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messages.scala
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package dotty.tools
package dotc
package reporting
import core._
import Contexts._
import Decorators._, Symbols._, Names._, NameOps._, Types._, Flags._, Phases._
import Denotations.SingleDenotation
import SymDenotations.SymDenotation
import NameKinds.WildcardParamName
import parsing.Scanners.Token
import parsing.Tokens
import printing.Highlighting._
import printing.Formatting
import ErrorMessageID._
import ast.Trees
import config.{Feature, ScalaVersion}
import typer.ErrorReporting.{err, matchReductionAddendum}
import typer.ProtoTypes.ViewProto
import typer.Implicits.Candidate
import scala.util.control.NonFatal
import StdNames.nme
import printing.Formatting.hl
import ast.Trees._
import ast.untpd
import ast.tpd
import transform.SymUtils._
import cc.CaptureSet.IdentityCaptRefMap
/** Messages
* ========
* The role of messages is to provide the necessary details for a simple to
* understand diagnostic event. Each message can be turned into a message
* container (one of the above) by calling the appropriate method on them.
* For instance:
*
* ```scala
* EmptyCatchBlock(tree).error(pos) // res: Error
* EmptyCatchBlock(tree).warning(pos) // res: Warning
* ```
*/
abstract class SyntaxMsg(errorId: ErrorMessageID) extends Message(errorId):
def kind = MessageKind.Syntax
abstract class TypeMsg(errorId: ErrorMessageID) extends Message(errorId):
def kind = MessageKind.Type
trait ShowMatchTrace(tps: Type*)(using Context) extends Message:
override def msgSuffix: String = matchReductionAddendum(tps*)
abstract class TypeMismatchMsg(found: Type, expected: Type)(errorId: ErrorMessageID)(using Context)
extends Message(errorId), ShowMatchTrace(found, expected):
def kind = MessageKind.TypeMismatch
def explain = err.whyNoMatchStr(found, expected)
override def canExplain = true
abstract class NamingMsg(errorId: ErrorMessageID) extends Message(errorId):
def kind = MessageKind.Naming
abstract class DeclarationMsg(errorId: ErrorMessageID) extends Message(errorId):
def kind = MessageKind.Declaration
/** A simple not found message (either for idents, or member selection.
* Messages of this class are sometimes dropped in favor of other, more
* specific messages.
*/
abstract class NotFoundMsg(errorId: ErrorMessageID) extends Message(errorId):
def kind = MessageKind.NotFound
def name: Name
abstract class PatternMatchMsg(errorId: ErrorMessageID) extends Message(errorId):
def kind = MessageKind.PatternMatch
abstract class CyclicMsg(errorId: ErrorMessageID) extends Message(errorId):
def kind = MessageKind.Cyclic
abstract class ReferenceMsg(errorId: ErrorMessageID) extends Message(errorId):
def kind = MessageKind.Reference
abstract class EmptyCatchOrFinallyBlock(tryBody: untpd.Tree, errNo: ErrorMessageID)(using Context)
extends SyntaxMsg(errNo) {
def explain = {
val tryString = tryBody match {
case Block(Nil, untpd.EmptyTree) => "{}"
case _ => tryBody.show
}
val code1 =
s"""|import scala.util.control.NonFatal
|
|try $tryString catch {
| case NonFatal(e) => ???
|}""".stripMargin
val code2 =
s"""|try $tryString finally {
| // perform your cleanup here!
|}""".stripMargin
em"""|A ${hl("try")} expression should be followed by some mechanism to handle any exceptions
|thrown. Typically a ${hl("catch")} expression follows the ${hl("try")} and pattern matches
|on any expected exceptions. For example:
|
|$code1
|
|It is also possible to follow a ${hl("try")} immediately by a ${hl("finally")} - letting the
|exception propagate - but still allowing for some clean up in ${hl("finally")}:
|
|$code2
|
|It is recommended to use the ${hl("NonFatal")} extractor to catch all exceptions as it
|correctly handles transfer functions like ${hl("return")}."""
}
}
class EmptyCatchBlock(tryBody: untpd.Tree)(using Context)
extends EmptyCatchOrFinallyBlock(tryBody, EmptyCatchBlockID) {
def msg =
em"""|The ${hl("catch")} block does not contain a valid expression, try
|adding a case like - ${hl("case e: Exception =>")} to the block"""
}
class EmptyCatchAndFinallyBlock(tryBody: untpd.Tree)(using Context)
extends EmptyCatchOrFinallyBlock(tryBody, EmptyCatchAndFinallyBlockID) {
def msg =
em"""|A ${hl("try")} without ${hl("catch")} or ${hl("finally")} is equivalent to putting
|its body in a block; no exceptions are handled."""
}
class DeprecatedWithOperator()(using Context)
extends SyntaxMsg(DeprecatedWithOperatorID) {
def msg =
em"""${hl("with")} as a type operator has been deprecated; use ${hl("&")} instead"""
def explain =
em"""|Dotty introduces intersection types - ${hl("&")} types. These replace the
|use of the ${hl("with")} keyword. There are a few differences in
|semantics between intersection types and using ${hl("with")}."""
}
class CaseClassMissingParamList(cdef: untpd.TypeDef)(using Context)
extends SyntaxMsg(CaseClassMissingParamListID) {
def msg =
em"""|A ${hl("case class")} must have at least one parameter list"""
def explain =
em"""|${cdef.name} must have at least one parameter list, if you would rather
|have a singleton representation of ${cdef.name}, use a "${hl("case object")}".
|Or, add an explicit ${hl("()")} as a parameter list to ${cdef.name}."""
}
class AnonymousFunctionMissingParamType(param: untpd.ValDef,
tree: untpd.Function,
pt: Type)
(using Context)
extends TypeMsg(AnonymousFunctionMissingParamTypeID) {
def msg = {
val ofFun =
if param.name.is(WildcardParamName)
|| (MethodType.syntheticParamNames(tree.args.length + 1) contains param.name)
then i" of expanded function:\n$tree"
else ""
val inferred =
if (pt == WildcardType) ""
else i"\nWhat I could infer was: $pt"
i"""Missing parameter type
|
|I could not infer the type of the parameter ${param.name}$ofFun.$inferred"""
}
def explain = ""
}
class WildcardOnTypeArgumentNotAllowedOnNew()(using Context)
extends SyntaxMsg(WildcardOnTypeArgumentNotAllowedOnNewID) {
def msg = "Type argument must be fully defined"
def explain =
val code1: String =
"""
|object TyperDemo {
| class Team[A]
| val team = new Team[?]
|}
""".stripMargin
val code2: String =
"""
|object TyperDemo {
| class Team[A]
| val team = new Team[Int]
|}
""".stripMargin
em"""|Wildcard on arguments is not allowed when declaring a new type.
|
|Given the following example:
|
|$code1
|
|You must complete all the type parameters, for instance:
|
|$code2 """
}
// Type Errors ------------------------------------------------------------ //
class DuplicateBind(bind: untpd.Bind, tree: untpd.CaseDef)(using Context)
extends NamingMsg(DuplicateBindID) {
def msg = em"duplicate pattern variable: ${bind.name}"
def explain = {
val pat = tree.pat.show
val guard = tree.guard match {
case untpd.EmptyTree => ""
case guard => s"if ${guard.show}"
}
val body = tree.body match {
case Block(Nil, untpd.EmptyTree) => ""
case body => s" ${body.show}"
}
val caseDef = s"case $pat$guard => $body"
em"""|For each ${hl("case")} bound variable names have to be unique. In:
|
|$caseDef
|
|${bind.name} is not unique. Rename one of the bound variables!"""
}
}
class MissingIdent(tree: untpd.Ident, treeKind: String, val name: Name)(using Context)
extends NotFoundMsg(MissingIdentID) {
def msg = em"Not found: $treeKind$name"
def explain = {
em"""|The identifier for `$treeKind$name` is not bound, that is,
|no declaration for this identifier can be found.
|That can happen, for example, if `$name` or its declaration has either been
|misspelt or if an import is missing."""
}
}
class TypeMismatch(found: Type, expected: Type, inTree: Option[untpd.Tree], addenda: => String*)(using Context)
extends TypeMismatchMsg(found, expected)(TypeMismatchID):
// replace constrained TypeParamRefs and their typevars by their bounds where possible
// and the bounds are not f-bounds.
// The idea is that if the bounds are also not-subtypes of each other to report
// the type mismatch on the bounds instead of the original TypeParamRefs, since
// these are usually easier to analyze. We exclude F-bounds since these would
// lead to a recursive infinite expansion.
object reported extends TypeMap, IdentityCaptRefMap:
def setVariance(v: Int) = variance = v
val constraint = mapCtx.typerState.constraint
var fbounded = false
def apply(tp: Type): Type = tp match
case tp: TypeParamRef =>
constraint.entry(tp) match
case bounds: TypeBounds =>
if variance < 0 then apply(TypeComparer.fullUpperBound(tp))
else if variance > 0 then apply(TypeComparer.fullLowerBound(tp))
else tp
case NoType => tp
case instType => apply(instType)
case tp: TypeVar =>
apply(tp.stripTypeVar)
case tp: LazyRef =>
fbounded = true
tp
case _ =>
mapOver(tp)
def msg =
val found1 = reported(found)
reported.setVariance(-1)
val expected1 = reported(expected)
val (found2, expected2) =
if (found1 frozen_<:< expected1) || reported.fbounded then (found, expected)
else (found1, expected1)
val postScript = addenda.find(!_.isEmpty) match
case Some(p) => p
case None =>
if expected.isTopType || found.isBottomType
then ""
else ctx.typer.importSuggestionAddendum(ViewProto(found.widen, expected))
val (where, printCtx) = Formatting.disambiguateTypes(found2, expected2)
val whereSuffix = if (where.isEmpty) where else s"\n\n$where"
val (foundStr, expectedStr) = Formatting.typeDiff(found2, expected2)(using printCtx)
s"""|Found: $foundStr
|Required: $expectedStr""".stripMargin
+ whereSuffix + postScript
override def explain =
val treeStr = inTree.map(x => s"\nTree: ${x.show}").getOrElse("")
treeStr + "\n" + super.explain
end TypeMismatch
class NotAMember(site: Type, val name: Name, selected: String, addendum: => String = "")(using Context)
extends NotFoundMsg(NotAMemberID), ShowMatchTrace(site) {
//println(i"site = $site, decls = ${site.decls}, source = ${site.typeSymbol.sourceFile}") //DEBUG
def msg = {
import core.Flags._
val maxDist = 3 // maximal number of differences to be considered for a hint
val missing = name.show
// The symbols of all non-synthetic, non-private members of `site`
// that are of the same type/term kind as the missing member.
def candidates: Set[Symbol] =
for
bc <- site.widen.baseClasses.toSet
sym <- bc.info.decls.filter(sym =>
sym.isType == name.isTypeName
&& !sym.isConstructor
&& !sym.flagsUNSAFE.isOneOf(Synthetic | Private))
yield sym
// Calculate Levenshtein distance
def distance(s1: String, s2: String): Int =
val dist = Array.ofDim[Int](s2.length + 1, s1.length + 1)
for
j <- 0 to s2.length
i <- 0 to s1.length
do
dist(j)(i) =
if j == 0 then i
else if i == 0 then j
else if s2(j - 1) == s1(i - 1) then dist(j - 1)(i - 1)
else (dist(j - 1)(i) min dist(j)(i - 1) min dist(j - 1)(i - 1)) + 1
dist(s2.length)(s1.length)
// A list of possible candidate symbols with their Levenstein distances
// to the name of the missing member
def closest: List[(Int, Symbol)] = candidates
.toList
.map(sym => (distance(sym.name.show, missing), sym))
.filter((d, sym) => d <= maxDist && d < missing.length && d < sym.name.show.length)
.sortBy((d, sym) => (d, sym.name.show)) // sort by distance first, alphabetically second
val enumClause =
if ((name eq nme.values) || (name eq nme.valueOf)) && site.classSymbol.companionClass.isEnumClass then
val kind = if name eq nme.values then i"${nme.values} array" else i"${nme.valueOf} lookup method"
// an assumption is made here that the values and valueOf methods were not generated
// because the enum defines non-singleton cases
i"""
|Although ${site.classSymbol.companionClass} is an enum, it has non-singleton cases,
|meaning a $kind is not defined"""
else
""
def prefixEnumClause(addendum: String) =
if enumClause.nonEmpty then s".$enumClause$addendum" else addendum
val finalAddendum =
if addendum.nonEmpty then prefixEnumClause(addendum)
else closest match
case (d, sym) :: _ =>
val siteName = site match
case site: NamedType => site.name.show