package dotty.tools
package dotc
package typer
import core._
import ast._
import Contexts._, Types._, Flags._, Denotations._, Names._, StdNames._, NameOps._, Symbols._
import Trees._
import Constants._
import annotation.unchecked
import util.Positions._
import util.{Stats, SimpleMap}
import Decorators._
import ErrorReporting.{errorType, InfoString}
import collection.mutable.ListBuffer
object Inferencing {
import tpd._
/** A trait defining an `isCompatible` method. */
trait Compatibility {
/** Is there an implicit conversion from `tp` to `pt`? */
def viewExists(tp: Type, pt: Type)(implicit ctx: Context): Boolean
/** A type `tp` is compatible with a type `pt` if one of the following holds:
* 1. `tp` is a subtype of `pt`
* 2. `pt` is by name parameter type, and `tp` is compatible with its underlying type
* 3. there is an implicit conversion from `tp` to `pt`.
*/
def isCompatible(tp: Type, pt: Type)(implicit ctx: Context): Boolean = {
def skipByName(tp: Type): Type =
if (tp isRef defn.ByNameParamClass) tp.typeArgs.head else tp
skipByName(tp) <:< skipByName(pt) || viewExists(tp, pt)
}
/** Test compatibility after normalization in a fresh typerstate */
def normalizedCompatible(tp: Type, pt: Type)(implicit ctx: Context) = {
val nestedCtx = ctx.fresh.withExploreTyperState
isCompatible(normalize(tp)(nestedCtx), pt)(nestedCtx)
}
}
/** A prototype for expressions [] that are part of a selection operation:
*
* [ ].name: proto
*/
class SelectionProto(name: Name, proto: Type)
extends RefinedType(WildcardType, name)(_ => proto) with ProtoType with Compatibility {
override def viewExists(tp: Type, pt: Type)(implicit ctx: Context): Boolean = false
override def isMatchedBy(tp1: Type)(implicit ctx: Context) =
name == nme.WILDCARD || {
val mbr = tp1.member(name)
mbr.exists && mbr.hasAltWith(m => normalizedCompatible(m.info, proto))
}
override def toString = "Proto" + super.toString
}
/** Create a selection proto-type, but only one level deep;
* treat constructors specially
*/
def selectionProto(name: Name, tp: Type) =
if (name.isConstructorName) WildcardType
else tp match {
case tp: UnapplyFunProto => new UnapplySelectionProto(name)
case tp: ProtoType => new SelectionProto(name, WildcardType)
case _ => new SelectionProto(name, tp)
}
/** A prototype for expressions [] that are in some unspecified selection operation
*
* [].?: ?
*
* Used to indicate that expression is in a context where the only valid
* operation is further selection. In this case, the expression need not be a value.
* @see checkValue
*/
object AnySelectionProto extends SelectionProto(nme.WILDCARD, WildcardType)
/** A prototype for selections in pattern constructors */
class UnapplySelectionProto(name: Name) extends SelectionProto(name, WildcardType)
/** A prototype for expressions that appear in function position
*
* [](args): resultType
*/
case class FunProto(args: List[untpd.Tree], override val resultType: Type, typer: Typer)(implicit ctx: Context)
extends UncachedGroundType with ProtoType {
private var myTypedArgs: List[Tree] = Nil
/** A map in which typed arguments can be stored to be later integrated in `typedArgs`. */
private var myTypedArg: SimpleMap[untpd.Tree, Tree] = SimpleMap.Empty
def isMatchedBy(tp: Type)(implicit ctx: Context) =
typer.isApplicable(tp, typedArgs, resultType)
def argsAreTyped: Boolean = myTypedArgs.nonEmpty || args.isEmpty
/** The typed arguments. This takes any arguments already typed using
* `typedArg` into account.
*/
def typedArgs: List[Tree] = {
if (!argsAreTyped)
myTypedArgs = args mapconserve { arg =>
val targ = myTypedArg(arg)
if (targ != null) targ else typer.typed(arg)
}
myTypedArgs
}
/** Type single argument and remember the unadapted result in `myTypedArg`.
* used to avoid repreated typings of trees when backtracking.
*/
def typedArg(arg: untpd.Tree, formal: Type)(implicit ctx: Context): Tree = {
var targ = myTypedArg(arg)
if (targ == null) {
targ = typer.typedUnadapted(arg, formal)
myTypedArg = myTypedArg.updated(arg, targ)
}
typer.adapt(targ, formal)
}
override def toString = s"FunProto(${args mkString ","} => $resultType)"
}
/** A prototype for implicitly inferred views:
*
* []: argType => resultType
*/
case class ViewProto(argType: Type, override val resultType: Type)(implicit ctx: Context)
extends CachedGroundType with ProtoType {
def isMatchedBy(tp: Type)(implicit ctx: Context) =
ctx.typer.isApplicable(tp, argType :: Nil, resultType)
override def namedPartsWith(p: NamedType => Boolean)(implicit ctx: Context): collection.Set[NamedType] =
AndType(argType, resultType).namedPartsWith(p) // this is more efficient than oring two namedParts sets
override def computeHash = doHash(argType, resultType)
}
class UnapplyFunProto(typer: Typer)(implicit ctx: Context) extends FunProto(
untpd.TypedSplice(dummyTreeOfType(WildcardType)) :: Nil, WildcardType, typer)
/** A prototype for expressions [] that are type-parameterized:
*
* [] [?_, ..., ?_nargs] resultType
*/
case class PolyProto(nargs: Int, override val resultType: Type) extends UncachedGroundType
/** A prototype for expressions [] that are known to be functions:
*
* [] _
*/
object AnyFunctionProto extends UncachedGroundType with ProtoType {
def isMatchedBy(tp: Type)(implicit ctx: Context) = true
}
/** The normalized form of a type
* - unwraps polymorphic types, tracking their parameters in the current constraint
* - skips implicit parameters
* - converts non-dependent method types to the corresponding function types
* - dereferences parameterless method types
*/
def normalize(tp: Type)(implicit ctx: Context): Type = Stats.track("normalize") {
tp.widenSingleton match {
case pt: PolyType => normalize(constrained(pt).resultType)
case mt: MethodType if !mt.isDependent =>
if (mt.isImplicit) mt.resultType
else defn.FunctionType(mt.paramTypes, mt.resultType)
case et: ExprType => et.resultType
case _ => tp
}
}
/** An enumeration controlling the degree of forcing in "is-dully-defined" checks. */
object ForceDegree extends Enumeration {
val none, // don't force type variables
noBottom, // force type variables, fail if forced to Nothing or Null
all = Value // force type variables, don't fail
}
/** Is type fully defined, meaning the type does not contain wildcard types
* or uninstantiated type variables. As a side effect, this will minimize
* any uninstantiated type variables, according to the given force degree,
* but only if the overall result of `isFullyDefined` is `true`.
* Variables that are successfully minimized do not count as uninstantiated.
*/
def isFullyDefined(tp: Type, force: ForceDegree.Value)(implicit ctx: Context): Boolean = {
val nestedCtx = ctx.fresh.withNewTyperState
val result = new IsFullyDefinedAccumulator(force)(nestedCtx).traverse(tp)
if (result) nestedCtx.typerState.commit()
result
}
/** The fully defined type, where all type variables are forced.
* Throws an error if type contains wildcards.
*/
def fullyDefinedType(tp: Type, what: String, pos: Position)(implicit ctx: Context) =
if (isFullyDefined(tp, ForceDegree.all)) tp
else throw new Error(i"internal error: type of $what $tp is not fully defined, pos = $pos") // !!! DEBUG
private class IsFullyDefinedAccumulator(force: ForceDegree.Value)(implicit ctx: Context) extends TypeAccumulator[Boolean] {
def traverse(tp: Type): Boolean = apply(true, tp)
def apply(x: Boolean, tp: Type) = !x || isOK(tp) && foldOver(x, tp)
def isOK(tp: Type): Boolean = tp match {
case _: WildcardType =>
false
case tvar: TypeVar if force != ForceDegree.none && !tvar.isInstantiated =>
val inst = tvar.instantiate(fromBelow = true)
println(i"forced instantiation of ${tvar.origin} = $inst")
(force == ForceDegree.all || inst != defn.NothingType && inst != defn.NullType) && traverse(inst)
case _ =>
true
}
}
/** Recursively widen and also follow type declarations and type aliases. */
def widenForMatchSelector(tp: Type)(implicit ctx: Context): Type = tp.widen match {
case tp: TypeRef if !tp.symbol.isClass => widenForMatchSelector(tp.bounds.hi)
case tp => tp
}
/** Check that type arguments `args` conform to corresponding bounds in `poly` */
def checkBounds(args: List[tpd.Tree], poly: PolyType, pos: Position)(implicit ctx: Context): Unit =
for ((arg, bounds) <- args zip poly.paramBounds) {
def notConforms(which: String, bound: Type) =
ctx.error(i"Type argument ${arg.tpe} does not conform to $which bound $bound", arg.pos)
if (!(arg.tpe <:< bounds.hi)) notConforms("upper", bounds.hi)
if (!(bounds.lo <:< arg.tpe)) notConforms("lower", bounds.lo)
}
/** Check that type `tp` is stable.
* @return The type itself
*/
def checkStable(tp: Type, pos: Position)(implicit ctx: Context): Type = {
if (!tp.isStable) ctx.error(i"Prefix $tp is not stable", pos)
tp
}
/** Check that `tp` is a class type with a stable prefix.
* @return Underlying class symbol if type checks out OK, ObjectClass if not.
*/
def checkClassTypeWithStablePrefix(tp: Type, pos: Position)(implicit ctx: Context): ClassSymbol = tp.dealias match {
case tp: TypeRef if tp.symbol.isClass =>
checkStable(tp.prefix, pos)
tp.symbol.asClass
case _: TypeVar | _: AnnotatedType =>
checkClassTypeWithStablePrefix(tp.asInstanceOf[TypeProxy].underlying, pos)
case _ =>
ctx.error(i"$tp is not a class type", pos)
defn.ObjectClass
}
def checkInstantiatable(cls: ClassSymbol, pos: Position): Unit = {
??? // to be done in later phase: check that class `cls` is legal in a new.
}
/** Add all parameters in given polytype `pt` to the constraint's domain.
* If the constraint contains already some of these parameters in its domain,
* make a copy of the polytype and add the copy's type parameters instead.
* Return either the original polytype, or the copy, if one was made.
* Also, if `owningTree` is non-empty, add a type variable for each parameter.
* @return The added polytype, and the list of created type variables.
*/
def constrained(pt: PolyType, owningTree: untpd.Tree)(implicit ctx: Context): (PolyType, List[TypeVar]) = {
val state = ctx.typerState
def howmany = if (owningTree.isEmpty) "no" else "some"
def committable = if (ctx.typerState.isCommittable) "committable" else "uncommittable"
assert(owningTree.isEmpty != ctx.typerState.isCommittable,
s"inconsistent: $howmany typevars were added to $committable constraint ${state.constraint}")
def newTypeVars(pt: PolyType): List[TypeVar] =
for (n <- (0 until pt.paramNames.length).toList)
yield new TypeVar(PolyParam(pt, n), state, owningTree)
val added =
if (state.constraint contains pt) pt.copy(pt.paramNames, pt.paramBounds, pt.resultType)
else pt
val tvars = if (owningTree.isEmpty) Nil else newTypeVars(added)
state.constraint = state.constraint.add(added, tvars)
(added, tvars)
}
/** Same as `constrained(pt, EmptyTree)`, but returns just the created polytype */
def constrained(pt: PolyType)(implicit ctx: Context): PolyType = constrained(pt, EmptyTree)._1
/** Interpolate those undetermined type variables in the widened type of this tree
* which are introduced by type application contained in the tree.
* If such a variable appears covariantly in type `tp` or does not appear at all,
* approximate it by its lower bound. Otherwise, if it appears contravariantly
* in type `tp` approximate it by its upper bound.
*/
def interpolateUndetVars(tree: Tree)(implicit ctx: Context): Unit = Stats.track("interpolateUndetVars") {
val tp = tree.tpe.widen
val constraint = ctx.typerState.constraint
println(s"interpolate undet vars in ${tp.show}, pos = ${tree.pos}, mode = ${ctx.mode}, undets = ${constraint.uninstVars map (tvar => s"${tvar.show}@${tvar.owningTree.pos}")}")
println(s"qualifying undet vars: ${constraint.uninstVars filter qualifies map (_.show)}")
println(s"fulltype: $tp") // !!! DEBUG
println(s"constraint: ${constraint.show}")
def qualifies(tvar: TypeVar) = tree contains tvar.owningTree
val vs = tp.variances(tvar => (constraint contains tvar) && qualifies(tvar))
println(s"variances = $vs")
var changed = false
vs foreachBinding { (tvar, v) =>
if (v != 0) {
println(s"interpolate ${if (v == 1) "co" else "contra"}variant ${tvar.show} in ${tp.show}")
tvar.instantiate(fromBelow = v == 1)
changed = true
}
}
if (changed) // instantiations might have uncovered new typevars to interpolate
interpolateUndetVars(tree)
else
constraint.foreachUninstVar { tvar =>
if (!(vs contains tvar) && qualifies(tvar)) {
println(s"instantiating non-occurring $tvar in $tp")
tvar.instantiate(fromBelow = true)
}
}
}
/** Instantiate undetermined type variables to that type `tp` is
* maximized and return None. If this is not possible, because a non-variant
* typevar is not uniquely determined, return that typevar in a Some.
*/
def maximizeType(tp: Type)(implicit ctx: Context): Option[TypeVar] = Stats.track("maximizeType") {
val constraint = ctx.typerState.constraint
val vs = tp.variances(constraint contains _)
var result: Option[TypeVar] = None
vs foreachBinding { (tvar, v) =>
if (v == 1) tvar.instantiate(fromBelow = false)
else if (v == -1) tvar.instantiate(fromBelow = true)
else {
val bounds = ctx.typerState.constraint.bounds(tvar.origin)
if (!(bounds.hi <:< bounds.lo)) result = Some(tvar)
tvar.instantiate(fromBelow = false)
}
}
result
}
private lazy val dummyTree = untpd.Literal(Constant(null))
/** Dummy tree to be used as an argument of a FunProto or ViewProto type */
def dummyTreeOfType(tp: Type): Tree = dummyTree withTypeUnchecked tp
}
/* not needed right now
def isSubTypes(actuals: List[Type], formals: List[Type])(implicit ctx: Context): Boolean = formals match {
case formal :: formals1 =>
actuals match {
case actual :: actuals1 => actual <:< formal && isSubTypes(actuals1, formals1)
case _ => false
}
case nil =>
actuals.isEmpty
}
def formalParameters[T](mtp: MethodType, actuals: List[T])(isRepeated: T => Boolean)(implicit ctx: Context) =
if (mtp.isVarArgs && !(actuals.nonEmpty && isRepeated(actuals.last))) {
val leading = mtp.paramTypes.init
val repeated = mtp.paramTypes.last.typeArgs.head
val trailing = List.fill(actuals.length - leading.length)(repeated)
leading ++ trailing
}
else mtp.paramTypes
*/
