Fix #4368: Avoid stackoverflows for some cyclic definitions #4385
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,158 @@ | ||
| package dotty.tools | ||
| package dotc | ||
| package core | ||
|
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| import util.common._ | ||
| import Types._ | ||
| import Symbols._ | ||
| import Flags._ | ||
| import Names._ | ||
| import Contexts._ | ||
| import SymDenotations._ | ||
| import Denotations._ | ||
| import Decorators._ | ||
| import reporting.diagnostic.Message | ||
| import reporting.diagnostic.messages._ | ||
| import ast.untpd | ||
| import config.Printers.cyclicErrors | ||
|
|
||
| class TypeError(msg: String) extends Exception(msg) { | ||
| def this() = this("") | ||
| def toMessage(implicit ctx: Context): Message = getMessage | ||
| } | ||
|
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| class MalformedType(pre: Type, denot: Denotation, absMembers: Set[Name]) extends TypeError { | ||
| override def toMessage(implicit ctx: Context): Message = | ||
| i"malformed type: $pre is not a legal prefix for $denot because it contains abstract type member${if (absMembers.size == 1) "" else "s"} ${absMembers.mkString(", ")}" | ||
| } | ||
|
|
||
| class MissingType(pre: Type, name: Name) extends TypeError { | ||
| private def otherReason(pre: Type)(implicit ctx: Context): String = pre match { | ||
| case pre: ThisType if pre.cls.givenSelfType.exists => | ||
| i"\nor the self type of $pre might not contain all transitive dependencies" | ||
| case _ => "" | ||
| } | ||
|
|
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| override def toMessage(implicit ctx: Context): Message = { | ||
| if (ctx.debug) printStackTrace() | ||
| i"""cannot resolve reference to type $pre.$name | ||
| |the classfile defining the type might be missing from the classpath${otherReason(pre)}""" | ||
| } | ||
| } | ||
|
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| class RecursionOverflow(val op: String, details: => String, previous: Throwable, val weight: Int) extends TypeError { | ||
|
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| def explanation = s"$op $details" | ||
|
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| private def recursions: List[RecursionOverflow] = { | ||
| val nested = previous match { | ||
| case previous: RecursionOverflow => previous.recursions | ||
| case _ => Nil | ||
| } | ||
| this :: nested | ||
| } | ||
|
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| def opsString(rs: List[RecursionOverflow])(implicit ctx: Context): String = { | ||
| val maxShown = 20 | ||
| if (rs.lengthCompare(maxShown) > 0) | ||
| i"""${opsString(rs.take(maxShown / 2))} | ||
| | ... | ||
| |${opsString(rs.takeRight(maxShown / 2))}""" | ||
| else | ||
| (rs.map(_.explanation): List[String]).mkString("\n ", "\n| ", "") | ||
| } | ||
|
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| override def toMessage(implicit ctx: Context): Message = { | ||
| val mostCommon = recursions.groupBy(_.op).toList.maxBy(_._2.map(_.weight).sum)._2.reverse | ||
| s"""Recursion limit exceeded. | ||
| |Maybe there is an illegal cyclic reference? | ||
| |If that's not the case, you could also try to increase the stacksize using the -Xss JVM option. | ||
| |A recurring operation is (inner to outer): | ||
| |${opsString(mostCommon)}""".stripMargin | ||
| } | ||
|
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| override def fillInStackTrace(): Throwable = this | ||
| override def getStackTrace() = previous.getStackTrace() | ||
| } | ||
|
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| /** Post-process exceptions that might result from StackOverflow to add | ||
| * tracing information while unwalking the stack. | ||
| */ | ||
| // Beware: Since this object is only used when handling a StackOverflow, this code | ||
| // cannot consume significant amounts of stack. | ||
| object handleRecursive { | ||
| def apply(op: String, details: => String, exc: Throwable, weight: Int = 1)(implicit ctx: Context): Nothing = { | ||
| if (ctx.settings.YnoDecodeStacktraces.value) { | ||
| throw exc | ||
| } else { | ||
| exc match { | ||
| case _: RecursionOverflow => | ||
| throw new RecursionOverflow(op, details, exc, weight) | ||
| case _ => | ||
| var e = exc | ||
| while (e != null && !e.isInstanceOf[StackOverflowError]) e = e.getCause | ||
| if (e != null) throw new RecursionOverflow(op, details, e, weight) | ||
| else throw exc | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
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| class CyclicReference private (val denot: SymDenotation) extends TypeError { | ||
|
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| override def toMessage(implicit ctx: Context) = { | ||
|
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| def errorMsg(cx: Context): Message = | ||
| if (cx.mode is Mode.InferringReturnType) { | ||
| cx.tree match { | ||
| case tree: untpd.DefDef if !tree.tpt.typeOpt.exists => | ||
| OverloadedOrRecursiveMethodNeedsResultType(tree.name) | ||
| case tree: untpd.ValDef if !tree.tpt.typeOpt.exists => | ||
| RecursiveValueNeedsResultType(tree.name) | ||
| case _ => | ||
| errorMsg(cx.outer) | ||
| } | ||
| } | ||
| else CyclicReferenceInvolving(denot) | ||
|
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| val cycleSym = denot.symbol | ||
| if (cycleSym.is(Implicit, butNot = Method) && cycleSym.owner.isTerm) | ||
| CyclicReferenceInvolvingImplicit(cycleSym) | ||
| else | ||
| errorMsg(ctx) | ||
| } | ||
| } | ||
|
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| object CyclicReference { | ||
| def apply(denot: SymDenotation)(implicit ctx: Context): CyclicReference = { | ||
| val ex = new CyclicReference(denot) | ||
| if (!(ctx.mode is Mode.CheckCyclic)) { | ||
| cyclicErrors.println(ex.getMessage) | ||
| for (elem <- ex.getStackTrace take 200) | ||
| cyclicErrors.println(elem.toString) | ||
| } | ||
| ex | ||
| } | ||
| } | ||
|
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| class MergeError(val sym1: Symbol, val sym2: Symbol, val tp1: Type, val tp2: Type, prefix: Type) extends TypeError { | ||
|
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| private def showSymbol(sym: Symbol)(implicit ctx: Context): String = | ||
| if (sym.exists) sym.showLocated else "[unknown]" | ||
|
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| private def showType(tp: Type)(implicit ctx: Context) = tp match { | ||
| case ClassInfo(_, cls, _, _, _) => cls.showLocated | ||
| case _ => tp.show | ||
|
There was a problem hiding this comment. Does this refactoring intentionally drop the case for type bounds here (search and compare with the removed |
||
| } | ||
|
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| protected def addendum(implicit ctx: Context) = | ||
| if (prefix `eq` NoPrefix) "" else i"\nas members of type $prefix" | ||
|
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| override def toMessage(implicit ctx: Context): Message = { | ||
| if (ctx.debug) printStackTrace() | ||
| i"""cannot merge | ||
| | ${showSymbol(sym1)} of type ${showType(tp1)} and | ||
| | ${showSymbol(sym2)} of type ${showType(tp2)}$addendum | ||
| """ | ||
| } | ||
| } | ||
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Comment is misleading. How I understand it: "if you pass the flag, you won't see original stack traces". I guess it is the opposite
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Oh right, fixing it