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/* NSC -- new Scala compiler
* Copyright 2005-2013 LAMP/EPFL
* @author Paul Phillips
*/
package scala.tools.nsc
package typechecker
import scala.collection.mutable
import scala.collection.mutable.ListBuffer
import scala.util.control.ControlThrowable
import scala.util.control.Exception.ultimately
import symtab.Flags._
import PartialFunction._
/** An interface to enable higher configurability of diagnostic messages
* regarding type errors. This is barely a beginning as error messages are
* distributed far and wide across the codebase. The plan is to partition
* error messages into some broad groups and provide some mechanism for
* being more or less verbose on a selective basis. Possible groups include
* such examples as
*
* arity errors
* kind errors
* variance errors
* ambiguity errors
* volatility/stability errors
* implementation restrictions
*
* And more, and there is plenty of overlap, so it'll be a process.
*
* @author Paul Phillips
* @version 1.0
*/
trait TypeDiagnostics {
self: Analyzer =>
import global._
import definitions._
import global.typer.{ infer, context }
/** The common situation of making sure nothing is erroneous could be
* nicer if Symbols, Types, and Trees all implemented some common interface
* in which isErroneous and similar would be placed.
*/
def noErroneousTypes(tps: Type*) = tps forall (x => !x.isErroneous)
def noErroneousSyms(syms: Symbol*) = syms forall (x => !x.isErroneous)
def noErroneousTrees(trees: Tree*) = trees forall (x => !x.isErroneous)
/** For errors which are artifacts of the implementation: such messages
* indicate that the restriction may be lifted in the future.
*/
def restrictionWarning(pos: Position, unit: CompilationUnit, msg: String): Unit =
unit.warning(pos, "Implementation restriction: " + msg)
def restrictionError(pos: Position, unit: CompilationUnit, msg: String): Unit =
unit.error(pos, "Implementation restriction: " + msg)
/** A map of Positions to addendums - if an error involves a position in
* the map, the addendum should also be printed.
*/
private var addendums = perRunCaches.newMap[Position, () => String]()
private var isTyperInPattern = false
/** Devising new ways of communicating error info out of
* desperation to work on error messages. This is used
* by typedPattern to wrap its business so we can generate
* a sensible error message when things go south.
*/
def typingInPattern[T](body: => T): T = {
val saved = isTyperInPattern
isTyperInPattern = true
try body
finally isTyperInPattern = saved
}
def setAddendum(pos: Position, msg: () => String) =
if (pos != NoPosition)
addendums(pos) = msg
def withAddendum(pos: Position) = (_: String) + addendums.getOrElse(pos, () => "")()
def decodeWithKind(name: Name, owner: Symbol): String = {
val prefix = (
if (name.isTypeName) "type "
else if (owner.isPackageClass) "object "
else "value "
)
prefix + name.decode
}
/** Does the positioned line assigned to t1 precede that of t2?
*/
def posPrecedes(p1: Position, p2: Position) = p1.isDefined && p2.isDefined && p1.line < p2.line
def linePrecedes(t1: Tree, t2: Tree) = posPrecedes(t1.pos, t2.pos)
private object DealiasedType extends TypeMap {
def apply(tp: Type): Type = tp match {
// Avoid "explaining" that String is really java.lang.String,
// while still dealiasing types from non-default namespaces.
case TypeRef(pre, sym, args) if sym.isAliasType && !sym.isInDefaultNamespace =>
mapOver(tp.dealias)
case _ =>
mapOver(tp)
}
}
/** An explanatory note to be added to error messages
* when there's a problem with abstract var defs */
def abstractVarMessage(sym: Symbol): String =
if (underlyingSymbol(sym).isVariable)
"\n(Note that variables need to be initialized to be defined)"
else ""
private def methodTypeErrorString(tp: Type) = tp match {
case mt @ MethodType(params, resultType) =>
def forString = params map (_.defString)
forString.mkString("(", ",", ")") + resultType
case x => x.toString
}
def alternatives(tree: Tree): List[Type] = tree.tpe match {
case OverloadedType(pre, alternatives) => alternatives map pre.memberType
case _ => Nil
}
def alternativesString(tree: Tree) =
alternatives(tree) map (x => " " + methodTypeErrorString(x)) mkString ("", " <and>\n", "\n")
/** The symbol which the given accessor represents (possibly in part).
* This is used for error messages, where we want to speak in terms
* of the actual declaration or definition, not in terms of the generated setters
* and getters.
*/
def underlyingSymbol(member: Symbol): Symbol =
if (!member.hasAccessorFlag) member
else if (!member.isDeferred) member.accessed
else {
val getter = if (member.isSetter) member.getter(member.owner) else member
val flags = if (getter.setter(member.owner) != NoSymbol) DEFERRED | MUTABLE else DEFERRED
getter.owner.newValue(getter.name.toTermName, getter.pos, flags) setInfo getter.tpe.resultType
}
def treeSymTypeMsg(tree: Tree): String = {
val sym = tree.symbol
def hasParams = tree.tpe.paramSectionCount > 0
def preResultString = if (hasParams) ": " else " of type "
def patternMessage = "pattern " + tree.tpe.finalResultType + valueParamsString(tree.tpe)
def exprMessage = "expression of type " + tree.tpe
def overloadedMessage = s"overloaded method $sym with alternatives:\n" + alternativesString(tree)
def moduleMessage = "" + sym
def defaultMessage = moduleMessage + preResultString + tree.tpe
def applyMessage = defaultMessage + tree.symbol.locationString
if ((sym eq null) || (sym eq NoSymbol)) {
if (isTyperInPattern) patternMessage
else exprMessage
}
else if (sym.isOverloaded) overloadedMessage
else if (sym.isModule) moduleMessage
else if (sym.name == nme.apply) applyMessage
else defaultMessage
}
def disambiguate(ss: List[String]) = ss match {
case Nil => Nil
case s :: ss => s :: (ss map { case `s` => "(some other)"+s ; case x => x })
}
// todo: use also for other error messages
def existentialContext(tp: Type) = tp.skolemsExceptMethodTypeParams match {
case Nil => ""
case xs => " where " + (disambiguate(xs map (_.existentialToString)) mkString ", ")
}
def varianceWord(sym: Symbol): String =
if (sym.variance == 1) "covariant"
else if (sym.variance == -1) "contravariant"
else "invariant"
def explainAlias(tp: Type) = {
// Don't automatically normalize standard aliases; they still will be
// expanded if necessary to disambiguate simple identifiers.
if ((tp eq tp.normalize) || tp.typeSymbolDirect.isInDefaultNamespace) ""
else {
// A sanity check against expansion being identical to original.
val s = "" + DealiasedType(tp)
if (s == "" + tp) ""
else "\n (which expands to) " + s
}
}
/** Look through the base types of the found type for any which
* might have been valid subtypes if given conformant type arguments.
* Examine those for situations where the type error would have been
* eliminated if the variance were different. In such cases, append
* an additional explanatory message.
*
* TODO: handle type aliases better.
*/
def explainVariance(found: Type, req: Type): String = {
found.baseTypeSeq.toList foreach { tp =>
if (tp.typeSymbol isSubClass req.typeSymbol) {
val foundArgs = tp.typeArgs
val reqArgs = req.typeArgs
val params = req.typeConstructor.typeParams
if (foundArgs.nonEmpty && foundArgs.length == reqArgs.length) {
val relationships = (foundArgs, reqArgs, params).zipped map {
case (arg, reqArg, param) =>
def mkMsg(isSubtype: Boolean) = {
val op = if (isSubtype) "<:" else ">:"
val suggest = if (isSubtype) "+" else "-"
val reqsym = req.typeSymbol
def isJava = reqsym.isJavaDefined
def isScala = reqsym hasTransOwner ScalaPackageClass
val explainFound = "%s %s %s%s, but ".format(
arg, op, reqArg,
// If the message involves a type from the base type sequence rather than the
// actual found type, we need to explain why we're talking about it. Less brute
// force measures than comparing normalized Strings were producing error messages
// like "and java.util.ArrayList[String] <: java.util.ArrayList[String]" but there
// should be a cleaner way to do this.
if (found.normalize.toString == tp.normalize.toString) ""
else " (and %s <: %s)".format(found, tp)
)
val explainDef = {
val prepend = if (isJava) "Java-defined " else ""
"%s%s is %s in %s.".format(prepend, reqsym, varianceWord(param), param)
}
// Don't suggest they change the class declaration if it's somewhere
// under scala.* or defined in a java class, because attempting either
// would be fruitless.
val suggestChange = "\nYou may wish to " + (
if (isScala || isJava)
"investigate a wildcard type such as `_ %s %s`. (SLS 3.2.10)".format(op, reqArg)
else
"define %s as %s%s instead. (SLS 4.5)".format(param.name, suggest, param.name)
)
Some("Note: " + explainFound + explainDef + suggestChange)
}
// In these cases the arg is OK and needs no explanation.
val conforms = (
(arg =:= reqArg)
|| ((arg <:< reqArg) && param.isCovariant)
|| ((reqArg <:< arg) && param.isContravariant)
)
val invariant = param.variance == 0
if (conforms) Some("")
else if ((arg <:< reqArg) && invariant) mkMsg(true) // covariant relationship
else if ((reqArg <:< arg) && invariant) mkMsg(false) // contravariant relationship
else None // we assume in other cases our ham-fisted advice will merely serve to confuse
}
val messages = relationships.flatten
// the condition verifies no type argument came back None
if (messages.size == foundArgs.size)
return messages filterNot (_ == "") mkString ("\n", "\n", "")
}
}
}
"" // no elaborable variance situation found
}
// For found/required errors where AnyRef would have sufficed:
// explain in greater detail.
def explainAnyVsAnyRef(found: Type, req: Type): String = {
if (AnyRefClass.tpe <:< req) notAnyRefMessage(found) else ""
}
// TODO - figure out how to avoid doing any work at all
// when the message will never be seen. I though context.reportErrors
// being false would do that, but if I return "<suppressed>" under
// that condition, I see it.
def foundReqMsg(found: Type, req: Type): String = {
def baseMessage = (
";\n found : " + found.toLongString + existentialContext(found) + explainAlias(found) +
"\n required: " + req + existentialContext(req) + explainAlias(req)
)
( withDisambiguation(Nil, found, req)(baseMessage)
+ explainVariance(found, req)
+ explainAnyVsAnyRef(found, req)
)
}
def typePatternAdvice(sym: Symbol, ptSym: Symbol) = {
val clazz = if (sym.isModuleClass) sym.companionClass else sym
val caseString =
if (clazz.isCaseClass && (clazz isSubClass ptSym))
( clazz.caseFieldAccessors
map (_ => "_") // could use the actual param names here
mkString (s"`case ${clazz.name}(", ",", ")`")
)
else
"`case _: " + (clazz.typeParams match {
case Nil => "" + clazz.name
case xs => xs map (_ => "_") mkString (clazz.name + "[", ",", "]")
})+ "`"
"\nNote: if you intended to match against the class, try "+ caseString
}
case class TypeDiag(tp: Type, sym: Symbol) extends Ordered[TypeDiag] {
// save the name because it will be mutated until it has been
// distinguished from the other types in the same error message
private val savedName = sym.name
def restoreName() = sym.name = savedName
def isAltered = sym.name != savedName
def modifyName(f: String => String) = sym setName newTypeName(f(sym.name.toString))
/** Prepend java.lang, scala., or Predef. if this type originated
* in one of those.
*/
def qualifyDefaultNamespaces() = {
val intersect = Set(trueOwner, aliasOwner) intersect UnqualifiedOwners
if (intersect.nonEmpty) preQualify()
}
// functions to manipulate the name
def preQualify() = modifyName(trueOwner.fullName + "." + _)
def postQualify() = modifyName(_ + "(in " + trueOwner + ")")
def typeQualify() = if (sym.isTypeParameterOrSkolem) postQualify()
def nameQualify() = if (trueOwner.isPackageClass) preQualify() else postQualify()
def trueOwner = tp.typeSymbol.effectiveOwner
def aliasOwner = tp.typeSymbolDirect.effectiveOwner
def sym_==(other: TypeDiag) = tp.typeSymbol == other.tp.typeSymbol
def owner_==(other: TypeDiag) = trueOwner == other.trueOwner
def string_==(other: TypeDiag) = tp.toString == other.tp.toString
def name_==(other: TypeDiag) = sym.name == other.sym.name
def compare(other: TypeDiag) =
if (this == other) 0
else if (sym isLess other.sym) -1
else 1
override def toString = {
"""
|tp = %s
|tp.typeSymbol = %s
|tp.typeSymbol.owner = %s
|tp.typeSymbolDirect = %s
|tp.typeSymbolDirect.owner = %s
""".stripMargin.format(
tp, tp.typeSymbol, tp.typeSymbol.owner, tp.typeSymbolDirect, tp.typeSymbolDirect.owner
)
}
}
/** This is tricky stuff - we need to traverse types deeply to
* explain name ambiguities, which may occur anywhere. However
* when lub explosions come through it knocks us into an n^2
* disaster, see SI-5580. This is trying to perform the initial
* filtering of possibly ambiguous types in a sufficiently
* aggressive way that the state space won't explode.
*/
private def typeDiags(locals: List[Symbol], types0: Type*): List[TypeDiag] = {
val types = types0.toList
// If two different type diag instances are seen for a given
// key (either the string representation of a type, or the simple
// name of a symbol) then keep them for disambiguation.
val strings = mutable.Map[String, Set[TypeDiag]]() withDefaultValue Set()
val names = mutable.Map[Name, Set[TypeDiag]]() withDefaultValue Set()
def record(t: Type, sym: Symbol) = {
val diag = TypeDiag(t, sym)
strings("" + t) += diag
names(sym.name) += diag
}
for (tpe <- types ; t <- tpe) {
t match {
case ConstantType(_) => record(t, t.underlying.typeSymbol)
case TypeRef(_, sym, _) => record(t, sym)
case _ => ()
}
}
val collisions = strings.values ++ names.values filter (_.size > 1)
collisions.flatten.toList
}
/** The distinct pairs from an ordered list. */
private def pairs[T <: Ordered[T]](xs: Seq[T]): Seq[(T, T)] = {
for (el1 <- xs ; el2 <- xs ; if el1 < el2) yield
((el1, el2))
}
/** Given any number of types, alters the name information in the symbols
* until they can be distinguished from one another: then executes the given
* code. The names are restored and the result is returned.
*/
def withDisambiguation[T](locals: List[Symbol], types: Type*)(op: => T): T = {
val typeRefs = typeDiags(locals, types: _*)
val toCheck = pairs(typeRefs) filterNot { case (td1, td2) => td1 sym_== td2 }
ultimately(typeRefs foreach (_.restoreName())) {
for ((td1, td2) <- toCheck) {
val tds = List(td1, td2)
// If the types print identically, qualify them:
// a) If the dealiased owner is a package, the full path
// b) Otherwise, append (in <owner>)
if (td1 string_== td2)
tds foreach (_.nameQualify())
// If they have the same simple name, and either of them is in the
// scala package or predef, qualify with scala so it is not confusing why
// e.g. java.util.Iterator and Iterator are different types.
if (td1 name_== td2)
tds foreach (_.qualifyDefaultNamespaces())
// If they still print identically:
// a) If they are type parameters with different owners, append (in <owner>)
// b) Failing that, the best we can do is append "(some other)" to the latter.
if (td1 string_== td2) {
if (td1 owner_== td2)
td2.modifyName("(some other)" + _)
else
tds foreach (_.typeQualify())
}
}
// performing the actual operation
op
}
}
trait TyperDiagnostics {
self: Typer =>
private def contextError(context0: Analyzer#Context, pos: Position, msg: String) = context0.error(pos, msg)
private def contextError(context0: Analyzer#Context, pos: Position, err: Throwable) = context0.error(pos, err)
private def contextWarning(pos: Position, msg: String) = context.unit.warning(pos, msg)
def permanentlyHiddenWarning(pos: Position, hidden: Name, defn: Symbol) =
contextWarning(pos, "imported `%s' is permanently hidden by definition of %s".format(hidden, defn.fullLocationString))
object checkDead {
private val exprStack: mutable.Stack[Symbol] = mutable.Stack(NoSymbol)
// The method being applied to `tree` when `apply` is called.
private def expr = exprStack.top
private def exprOK =
(expr != Object_synchronized) &&
!(expr.isLabel && treeInfo.isSynthCaseSymbol(expr)) // it's okay to jump to matchEnd (or another case) with an argument of type nothing
private def treeOK(tree: Tree) = {
val isLabelDef = tree match { case _: LabelDef => true; case _ => false}
tree.tpe != null && tree.tpe.typeSymbol == NothingClass && !isLabelDef
}
@inline def updateExpr[A](fn: Tree)(f: => A) = {
if (fn.symbol != null && fn.symbol.isMethod && !fn.symbol.isConstructor) {
exprStack push fn.symbol
try f finally exprStack.pop()
} else f
}
def apply(tree: Tree): Tree = {
// Error suppression will squash some of these warnings unless we circumvent it.
// It is presumed if you are using a -Y option you would really like to hear
// the warnings you've requested.
if (settings.warnDeadCode.value && context.unit.exists && treeOK(tree) && exprOK)
context.warning(tree.pos, "dead code following this construct", true)
tree
}
// The checkDead call from typedArg is more selective.
def inMode(mode: Int, tree: Tree): Tree = {
val modeOK = (mode & (EXPRmode | BYVALmode | POLYmode)) == (EXPRmode | BYVALmode)
if (modeOK) apply(tree)
else tree
}
}
private def symWasOverloaded(sym: Symbol) = sym.owner.isClass && sym.owner.info.member(sym.name).isOverloaded
private def cyclicAdjective(sym: Symbol) = if (symWasOverloaded(sym)) "overloaded" else "recursive"
/** Returns Some(msg) if the given tree is untyped apparently due
* to a cyclic reference, and None otherwise.
*/
def cyclicReferenceMessage(sym: Symbol, tree: Tree) = condOpt(tree) {
case ValDef(_, _, tpt, _) if tpt.tpe == null => "recursive "+sym+" needs type"
case DefDef(_, _, _, _, tpt, _) if tpt.tpe == null => List(cyclicAdjective(sym), sym, "needs result type") mkString " "
case Import(expr, selectors) =>
( "encountered unrecoverable cycle resolving import." +
"\nNote: this is often due in part to a class depending on a definition nested within its companion." +
"\nIf applicable, you may wish to try moving some members into another object."
)
}
/** Report a type error.
*
* @param pos0 The position where to report the error
* @param ex The exception that caused the error
*/
def reportTypeError(context0: Context, pos: Position, ex: TypeError) {
if (ex.pos == NoPosition) ex.pos = pos
// TODO: should be replaced by throwErrors
// but it seems that throwErrors excludes some of the errors that should actually be
// buffered, causing TypeErrors to fly around again. This needs some more investigation.
if (!context0.reportErrors) throw ex
if (settings.debug.value) ex.printStackTrace()
ex match {
case CyclicReference(sym, info: TypeCompleter) =>
if (context0.owner.isTermMacro) {
// see comments to TypeSigError for an explanation of this special case
throw ex
} else {
val pos = info.tree match {
case Import(expr, _) => expr.pos
case _ => ex.pos
}
contextError(context0, pos, cyclicReferenceMessage(sym, info.tree) getOrElse ex.getMessage())
if (sym == ObjectClass)
throw new FatalError("cannot redefine root "+sym)
}
case _ =>
contextError(context0, ex.pos, ex)
}
}
}
}
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