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Detect direct cycles of typerefs referring to themselves #2751

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Merged
merged 5 commits into from
Jul 18, 2017
Merged

Detect direct cycles of typerefs referring to themselves #2751

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674333a
Detect direct cycles of typerefs referring to themselves
odersky Jun 14, 2017
2fdc581
Acoid CyclicReference errors due to check
odersky Jun 14, 2017
f2a74c9
Fix checking code
odersky Jun 14, 2017
13cd505
Give more info on failure
odersky Jun 14, 2017
d69fb6c
Make checkCycles option false by default
odersky Jul 15, 2017
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5 changes: 5 additions & 0 deletions compiler/src/dotty/tools/dotc/config/Config.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -108,6 +108,11 @@ object Config {
*/
final val checkMethodTypes = false

/** If this flag is set, it is checked that TypeRefs don't refer directly
* to themselves.
*/
final val checkTypeRefCycles = false

/** The recursion depth for showing a summarized string */
final val summarizeDepth = 2

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15 changes: 13 additions & 2 deletions compiler/src/dotty/tools/dotc/core/Types.scala
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Expand Up @@ -1526,7 +1526,18 @@ object Types {
}

/** Hook for adding debug check code when denotations are assigned */
final def checkDenot()(implicit ctx: Context) = {}
final def checkDenot()(implicit ctx: Context) =
if (Config.checkTypeRefCycles)
lastDenotation match {
case d: SingleDenotation =>
d.infoOrCompleter match {
case TypeBounds(lo, hi) =>
assert(lo ne this, this)
assert(hi ne this, this)
case _ =>
}
case _ =>
}

/** A second fallback to recompute the denotation if necessary */
private def computeDenot(implicit ctx: Context): Denotation = {
Expand Down Expand Up @@ -1562,9 +1573,9 @@ object Types {

// Don't use setDenot here; double binding checks can give spurious failures after erasure
lastDenotation = d
checkDenot()
lastSymbol = d.symbol
checkedPeriod = ctx.period
checkDenot()
}
d
}
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