing args", it is too weak. It is
* better to say nothing than to offer misleading guesses.
(found.resultApprox ne found)
&& isWeaklyCompatible(found.resultApprox, req)
*/
)
def explainTypes(tp1: Type, tp2: Type) =
withDisambiguation(List(), tp1, tp2)(global.explainTypes(tp1, tp2))
/* -- Tests & Checks---------------------------------------------------- */
/** Check that <code>sym</code> is defined and accessible as a member of
* tree <code>site</code> with type <code>pre</code> in current context.
*
* Note: pre is not refchecked -- moreover, refchecking the resulting tree may not refcheck pre,
* since pre may not occur in its type (callers should wrap the result in a TypeTreeWithDeferredRefCheck)
*/
def checkAccessible(tree: Tree, sym: Symbol, pre: Type, site: Tree): Tree =
if (sym.isError) {
tree setSymbol sym setType ErrorType
} else {
val topClass = context.owner.enclosingTopLevelClass
if (context.unit.exists)
context.unit.depends += sym.enclosingTopLevelClass
var sym1 = sym filter (alt => context.isAccessible(alt, pre, site.isInstanceOf[Super]))
// Console.println("check acc " + (sym, sym1) + ":" + (sym.tpe, sym1.tpe) + " from " + pre);//DEBUG
if (sym1 == NoSymbol && sym.isJavaDefined && context.unit.isJava) // don't try to second guess Java; see #4402
sym1 = sym
if (sym1 == NoSymbol) {
if (settings.debug.value) {
Console.println(context)
Console.println(tree)
Console.println("" + pre + " " + sym.owner + " " + context.owner + " " + context.outer.enclClass.owner + " " + sym.owner.thisType + (pre =:= sym.owner.thisType))
}
ErrorUtils.issueTypeError(AccessError(tree, sym, pre, context.enclClass.owner,
if (settings.check.isDefault)
analyzer.lastAccessCheckDetails
else
ptBlock("because of an internal error (no accessible symbol)",
"sym.ownerChain" -> sym.ownerChain,
"underlyingSymbol(sym)" -> underlyingSymbol(sym),
"pre" -> pre,
"site" -> site,
"tree" -> tree,
"sym.accessBoundary(sym.owner)" -> sym.accessBoundary(sym.owner),
"context.owner" -> context.owner,
"context.outer.enclClass.owner" -> context.outer.enclClass.owner
)
))(context)
setError(tree)
}
else {
if (context.owner.isTermMacro && (sym1 hasFlag LOCKED)) {
// we must not let CyclicReference to be thrown from sym1.info
// because that would mark sym1 erroneous, which it is not
// but if it's a true CyclicReference then macro def will report it
// see comments to TypeSigError for an explanation of this special case
// [Eugene] is there a better way?
val dummy = new TypeCompleter { val tree = EmptyTree; override def complete(sym: Symbol) {} }
throw CyclicReference(sym1, dummy)
}
if (sym1.isTerm)
sym1.cookJavaRawInfo() // xform java rawtypes into existentials
val owntype = {
try pre.memberType(sym1)
catch {
case ex: MalformedType =>
if (settings.debug.value) ex.printStackTrace
val sym2 = underlyingSymbol(sym1)
val itype = pre.memberType(sym2)
ErrorUtils.issueTypeError(
AccessError(tree, sym, pre, context.enclClass.owner,
"\n because its instance type "+itype+
(if ("malformed type: "+itype.toString==ex.msg) " is malformed"
else " contains a "+ex.msg)))(context)
ErrorType
}
}
tree setSymbol sym1 setType {
pre match {
case _: SuperType => owntype map (tp => if (tp eq pre) site.symbol.thisType else tp)
case _ => owntype
}
}
}
}
/** "Compatible" means conforming after conversions.
* "Raising to a thunk" is not implicit; therefore, for purposes of applicability and
* specificity, an arg type `A` is considered compatible with cbn formal parameter type `=>A`.
* For this behavior, the type `pt` must have cbn params preserved; for instance, `formalTypes(removeByName = false)`.
*
* `isAsSpecific` no longer prefers A by testing applicability to A for both m(A) and m(=>A)
* since that induces a tie between m(=>A) and m(=>A,B*) [SI-3761]
*/
private def isCompatible(tp: Type, pt: Type): Boolean = {
def isCompatibleByName(tp: Type, pt: Type): Boolean = pt match {
case TypeRef(_, ByNameParamClass, List(res)) if !isByNameParamType(tp) => isCompatible(tp, res)
case _ => false
}
val tp1 = normalize(tp)
(tp1 weak_<:< pt) || isCoercible(tp1, pt) || isCompatibleByName(tp, pt)
}
def isCompatibleArgs(tps: List[Type], pts: List[Type]) =
(tps corresponds pts)(isCompatible)
def isWeaklyCompatible(tp: Type, pt: Type): Boolean =
pt.typeSymbol == UnitClass || // can perform unit coercion
isCompatible(tp, pt) ||
tp.isInstanceOf[MethodType] && // can perform implicit () instantiation
tp.params.isEmpty && isCompatible(tp.resultType, pt)
/** Like weakly compatible but don't apply any implicit conversions yet.
* Used when comparing the result type of a method with its prototype.
*
* [Martin] I think Infer is also created by Erasure, with the default
* implementation of isCoercible
* [Paulp] (Assuming the above must refer to my comment on isCoercible)
* Nope, I examined every occurrence of Inferencer in trunk. It
* appears twice as a self-type, once at its definition, and once
* where it is instantiated in Typers. There are no others.
*
% ack -A0 -B0 --no-filename '\bInferencer\b' src
self: Inferencer =>
self: Inferencer =>
class Inferencer(context: Context) extends InferencerContextErrors with InferCheckable {
val infer = new Inferencer(context0) {
*/
def isConservativelyCompatible(tp: Type, pt: Type): Boolean =
context.withImplicitsDisabled(isWeaklyCompatible(tp, pt))
/** This is overridden in the Typer.infer with some logic, but since
* that's the only place in the compiler an Inferencer is ever created,
* I suggest this should either be abstract or have the implementation.
*/
def isCoercible(tp: Type, pt: Type): Boolean = false
/* -- Type instantiation------------------------------------------------ */
/** Replace any (possibly bounded) wildcard types in type `tp`
* by existentially bound variables.
*/
def makeFullyDefined(tp: Type): Type = {
val tparams = new ListBuffer[Symbol]
def addTypeParam(bounds: TypeBounds): Type = {
val tparam = context.owner.newExistential(newTypeName("_"+tparams.size), context.tree.pos.focus) setInfo bounds
tparams += tparam
tparam.tpe
}
val tp1 = tp map {
case WildcardType =>
addTypeParam(TypeBounds.empty)
case BoundedWildcardType(bounds) =>
addTypeParam(bounds)
case t => t
}
existentialAbstraction(tparams.toList, tp1)
}
/** Return inferred type arguments of polymorphic expression, given
* its type parameters and result type and a prototype <code>pt</code>.
* If no minimal type variables exist that make the
* instantiated type a subtype of <code>pt</code>, return null.
*
* @param tparams ...
* @param restpe ...
* @param pt ...
* @return ...
*/
private def exprTypeArgs(tparams: List[Symbol], restpe: Type, pt: Type, useWeaklyCompatible: Boolean = false): (List[Type], List[TypeVar]) = {
val tvars = tparams map freshVar
val instResTp = restpe.instantiateTypeParams(tparams, tvars)
if ( if (useWeaklyCompatible) isWeaklyCompatible(instResTp, pt) else isCompatible(instResTp, pt) ) {
try {
// If the restpe is an implicit method, and the expected type is fully defined
// optimize type variables wrt to the implicit formals only; ignore the result type.
// See test pos/jesper.scala
val varianceType = restpe match {
case mt: MethodType if mt.isImplicit && isFullyDefined(pt) =>
MethodType(mt.params, AnyClass.tpe)
case _ =>
restpe
}
//println("try to solve "+tvars+" "+tparams)
(solvedTypes(tvars, tparams, tparams map varianceInType(varianceType),
false, lubDepth(List(restpe, pt))), tvars)
} catch {
case ex: NoInstance => (null, null)
}
} else (null, null)
}
/** Return inferred proto-type arguments of function, given
* its type and value parameters and result type, and a
* prototype <code>pt</code> for the function result.
* Type arguments need to be either determined precisely by
* the prototype, or they are maximized, if they occur only covariantly
* in the value parameter list.
* If instantiation of a type parameter fails,
* take WildcardType for the proto-type argument.
*
* @param tparams ...
* @param formals ...
* @param restype ...
* @param pt ...
* @return ...
*/
def protoTypeArgs(tparams: List[Symbol], formals: List[Type], restpe: Type,
pt: Type): List[Type] = {
/** Map type variable to its instance, or, if `variance` is covariant/contravariant,
* to its upper/lower bound */
def instantiateToBound(tvar: TypeVar, variance: Int): Type = try {
lazy val hiBounds = tvar.constr.hiBounds
lazy val loBounds = tvar.constr.loBounds
lazy val upper = glb(hiBounds)
lazy val lower = lub(loBounds)
def setInst(tp: Type): Type = {
tvar setInst tp
assertNonCyclic(tvar)//debug
instantiate(tvar.constr.inst)
}
//Console.println("instantiate "+tvar+tvar.constr+" variance = "+variance);//DEBUG
if (tvar.constr.inst != NoType)
instantiate(tvar.constr.inst)
else if ((variance & COVARIANT) != 0 && hiBounds.nonEmpty)
setInst(upper)
else if ((variance & CONTRAVARIANT) != 0 && loBounds.nonEmpty)
setInst(lower)
else if (hiBounds.nonEmpty && loBounds.nonEmpty && upper <:< lower)
setInst(upper)
else
WildcardType
} catch {
case ex: NoInstance => WildcardType
}
val tvars = tparams map freshVar
if (isConservativelyCompatible(restpe.instantiateTypeParams(tparams, tvars), pt))
map2(tparams, tvars)((tparam, tvar) =>
instantiateToBound(tvar, varianceInTypes(formals)(tparam)))
else
tvars map (tvar => WildcardType)
}
/** [Martin] Can someone comment this please? I have no idea what it's for
* and the code is not exactly readable.
*/
object AdjustedTypeArgs {
val Result = scala.collection.mutable.LinkedHashMap
type Result = scala.collection.mutable.LinkedHashMap[Symbol, Option[Type]]
def unapply(m: Result): Some[(List[Symbol], List[Type])] = Some(toLists(
(m collect {case (p, Some(a)) => (p, a)}).unzip ))
object Undets {
def unapply(m: Result): Some[(List[Symbol], List[Type], List[Symbol])] = Some(toLists{
val (ok, nok) = m.map{case (p, a) => (p, a.getOrElse(null))}.partition(_._2 ne null)
val (okArgs, okTparams) = ok.unzip
(okArgs, okTparams, nok.keys)
})
}
object AllArgsAndUndets {
def unapply(m: Result): Some[(List[Symbol], List[Type], List[Type], List[Symbol])] = Some(toLists{
val (ok, nok) = m.map{case (p, a) => (p, a.getOrElse(null))}.partition(_._2 ne null)
val (okArgs, okTparams) = ok.unzip
(okArgs, okTparams, m.values.map(_.getOrElse(NothingClass.tpe)), nok.keys)
})
}
private def toLists[A1, A2](pxs: (Iterable[A1], Iterable[A2])) = (pxs._1.toList, pxs._2.toList)
private def toLists[A1, A2, A3](pxs: (Iterable[A1], Iterable[A2], Iterable[A3])) = (pxs._1.toList, pxs._2.toList, pxs._3.toList)
private def toLists[A1, A2, A3, A4](pxs: (Iterable[A1], Iterable[A2], Iterable[A3], Iterable[A4])) = (pxs._1.toList, pxs._2.toList, pxs._3.toList, pxs._4.toList)
}
/** Retract arguments that were inferred to Nothing because inference failed. Correct types for repeated params.
*
* We detect Nothing-due-to-failure by only retracting a parameter if either:
* - it occurs in an invariant/contravariant position in `restpe`
* - `restpe == WildcardType`
*
* Retracted parameters are mapped to None.
* TODO:
* - make sure the performance hit of storing these in a map is acceptable (it's going to be a small map in 90% of the cases, I think)
* - refactor further up the callstack so that we don't have to do this post-factum adjustment?
*
* Rewrite for repeated param types: Map T* entries to Seq[T].
* @return map from tparams to inferred arg, if inference was successful, tparams that map to None are considered left undetermined
* type parameters that are inferred as `scala.Nothing` and that are not covariant in <code>restpe</code> are taken to be undetermined
*/
def adjustTypeArgs(tparams: List[Symbol], tvars: List[TypeVar], targs: List[Type], restpe: Type = WildcardType): AdjustedTypeArgs.Result = {
val buf = AdjustedTypeArgs.Result.newBuilder[Symbol, Option[Type]]
foreach3(tparams, tvars, targs) { (tparam, tvar, targ) =>
val retract = (
targ.typeSymbol == NothingClass // only retract Nothings
&& (restpe.isWildcard || (varianceInType(restpe)(tparam) & COVARIANT) == 0) // don't retract covariant occurrences
)
// checks opt.virtPatmat directly so one need not run under -Xexperimental to use virtpatmat
buf += ((tparam,
if (retract) None
else Some(
if (targ.typeSymbol == RepeatedParamClass) targ.baseType(SeqClass)
else if (targ.typeSymbol == JavaRepeatedParamClass) targ.baseType(ArrayClass)
// this infers Foo.type instead of "object Foo" (see also widenIfNecessary)
else if (targ.typeSymbol.isModuleClass || ((opt.experimental || opt.virtPatmat) && tvar.constr.avoidWiden)) targ
else targ.widen
)
))
}
buf.result
}
/** Return inferred type arguments, given type parameters, formal parameters,
* argument types, result type and expected result type.
* If this is not possible, throw a <code>NoInstance</code> exception.
* Undetermined type arguments are represented by `definitions.NothingClass.tpe`.
* No check that inferred parameters conform to their bounds is made here.
*
* @param tparams the type parameters of the method
* @param formals the value parameter types of the method
* @param restp the result type of the method
* @param argtpes the argument types of the application
* @param pt the expected return type of the application
* @return @see adjustTypeArgs
*
* @throws NoInstance
*/
def methTypeArgs(tparams: List[Symbol], formals: List[Type], restpe: Type,
argtpes: List[Type], pt: Type): AdjustedTypeArgs.Result = {
val tvars = tparams map freshVar
if (!sameLength(formals, argtpes))
throw new NoInstance("parameter lists differ in length")
val restpeInst = restpe.instantiateTypeParams(tparams, tvars)
// first check if typevars can be fully defined from the expected type.
// The return value isn't used so I'm making it obvious that this side
// effects, because a function called "isXXX" is not the most obvious
// side effecter.
isConservativelyCompatible(restpeInst, pt)
// Return value unused with the following explanation:
//
// Just wait and instantiate from the arguments. That way,
// we can try to apply an implicit conversion afterwards.
// This case could happen if restpe is not fully defined, so the
// search for an implicit from restpe => pt fails due to ambiguity.
// See #347. Therefore, the following two lines are commented out.
//
// throw new DeferredNoInstance(() =>
// "result type " + normalize(restpe) + " is incompatible with expected type " + pt)
for (tvar <- tvars)
if (!isFullyDefined(tvar)) tvar.constr.inst = NoType
// Then define remaining type variables from argument types.
map2(argtpes, formals) { (argtpe, formal) =>
val tp1 = argtpe.deconst.instantiateTypeParams(tparams, tvars)
val pt1 = formal.instantiateTypeParams(tparams, tvars)
// Note that isCompatible side-effects: subtype checks involving typevars
// are recorded in the typevar's bounds (see TypeConstraint)
if (!isCompatible(tp1, pt1)) {
throw new DeferredNoInstance(() =>
"argument expression's type is not compatible with formal parameter type" + foundReqMsg(tp1, pt1))
}
}
val targs = solvedTypes(
tvars, tparams, tparams map varianceInTypes(formals),
false, lubDepth(formals) max lubDepth(argtpes)
)
adjustTypeArgs(tparams, tvars, targs, restpe)
}
private[typechecker] def followApply(tp: Type): Type = tp match {
case NullaryMethodType(restp) =>
val restp1 = followApply(restp)
if (restp1 eq restp) tp else restp1
case _ =>
val appmeth = {
//OPT cut down on #closures by special casing non-overloaded case
// was: tp.nonPrivateMember(nme.apply) filter (_.isPublic)
val result = tp.nonPrivateMember(nme.apply)
if ((result eq NoSymbol) || !result.isOverloaded && result.isPublic) result
else result filter (_.isPublic)
}
if (appmeth == NoSymbol) tp
else OverloadedType(tp, appmeth.alternatives)
}
def hasExactlyNumParams(tp: Type, n: Int): Boolean = tp match {
case OverloadedType(pre, alts) =>
alts exists (alt => hasExactlyNumParams(pre.memberType(alt), n))
case _ =>
val len = tp.params.length
len == n || isVarArgsList(tp.params) && len <= n + 1
}
/**
* Verifies whether the named application is valid. The logic is very
* similar to the one in NamesDefaults.removeNames.
*
* @return a triple (argtpes1, argPos, namesOk) where
* - argtpes1 the argument types in named application (assignments to
* non-parameter names are treated as assignments, i.e. type Unit)
* - argPos a Function1[Int, Int] mapping arguments from their current
* to the corresponding position in params
* - namesOK is false when there's an invalid use of named arguments
*/
private def checkNames(argtpes: List[Type], params: List[Symbol]) = {
val argPos = Array.fill(argtpes.length)(-1)
var positionalAllowed, namesOK = true
var index = 0
val argtpes1 = argtpes map {
case NamedType(name, tp) => // a named argument
var res = tp
val pos = params.indexWhere(p => paramMatchesName(p, name) && !p.isSynthetic)
if (pos == -1) {
if (positionalAllowed) { // treat assignment as positional argument
argPos(index) = index
res = UnitClass.tpe
} else // unknown parameter name
namesOK = false
} else if (argPos.contains(pos)) { // parameter specified twice
namesOK = false
} else {
if (index != pos)
positionalAllowed = false
argPos(index) = pos
}
index += 1
res
case tp => // a positional argument
argPos(index) = index
if (!positionalAllowed)
namesOK = false // positional after named
index += 1
tp
}
(argtpes1, argPos, namesOK)
}
/** don't do a () to (()) conversion for methods whose second parameter
* is a varargs. This is a fairly kludgey way to address #3224.
* We'll probably find a better way to do this by identifying
* tupled and n-ary methods, but thiws is something for a future major revision.
*/
def isUnitForVarArgs(args: List[AnyRef], params: List[Symbol]): Boolean =
args.isEmpty && hasLength(params, 2) && isVarArgsList(params)
/** Is there an instantiation of free type variables <code>undetparams</code>
* such that function type <code>ftpe</code> is applicable to
* <code>argtpes</code> and its result conform to <code>pt</code>?
*
* @param undetparams ...
* @param ftpe the type of the function (often a MethodType)
* @param argtpes the argument types; a NamedType(name, tp) for named
* arguments. For each NamedType, if `name` does not exist in `ftpe`, that
* type is set to `Unit`, i.e. the corresponding argument is treated as
* an assignment expression (@see checkNames).
* @param pt ...
* @return ...
*/
private def isApplicable(undetparams: List[Symbol], ftpe: Type,
argtpes0: List[Type], pt: Type): Boolean =
ftpe match {
case OverloadedType(pre, alts) =>
alts exists (alt => isApplicable(undetparams, pre.memberType(alt), argtpes0, pt))
case ExistentialType(tparams, qtpe) =>
isApplicable(undetparams, qtpe, argtpes0, pt)
case mt @ MethodType(params, _) =>
val formals = formalTypes(mt.paramTypes, argtpes0.length, removeByName = false)
def tryTupleApply: Boolean = {
// if 1 formal, 1 argtpe (a tuple), otherwise unmodified argtpes0
val tupleArgTpes = actualTypes(argtpes0 map {
// no assignment is treated as named argument here
case NamedType(name, tp) => UnitClass.tpe
case tp => tp
}, formals.length)
!sameLength(argtpes0, tupleArgTpes) &&
!isUnitForVarArgs(argtpes0, params) &&
isApplicable(undetparams, ftpe, tupleArgTpes, pt)
}
def typesCompatible(argtpes: List[Type]) = {
val restpe = ftpe.resultType(argtpes)
if (undetparams.isEmpty) {
isCompatibleArgs(argtpes, formals) && isWeaklyCompatible(restpe, pt)
} else {
try {
val AdjustedTypeArgs.Undets(okparams, okargs, leftUndet) = methTypeArgs(undetparams, formals, restpe, argtpes, pt)
// #2665: must use weak conformance, not regular one (follow the monomorphic case above)
(exprTypeArgs(leftUndet, restpe.instantiateTypeParams(okparams, okargs), pt, useWeaklyCompatible = true)._1 ne null) &&
isWithinBounds(NoPrefix, NoSymbol, okparams, okargs)
} catch {
case ex: NoInstance => false
}
}
}
// very similar logic to doTypedApply in typechecker
val lencmp = compareLengths(argtpes0, formals)
if (lencmp > 0) tryTupleApply
else if (lencmp == 0) {
if (!argtpes0.exists(_.isInstanceOf[NamedType])) {
// fast track if no named arguments are used
typesCompatible(argtpes0)
}
else {
// named arguments are used
val (argtpes1, argPos, namesOK) = checkNames(argtpes0, params)
// when using named application, the vararg param has to be specified exactly once
( namesOK && (isIdentity(argPos) || sameLength(formals, params)) &&
// nb. arguments and names are OK, check if types are compatible
typesCompatible(reorderArgs(argtpes1, argPos))
)
}
}
else {
// not enough arguments, check if applicable using defaults
val missing = missingParams[Type](argtpes0, params, {
case NamedType(name, _) => Some(name)
case _ => None
})._1
if (missing forall (_.hasDefault)) {
// add defaults as named arguments
val argtpes1 = argtpes0 ::: (missing map (p => NamedType(p.name, p.tpe)))
isApplicable(undetparams, ftpe, argtpes1, pt)
}
else tryTupleApply
}
case NullaryMethodType(restpe) => // strip nullary method type, which used to be done by the polytype case below
isApplicable(undetparams, restpe, argtpes0, pt)
case PolyType(tparams, restpe) =>
createFromClonedSymbols(tparams, restpe)((tps1, restpe1) => isApplicable(tps1 ::: undetparams, restpe1, argtpes0, pt))
case ErrorType =>
true
case _ =>
false
}
/**
* Todo: Try to make isApplicable always safe (i.e. not cause TypeErrors).
* The chance of TypeErrors should be reduced through context errors
*/
private[typechecker] def isApplicableSafe(undetparams: List[Symbol], ftpe: Type,
argtpes0: List[Type], pt: Type): Boolean = {
val silentContext = context.makeSilent(false)
val typer0 = newTyper(silentContext)
val res1 = typer0.infer.isApplicable(undetparams, ftpe, argtpes0, pt)
if (pt != WildcardType && silentContext.hasErrors) {
silentContext.flushBuffer()
val res2 = typer0.infer.isApplicable(undetparams, ftpe, argtpes0, WildcardType)
if (silentContext.hasErrors) false else res2
} else res1
}
/** Is type <code>ftpe1</code> strictly more specific than type <code>ftpe2</code>
* when both are alternatives in an overloaded function?
* @see SLS (sec:overloading-resolution)
*
* @param ftpe1 ...
* @param ftpe2 ...
* @return ...
*/
def isAsSpecific(ftpe1: Type, ftpe2: Type): Boolean = ftpe1 match {
case OverloadedType(pre, alts) =>
alts exists (alt => isAsSpecific(pre.memberType(alt), ftpe2))
case et: ExistentialType =>
isAsSpecific(ftpe1.skolemizeExistential, ftpe2)
//et.withTypeVars(isAsSpecific(_, ftpe2))
case NullaryMethodType(res) =>
isAsSpecific(res, ftpe2)
case mt: MethodType if mt.isImplicit =>
isAsSpecific(ftpe1.resultType, ftpe2)
case mt @ MethodType(params, _) if params.nonEmpty =>
var argtpes = mt.paramTypes
if (isVarArgsList(params) && isVarArgsList(ftpe2.params))
argtpes = argtpes map (argtpe =>
if (isRepeatedParamType(argtpe)) argtpe.typeArgs.head else argtpe)
isApplicable(List(), ftpe2, argtpes, WildcardType)
case PolyType(tparams, NullaryMethodType(res)) =>
isAsSpecific(PolyType(tparams, res), ftpe2)
case PolyType(tparams, mt: MethodType) if mt.isImplicit =>
isAsSpecific(PolyType(tparams, mt.resultType), ftpe2)
case PolyType(_, (mt @ MethodType(params, _))) if params.nonEmpty =>
isApplicable(List(), ftpe2, mt.paramTypes, WildcardType)
// case NullaryMethodType(res) =>
// isAsSpecific(res, ftpe2)
case ErrorType =>
true
case _ =>
ftpe2 match {
case OverloadedType(pre, alts) =>
alts forall (alt => isAsSpecific(ftpe1, pre.memberType(alt)))
case et: ExistentialType =>
et.withTypeVars(isAsSpecific(ftpe1, _))
case mt: MethodType =>
!mt.isImplicit || isAsSpecific(ftpe1, mt.resultType)
case NullaryMethodType(res) =>
isAsSpecific(ftpe1, res)
case PolyType(tparams, NullaryMethodType(res)) =>
isAsSpecific(ftpe1, PolyType(tparams, res))
case PolyType(tparams, mt: MethodType) =>
!mt.isImplicit || isAsSpecific(ftpe1, PolyType(tparams, mt.resultType))
case _ =>
isAsSpecificValueType(ftpe1, ftpe2, List(), List())
}
}
private def isAsSpecificValueType(tpe1: Type, tpe2: Type, undef1: List[Symbol], undef2: List[Symbol]): Boolean = (tpe1, tpe2) match {
case (PolyType(tparams1, rtpe1), _) =>
isAsSpecificValueType(rtpe1, tpe2, undef1 ::: tparams1, undef2)
case (_, PolyType(tparams2, rtpe2)) =>
isAsSpecificValueType(tpe1, rtpe2, undef1, undef2 ::: tparams2)
case _ =>
existentialAbstraction(undef1, tpe1) <:< existentialAbstraction(undef2, tpe2)
}
/*
def isStrictlyMoreSpecific(ftpe1: Type, ftpe2: Type): Boolean =
ftpe1.isError || isAsSpecific(ftpe1, ftpe2) &&
(!isAsSpecific(ftpe2, ftpe1) ||
!ftpe1.isInstanceOf[OverloadedType] && ftpe2.isInstanceOf[OverloadedType] ||
phase.erasedTypes && covariantReturnOverride(ftpe1, ftpe2))
*/
/** Is sym1 (or its companion class in case it is a module) a subclass of
* sym2 (or its companion class in case it is a module)?
*/
def isProperSubClassOrObject(sym1: Symbol, sym2: Symbol): Boolean = (
(sym1 != sym2) && (sym1 != NoSymbol) && (
(sym1 isSubClass sym2)
|| (sym1.isModuleClass && isProperSubClassOrObject(sym1.linkedClassOfClass, sym2))
|| (sym2.isModuleClass && isProperSubClassOrObject(sym1, sym2.linkedClassOfClass))
)
)
/** is symbol `sym1` defined in a proper subclass of symbol `sym2`?
*/
def isInProperSubClassOrObject(sym1: Symbol, sym2: Symbol) =
sym2 == NoSymbol || isProperSubClassOrObject(sym1.owner, sym2.owner)
def isStrictlyMoreSpecific(ftpe1: Type, ftpe2: Type, sym1: Symbol, sym2: Symbol): Boolean = {
// ftpe1 / ftpe2 are OverloadedTypes (possibly with one single alternative) if they
// denote the type of an "apply" member method (see "followApply")
ftpe1.isError || {
val specificCount = (if (isAsSpecific(ftpe1, ftpe2)) 1 else 0) -
(if (isAsSpecific(ftpe2, ftpe1) &&
// todo: move to isAsSpecific test
// (!ftpe2.isInstanceOf[OverloadedType] || ftpe1.isInstanceOf[OverloadedType]) &&
(!phase.erasedTypes || covariantReturnOverride(ftpe1, ftpe2))) 1 else 0)
val subClassCount = (if (isInProperSubClassOrObject(sym1, sym2)) 1 else 0) -
(if (isInProperSubClassOrObject(sym2, sym1)) 1 else 0)
// println("is more specific? "+sym1+":"+ftpe1+sym1.locationString+"/"+sym2+":"+ftpe2+sym2.locationString+":"+
// specificCount+"/"+subClassCount)
specificCount + subClassCount > 0
}
}
/*
ftpe1.isError || {
if (isAsSpecific(ftpe1, ftpe2))
(!isAsSpecific(ftpe2, ftpe1) ||
isProperSubClassOrObject(sym1.owner, sym2.owner) ||
!ftpe1.isInstanceOf[OverloadedType] && ftpe2.isInstanceOf[OverloadedType] ||
phase.erasedTypes && covariantReturnOverride(ftpe1, ftpe2))
else
!isAsSpecific(ftpe2, ftpe1) &&
isProperSubClassOrObject(sym1.owner, sym2.owner)
}
*/
private def covariantReturnOverride(ftpe1: Type, ftpe2: Type): Boolean = (ftpe1, ftpe2) match {
case (MethodType(_, rtpe1), MethodType(_, rtpe2)) =>
rtpe1 <:< rtpe2 || rtpe2.typeSymbol == ObjectClass
case _ =>
false
}
/*