package dotty.tools
package dotc
package reporting
package diagnostic
import dotc.core._
import Contexts.Context
import Decorators._
import Symbols._
import Names._
import NameOps._
import Types._
import util.SourcePosition
import config.Settings.Setting
import interfaces.Diagnostic.{ERROR, INFO, WARNING}
import dotc.parsing.Scanners.Token
import dotc.parsing.Tokens
import printing.Highlighting._
import printing.Formatting
import ErrorMessageID._
object messages {
// `MessageContainer`s to be consumed by `Reporter` ---------------------- //
class Error(
msgFn: => Message,
pos: SourcePosition
) extends MessageContainer(msgFn, pos, ERROR)
class Warning(
msgFn: => Message,
pos: SourcePosition
) extends MessageContainer(msgFn, pos, WARNING)
class Info(
msgFn: => Message,
pos: SourcePosition
) extends MessageContainer(msgFn, pos, INFO)
abstract class ConditionalWarning(
msgFn: => Message,
pos: SourcePosition
) extends Warning(msgFn, pos) {
def enablingOption(implicit ctx: Context): Setting[Boolean]
}
class FeatureWarning(
msgFn: => Message,
pos: SourcePosition
) extends ConditionalWarning(msgFn, pos) {
def enablingOption(implicit ctx: Context) = ctx.settings.feature
}
class UncheckedWarning(
msgFn: => Message,
pos: SourcePosition
) extends ConditionalWarning(msgFn, pos) {
def enablingOption(implicit ctx: Context) = ctx.settings.unchecked
}
class DeprecationWarning(
msgFn: => Message,
pos: SourcePosition
) extends ConditionalWarning(msgFn, pos) {
def enablingOption(implicit ctx: Context) = ctx.settings.deprecation
}
class MigrationWarning(
msgFn: => Message,
pos: SourcePosition
) extends ConditionalWarning(msgFn, pos) {
def enablingOption(implicit ctx: Context) = ctx.settings.migration
}
/** 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
* ```
*/
import ast.Trees._
import ast.untpd
import ast.tpd
/** Helper methods for messages */
def implicitClassRestrictionsText(implicit ctx: Context) =
hl"""|${NoColor("For a full list of restrictions on implicit classes visit")}
|${Blue("http://docs.scala-lang.org/overviews/core/implicit-classes.html")}"""
// Syntax Errors ---------------------------------------------------------- //
abstract class EmptyCatchOrFinallyBlock(tryBody: untpd.Tree, errNo: ErrorMessageID)(implicit ctx: Context)
extends Message(EmptyCatchOrFinallyBlockID) {
val explanation = {
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
hl"""|A ${"try"} expression should be followed by some mechanism to handle any exceptions
|thrown. Typically a ${"catch"} expression follows the ${"try"} and pattern matches
|on any expected exceptions. For example:
|
|$code1
|
|It is also possible to follow a ${"try"} immediately by a ${"finally"} - letting the
|exception propagate - but still allowing for some clean up in ${"finally"}:
|
|$code2
|
|It is recommended to use the ${"NonFatal"} extractor to catch all exceptions as it
|correctly handles transfer functions like ${"return"}."""
}
}
case class EmptyCatchBlock(tryBody: untpd.Tree)(implicit ctx: Context)
extends EmptyCatchOrFinallyBlock(tryBody, EmptyCatchBlockID) {
val kind = "Syntax"
val msg =
hl"""|The ${"catch"} block does not contain a valid expression, try
|adding a case like - `${"case e: Exception =>"}` to the block"""
}
case class EmptyCatchAndFinallyBlock(tryBody: untpd.Tree)(implicit ctx: Context)
extends EmptyCatchOrFinallyBlock(tryBody, EmptyCatchAndFinallyBlockID) {
val kind = "Syntax"
val msg =
hl"""|A ${"try"} without ${"catch"} or ${"finally"} is equivalent to putting
|its body in a block; no exceptions are handled."""
}
case class DeprecatedWithOperator()(implicit ctx: Context)
extends Message(DeprecatedWithOperatorID) {
val kind = "Syntax"
val msg =
hl"""${"with"} as a type operator has been deprecated; use `&' instead"""
val explanation =
hl"""|Dotty introduces intersection types - `&' types. These replace the
|use of the ${"with"} keyword. There are a few differences in
|semantics between intersection types and using `${"with"}'."""
}
case class CaseClassMissingParamList(cdef: untpd.TypeDef)(implicit ctx: Context)
extends Message(CaseClassMissingParamListID) {
val kind = "Syntax"
val msg =
hl"""|A ${"case class"} must have at least one parameter list"""
val explanation =
hl"""|${cdef.name} must have at least one parameter list, if you would rather
|have a singleton representation of ${cdef.name}, use a "${"case object"}".
|Or, add an explicit `()' as a parameter list to ${cdef.name}."""
}
// Type Errors ------------------------------------------------------------ //
case class DuplicateBind(bind: untpd.Bind, tree: untpd.CaseDef)(implicit ctx: Context)
extends Message(DuplicateBindID) {
val kind = "Naming"
val msg = em"duplicate pattern variable: `${bind.name}`"
val explanation = {
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"
hl"""|For each ${"case"} bound variable names have to be unique. In:
|
|$caseDef
|
|`${bind.name}` is not unique. Rename one of the bound variables!"""
}
}
case class MissingIdent(tree: untpd.Ident, treeKind: String, name: String)(implicit ctx: Context)
extends Message(MissingIdentID) {
val kind = "Unbound Identifier"
val msg = em"not found: $treeKind$name"
val explanation = {
hl"""|The identifier for `$treeKind$name` is not bound, that is,
|no declaration for this identifier can be found.
|That can happen for instance if $name or its declaration has either been
|misspelt, or if you're forgetting an import"""
}
}
case class TypeMismatch(found: Type, expected: Type, whyNoMatch: String = "", implicitFailure: String = "")(implicit ctx: Context)
extends Message(TypeMismatchID) {
val kind = "Type Mismatch"
val msg = {
val (where, printCtx) = Formatting.disambiguateTypes(found, expected)
val (fnd, exp) = Formatting.typeDiff(found, expected)(printCtx)
s"""|found: $fnd
|required: $exp
|
|$where""".stripMargin + whyNoMatch + implicitFailure
}
val explanation = ""
}
case class NotAMember(site: Type, name: Name, selected: String)(implicit ctx: Context)
extends Message(NotAMemberID) {
val kind = "Member Not Found"
//println(i"site = $site, decls = ${site.decls}, source = ${site.widen.typeSymbol.sourceFile}") //DEBUG
val msg = {
import core.Flags._
val maxDist = 3
val decls = site.decls.flatMap { sym =>
if (sym.is(Synthetic | PrivateOrLocal) || sym.isConstructor) Nil
else List((sym.name.show, sym))
}
// Calculate Levenshtein distance
def distance(n1: Iterable[_], n2: Iterable[_]) =
n1.foldLeft(List.range(0, n2.size)) { (prev, x) =>
(prev zip prev.tail zip n2).scanLeft(prev.head + 1) {
case (h, ((d, v), y)) => math.min(
math.min(h + 1, v + 1),
if (x == y) d else d + 1
)
}
}.last
// Count number of wrong characters
def incorrectChars(x: (String, Int, Symbol)): (String, Symbol, Int) = {
val (currName, _, sym) = x
val matching = name.show.zip(currName).foldLeft(0) {
case (acc, (x,y)) => if (x != y) acc + 1 else acc
}
(currName, sym, matching)
}
// Get closest match in `site`
val closest =
decls
.map { case (n, sym) => (n, distance(n, name.show), sym) }
.collect { case (n, dist, sym) if dist <= maxDist => (n, dist, sym) }
.groupBy(_._2).toList
.sortBy(_._1)
.headOption.map(_._2).getOrElse(Nil)
.map(incorrectChars).toList
.sortBy(_._3)
.take(1).map { case (n, sym, _) => (n, sym) }
val siteName = site match {
case site: NamedType => site.name.show
case site => i"$site"
}
val closeMember = closest match {
case (n, sym) :: Nil => hl""" - did you mean `${s"$siteName.$n"}`?"""
case Nil => ""
case _ => assert(
false,
"Could not single out one distinct member to match on input with"
)
}
ex"$selected `$name` is not a member of $site$closeMember"
}
val explanation = ""
}
case class EarlyDefinitionsNotSupported()(implicit ctx: Context)
extends Message(EarlyDefinitionsNotSupportedID) {
val kind = "Syntax"
val msg = "early definitions are not supported; use trait parameters instead"
val explanation = {
val code1 =
"""|trait Logging {
| val f: File
| f.open()
| onExit(f.close())
| def log(msg: String) = f.write(msg)
|}
|
|class B extends Logging {
| val f = new File("log.data") // triggers a NullPointerException
|}
|
|// early definition gets around the NullPointerException
|class C extends {
| val f = new File("log.data")
|} with Logging""".stripMargin
val code2 =
"""|trait Logging(f: File) {
| f.open()
| onExit(f.close())
| def log(msg: String) = f.write(msg)
|}
|
|class C extends Logging(new File("log.data"))""".stripMargin
hl"""|Earlier versions of Scala did not support trait parameters and "early
|definitions" (also known as "early initializers") were used as an alternative.
|
|Example of old syntax:
|
|$code1
|
|The above code can now be written as:
|
|$code2
|"""
}
}
case class TopLevelImplicitClass(cdef: untpd.TypeDef)(implicit ctx: Context)
extends Message(TopLevelImplicitClassID) {
val kind = "Syntax"
val msg = hl"""An ${"implicit class"} may not be top-level"""
val explanation = {
val TypeDef(name, impl @ Template(constr0, parents, self, _)) = cdef
val exampleArgs =
constr0.vparamss(0).map(_.withMods(untpd.Modifiers()).show).mkString(", ")
def defHasBody[T] = impl.body.exists(!_.isEmpty)
val exampleBody = if (defHasBody) "{\n ...\n }" else ""
hl"""|There may not be any method, member or object in scope with the same name as
|the implicit class and a case class automatically gets a companion object with
|the same name created by the compiler which would cause a naming conflict if it
|were allowed.
|
|""" + implicitClassRestrictionsText + hl"""|
|
|To resolve the conflict declare ${cdef.name} inside of an ${"object"} then import the class
|from the object at the use site if needed, for example:
|
|object Implicits {
| implicit class ${cdef.name}($exampleArgs)$exampleBody
|}
|
|// At the use site:
|import Implicits.${cdef.name}"""
}
}
case class ImplicitCaseClass(cdef: untpd.TypeDef)(implicit ctx: Context)
extends Message(ImplicitCaseClassID) {
val kind = "Syntax"
val msg = hl"""A ${"case class"} may not be defined as ${"implicit"}"""
val explanation =
hl"""|implicit classes may not be case classes. Instead use a plain class:
|
|implicit class ${cdef.name}...
|
|""" + implicitClassRestrictionsText
}
case class ObjectMayNotHaveSelfType(mdef: untpd.ModuleDef)(implicit ctx: Context)
extends Message(ObjectMayNotHaveSelfTypeID) {
val kind = "Syntax"
val msg = hl"""${"object"}s must not have a self ${"type"}"""
val explanation = {
val untpd.ModuleDef(name, tmpl) = mdef
val ValDef(_, selfTpt, _) = tmpl.self
hl"""|${"object"}s must not have a self ${"type"}:
|
|Consider these alternative solutions:
| - Create a trait or a class instead of an object
| - Let the object extend a trait containing the self type:
|
| object $name extends ${selfTpt.show}"""
}
}
case class TupleTooLong(ts: List[untpd.Tree])(implicit ctx: Context)
extends Message(TupleTooLongID) {
import Definitions.MaxTupleArity
val kind = "Syntax"
val msg = hl"""A ${"tuple"} cannot have more than ${MaxTupleArity} members"""
val explanation = {
val members = ts.map(_.showSummary).grouped(MaxTupleArity)
val nestedRepresentation = members.map(_.mkString(", ")).mkString(")(")
hl"""|This restriction will be removed in the future.
|Currently it is possible to use nested tuples when more than $MaxTupleArity are needed, for example:
|
|((${nestedRepresentation}))"""
}
}
case class RepeatedModifier(modifier: String)(implicit ctx:Context)
extends Message(RepeatedModifierID) {
val kind = "Syntax"
val msg = hl"""repeated modifier $modifier"""
val explanation = {
val code1 = hl"""private private val Origin = Point(0, 0)"""
val code2 = hl"""private final val Origin = Point(0, 0)"""
hl"""This happens when you accidentally specify the same modifier twice.
|
|Example:
|
|$code1
|
|instead of
|
|$code2
|
|"""
}
}
case class InterpolatedStringError()(implicit ctx:Context)
extends Message(InterpolatedStringErrorID) {
val kind = "Syntax"
val msg = "error in interpolated string: identifier or block expected"
val explanation = {
val code1 = "s\"$new Point(0, 0)\""
val code2 = "s\"${new Point(0, 0)}\""
hl"""|This usually happens when you forget to place your expressions inside curly braces.
|
|$code1
|
|should be written as
|
|$code2
|"""
}
}
case class UnboundPlaceholderParameter()(implicit ctx:Context)
extends Message(UnboundPlaceholderParameterID) {
val kind = "Syntax"
val msg = "unbound placeholder parameter; incorrect use of `_`"
val explanation =
hl"""|The `_` placeholder syntax was used where it could not be bound.
|Consider explicitly writing the variable binding.
|
|This can be done by replacing `_` with a variable (eg. `x`)
|and adding ${"x =>"} where applicable.
|
|Example before:
|
|${"{ _ }"}
|
|Example after:
|
|${"x => { x }"}
|
|Another common occurrence for this error is defining a val with `_`:
|
|${"val a = _"}
|
|But this val definition isn't very useful, it can never be assigned
|another value. And thus will always remain uninitialized.
|Consider replacing the ${"val"} with ${"var"}:
|
|${"var a = _"}
|
|Note that this use of `_` is not placeholder syntax,
|but an uninitialized var definition"""
}
case class IllegalStartSimpleExpr(illegalToken: String)(implicit ctx: Context)
extends Message(IllegalStartSimpleExprID) {
val kind = "Syntax"
val msg = "illegal start of simple expression"
val explanation = {
hl"""|An expression yields a value. In the case of the simple expression, this error
|commonly occurs when there's a missing parenthesis or brace. The reason being
|that a simple expression is one of the following:
|
|- Block
|- Expression in parenthesis
|- Identifier
|- Object creation
|- Literal
|
|which cannot start with ${Red(illegalToken)}."""
}
}
case class MissingReturnType()(implicit ctx:Context)
extends Message(MissingReturnTypeID) {
val kind = "Syntax"
val msg = "missing return type"
val explanation =
hl"""|An abstract declaration must have a return type. For example:
|
|trait Shape {
| def area: Double // abstract declaration returning a ${"Double"}
|}"""
}
case class YieldOrDoExpectedInForComprehension()(implicit ctx: Context)
extends Message(YieldOrDoExpectedInForComprehensionID) {
val kind = "Syntax"
val msg = hl"${"yield"} or ${"do"} expected"
val explanation =
hl"""|When the enumerators in a for comprehension are not placed in parentheses or
|braces, a ${"do"} or ${"yield"} statement is required after the enumerators
|section of the comprehension.
|
|You can save some keystrokes by omitting the parentheses and writing
|
|${"val numbers = for i <- 1 to 3 yield i"}
|
| instead of
|
|${"val numbers = for (i <- 1 to 3) yield i"}
|
|but the ${"yield"} keyword is still required.
|
|For comprehensions that simply perform a side effect without yielding anything
|can also be written without parentheses but a ${"do"} keyword has to be
|included. For example,
|
|${"for (i <- 1 to 3) println(i)"}
|
|can be written as
|
|${"for i <- 1 to 3 do println(i) // notice the 'do' keyword"}
|
|"""
}
case class ProperDefinitionNotFound()(implicit ctx: Context)
extends Message(ProperDefinitionNotFoundID) {
val kind = "Definition Not Found"
val msg = hl"""Proper definition was not found in ${"@usecase"}"""
val explanation = {
val noUsecase =
"def map[B, That](f: A => B)(implicit bf: CanBuildFrom[List[A], B, That]): That"
val usecase =
"""|/** Map from List[A] => List[B]
| *
| * @usecase def map[B](f: A => B): List[B]
| */
|def map[B, That](f: A => B)(implicit bf: CanBuildFrom[List[A], B, That]): That
|""".stripMargin
hl"""|Usecases are only supported for ${"def"}s. They exist because with Scala's
|advanced type-system, we sometimes end up with seemingly scary signatures.
|The usage of these methods, however, needs not be - for instance the `map`
|function
|
|${"List(1, 2, 3).map(2 * _) // res: List(2, 4, 6)"}
|
|is easy to understand and use - but has a rather bulky signature:
|
|$noUsecase
|
|to mitigate this and ease the usage of such functions we have the ${"@usecase"}
|annotation for docstrings. Which can be used like this:
|
|$usecase
|
|When creating the docs, the signature of the method is substituted by the
|usecase and the compiler makes sure that it is valid. Because of this, you're
|only allowed to use ${"def"}s when defining usecases."""
}
}
case class ByNameParameterNotSupported()(implicit ctx: Context)
extends Message(ByNameParameterNotSupportedID) {
val kind = "Syntax"
val msg = "By-name parameter type not allowed here."
val explanation =
hl"""|By-name parameters act like functions that are only evaluated when referenced,
|allowing for lazy evaluation of a parameter.
|
|An example of using a by-name parameter would look like:
|${"def func(f: => Boolean) = f // 'f' is evaluated when referenced within the function"}
|
|An example of the syntax of passing an actual function as a parameter:
|${"def func(f: (Boolean => Boolean)) = f(true)"}
|
|or:
|
|${"def func(f: Boolean => Boolean) = f(true)"}
|
|And the usage could be as such:
|${"func(bool => // do something...)"}
|"""
}
case class WrongNumberOfTypeArgs(fntpe: Type, expectedArgs: List[TypeParamInfo], actual: List[untpd.Tree])(implicit ctx: Context)
extends Message(WrongNumberOfTypeArgsID) {
val kind = "Syntax"
private val expectedCount = expectedArgs.length
private val actualCount = actual.length
private val msgPrefix = if (actualCount > expectedCount) "Too many" else "Not enough"
//TODO add def simpleParamName to TypeParamInfo
private val expectedArgString = fntpe
.widen.typeParams
.map(_.paramName.unexpandedName.show)
.mkString("[", ", ", "]")
private val actualArgString = actual.map(_.show).mkString("[", ", ", "]")
private val prettyName = fntpe.termSymbol match {
case NoSymbol => fntpe.show
case symbol => symbol.showFullName
}
val msg =
hl"""|${NoColor(msgPrefix)} type arguments for $prettyName$expectedArgString
|expected: $expectedArgString
|actual: $actualArgString""".stripMargin
val explanation = {
val tooManyTypeParams =
"""|val tuple2: (Int, String) = (1, "one")
|val list: List[(Int, String)] = List(tuple2)""".stripMargin
if (actualCount > expectedCount)
hl"""|You have supplied too many type parameters
|
|For example List takes a single type parameter (List[A])
|If you need to hold more types in a list then you need to combine them
|into another data type that can contain the number of types you need,
|In this example one solution would be to use a Tuple:
|
|${tooManyTypeParams}"""
else
hl"""|You have not supplied enough type parameters
|If you specify one type parameter then you need to specify every type parameter."""
}
}
case class IllegalVariableInPatternAlternative()(implicit ctx: Context)
extends Message(IllegalVariableInPatternAlternativeID) {
val kind = "Syntax"
val msg = "Variables are not allowed in alternative patterns"
val explanation = {
val varInAlternative =
"""|def g(pair: (Int,Int)): Int = pair match {
| case (1, n) | (n, 1) => n
| case _ => 0
|}""".stripMargin
val fixedVarInAlternative =
"""|def g(pair: (Int,Int)): Int = pair match {
| case (1, n) => n
| case (n, 1) => n
| case _ => 0
|}""".stripMargin
hl"""|Variables are not allowed within alternate pattern matches. You can workaround
|this issue by adding additional cases for each alternative. For example, the
|illegal function:
|
|$varInAlternative
|could be implemented by moving each alternative into a separate case:
|
|$fixedVarInAlternative"""
}
}
case class TypeParamsTypeExpected(mods: untpd.Modifiers, identifier: TermName)(implicit ctx: Context)
extends Message(TypeParamsTypeExpectedID) {
val kind = "Syntax"
val msg = hl"""Expected ${"type"} keyword for type parameter $identifier"""
val explanation =
hl"""|This happens when you add modifiers like ${"private"} or ${"protected"}
|to your type parameter definition without adding the ${"type"} keyword.
|
|Add ${"type"} to your code, e.g.:
|${s"trait A[${mods.flags} type $identifier]"}
|"""
}
case class IdentifierExpected(identifier: String)(implicit ctx: Context)
extends Message(IdentifierExpectedID) {
val kind = "Syntax"
val msg = "identifier expected"
val explanation = {
val wrongIdentifier = s"def foo: $identifier = {...}"
val validIdentifier = s"def foo = {...}"
hl"""|An identifier expected, but `$identifier` found. This could be because
|`$identifier` is not a valid identifier. As a workaround, the compiler could
|infer the type for you. For example, instead of:
|
|$wrongIdentifier
|
|Write your code like:
|
|$validIdentifier
|
|"""
}
}
case class AuxConstructorNeedsNonImplicitParameter()(implicit ctx:Context)
extends Message(AuxConstructorNeedsNonImplicitParameterID) {
val kind = "Syntax"
val msg = "auxiliary constructor needs non-implicit parameter list"
val explanation =
hl"""|Only the primary constructor is allowed an ${"implicit"} parameter list;
|auxiliary constructors need non-implicit parameter lists. When a primary
|constructor has an implicit argslist, auxiliary constructors that call the
|primary constructor must specify the implicit value.
|
|To resolve this issue check for:
| - forgotten parenthesis on ${"this"} (${"def this() = { ... }"})
| - auxiliary constructors specify the implicit value
|"""
}
case class IncorrectRepeatedParameterSyntax()(implicit ctx: Context)
extends Message(IncorrectRepeatedParameterSyntaxID) {
val kind = "Syntax"
val msg = "'*' expected"
val explanation =
hl"""|Expected * in '_*' operator.
|
|The '_*' operator can be used to supply a sequence-based argument
|to a method with a variable-length or repeated parameter. It is used
|to expand the sequence to a variable number of arguments, such that:
|func(args: _*) would expand to func(arg1, arg2 ... argN).
|
|Below is an example of how a method with a variable-length
|parameter can be declared and used.
|
|Squares the arguments of a variable-length parameter:
|${"def square(args: Int*) = args.map(a => a * a)"}
|
|Usage:
|${"square(1, 2, 3) // res0: List[Int] = List(1, 4, 9)"}
|
|Secondary Usage with '_*':
|${"val ints = List(2, 3, 4) // ints: List[Int] = List(2, 3, 4)"}
|${"square(ints: _*) // res1: List[Int] = List(4, 9, 16)"}
|""".stripMargin
}
case class IllegalLiteral()(implicit ctx: Context)
extends Message(IllegalLiteralID) {
val kind = "Syntax"
val msg = "illegal literal"
val explanation =
hl"""|Available literals can be divided into several groups:
| - Integer literals: 0, 21, 0xFFFFFFFF, -42L
| - Floating Point Literals: 0.0, 1e30f, 3.14159f, 1.0e-100, .1
| - Boolean Literals: true, false
| - Character Literals: 'a', '\u0041', '\n'
| - String Literals: "Hello, World!"
| - null
|"""
}
case class PatternMatchExhaustivity(uncovered: String)(implicit ctx: Context)
extends Message(PatternMatchExhaustivityID) {
val kind = "Pattern Match Exhaustivity"
val msg =
hl"""|match may not be exhaustive.
|
|It would fail on: $uncovered"""
val explanation = ""
}
case class MatchCaseUnreachable()(implicit ctx: Context)
extends Message(MatchCaseUnreachableID) {
val kind = s"""Match ${hl"case"} Unreachable"""
val msg = "unreachable code"
val explanation = ""
}
case class SeqWildcardPatternPos()(implicit ctx: Context)
extends Message(SeqWildcardPatternPosID) {
val kind = "Syntax"
val msg = "`_*' can be used only for last argument"
val explanation = {
val code =
"""def sumOfTheFirstTwo(list: List[Int]): Int = list match {
| case List(first, second, x:_*) => first + second
| case _ => 0
|}"""
hl"""|Sequence wildcard pattern is expected at the end of an argument list.
|This pattern matches any remaining elements in a sequence.
|Consider the following example:
|
|$code
|
|Calling:
|
|${"sumOfTheFirstTwo(List(1, 2, 10))"}
|
|would give 3 as a result"""
}
}
case class IllegalStartOfSimplePattern()(implicit ctx: Context)
extends Message(IllegalStartOfSimplePatternID) {
val kind = "Syntax"
val msg = "illegal start of simple pattern"
val explanation = {
val sipCode =
"""def f(x: Int, y: Int) = x match {
| case `y` => ...
|}
"""
val constructorPatternsCode =
"""case class Person(name: String, age: Int)
|
|def test(p: Person) = p match {
| case Person(name, age) => ...
|}
"""
val tupplePatternsCode =
"""def swap(tuple: (String, Int)): (Int, String) = tuple match {
| case (text, number) => (number, text)
|}
"""
val patternSequencesCode =
"""def getSecondValue(list: List[Int]): Int = list match {
| case List(_, second, x:_*) => second
| case _ => 0
|}"""
hl"""|Simple patterns can be divided into several groups:
|- Variable Patterns: ${"case x => ..."}.
| It matches any value, and binds the variable name to that value.
| A special case is the wild-card pattern _ which is treated as if it was a fresh
| variable on each occurrence.
|
|- Typed Patterns: ${"case x: Int => ..."} or ${"case _: Int => ..."}.
| This pattern matches any value matched by the specified type; it binds the variable
| name to that value.
|
|- Literal Patterns: ${"case 123 => ..."} or ${"case 'A' => ..."}.
| This type of pattern matches any value that is equal to the specified literal.
|
|- Stable Identifier Patterns:
|
| $sipCode
|
| the match succeeds only if the x argument and the y argument of f are equal.
|
|- Constructor Patterns:
|
| $constructorPatternsCode
|
| The pattern binds all object's fields to the variable names (name and age, in this
| case).
|
|- Tuple Patterns:
|
| $tupplePatternsCode
|
| Calling:
|
| ${"""swap(("Luftballons", 99)"""}
|
| would give ${"""(99, "Luftballons")"""} as a result.
|
|- Pattern Sequences:
|
| $patternSequencesCode
|
| Calling:
|
| ${"getSecondValue(List(1, 10, 2))"}
|
| would give 10 as a result.
| This pattern is possible because a companion object for the List class has a method
| with the following signature:
|
| ${"def unapplySeq[A](x: List[A]): Some[List[A]]"}
|"""
}
}
case class PkgDuplicateSymbol(existing: Symbol)(implicit ctx: Context)
extends Message(PkgDuplicateSymbolID) {
val kind = "Duplicate Symbol"
val msg = hl"trying to define package with same name as `$existing`"
val explanation = ""
}
case class ExistentialTypesNoLongerSupported()(implicit ctx: Context)
extends Message(ExistentialTypesNoLongerSupportedID) {
val kind = "Syntax"
val msg =
hl"""|Existential types are no longer supported -
|use a wildcard or dependent type instead"""
val explanation =
hl"""|The use of existential types is no longer supported.
|
|You should use a wildcard or dependent type instead.
|
|For example:
|
|Instead of using ${"forSome"} to specify a type variable
|
|${"List[T forSome { type T }]"}
|
|Try using a wildcard type variable
|
|${"List[_]"}
|"""
}
case class UnboundWildcardType()(implicit ctx: Context)
extends Message(UnboundWildcardTypeID) {
val kind = "Syntax"
val msg = "Unbound wildcard type"
val explanation =
hl"""|The wildcard type syntax (`_`) was used where it could not be bound.
|Replace `_` with a non-wildcard type. If the type doesn't matter,
|try replacing `_` with ${"Any"}.
|
|Examples:
|
|- Parameter lists
|
| Instead of:
| ${"def foo(x: _) = ..."}
|
| Use ${"Any"} if the type doesn't matter:
| ${"def foo(x: Any) = ..."}
|
|- Type arguments
|
| Instead of:
| ${"val foo = List[_](1, 2)"}
|
| Use:
| ${"val foo = List[Int](1, 2)"}
|
|- Type bounds
|
| Instead of:
| ${"def foo[T <: _](x: T) = ..."}
|
| Remove the bounds if the type doesn't matter:
| ${"def foo[T](x: T) = ..."}
|
|- ${"val"} and ${"def"} types
|
| Instead of:
| ${"val foo: _ = 3"}
|
| Use:
| ${"val foo: Int = 3"}
|"""
}
case class DanglingThisInPath()(implicit ctx: Context) extends Message(DanglingThisInPathID) {
val kind = "Syntax"
val msg = hl"""Expected an additional member selection after the keyword ${"this"}"""
val contextCode =
""" trait Outer {
| val member: Int
| type Member
| trait Inner {
| ...
| }
| }"""
val importCode =
""" import Outer.this.member
| // ^^^^^^^"""
val typeCode =
""" type T = Outer.this.Member
| // ^^^^^^^"""
val explanation =
hl"""|Paths of imports and type selections must not end with the keyword ${"this"}.
|
|Maybe you forgot to select a member of ${"this"}? As an example, in the
|following context:
|${contextCode}
|
|- this is a valid import expression using a path
|${importCode}
|
|- this is a valid type using a path
|${typeCode}
|"""
}
case class OverridesNothing(member: Symbol)(implicit ctx: Context)
extends Message(OverridesNothingID) {
val kind = "Reference"
val msg = hl"""${member} overrides nothing"""
val explanation =
hl"""|There must be a field or method with the name `${member.name}` in a super
|class of `${member.owner}` to override it. Did you misspell it?
|Are you extending the right classes?
|"""
}
case class OverridesNothingButNameExists(member: Symbol, existing: List[Denotations.SingleDenotation])(implicit ctx: Context)
extends Message(OverridesNothingButNameExistsID) {
val kind = "Reference"
val msg = hl"""${member} has a different signature than the overridden declaration"""
val existingDecl = existing.map(_.showDcl).mkString(" \n")
val explanation =
hl"""|There must be a non-final field or method with the name `${member.name}` and the
|same parameter list in a super class of `${member.owner}` to override it.
|
| ${member.showDcl}
|
|The super classes of `${member.owner}` contain the following members
|named `${member.name}`:
| ${existingDecl}
|"""
}
case class ForwardReferenceExtendsOverDefinition(value: Symbol, definition: Symbol)(implicit ctx: Context)
extends Message(ForwardReferenceExtendsOverDefinitionID) {
val kind = "Reference"
val msg = hl"`${definition.name}` is a forward reference extending over the definition of `${value.name}`"
val explanation =
hl"""|`${definition.name}` is used before you define it, and the definition of `${value.name}`
|appears between that use and the definition of `${definition.name}`.
|
|Forward references are allowed only, if there are no value definitions between
|the reference and the referred method definition.
|
|Define `${definition.name}` before it is used,
|or move the definition of `${value.name}` so it does not appear between
|the declaration of `${definition.name}` and its use,
|or define `${value.name}` as lazy.
|""".stripMargin
}
case class ExpectedTokenButFound(expected: Token, found: Token, foundName: TermName)(implicit ctx: Context)
extends Message(ExpectedTokenButFoundID) {
val kind = "Syntax"
private val expectedText =
if (Tokens.isIdentifier(expected)) "an identifier"
else Tokens.showToken(expected)
private val foundText =
if (foundName != null) hl"`${foundName.show}`"
else Tokens.showToken(found)
val msg = hl"""${expectedText} expected, but ${foundText} found"""
private val ifKeyword =
if (Tokens.isIdentifier(expected) && Tokens.isKeyword(found))
s"""
|If you necessarily want to use $foundText as identifier, you may put it in backticks.""".stripMargin
else
""
val explanation =
s"""|The text ${foundText} may not occur at that position, the compiler expected ${expectedText}.$ifKeyword
|""".stripMargin
}
case class MixedLeftAndRightAssociativeOps(op1: Name, op2: Name, op2LeftAssoc: Boolean)(implicit ctx: Context)
extends Message(MixedLeftAndRightAssociativeOpsID) {
val kind = "Syntax"
val op1Asso = if (op2LeftAssoc) "which is right-associative" else "which is left-associative"
val op2Asso = if (op2LeftAssoc) "which is left-associative" else "which is right-associative"
val msg = s"`${op1}` (${op1Asso}) and `${op2}` ($op2Asso) have same precedence and may not be mixed"
val explanation =
s"""|The operators ${op1} and ${op2} are used as infix operators in the same expression,
|but they bind to different sides:
|${op1} is applied to the operand to its ${if (op2LeftAssoc) "right" else "left"}
|${op2} is applied to the operand to its ${if (op2LeftAssoc) "left" else "right"}
|As both have the same precedence the compiler can't decide which to apply first.
|
|You may use parenthesis to make the application order explicit,
|or use method application syntax `operand1.${op1}(operand2)`.
|
|Operators ending in a colon `:` are right-associative. All other operators are left-associative.
|
|Infix operator precedence is determined by the operator's first character. Characters are listed
|below in increasing order of precedence, with characters on the same line having the same precedence.
| (all letters)
| |
| ^
| &
| = !
| < >
| :
| + -
| * / %
| (all other special characters)
|Operators starting with a letter have lowest precedence, followed by operators starting with `|`, etc.
|""".stripMargin
}
}