From 273c8672ddab62e3365f7ec31af9aa79bf3d2c21 Mon Sep 17 00:00:00 2001 From: noti0na1 Date: Sun, 22 Sep 2024 17:03:39 +0200 Subject: [PATCH] Use a different rule for NotNullInfo --- .../dotty/tools/dotc/typer/Nullables.scala | 44 ++++++------------- .../src/dotty/tools/dotc/typer/Typer.scala | 34 +++++++------- tests/explicit-nulls/neg/i21619.scala | 19 +++++++- 3 files changed, 50 insertions(+), 47 deletions(-) diff --git a/compiler/src/dotty/tools/dotc/typer/Nullables.scala b/compiler/src/dotty/tools/dotc/typer/Nullables.scala index 74623ed7b4e9..62d2ccfb7200 100644 --- a/compiler/src/dotty/tools/dotc/typer/Nullables.scala +++ b/compiler/src/dotty/tools/dotc/typer/Nullables.scala @@ -53,48 +53,35 @@ object Nullables: TypeBoundsTree(lo, hiTree, alias) /** A set of val or var references that are known to be not null, - * a set of variable references that are not known (anymore) to be not null, - * plus a set of variables that are known to be not null at any point. + * plus a set of variable references that are once assigned to null. */ - case class NotNullInfo(asserted: Set[TermRef], retracted: Set[TermRef], onceRetracted: Set[TermRef]): - assert((asserted & retracted).isEmpty) - assert(retracted.subsetOf(onceRetracted)) - + case class NotNullInfo(asserted: Set[TermRef], retracted: Set[TermRef]): def isEmpty = this eq NotNullInfo.empty - def retractedInfo = NotNullInfo(Set(), retracted, onceRetracted) - - def onceRetractedInfo = NotNullInfo(Set(), onceRetracted, onceRetracted) + def retractedInfo = NotNullInfo(Set(), retracted) /** The sequential combination with another not-null info */ def seq(that: NotNullInfo): NotNullInfo = if this.isEmpty then that else if that.isEmpty then this else NotNullInfo( - this.asserted.union(that.asserted).diff(that.retracted), - this.retracted.union(that.retracted).diff(that.asserted), - this.onceRetracted.union(that.onceRetracted)) + this.asserted.diff(that.retracted).union(that.asserted), + this.retracted.union(that.retracted)) /** The alternative path combination with another not-null info. Used to merge * the nullability info of the two branches of an if. */ def alt(that: NotNullInfo): NotNullInfo = - NotNullInfo( - this.asserted.intersect(that.asserted), - this.retracted.union(that.retracted), - this.onceRetracted.union(that.onceRetracted)) + NotNullInfo(this.asserted.intersect(that.asserted), this.retracted.union(that.retracted)) - def withOnceRetracted(that: NotNullInfo): NotNullInfo = - if that.isEmpty then this - else NotNullInfo(this.asserted, this.retracted, this.onceRetracted.union(that.onceRetracted)) + def withRetracted(that: NotNullInfo): NotNullInfo = + NotNullInfo(this.asserted, this.retracted.union(that.retracted)) object NotNullInfo: - val empty = new NotNullInfo(Set(), Set(), Set()) + val empty = new NotNullInfo(Set(), Set()) def apply(asserted: Set[TermRef], retracted: Set[TermRef]): NotNullInfo = - apply(asserted, retracted, retracted) - def apply(asserted: Set[TermRef], retracted: Set[TermRef], onceRetracted: Set[TermRef]): NotNullInfo = - if asserted.isEmpty && onceRetracted.isEmpty then empty - else new NotNullInfo(asserted, retracted, onceRetracted) + if asserted.isEmpty && retracted.isEmpty then empty + else new NotNullInfo(asserted, retracted) end NotNullInfo /** A pair of not-null sets, depending on whether a condition is `true` or `false` */ @@ -247,16 +234,13 @@ object Nullables: * or retractions in `info` supersede infos in existing entries of `infos`. */ def extendWith(info: NotNullInfo) = - if info.isEmpty - || info.asserted.forall(infos.impliesNotNull(_)) - && !info.retracted.exists(infos.impliesNotNull(_)) - then infos + if info.isEmpty then infos else info :: infos /** Retract all references to mutable variables */ def retractMutables(using Context) = - val mutables = infos.foldLeft(Set[TermRef]())((ms, info) => - ms.union(info.asserted.filter(_.symbol.is(Mutable)))) + val mutables = infos.foldLeft(Set[TermRef]()): + (ms, info) => ms.union(info.asserted.filter(_.symbol.is(Mutable))) infos.extendWith(NotNullInfo(Set(), mutables)) end extension diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala index 50dc976e4f69..9c3d816978cf 100644 --- a/compiler/src/dotty/tools/dotc/typer/Typer.scala +++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala @@ -1544,9 +1544,9 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer def elsePathInfo = cond1.notNullInfoIf(false).seq(result.elsep.notNullInfo) result.withNotNullInfo( if result.thenp.tpe.isRef(defn.NothingClass) then - elsePathInfo.withOnceRetracted(thenPathInfo) + elsePathInfo.withRetracted(thenPathInfo) else if result.elsep.tpe.isRef(defn.NothingClass) then - thenPathInfo.withOnceRetracted(elsePathInfo) + thenPathInfo.withRetracted(elsePathInfo) else thenPathInfo.alt(elsePathInfo) ) end typedIf @@ -2143,9 +2143,9 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer def typedMatchFinish(tree: untpd.Match, sel: Tree, wideSelType: Type, cases: List[untpd.CaseDef], pt: Type)(using Context): Tree = { val cases1 = harmonic(harmonize, pt)(typedCases(cases, sel, wideSelType, pt.dropIfProto)) .asInstanceOf[List[CaseDef]] - var nni = sel.notNullInfo - if cases1.nonEmpty then nni = nni.seq(cases1.map(_.notNullInfo).reduce(_.alt(_))) - assignType(cpy.Match(tree)(sel, cases1), sel, cases1).withNotNullInfo(nni) + var nnInfo = sel.notNullInfo + if cases1.nonEmpty then nnInfo = nnInfo.seq(cases1.map(_.notNullInfo).reduce(_.alt(_))) + assignType(cpy.Match(tree)(sel, cases1), sel, cases1).withNotNullInfo(nnInfo) } def typedCases(cases: List[untpd.CaseDef], sel: Tree, wideSelType0: Type, pt: Type)(using Context): List[CaseDef] = @@ -2327,7 +2327,8 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer val capabilityProof = caughtExceptions.reduce(OrType(_, _, true)) untpd.Block(makeCanThrow(capabilityProof), expr) - def typedTry(tree: untpd.Try, pt: Type)(using Context): Try = { + def typedTry(tree: untpd.Try, pt: Type)(using Context): Try = + var nnInfo = NotNullInfo.empty val expr2 :: cases2x = harmonic(harmonize, pt) { // We want to type check tree.expr first to comput NotNullInfo, but `addCanThrowCapabilities` // uses the types of patterns in `tree.cases` to determine the capabilities. @@ -2339,25 +2340,26 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer val casesEmptyBody1 = tree.cases.mapconserve(cpy.CaseDef(_)(body = EmptyTree)) val casesEmptyBody2 = typedCases(casesEmptyBody1, EmptyTree, defn.ThrowableType, WildcardType) val expr1 = typed(addCanThrowCapabilities(tree.expr, casesEmptyBody2), pt.dropIfProto) - val casesCtx = ctx.addNotNullInfo(expr1.notNullInfo.retractedInfo) + + // Since we don't know at which point the the exception is thrown in the body, + // we have to collect any reference that is once retracted. + nnInfo = expr1.notNullInfo.retractedInfo + + val casesCtx = ctx.addNotNullInfo(nnInfo) val cases1 = typedCases(tree.cases, EmptyTree, defn.ThrowableType, pt.dropIfProto)(using casesCtx) expr1 :: cases1 }: @unchecked val cases2 = cases2x.asInstanceOf[List[CaseDef]] - // Since we don't know at which point the the exception is thrown in the body, - // we have to collect any reference that is once retracted. - var nni = expr2.notNullInfo.onceRetractedInfo // It is possible to have non-exhaustive cases, and some exceptions are thrown and not caught. // Therefore, the code in the finallizer and after the try block can only rely on the retracted // info from the cases' body. - if cases2.nonEmpty then nni = nni.seq(cases2.map(_.notNullInfo.retractedInfo).reduce(_.alt(_))) - - val finalizer1 = typed(tree.finalizer, defn.UnitType)(using ctx.addNotNullInfo(nni)) - nni = nni.seq(finalizer1.notNullInfo) + if cases2.nonEmpty then + nnInfo = nnInfo.seq(cases2.map(_.notNullInfo.retractedInfo).reduce(_.alt(_))) - assignType(cpy.Try(tree)(expr2, cases2, finalizer1), expr2, cases2).withNotNullInfo(nni) - } + val finalizer1 = typed(tree.finalizer, defn.UnitType)(using ctx.addNotNullInfo(nnInfo)) + nnInfo = nnInfo.seq(finalizer1.notNullInfo) + assignType(cpy.Try(tree)(expr2, cases2, finalizer1), expr2, cases2).withNotNullInfo(nnInfo) def typedTry(tree: untpd.ParsedTry, pt: Type)(using Context): Try = val cases: List[untpd.CaseDef] = tree.handler match diff --git a/tests/explicit-nulls/neg/i21619.scala b/tests/explicit-nulls/neg/i21619.scala index 1c93af707b73..244f993fd4e1 100644 --- a/tests/explicit-nulls/neg/i21619.scala +++ b/tests/explicit-nulls/neg/i21619.scala @@ -59,4 +59,21 @@ def test4: String = x = "" catch case _ => - x.replace("", "") // error \ No newline at end of file + x.replace("", "") // error + +def test5: Unit = + var x: String | Null = null + var y: String | Null = null + x = "" + y = "" + var i: Int = 1 + try + i match + case _ => + x = null + throw new Exception() + x = "" + catch + case _ => + val z1: String = x.replace("", "") // error + val z2: String = y.replace("", "") \ No newline at end of file