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Avoid creating cyclic types when reporting errors in selectionType #12223

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Merged
merged 2 commits into from
May 3, 2021
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Avoid creating cyclic types when reporting errors in selectionType #12223

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8daf2b7
Avoid creating cyclic types when reporting errors in selectionType
odersky Apr 26, 2021
c62db94
Avoid creating a variable in the first place
odersky Apr 26, 2021
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6 changes: 3 additions & 3 deletions compiler/src/dotty/tools/dotc/reporting/Message.scala
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
package dotty.tools
package dotc
package reporting

import scala.annotation.threadUnsafe
import util.SourcePosition

object Message {
Expand Down Expand Up @@ -85,10 +85,10 @@ abstract class Message(val errorId: ErrorMessageID) { self =>
def rawMessage = message

/** The message to report. <nonsensical> tags are filtered out */
lazy val message: String = dropNonSensical(msg + msgSuffix)
@threadUnsafe lazy val message: String = dropNonSensical(msg + msgSuffix)

/** The explanation to report. <nonsensical> tags are filtered out */
lazy val explanation: String = dropNonSensical(explain)
@threadUnsafe lazy val explanation: String = dropNonSensical(explain)

/** A message is non-sensical if it contains references to <nonsensical>
* tags. Such tags are inserted by the error diagnostic framework if a
Expand Down
15 changes: 9 additions & 6 deletions compiler/src/dotty/tools/dotc/typer/TypeAssigner.scala
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Expand Up @@ -117,12 +117,15 @@ trait TypeAssigner {

/** The type of the selection `tree`, where `qual1` is the typed qualifier part. */
def selectionType(tree: untpd.RefTree, qual1: Tree)(using Context): Type =
var qualType = qual1.tpe.widenIfUnstable
if !qualType.hasSimpleKind && tree.name != nme.CONSTRUCTOR then
// constructors are selected on typeconstructor, type arguments are passed afterwards
qualType = errorType(em"$qualType takes type parameters", qual1.srcPos)
else if !qualType.isInstanceOf[TermType] then
qualType = errorType(em"$qualType is illegal as a selection prefix", qual1.srcPos)
val qualType0 = qual1.tpe.widenIfUnstable
val qualType =
if !qualType0.hasSimpleKind && tree.name != nme.CONSTRUCTOR then
// constructors are selected on typeconstructor, type arguments are passed afterwards
errorType(em"$qualType0 takes type parameters", qual1.srcPos)
else if !qualType0.isInstanceOf[TermType] && !qualType0.isError then
errorType(em"$qualType0 is illegal as a selection prefix", qual1.srcPos)
else
qualType0

def arrayElemType = qual1.tpe.widen match
case JavaArrayType(elemtp) => elemtp
Expand Down
3 changes: 3 additions & 0 deletions tests/neg/i12220.scala
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@@ -0,0 +1,3 @@
val a: List[Any] = List(List(1,2), List(3,4))
val _ = for(b <- a ; c <- b.asInstanceOf[List]) { println(c) } // error