From 688ed4f168d2bd40acf478f637d27f6e03c1a7d2 Mon Sep 17 00:00:00 2001
From: Matt Bovel <matthieu@bovel.net>
Date: Wed, 27 Nov 2024 23:01:26 +0000
Subject: [PATCH 01/17] Do not lift annotation arguments (bis)

---
 .../dotty/tools/dotc/typer/Applications.scala |  2 ++
 .../dependent-annot-default-args.check        | 23 +++++++++++++++++++
 .../dependent-annot-default-args.scala        | 10 ++++++++
 3 files changed, 35 insertions(+)

diff --git a/compiler/src/dotty/tools/dotc/typer/Applications.scala b/compiler/src/dotty/tools/dotc/typer/Applications.scala
index 41e48f7595dc..ff6c71f57355 100644
--- a/compiler/src/dotty/tools/dotc/typer/Applications.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Applications.scala
@@ -963,6 +963,8 @@ trait Applications extends Compatibility {
                 case (arg: NamedArg, _) => arg
                 case (arg, name)        => NamedArg(name, arg)
               }
+          else if isAnnotConstr(methRef.symbol) then
+            typedArgs
           else if !sameSeq(args, orderedArgs) && !typedArgs.forall(isSafeArg) then
             // need to lift arguments to maintain evaluation order in the
             // presence of argument reorderings.
diff --git a/tests/printing/dependent-annot-default-args.check b/tests/printing/dependent-annot-default-args.check
index 44c1fe31e2d1..f457d5d62edb 100644
--- a/tests/printing/dependent-annot-default-args.check
+++ b/tests/printing/dependent-annot-default-args.check
@@ -8,16 +8,39 @@ package <empty> {
   final module class annot() extends AnyRef() { this: annot.type =>
     def $lessinit$greater$default$2: Any @uncheckedVariance = 42
   }
+  class annot2(x: Any, y: Array[Any]) extends annotation.Annotation() {
+    private[this] val x: Any
+    private[this] val y: Array[Any]
+  }
+  final lazy module val annot2: annot2 = new annot2()
+  final module class annot2() extends AnyRef() { this: annot2.type =>
+    def $lessinit$greater$default$1: Any @uncheckedVariance = -1
+    def $lessinit$greater$default$2: Array[Any] @uncheckedVariance =
+      Array.apply[Any](["Hello" : Any]*)(scala.reflect.ClassTag.Any)
+  }
   final lazy module val dependent-annot-default-args$package:
     dependent-annot-default-args$package =
     new dependent-annot-default-args$package()
   final module class dependent-annot-default-args$package() extends Object() {
     this: dependent-annot-default-args$package.type =>
     def f(x: Int): Int @annot(x) = x
+    def f2(x: Int):
+      Int @annot2(
+        y = Array.apply[Any](["Hello",x : Any]*)(scala.reflect.ClassTag.Any))
+     = x
     def test: Unit =
       {
         val y: Int = ???
         val z: Int @annot(y) = f(y)
+        val z2:
+          Int @annot2(
+            y = Array.apply[Any](["Hello",y : Any]*)(scala.reflect.ClassTag.Any)
+            )
+         = f2(y)
+        @annot(44) val z3: Int = 45
+        @annot2(
+          y = Array.apply[Any](["Hello",y : Any]*)(scala.reflect.ClassTag.Any))
+          val z4: Int = 45
         ()
       }
   }
diff --git a/tests/printing/dependent-annot-default-args.scala b/tests/printing/dependent-annot-default-args.scala
index 7ddce711fedc..11fc9ef52cc9 100644
--- a/tests/printing/dependent-annot-default-args.scala
+++ b/tests/printing/dependent-annot-default-args.scala
@@ -1,5 +1,15 @@
 class annot(x: Any, y: Any = 42) extends annotation.Annotation
+class annot2(x: Any = -1, y: Array[Any] = Array("Hello")) extends annotation.Annotation
+
 def f(x: Int): Int @annot(x) = x
+def f2(x: Int): Int @annot2(y = Array("Hello", x)) = x
+
 def test =
   val y: Int = ???
+
   val z = f(y)
+  val z2 = f2(y)
+
+  @annot(44) val z3 = 45
+  @annot2(y = Array("Hello", y)) val z4 = 45
+

From 483920640f016c7ccdb31144df7ca602d99297fa Mon Sep 17 00:00:00 2001
From: odersky <odersky@gmail.com>
Date: Thu, 5 Dec 2024 16:45:53 +0100
Subject: [PATCH 02/17] Widen singleton types when computing fields from
 .Fields

Fixes #22018
---
 .../src/dotty/tools/dotc/typer/Typer.scala     |  2 +-
 tests/pos/i22018.scala                         | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 tests/pos/i22018.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 6bb5d1ee70ff..1a3f5c2d97c3 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -868,7 +868,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
           && pt != LhsProto
       then
         val pre = if !TypeOps.isLegalPrefix(qual.tpe) then SkolemType(qual.tpe) else qual.tpe
-        val fieldsType = pre.select(tpnme.Fields).dealias.simplified
+        val fieldsType = pre.select(tpnme.Fields).widenDealias.simplified
         val fields = fieldsType.namedTupleElementTypes
         typr.println(i"try dyn select $qual, $selName, $fields")
         fields.find(_._1 == selName) match
diff --git a/tests/pos/i22018.scala b/tests/pos/i22018.scala
new file mode 100644
index 000000000000..14f4733732be
--- /dev/null
+++ b/tests/pos/i22018.scala
@@ -0,0 +1,18 @@
+import scala.language.experimental.namedTuples
+
+class SelectableNT[A <: NamedTuple.AnyNamedTuple](val nt: A) extends Selectable:
+  type Fields = A
+  def selectDynamic(x: String) = ???
+
+object Test:
+
+  val a = (name = "foo", age = 1)
+
+  val sa = SelectableNT(a)
+  sa.name   // ok
+
+  type B = a.type
+  val b: B = a
+
+  val sb = SelectableNT(b)
+  sb.name   // fails
\ No newline at end of file

From 585dda9587bc95afb936eb18751fbf850cf3209c Mon Sep 17 00:00:00 2001
From: noti0na1 <noti0na1@users.noreply.github.com>
Date: Sat, 21 Sep 2024 19:54:39 +0200
Subject: [PATCH 03/17] Refactor NotNullInfo to record every reference which is
 retracted once.

---
 .../dotty/tools/dotc/typer/Nullables.scala    | 32 +++++++---
 .../src/dotty/tools/dotc/typer/Typer.scala    | 15 ++++-
 tests/explicit-nulls/neg/i21380c.scala        |  6 +-
 tests/explicit-nulls/neg/i21619.scala         | 62 +++++++++++++++++++
 4 files changed, 100 insertions(+), 15 deletions(-)
 create mode 100644 tests/explicit-nulls/neg/i21619.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/Nullables.scala b/compiler/src/dotty/tools/dotc/typer/Nullables.scala
index 3f071dad2d03..74623ed7b4e9 100644
--- a/compiler/src/dotty/tools/dotc/typer/Nullables.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Nullables.scala
@@ -52,15 +52,19 @@ object Nullables:
     val hiTree = if(hiTpe eq hi.typeOpt) hi else TypeTree(hiTpe)
     TypeBoundsTree(lo, hiTree, alias)
 
-  /** A set of val or var references that are known to be not null, plus a set of
-   *  variable references that are not known (anymore) to be not null
+  /** 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.
    */
-  case class NotNullInfo(asserted: Set[TermRef], retracted: Set[TermRef]):
+  case class NotNullInfo(asserted: Set[TermRef], retracted: Set[TermRef], onceRetracted: Set[TermRef]):
     assert((asserted & retracted).isEmpty)
+    assert(retracted.subsetOf(onceRetracted))
 
     def isEmpty = this eq NotNullInfo.empty
 
-    def retractedInfo = NotNullInfo(Set(), retracted)
+    def retractedInfo = NotNullInfo(Set(), retracted, onceRetracted)
+
+    def onceRetractedInfo = NotNullInfo(Set(), onceRetracted, onceRetracted)
 
     /** The sequential combination with another not-null info */
     def seq(that: NotNullInfo): NotNullInfo =
@@ -68,19 +72,29 @@ object Nullables:
       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.retracted.union(that.retracted).diff(that.asserted),
+        this.onceRetracted.union(that.onceRetracted))
 
     /** 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))
+      NotNullInfo(
+        this.asserted.intersect(that.asserted),
+        this.retracted.union(that.retracted),
+        this.onceRetracted.union(that.onceRetracted))
+
+    def withOnceRetracted(that: NotNullInfo): NotNullInfo =
+      if that.isEmpty then this
+      else NotNullInfo(this.asserted, this.retracted, this.onceRetracted.union(that.onceRetracted))
 
   object NotNullInfo:
-    val empty = new NotNullInfo(Set(), Set())
+    val empty = new NotNullInfo(Set(), Set(), Set())
     def apply(asserted: Set[TermRef], retracted: Set[TermRef]): NotNullInfo =
-      if asserted.isEmpty && retracted.isEmpty then empty
-      else new NotNullInfo(asserted, retracted)
+      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)
   end NotNullInfo
 
   /** A pair of not-null sets, depending on whether a condition is `true` or `false` */
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 6bb5d1ee70ff..588e4188c7bc 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -1552,8 +1552,10 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
     def thenPathInfo = cond1.notNullInfoIf(true).seq(result.thenp.notNullInfo)
     def elsePathInfo = cond1.notNullInfoIf(false).seq(result.elsep.notNullInfo)
     result.withNotNullInfo(
-      if result.thenp.tpe.isRef(defn.NothingClass) then elsePathInfo
-      else if result.elsep.tpe.isRef(defn.NothingClass) then thenPathInfo
+      if result.thenp.tpe.isRef(defn.NothingClass) then
+        elsePathInfo.withOnceRetracted(thenPathInfo)
+      else if result.elsep.tpe.isRef(defn.NothingClass) then
+        thenPathInfo.withOnceRetracted(elsePathInfo)
       else thenPathInfo.alt(elsePathInfo)
     )
   end typedIf
@@ -2350,10 +2352,17 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
     }: @unchecked
     val cases2 = cases2x.asInstanceOf[List[CaseDef]]
 
-    var nni = expr2.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.
+    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)
+
     assignType(cpy.Try(tree)(expr2, cases2, finalizer1), expr2, cases2).withNotNullInfo(nni)
   }
 
diff --git a/tests/explicit-nulls/neg/i21380c.scala b/tests/explicit-nulls/neg/i21380c.scala
index f86a5638e4c8..de3cd5bafd6b 100644
--- a/tests/explicit-nulls/neg/i21380c.scala
+++ b/tests/explicit-nulls/neg/i21380c.scala
@@ -32,9 +32,9 @@ def test4: Int =
     case npe: NullPointerException => x = ""
     case _ => x = ""
   x.length // error
-  // Although the catch block here is exhaustive,
-  // it is possible that the exception is thrown and not caught.
-  // Therefore, the code after the try block can only rely on the retracted info.
+  // Although the catch block here is exhaustive, 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.
 
 def test5: Int =
   var x: String | Null = null
diff --git a/tests/explicit-nulls/neg/i21619.scala b/tests/explicit-nulls/neg/i21619.scala
new file mode 100644
index 000000000000..1c93af707b73
--- /dev/null
+++ b/tests/explicit-nulls/neg/i21619.scala
@@ -0,0 +1,62 @@
+def test1: String =
+  var x: String | Null = null
+  x = ""
+  var i: Int = 1
+  try
+    i match
+      case _ =>
+        x = null
+        throw new Exception()
+    x = ""
+  catch
+    case e: Exception =>
+  x.replace("", "") // error
+
+def test2: String =
+  var x: String | Null = null
+  x = ""
+  var i: Int = 1
+  try
+    i match
+      case _ =>
+        x = null
+        throw new Exception()
+    x = ""
+  catch
+    case e: Exception =>
+      x = "e"
+  x.replace("", "") // error
+
+def test3: String =
+  var x: String | Null = null
+  x = ""
+  var i: Int = 1
+  try
+    i match
+      case _ =>
+        x = null
+        throw new Exception()
+    x = ""
+  catch
+    case e: Exception =>
+  finally
+    x = "f"
+  x.replace("", "") // ok
+
+def test4: String =
+  var x: String | Null = null
+  x = ""
+  var i: Int = 1
+  try
+    try
+      if i == 1 then
+        x = null
+        throw new Exception()
+      else
+        x = ""
+    catch
+      case _ =>
+    x = ""
+  catch
+    case _ =>
+  x.replace("", "") // error
\ No newline at end of file

From bcc9e68c778da3faa4dcb8b6c0258a48befff819 Mon Sep 17 00:00:00 2001
From: noti0na1 <noti0na1@users.noreply.github.com>
Date: Sun, 22 Sep 2024 17:03:39 +0200
Subject: [PATCH 04/17] 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 588e4188c7bc..8a72076527b9 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -1553,9 +1553,9 @@ 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
@@ -2150,9 +2150,9 @@ 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] =
@@ -2334,7 +2334,8 @@ 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.
@@ -2346,25 +2347,26 @@ 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

From 05c630acf9dd8b2ecb98f34b1f40bfc8ddb55ce8 Mon Sep 17 00:00:00 2001
From: noti0na1 <noti0na1@users.noreply.github.com>
Date: Fri, 11 Oct 2024 06:24:24 +0200
Subject: [PATCH 05/17] Consider cases with Nothing type

---
 .../src/dotty/tools/dotc/typer/Typer.scala    | 24 ++++++++++++-------
 tests/explicit-nulls/neg/i21380b.scala        | 18 ++++++++++++++
 2 files changed, 34 insertions(+), 8 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 8a72076527b9..5731b44368e6 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -1552,9 +1552,9 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
     def thenPathInfo = cond1.notNullInfoIf(true).seq(result.thenp.notNullInfo)
     def elsePathInfo = cond1.notNullInfoIf(false).seq(result.elsep.notNullInfo)
     result.withNotNullInfo(
-      if result.thenp.tpe.isRef(defn.NothingClass) then
+      if result.thenp.tpe.isNothingType then
         elsePathInfo.withRetracted(thenPathInfo)
-      else if result.elsep.tpe.isRef(defn.NothingClass) then
+      else if result.elsep.tpe.isNothingType then
         thenPathInfo.withRetracted(elsePathInfo)
       else thenPathInfo.alt(elsePathInfo)
     )
@@ -2141,20 +2141,28 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
         case1
       }
       .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).cast(pt).withNotNullInfo(nni)
+    assignType(cpy.Match(tree)(sel, cases1), sel, cases1).cast(pt)
+      .withNotNullInfo(notNullInfoFromCases(sel.notNullInfo, cases1))
   }
 
   // Overridden in InlineTyper for inline matches
   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 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)
+    assignType(cpy.Match(tree)(sel, cases1), sel, cases1)
+      .withNotNullInfo(notNullInfoFromCases(sel.notNullInfo, cases1))
   }
 
+  private def notNullInfoFromCases(initInfo: NotNullInfo, cases: List[CaseDef])(using Context): NotNullInfo =
+    var nnInfo = initInfo
+    if cases.nonEmpty then
+      val (nothingCases, normalCases) = cases.partition(_.body.tpe.isNothingType)
+      nnInfo = nothingCases.foldLeft(nnInfo):
+        (nni, c) => nni.withRetracted(c.notNullInfo)
+      if normalCases.nonEmpty then
+        nnInfo = nnInfo.seq(normalCases.map(_.notNullInfo).reduce(_.alt(_)))
+    nnInfo
+
   def typedCases(cases: List[untpd.CaseDef], sel: Tree, wideSelType0: Type, pt: Type)(using Context): List[CaseDef] =
     var caseCtx = ctx
     var wideSelType = wideSelType0
diff --git a/tests/explicit-nulls/neg/i21380b.scala b/tests/explicit-nulls/neg/i21380b.scala
index 83e23053547c..e4d0caa9e32f 100644
--- a/tests/explicit-nulls/neg/i21380b.scala
+++ b/tests/explicit-nulls/neg/i21380b.scala
@@ -18,4 +18,22 @@ def test3(i: Int) =
   i match
     case 1 if x != null => ()
     case _ => x = " "
+  x.trim() // ok
+
+def test4(i: Int) =
+  var x: String | Null = null
+  var y: String | Null = null
+  i match
+    case 1 => x = "1"
+    case _ => y = " "
+  x.trim() // error
+
+def test5(i: Int): String =
+  var x: String | Null = null
+  var y: String | Null = null
+  i match
+    case 1 => x = "1"
+    case _ =>
+      y = " "
+      return y
   x.trim() // ok
\ No newline at end of file

From d44147bc6ff5496dab9cc1569274dfb4b673ee09 Mon Sep 17 00:00:00 2001
From: noti0na1 <noti0na1@users.noreply.github.com>
Date: Mon, 14 Oct 2024 15:21:03 +0200
Subject: [PATCH 06/17] Apply suggestions from code review
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Ondřej Lhoták <olhotak@uwaterloo.ca>
---
 compiler/src/dotty/tools/dotc/typer/Nullables.scala | 7 +++++--
 compiler/src/dotty/tools/dotc/typer/Typer.scala     | 2 +-
 tests/explicit-nulls/neg/i21380c.scala              | 2 +-
 3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/typer/Nullables.scala b/compiler/src/dotty/tools/dotc/typer/Nullables.scala
index 62d2ccfb7200..e6d764dc1be4 100644
--- a/compiler/src/dotty/tools/dotc/typer/Nullables.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Nullables.scala
@@ -52,8 +52,11 @@ object Nullables:
     val hiTree = if(hiTpe eq hi.typeOpt) hi else TypeTree(hiTpe)
     TypeBoundsTree(lo, hiTree, alias)
 
-  /** A set of val or var references that are known to be not null,
-   *  plus a set of variable references that are once assigned to null.
+  /** A set of val or var references that are known to be not null
+  * after the tree finishes executing normally (non-exceptionally),
+   *  plus a set of variable references that are ever assigned to null,
+   *  and may therefore be null if execution of the tree is interrupted
+   *  by an exception.
    */
   case class NotNullInfo(asserted: Set[TermRef], retracted: Set[TermRef]):
     def isEmpty = this eq NotNullInfo.empty
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 5731b44368e6..392a4e18c454 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -2367,7 +2367,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
     val cases2 = cases2x.asInstanceOf[List[CaseDef]]
 
     // 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
+    // Therefore, the code in the finalizer and after the try block can only rely on the retracted
     // info from the cases' body.
     if cases2.nonEmpty then
       nnInfo = nnInfo.seq(cases2.map(_.notNullInfo.retractedInfo).reduce(_.alt(_)))
diff --git a/tests/explicit-nulls/neg/i21380c.scala b/tests/explicit-nulls/neg/i21380c.scala
index de3cd5bafd6b..9b7a721fbdf0 100644
--- a/tests/explicit-nulls/neg/i21380c.scala
+++ b/tests/explicit-nulls/neg/i21380c.scala
@@ -33,7 +33,7 @@ def test4: Int =
     case _ => x = ""
   x.length // error
   // Although the catch block here is exhaustive, it is possible to have non-exhaustive cases,
-  // and some exceptions are thrown and not caught. Therefore, the code in the finallizer and
+  // and some exceptions are thrown and not caught. Therefore, the code in the finalizer and
   // after the try block can only rely on the retracted info from the cases' body.
 
 def test5: Int =

From f859afe8e4ace35e026600bb784664dcbcdbda98 Mon Sep 17 00:00:00 2001
From: noti0na1 <noti0na1@users.noreply.github.com>
Date: Fri, 1 Nov 2024 09:07:18 +0100
Subject: [PATCH 07/17] Add terminated info

---
 .../dotty/tools/dotc/typer/Nullables.scala    | 43 ++++++++++++-------
 .../src/dotty/tools/dotc/typer/Typer.scala    | 27 ++++--------
 2 files changed, 36 insertions(+), 34 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/typer/Nullables.scala b/compiler/src/dotty/tools/dotc/typer/Nullables.scala
index e6d764dc1be4..30c65771d9c2 100644
--- a/compiler/src/dotty/tools/dotc/typer/Nullables.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Nullables.scala
@@ -53,37 +53,45 @@ object Nullables:
     TypeBoundsTree(lo, hiTree, alias)
 
   /** A set of val or var references that are known to be not null
-  * after the tree finishes executing normally (non-exceptionally),
+   *  after the tree finishes executing normally (non-exceptionally),
    *  plus a set of variable references that are ever assigned to null,
    *  and may therefore be null if execution of the tree is interrupted
    *  by an exception.
    */
-  case class NotNullInfo(asserted: Set[TermRef], retracted: Set[TermRef]):
+  case class NotNullInfo(asserted: Set[TermRef] | Null, retracted: Set[TermRef]):
     def isEmpty = this eq NotNullInfo.empty
 
     def retractedInfo = NotNullInfo(Set(), retracted)
 
+    def terminatedInfo = NotNullInfo(null, 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.diff(that.retracted).union(that.asserted),
-        this.retracted.union(that.retracted))
+      else
+        val newAsserted =
+          if this.asserted == null || that.asserted == null then null
+          else this.asserted.diff(that.retracted).union(that.asserted)
+        val newRetracted = this.retracted.union(that.retracted)
+        NotNullInfo(newAsserted, newRetracted)
 
     /** The alternative path combination with another not-null info. Used to merge
-     *  the nullability info of the two branches of an if.
+     *  the nullability info of the branches of an if or match.
      */
     def alt(that: NotNullInfo): NotNullInfo =
-      NotNullInfo(this.asserted.intersect(that.asserted), this.retracted.union(that.retracted))
-
-    def withRetracted(that: NotNullInfo): NotNullInfo =
-      NotNullInfo(this.asserted, this.retracted.union(that.retracted))
+      val newAsserted =
+        if this.asserted == null then that.asserted
+        else if that.asserted == null then this.asserted
+        else this.asserted.intersect(that.asserted)
+      val newRetracted = this.retracted.union(that.retracted)
+      NotNullInfo(newAsserted, newRetracted)
+  end NotNullInfo
 
   object NotNullInfo:
     val empty = new NotNullInfo(Set(), Set())
-    def apply(asserted: Set[TermRef], retracted: Set[TermRef]): NotNullInfo =
-      if asserted.isEmpty && retracted.isEmpty then empty
+    def apply(asserted: Set[TermRef] | Null, retracted: Set[TermRef]): NotNullInfo =
+      if asserted != null && asserted.isEmpty && retracted.isEmpty then empty
       else new NotNullInfo(asserted, retracted)
   end NotNullInfo
 
@@ -227,7 +235,7 @@ object Nullables:
     */
     @tailrec def impliesNotNull(ref: TermRef): Boolean = infos match
       case info :: infos1 =>
-        if info.asserted.contains(ref) then true
+        if info.asserted != null && info.asserted.contains(ref) then true
         else if info.retracted.contains(ref) then false
         else infos1.impliesNotNull(ref)
       case _ =>
@@ -243,7 +251,9 @@ object Nullables:
     /** 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)))
+        (ms, info) => ms.union(
+                        if info.asserted == null then Set.empty
+                        else info.asserted.filter(_.symbol.is(Mutable)))
       infos.extendWith(NotNullInfo(Set(), mutables))
 
   end extension
@@ -516,7 +526,10 @@ object Nullables:
       && assignmentSpans.getOrElse(sym.span.start, Nil).exists(whileSpan.contains(_))
       && ctx.notNullInfos.impliesNotNull(ref)
 
-    val retractedVars = ctx.notNullInfos.flatMap(_.asserted.filter(isRetracted)).toSet
+    val retractedVars = ctx.notNullInfos.flatMap(info =>
+      if info.asserted == null then Set.empty
+      else info.asserted.filter(isRetracted)
+    ).toSet
     ctx.addNotNullInfo(NotNullInfo(Set(), retractedVars))
   end whileContext
 
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 392a4e18c454..5ec9dbbe28b9 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -1551,13 +1551,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
 
     def thenPathInfo = cond1.notNullInfoIf(true).seq(result.thenp.notNullInfo)
     def elsePathInfo = cond1.notNullInfoIf(false).seq(result.elsep.notNullInfo)
-    result.withNotNullInfo(
-      if result.thenp.tpe.isNothingType then
-        elsePathInfo.withRetracted(thenPathInfo)
-      else if result.elsep.tpe.isNothingType then
-        thenPathInfo.withRetracted(elsePathInfo)
-      else thenPathInfo.alt(elsePathInfo)
-    )
+    result.withNotNullInfo(thenPathInfo.alt(elsePathInfo))
   end typedIf
 
   /** Decompose function prototype into a list of parameter prototypes and a result
@@ -2154,14 +2148,9 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
   }
 
   private def notNullInfoFromCases(initInfo: NotNullInfo, cases: List[CaseDef])(using Context): NotNullInfo =
-    var nnInfo = initInfo
     if cases.nonEmpty then
-      val (nothingCases, normalCases) = cases.partition(_.body.tpe.isNothingType)
-      nnInfo = nothingCases.foldLeft(nnInfo):
-        (nni, c) => nni.withRetracted(c.notNullInfo)
-      if normalCases.nonEmpty then
-        nnInfo = nnInfo.seq(normalCases.map(_.notNullInfo).reduce(_.alt(_)))
-    nnInfo
+      initInfo.seq(cases.map(_.notNullInfo).reduce(_.alt(_)))
+    else initInfo
 
   def typedCases(cases: List[untpd.CaseDef], sel: Tree, wideSelType0: Type, pt: Type)(using Context): List[CaseDef] =
     var caseCtx = ctx
@@ -2251,7 +2240,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
   def typedLabeled(tree: untpd.Labeled)(using Context): Labeled = {
     val bind1 = typedBind(tree.bind, WildcardType).asInstanceOf[Bind]
     val expr1 = typed(tree.expr, bind1.symbol.info)
-    assignType(cpy.Labeled(tree)(bind1, expr1))
+    assignType(cpy.Labeled(tree)(bind1, expr1)).withNotNullInfo(expr1.notNullInfo.retractedInfo)
   }
 
   /** Type a case of a type match */
@@ -2301,7 +2290,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
                             // Hence no adaptation is possible, and we assume WildcardType as prototype.
         (from, proto)
     val expr1 = typedExpr(tree.expr orElse untpd.syntheticUnitLiteral.withSpan(tree.span), proto)
-    assignType(cpy.Return(tree)(expr1, from))
+    assignType(cpy.Return(tree)(expr1, from)).withNotNullInfo(expr1.notNullInfo.terminatedInfo)
   end typedReturn
 
   def typedWhileDo(tree: untpd.WhileDo)(using Context): Tree =
@@ -2388,15 +2377,15 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
   def typedThrow(tree: untpd.Throw)(using Context): Tree =
     val expr1 = typed(tree.expr, defn.ThrowableType)
     val cap = checkCanThrow(expr1.tpe.widen, tree.span)
-    val res = Throw(expr1).withSpan(tree.span)
+    var res = Throw(expr1).withSpan(tree.span)
     if Feature.ccEnabled && !cap.isEmpty && !ctx.isAfterTyper then
       // Record access to the CanThrow capabulity recovered in `cap` by wrapping
       // the type of the `throw` (i.e. Nothing) in a `@requiresCapability` annotation.
-      Typed(res,
+      res = Typed(res,
         TypeTree(
           AnnotatedType(res.tpe,
             Annotation(defn.RequiresCapabilityAnnot, cap, tree.span))))
-    else res
+    res.withNotNullInfo(expr1.notNullInfo.terminatedInfo)
 
   def typedSeqLiteral(tree: untpd.SeqLiteral, pt: Type)(using Context): SeqLiteral = {
     val elemProto = pt.stripNull().elemType match {

From 158af7deed473826b5d16ade6b9472fd89948b6d Mon Sep 17 00:00:00 2001
From: noti0na1 <noti0na1@users.noreply.github.com>
Date: Fri, 6 Dec 2024 16:59:32 +0100
Subject: [PATCH 08/17] Fix deep NotNullInfo

---
 .../dotty/tools/dotc/typer/Applications.scala |  7 ++-
 .../dotty/tools/dotc/typer/Nullables.scala    | 54 +++++++++++++------
 .../src/dotty/tools/dotc/typer/Typer.scala    |  1 -
 tests/explicit-nulls/neg/i21619.scala         | 15 +++++-
 4 files changed, 57 insertions(+), 20 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/typer/Applications.scala b/compiler/src/dotty/tools/dotc/typer/Applications.scala
index 41e48f7595dc..96c38bcc80af 100644
--- a/compiler/src/dotty/tools/dotc/typer/Applications.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Applications.scala
@@ -1134,7 +1134,7 @@ trait Applications extends Compatibility {
             case _ => ()
         else ()
 
-      fun1.tpe match {
+      val result = fun1.tpe match {
         case err: ErrorType => cpy.Apply(tree)(fun1, proto.typedArgs()).withType(err)
         case TryDynamicCallType =>
           val isInsertedApply = fun1 match {
@@ -1208,6 +1208,11 @@ trait Applications extends Compatibility {
                   else tryWithImplicitOnQualifier(fun1, proto).getOrElse(fail))
             }
       }
+
+      if result.tpe.isNothingType then
+        val nnInfo = result.notNullInfo
+        result.withNotNullInfo(nnInfo.terminatedInfo)
+      else result
     }
 
     /** Convert expression like
diff --git a/compiler/src/dotty/tools/dotc/typer/Nullables.scala b/compiler/src/dotty/tools/dotc/typer/Nullables.scala
index 30c65771d9c2..2193866893f6 100644
--- a/compiler/src/dotty/tools/dotc/typer/Nullables.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Nullables.scala
@@ -319,11 +319,29 @@ object Nullables:
       if !info.isEmpty then tree.putAttachment(NNInfo, info)
       tree
 
+    /* Collect the nullability info from parts of `tree` */
+    def collectNotNullInfo(using Context): NotNullInfo = tree match
+      case Typed(expr, _) =>
+        expr.notNullInfo
+      case Apply(fn, args) =>
+        val argsInfo = args.map(_.notNullInfo)
+        val fnInfo = fn.notNullInfo
+        argsInfo.foldLeft(fnInfo)(_ seq _)
+      case TypeApply(fn, _) =>
+        fn.notNullInfo
+      case _ =>
+        // Other cases are handled specially in typer.
+        NotNullInfo.empty
+
     /* The nullability info of `tree` */
     def notNullInfo(using Context): NotNullInfo =
-      stripInlined(tree).getAttachment(NNInfo) match
+      val tree1 = stripInlined(tree)
+      tree1.getAttachment(NNInfo) match
         case Some(info) if !ctx.erasedTypes => info
-        case _ => NotNullInfo.empty
+        case _ =>
+          val nnInfo = tree1.collectNotNullInfo
+          tree1.withNotNullInfo(nnInfo)
+          nnInfo
 
     /* The nullability info of `tree`, assuming it is a condition that evaluates to `c` */
     def notNullInfoIf(c: Boolean)(using Context): NotNullInfo =
@@ -404,21 +422,23 @@ object Nullables:
   end extension
 
   extension (tree: Assign)
-    def computeAssignNullable()(using Context): tree.type = tree.lhs match
-      case TrackedRef(ref) =>
-        val rhstp = tree.rhs.typeOpt
-        if ctx.explicitNulls && ref.isNullableUnion then
-          if rhstp.isNullType || rhstp.isNullableUnion then
-            // If the type of rhs is nullable (`T|Null` or `Null`), then the nullability of the
-            // lhs variable is no longer trackable. We don't need to check whether the type `T`
-            // is correct here, as typer will check it.
-            tree.withNotNullInfo(NotNullInfo(Set(), Set(ref)))
-          else
-            // If the initial type is nullable and the assigned value is non-null,
-            // we add it to the NotNull.
-            tree.withNotNullInfo(NotNullInfo(Set(ref), Set()))
-        else tree
-      case _ => tree
+    def computeAssignNullable()(using Context): tree.type =
+      var nnInfo = tree.rhs.notNullInfo
+      tree.lhs match
+        case TrackedRef(ref) if ctx.explicitNulls && ref.isNullableUnion =>
+          nnInfo = nnInfo.seq:
+            val rhstp = tree.rhs.typeOpt
+            if rhstp.isNullType || rhstp.isNullableUnion then
+              // If the type of rhs is nullable (`T|Null` or `Null`), then the nullability of the
+              // lhs variable is no longer trackable. We don't need to check whether the type `T`
+              // is correct here, as typer will check it.
+              NotNullInfo(Set(), Set(ref))
+            else
+              // If the initial type is nullable and the assigned value is non-null,
+              // we add it to the NotNull.
+              NotNullInfo(Set(ref), Set())
+        case _ =>
+      tree.withNotNullInfo(nnInfo)
   end extension
 
   private val analyzedOps = Set(nme.EQ, nme.NE, nme.eq, nme.ne, nme.ZAND, nme.ZOR, nme.UNARY_!)
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 5ec9dbbe28b9..1e461a5e1cb7 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -1201,7 +1201,6 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
             untpd.unsplice(tree.expr).putAttachment(AscribedToUnit, ())
           typed(tree.expr, underlyingTreeTpe.tpe.widenSkolem)
       assignType(cpy.Typed(tree)(expr1, tpt), underlyingTreeTpe)
-        .withNotNullInfo(expr1.notNullInfo)
     }
 
     if (untpd.isWildcardStarArg(tree)) {
diff --git a/tests/explicit-nulls/neg/i21619.scala b/tests/explicit-nulls/neg/i21619.scala
index 244f993fd4e1..d7af27e3fe64 100644
--- a/tests/explicit-nulls/neg/i21619.scala
+++ b/tests/explicit-nulls/neg/i21619.scala
@@ -76,4 +76,17 @@ def test5: Unit =
   catch
     case _ =>
   val z1: String = x.replace("", "") // error
-  val z2: String = y.replace("", "")
\ No newline at end of file
+  val z2: String = y.replace("", "")
+
+def test6 = {
+  var x: String | Null = ""
+  var y: String = ""
+  x = ""
+  y = if (false) x else 1 match {
+    case _ => {
+      x = null
+      y
+    }
+  }
+  x.replace("", "") // error
+}
\ No newline at end of file

From 00430c042a9031059aefe638caba7c7e2e8c49f5 Mon Sep 17 00:00:00 2001
From: noti0na1 <noti0na1@users.noreply.github.com>
Date: Sat, 7 Dec 2024 04:28:02 +0100
Subject: [PATCH 09/17] Treat asserted set of terminated NotNullInfo as
 universal set; fix test

---
 .../src/dotty/tools/dotc/core/Contexts.scala  |  6 ++---
 .../dotty/tools/dotc/typer/Nullables.scala    | 22 ++++++++++---------
 .../src/dotty/tools/dotc/typer/Typer.scala    |  2 ++
 .../pos/after-termination.scala               | 17 ++++++++++++++
 .../unsafe-common/unsafe-overload.scala       | 12 +++++-----
 5 files changed, 40 insertions(+), 19 deletions(-)
 create mode 100644 tests/explicit-nulls/pos/after-termination.scala

diff --git a/compiler/src/dotty/tools/dotc/core/Contexts.scala b/compiler/src/dotty/tools/dotc/core/Contexts.scala
index d69c7408d0b1..7f5779bb6127 100644
--- a/compiler/src/dotty/tools/dotc/core/Contexts.scala
+++ b/compiler/src/dotty/tools/dotc/core/Contexts.scala
@@ -777,13 +777,13 @@ object Contexts {
 
   extension (c: Context)
     def addNotNullInfo(info: NotNullInfo) =
-      c.withNotNullInfos(c.notNullInfos.extendWith(info))
+      if c.explicitNulls then c.withNotNullInfos(c.notNullInfos.extendWith(info)) else c
 
     def addNotNullRefs(refs: Set[TermRef]) =
-      c.addNotNullInfo(NotNullInfo(refs, Set()))
+      if c.explicitNulls then c.addNotNullInfo(NotNullInfo(refs, Set())) else c
 
     def withNotNullInfos(infos: List[NotNullInfo]): Context =
-      if c.notNullInfos eq infos then c else c.fresh.setNotNullInfos(infos)
+      if !c.explicitNulls || (c.notNullInfos eq infos) then c else c.fresh.setNotNullInfos(infos)
 
     def relaxedOverrideContext: Context =
       c.withModeBits(c.mode &~ Mode.SafeNulls | Mode.RelaxedOverriding)
diff --git a/compiler/src/dotty/tools/dotc/typer/Nullables.scala b/compiler/src/dotty/tools/dotc/typer/Nullables.scala
index 2193866893f6..310ca999f4c5 100644
--- a/compiler/src/dotty/tools/dotc/typer/Nullables.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Nullables.scala
@@ -235,7 +235,7 @@ object Nullables:
     */
     @tailrec def impliesNotNull(ref: TermRef): Boolean = infos match
       case info :: infos1 =>
-        if info.asserted != null && info.asserted.contains(ref) then true
+        if info.asserted == null || info.asserted.contains(ref) then true
         else if info.retracted.contains(ref) then false
         else infos1.impliesNotNull(ref)
       case _ =>
@@ -315,8 +315,8 @@ object Nullables:
   extension (tree: Tree)
 
     /* The `tree` with added nullability attachment */
-    def withNotNullInfo(info: NotNullInfo): tree.type =
-      if !info.isEmpty then tree.putAttachment(NNInfo, info)
+    def withNotNullInfo(info: NotNullInfo)(using Context): tree.type =
+      if ctx.explicitNulls && !info.isEmpty then tree.putAttachment(NNInfo, info)
       tree
 
     /* Collect the nullability info from parts of `tree` */
@@ -335,13 +335,15 @@ object Nullables:
 
     /* The nullability info of `tree` */
     def notNullInfo(using Context): NotNullInfo =
-      val tree1 = stripInlined(tree)
-      tree1.getAttachment(NNInfo) match
-        case Some(info) if !ctx.erasedTypes => info
-        case _ =>
-          val nnInfo = tree1.collectNotNullInfo
-          tree1.withNotNullInfo(nnInfo)
-          nnInfo
+      if !ctx.explicitNulls then NotNullInfo.empty
+      else
+        val tree1 = stripInlined(tree)
+        tree1.getAttachment(NNInfo) match
+          case Some(info) if !ctx.erasedTypes => info
+          case _ =>
+            val nnInfo = tree1.collectNotNullInfo
+            tree1.withNotNullInfo(nnInfo)
+            nnInfo
 
     /* The nullability info of `tree`, assuming it is a condition that evaluates to `c` */
     def notNullInfoIf(c: Boolean)(using Context): NotNullInfo =
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 1e461a5e1cb7..cea47817bb88 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -2849,6 +2849,8 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
     val vdef1 = assignType(cpy.ValDef(vdef)(name, tpt1, rhs1), sym)
     postProcessInfo(vdef1, sym)
     vdef1.setDefTree
+    val nnInfo = rhs1.notNullInfo
+    vdef1.withNotNullInfo(if sym.is(Lazy) then nnInfo.retractedInfo else nnInfo)
   }
 
   private def retractDefDef(sym: Symbol)(using Context): Tree =
diff --git a/tests/explicit-nulls/pos/after-termination.scala b/tests/explicit-nulls/pos/after-termination.scala
new file mode 100644
index 000000000000..00a57e371281
--- /dev/null
+++ b/tests/explicit-nulls/pos/after-termination.scala
@@ -0,0 +1,17 @@
+class C(val x: Int, val next: C | Null)
+
+def test1(x: String | Null, c: C | Null): Int =
+  return 0
+  // We know that the following code is unreachable,
+  // so we can treat `x`, `c`, and any variable/path non-nullable.
+  x.length + c.next.x
+
+def test2(x: String | Null, c: C | Null): Int =
+  throw new Exception()
+  x.length + c.next.x
+
+def fail(): Nothing = ???
+
+def test3(x: String | Null, c: C | Null): Int =
+  fail()
+  x.length + c.next.x
diff --git a/tests/explicit-nulls/unsafe-common/unsafe-overload.scala b/tests/explicit-nulls/unsafe-common/unsafe-overload.scala
index e7e551f1bda1..21af320806d8 100644
--- a/tests/explicit-nulls/unsafe-common/unsafe-overload.scala
+++ b/tests/explicit-nulls/unsafe-common/unsafe-overload.scala
@@ -16,8 +16,8 @@ class S {
   val o: O = ???
 
   locally {
-    def h1(hh: String => String) = ???
-    def h2(hh: Array[String] => Array[String]) = ???
+    def h1(hh: String => String): Unit = ???
+    def h2(hh: Array[String] => Array[String]): Unit = ???
     def f1(x: String | Null): String | Null = ???
     def f2(x: Array[String | Null]):  Array[String | Null] = ???
 
@@ -29,10 +29,10 @@ class S {
   }
 
   locally {
-    def h1(hh: String | Null => String | Null) = ???
-    def h2(hh: Array[String | Null] => Array[String | Null]) = ???
+    def h1(hh: String | Null => String | Null): Unit = ???
+    def h2(hh: Array[String | Null] => Array[String | Null]): Unit = ???
     def g1(x: String): String = ???
-    def g2(x: Array[String]):  Array[String] = ???
+    def g2(x: Array[String]): Array[String] = ???
 
     h1(g1) // error
     h1(o.g) // error
@@ -51,7 +51,7 @@ class S {
 
   locally {
     def g1(x: String): String = ???
-    def g2(x: Array[String]):  Array[String] = ???
+    def g2(x: Array[String]): Array[String] = ???
 
     o.i(g1) // error
     o.i(g2) // error

From 200c038a818ed41d8a07a18b540abd0748a99f12 Mon Sep 17 00:00:00 2001
From: noti0na1 <noti0na1@users.noreply.github.com>
Date: Tue, 10 Dec 2024 12:24:34 +0100
Subject: [PATCH 10/17] Comment on the empty cases in notNullInfoFromCases.

---
 compiler/src/dotty/tools/dotc/typer/Typer.scala | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index cea47817bb88..2c513a41a039 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -2147,9 +2147,11 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
   }
 
   private def notNullInfoFromCases(initInfo: NotNullInfo, cases: List[CaseDef])(using Context): NotNullInfo =
-    if cases.nonEmpty then
-      initInfo.seq(cases.map(_.notNullInfo).reduce(_.alt(_)))
-    else initInfo
+    if cases.isEmpty then
+      // Empty cases is not allowed for match tree in the source code,
+      // but it can be generated by inlining: `tests/pos/i19198.scala`.
+      initInfo
+    else cases.map(_.notNullInfo).reduce(_.alt(_))
 
   def typedCases(cases: List[untpd.CaseDef], sel: Tree, wideSelType0: Type, pt: Type)(using Context): List[CaseDef] =
     var caseCtx = ctx

From ecf9be9532b9bd4729f4a6ec7358ef59ff96246a Mon Sep 17 00:00:00 2001
From: Wojciech Mazur <wmazur@virtuslab.com>
Date: Tue, 10 Dec 2024 16:46:19 +0100
Subject: [PATCH 11/17] Fix Chocolatey publish workflow

---
 .github/workflows/publish-chocolatey.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/publish-chocolatey.yml b/.github/workflows/publish-chocolatey.yml
index 3b31728a50ba..88a8a7913188 100644
--- a/.github/workflows/publish-chocolatey.yml
+++ b/.github/workflows/publish-chocolatey.yml
@@ -35,5 +35,5 @@ jobs:
         with:
           name: scala.nupkg
       - name: Publish the package to Chocolatey
-        run: choco push scala.nupkg --source https://push.chocolatey.org/ --api-key ${{ secrets.API-KEY }}
+        run: choco push scala.${{inputs.version}}.nupkg --source https://push.chocolatey.org/ --api-key ${{ secrets.API-KEY }}
         
\ No newline at end of file

From 70cc1a19da85f502fc58c8f0ed4fbe6ff9444e7d Mon Sep 17 00:00:00 2001
From: Rui Chen <rui@chenrui.dev>
Date: Tue, 10 Dec 2024 15:38:45 -0500
Subject: [PATCH 12/17] fix: update `scala-cli.jar` path

Signed-off-by: Rui Chen <rui@chenrui.dev>
---
 dist/libexec/cli-common-platform     | 2 +-
 dist/libexec/cli-common-platform.bat | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/dist/libexec/cli-common-platform b/dist/libexec/cli-common-platform
index a5906e882bb4..e56f5221dbf2 100644
--- a/dist/libexec/cli-common-platform
+++ b/dist/libexec/cli-common-platform
@@ -1,3 +1,3 @@
 #!/usr/bin/env bash
 
-SCALA_CLI_CMD_BASH=("\"$JAVACMD\"" "-jar \"$PROG_HOME/bin/scala-cli.jar\"")
+SCALA_CLI_CMD_BASH=("\"$JAVACMD\"" "-jar \"$PROG_HOME/libexec/scala-cli.jar\"")
diff --git a/dist/libexec/cli-common-platform.bat b/dist/libexec/cli-common-platform.bat
index 99103266c1d9..45b09f3460e6 100644
--- a/dist/libexec/cli-common-platform.bat
+++ b/dist/libexec/cli-common-platform.bat
@@ -2,4 +2,4 @@
 
 @rem we need to escape % in the java command path, for some reason this doesnt work in common.bat
 set "_JAVACMD=!_JAVACMD:%%=%%%%!"
-set SCALA_CLI_CMD_WIN="%_JAVACMD%" "-jar" "%_PROG_HOME%\bin\scala-cli.jar"
\ No newline at end of file
+set SCALA_CLI_CMD_WIN="%_JAVACMD%" "-jar" "%_PROG_HOME%\libexec\scala-cli.jar"

From 004cfc5ed76ea34245ca30c9cc3872e86f9e6d5e Mon Sep 17 00:00:00 2001
From: Eugene Yokota <eed3si9n@gmail.com>
Date: Wed, 11 Dec 2024 01:32:40 -0500
Subject: [PATCH 13/17] refactor: improve Given search preference warning

**Problem**
It wasn't clear what action users was suppose to take to suppress
the new-from-3.6 Given search preference warning.

**Solution**
1. This refactors the code to give the warning an error code E205.
2. In case of warnings, tell the user to choose -source 3.5 vs 3.7,
   or use nowarn annotation.
---
 .../tools/dotc/reporting/ErrorMessageID.scala |  1 +
 .../dotty/tools/dotc/reporting/messages.scala | 38 +++++++++++++++++++
 .../dotty/tools/dotc/typer/Implicits.scala    | 22 ++---------
 tests/neg/given-triangle.check                |  6 +--
 tests/warn/i21036a.check                      | 11 ++++--
 tests/warn/i21036b.check                      |  9 +++--
 tests/warn/i21036c.scala                      |  7 ++++
 7 files changed, 66 insertions(+), 28 deletions(-)
 create mode 100644 tests/warn/i21036c.scala

diff --git a/compiler/src/dotty/tools/dotc/reporting/ErrorMessageID.scala b/compiler/src/dotty/tools/dotc/reporting/ErrorMessageID.scala
index 2c3774b59a9a..d3467fe70c52 100644
--- a/compiler/src/dotty/tools/dotc/reporting/ErrorMessageID.scala
+++ b/compiler/src/dotty/tools/dotc/reporting/ErrorMessageID.scala
@@ -218,6 +218,7 @@ enum ErrorMessageID(val isActive: Boolean = true) extends java.lang.Enum[ErrorMe
   case QuotedTypeMissingID // errorNumber: 202
   case DeprecatedAssignmentSyntaxID // errorNumber: 203
   case DeprecatedInfixNamedArgumentSyntaxID // errorNumber: 204
+  case GivenSearchPriorityID // errorNumber: 205
 
   def errorNumber = ordinal - 1
 
diff --git a/compiler/src/dotty/tools/dotc/reporting/messages.scala b/compiler/src/dotty/tools/dotc/reporting/messages.scala
index b396aa62f599..75aa553827f2 100644
--- a/compiler/src/dotty/tools/dotc/reporting/messages.scala
+++ b/compiler/src/dotty/tools/dotc/reporting/messages.scala
@@ -3361,3 +3361,41 @@ class DeprecatedInfixNamedArgumentSyntax()(using Context) extends SyntaxMsg(Depr
         + Message.rewriteNotice("This", version = SourceVersion.`3.6-migration`)
 
   def explain(using Context) = ""
+
+class GivenSearchPriorityWarning(
+    pt: Type,
+    cmp: Int,
+    prev: Int,
+    winner: TermRef,
+    loser: TermRef,
+    isLastOldVersion: Boolean
+)(using Context) extends Message(GivenSearchPriorityID):
+  def kind = MessageKind.PotentialIssue
+  def choice(nth: String, c: Int) =
+    if c == 0 then "none - it's ambiguous"
+    else s"the $nth alternative"
+  val (change, whichChoice) =
+    if isLastOldVersion
+    then ("will change in the future release", "Current choice ")
+    else ("has changed",                       "Previous choice")
+  def warningMessage: String =
+    i"""Given search preference for $pt between alternatives
+       |  ${loser}
+       |and
+       |  ${winner}
+       |$change.
+       |$whichChoice       : ${choice("first", prev)}
+       |Choice from Scala 3.7 : ${choice("second", cmp)}"""
+  def migrationHints: String =
+    i"""Suppress this warning by choosing -source 3.5, -source 3.7, or
+       |by using @annotation.nowarn("id=205")"""
+  def ambiguousNote: String =
+    i"""
+       |
+       |Note: $warningMessage"""
+  def msg(using Context) =
+    i"""$warningMessage
+       |
+       |$migrationHints"""
+
+  def explain(using Context) = ""
diff --git a/compiler/src/dotty/tools/dotc/typer/Implicits.scala b/compiler/src/dotty/tools/dotc/typer/Implicits.scala
index 228206d8fb1e..193cc443b4ae 100644
--- a/compiler/src/dotty/tools/dotc/typer/Implicits.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Implicits.scala
@@ -549,10 +549,10 @@ object Implicits:
   /** An ambiguous implicits failure */
   class AmbiguousImplicits(val alt1: SearchSuccess, val alt2: SearchSuccess, val expectedType: Type, val argument: Tree, val nested: Boolean = false) extends SearchFailureType:
 
-    private[Implicits] var priorityChangeWarnings: List[Message] = Nil
+    private[Implicits] var priorityChangeWarnings: List[GivenSearchPriorityWarning] = Nil
 
     def priorityChangeWarningNote(using Context): String =
-      priorityChangeWarnings.map(msg => s"\n\nNote: $msg").mkString
+      priorityChangeWarnings.map(_.ambiguousNote).mkString
 
     def msg(using Context): Message =
       var str1 = err.refStr(alt1.ref)
@@ -1312,7 +1312,7 @@ trait Implicits:
       // A map that associates a priority change warning (between -source 3.6 and 3.7)
       // with the candidate refs mentioned in the warning. We report the associated
       // message if one of the critical candidates is part of the result of the implicit search.
-      val priorityChangeWarnings = mutable.ListBuffer[(/*critical:*/ List[TermRef], Message)]()
+      val priorityChangeWarnings = mutable.ListBuffer[(/*critical:*/ List[TermRef], GivenSearchPriorityWarning)]()
 
       val sv = Feature.sourceVersion
       val isLastOldVersion = sv.stable == SourceVersion.`3.6`
@@ -1353,21 +1353,7 @@ trait Implicits:
                     cmp match
                       case 1 => (alt2, alt1)
                       case -1 => (alt1, alt2)
-              def choice(nth: String, c: Int) =
-                if c == 0 then  "none - it's ambiguous"
-                else s"the $nth alternative"
-              val (change, whichChoice) =
-                if isLastOldVersion
-                then ("will change", "Current choice ")
-                else ("has changed", "Previous choice")
-              val msg =
-                em"""Given search preference for $pt between alternatives
-                    |  ${loser.ref}
-                    |and
-                    |  ${winner.ref}
-                    |$change.
-                    |$whichChoice          : ${choice("first", prev)}
-                    |New choice from Scala 3.7: ${choice("second", cmp)}"""
+              val msg = GivenSearchPriorityWarning(pt, cmp, prev, winner.ref, loser.ref, isLastOldVersion)
               val critical = alt1.ref :: alt2.ref :: Nil
               priorityChangeWarnings += ((critical, msg))
               if isLastOldVersion then prev else cmp
diff --git a/tests/neg/given-triangle.check b/tests/neg/given-triangle.check
index f366c18e78f0..8a05ed4b3129 100644
--- a/tests/neg/given-triangle.check
+++ b/tests/neg/given-triangle.check
@@ -7,6 +7,6 @@
    |  (given_B : B)
    |and
    |  (given_A : A)
-   |will change.
-   |Current choice           : the first alternative
-   |New choice from Scala 3.7: the second alternative
+   |will change in the future release.
+   |Current choice        : the first alternative
+   |Choice from Scala 3.7 : the second alternative
diff --git a/tests/warn/i21036a.check b/tests/warn/i21036a.check
index 63d611a6e246..6ce5b94d123f 100644
--- a/tests/warn/i21036a.check
+++ b/tests/warn/i21036a.check
@@ -1,10 +1,13 @@
--- Warning: tests/warn/i21036a.scala:7:17 ------------------------------------------------------------------------------
+-- [E205] Potential Issue Warning: tests/warn/i21036a.scala:7:17 -------------------------------------------------------
 7 |val y = summon[A] // warn
   |                 ^
   |                 Given search preference for A between alternatives
   |                   (b : B)
   |                 and
   |                   (a : A)
-  |                 will change.
-  |                 Current choice           : the first alternative
-  |                 New choice from Scala 3.7: the second alternative
+  |                 will change in the future release.
+  |                 Current choice        : the first alternative
+  |                 Choice from Scala 3.7 : the second alternative
+  |
+  |                 Suppress this warning by choosing -source 3.5, -source 3.7, or
+  |                 by using @annotation.nowarn("id=205")
diff --git a/tests/warn/i21036b.check b/tests/warn/i21036b.check
index dfa19a0e9bb1..da0639438c86 100644
--- a/tests/warn/i21036b.check
+++ b/tests/warn/i21036b.check
@@ -1,4 +1,4 @@
--- Warning: tests/warn/i21036b.scala:7:17 ------------------------------------------------------------------------------
+-- [E205] Potential Issue Warning: tests/warn/i21036b.scala:7:17 -------------------------------------------------------
 7 |val y = summon[A] // warn
   |                 ^
   |                 Given search preference for A between alternatives
@@ -6,5 +6,8 @@
   |                 and
   |                   (a : A)
   |                 has changed.
-  |                 Previous choice          : the first alternative
-  |                 New choice from Scala 3.7: the second alternative
+  |                 Previous choice       : the first alternative
+  |                 Choice from Scala 3.7 : the second alternative
+  |
+  |                 Suppress this warning by choosing -source 3.5, -source 3.7, or
+  |                 by using @annotation.nowarn("id=205")
diff --git a/tests/warn/i21036c.scala b/tests/warn/i21036c.scala
new file mode 100644
index 000000000000..4015cc8a84bb
--- /dev/null
+++ b/tests/warn/i21036c.scala
@@ -0,0 +1,7 @@
+trait A
+trait B extends A
+given b: B = ???
+given a: A = ???
+
+@annotation.nowarn("id=205")
+val y = summon[A] // don't warn
\ No newline at end of file

From 74417916fd97990a77c80462758ab240e52aa586 Mon Sep 17 00:00:00 2001
From: Wojciech Mazur <wmazur@virtuslab.com>
Date: Wed, 11 Dec 2024 17:54:57 +0100
Subject: [PATCH 14/17] Update reference, MiMa previous version and sync TASTy
 version (#22187)

* Update reference version to 3.6.3-RC1 (from 3.6.0)
* Update mima previous binary verison to 3.6.2 (instead of unofficial
3.6.1)
* Set TASTy version to `28.7-experimental-1` - it should have been set
when branching of 3.6.3.
* We now document better how and when tasty version should be set
* Add additional runtime test to ensure we don't emit invalid TASTy
version during Release / NIGHTLY releases and the expected version set
in build matches version defined in TastyFormat
---
 project/Build.scala                           | 63 +++++++++++++++++--
 tasty/src/dotty/tools/tasty/TastyFormat.scala |  2 +-
 .../tools/tasty/BuildTastyVersionTest.scala   | 26 ++++++++
 3 files changed, 85 insertions(+), 6 deletions(-)
 create mode 100644 tasty/test/dotty/tools/tasty/BuildTastyVersionTest.scala

diff --git a/project/Build.scala b/project/Build.scala
index f36171aabbcd..db3f149cbab6 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -93,11 +93,12 @@ object Build {
 
   /** Version of the Scala compiler used to build the artifacts.
    *  Reference version should track the latest version pushed to Maven:
-   *  - In main branch it should be the last RC version (using experimental TASTy required for non-bootstrapped tests)
+   *  - In main branch it should be the last RC version
    *  - In release branch it should be the last stable release
-   *  3.6.0-RC1 was released as 3.6.0 - it's having and experimental TASTy version
+   * 
+   *  Warning: Change of this variable needs to be consulted with `expectedTastyVersion` 
    */
-  val referenceVersion = "3.6.0"
+  val referenceVersion = "3.6.3-RC1"
 
   /** Version of the Scala compiler targeted in the current release cycle
    *  Contains a version without RC/SNAPSHOT/NIGHTLY specific suffixes
@@ -105,6 +106,8 @@ object Build {
    *
    *  Should only be referred from `dottyVersion` or settings/tasks requiring simplified version string,
    *  eg. `compatMode` or Windows native distribution version.
+   * 
+   *  Warning: Change of this variable might require updating `expectedTastyVersion` 
    */
   val developedVersion = "3.6.4"
 
@@ -116,6 +119,25 @@ object Build {
    *  During final, stable release is set exactly to `developedVersion`.
   */
   val baseVersion = s"$developedVersion-RC1"
+  
+  /** The version of TASTY that should be emitted, checked in runtime test 
+   *  For defails on how TASTY version should be set see related discussions: 
+   *    - https://github.com/scala/scala3/issues/13447#issuecomment-912447107
+   *    - https://github.com/scala/scala3/issues/14306#issuecomment-1069333516
+   *    - https://github.com/scala/scala3/pull/19321
+   *   
+   *  Simplified rules, given 3.$minor.$patch = $developedVersion
+   *    - Major version is always 28
+   *    - TASTY minor version:
+   *      - in main (NIGHTLY): {if $patch == 0 then $minor else ${minor + 1}}
+   *      - in release branch is always equal to $minor
+   *    - TASTY experimental version:
+   *      - in main (NIGHTLY) is always experimental
+   *      - in release candidate branch is experimental if {patch == 0}
+   *      - in stable release is always non-experimetnal
+   */
+  val expectedTastyVersion = "28.7-experimental-1"
+  checkReleasedTastyVersion()
 
   /** Final version of Scala compiler, controlled by environment variables. */
   val dottyVersion = {
@@ -149,9 +171,9 @@ object Build {
    *  For a developedVersion `3.M.P` the mimaPreviousDottyVersion should be set to:
    *   - `3.M.0`     if `P > 0`
    *   - `3.(M-1).0` if `P = 0`
-   *  3.6.1 is an exception from this rule - 3.6.0 was a broken release
+   *  3.6.2 is an exception from this rule - 3.6.0 was a broken release, 3.6.1 was hotfix (unstable) release
    */
-  val mimaPreviousDottyVersion = "3.6.1"
+  val mimaPreviousDottyVersion = "3.6.2"
 
   /** LTS version against which we check binary compatibility.
    *
@@ -2424,6 +2446,9 @@ object Build {
       settings(disableDocSetting).
       settings(
         versionScheme := Some("semver-spec"),
+        Test / envVars ++= Map(
+          "EXPECTED_TASTY_VERSION" -> expectedTastyVersion,
+        ),
         if (mode == Bootstrapped) Def.settings(
           commonMiMaSettings,
           mimaForwardIssueFilters := MiMaFilters.TastyCore.ForwardsBreakingChanges,
@@ -2473,6 +2498,34 @@ object Build {
       case Bootstrapped => commonBootstrappedSettings
     })
   }
+  
+  /* Tests TASTy version invariants during NIGHLY, RC or Stable releases */
+  def checkReleasedTastyVersion(): Unit = {
+    lazy val (scalaMinor, scalaPatch, scalaIsRC) = baseVersion.split("\\.|-").take(4) match {
+      case Array("3", minor, patch)    => (minor.toInt, patch.toInt, false)
+      case Array("3", minor, patch, _) => (minor.toInt, patch.toInt, true)
+      case other => sys.error(s"Invalid Scala base version string: $baseVersion")
+    }
+    lazy val (tastyMinor, tastyIsExperimental) = expectedTastyVersion.split("\\.|-").take(4) match {
+      case Array("28", minor)                    => (minor.toInt, false)
+      case Array("28", minor, "experimental", _) => (minor.toInt, true)
+      case other => sys.error(s"Invalid TASTy version string: $expectedTastyVersion")
+    }
+     
+    if(isNightly) {
+      assert(tastyIsExperimental, "TASTY needs to be experimental in nightly builds")
+      val expectedTastyMinor = if(scalaPatch == 0) scalaMinor else scalaMinor + 1
+      assert(tastyMinor == expectedTastyMinor, "Invalid TASTy minor version")
+    }
+    
+    if(isRelease) {
+      assert(scalaMinor == tastyMinor, "Minor versions of TASTY vesion and Scala version should match in release builds")
+      if (scalaIsRC && scalaPatch == 0)
+        assert(tastyIsExperimental, "TASTy should be experimental when releasing a new minor version RC")
+      else
+        assert(!tastyIsExperimental, "Stable version cannot use experimental TASTY") 
+    }
+  }
 }
 
 object ScaladocConfigs {
diff --git a/tasty/src/dotty/tools/tasty/TastyFormat.scala b/tasty/src/dotty/tools/tasty/TastyFormat.scala
index 8f5f9d57a8a5..8ff590fefec5 100644
--- a/tasty/src/dotty/tools/tasty/TastyFormat.scala
+++ b/tasty/src/dotty/tools/tasty/TastyFormat.scala
@@ -324,7 +324,7 @@ object TastyFormat {
    *  compatibility, but remains backwards compatible, with all
    *  preceding `MinorVersion`.
    */
-  final val MinorVersion: Int = 6
+  final val MinorVersion: Int = 7
 
   /** Natural Number. The `ExperimentalVersion` allows for
    *  experimentation with changes to TASTy without committing
diff --git a/tasty/test/dotty/tools/tasty/BuildTastyVersionTest.scala b/tasty/test/dotty/tools/tasty/BuildTastyVersionTest.scala
new file mode 100644
index 000000000000..d2e62e1f9eb0
--- /dev/null
+++ b/tasty/test/dotty/tools/tasty/BuildTastyVersionTest.scala
@@ -0,0 +1,26 @@
+package dotty.tools.tasty
+
+import org.junit.Assert._
+import org.junit.Test
+
+import TastyBuffer._
+
+// Tests ensuring TASTY version emitted by compiler is matching expected TASTY version
+class BuildTastyVersionTest {
+  
+  val CurrentTastyVersion = TastyVersion(TastyFormat.MajorVersion, TastyFormat.MinorVersion, TastyFormat.ExperimentalVersion)
+  
+  // Needs to be defined in build Test/envVars
+  val ExpectedTastyVersionEnvVar = "EXPECTED_TASTY_VERSION"
+  
+  @Test def testBuildTastyVersion(): Unit = {
+    val expectedVersion = sys.env.get(ExpectedTastyVersionEnvVar)
+      .getOrElse(fail(s"Env variable $ExpectedTastyVersionEnvVar not defined"))
+      .match {
+        case s"$major.$minor-experimental-$experimental" => TastyVersion(major.toInt, minor.toInt, experimental.toInt)
+        case s"$major.$minor" if minor.forall(_.isDigit) => TastyVersion(major.toInt, minor.toInt, 0)
+        case other => fail(s"Invalid TASTY version string: $other")
+      }
+    assertEquals(CurrentTastyVersion, expectedVersion)
+  }
+}

From 93ef8107c78d9a311f01716224130d7a7a5bd784 Mon Sep 17 00:00:00 2001
From: Matt Bovel <matthieu@bovel.net>
Date: Thu, 12 Dec 2024 10:17:29 +0100
Subject: [PATCH 15/17] Remove tests/pos-with-compiler-cc from VSCode ignored
 files

---
 .vscode-template/settings.json | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/.vscode-template/settings.json b/.vscode-template/settings.json
index 257da27b118f..8cf2d29e3bae 100644
--- a/.vscode-template/settings.json
+++ b/.vscode-template/settings.json
@@ -9,7 +9,6 @@
     "**/*.class": true,
     "**/*.tasty": true,
     "**/target/": true,
-    "community-build/community-projects": true,
-    "tests/pos-with-compiler-cc/dotc/**/*.scala": true
+    "community-build/community-projects": true
   }
 }

From 5b3d82a41aafcaccab99bad95aa5a035a5dacabb Mon Sep 17 00:00:00 2001
From: Wojciech Mazur <wmazur@virtuslab.com>
Date: Thu, 12 Dec 2024 15:21:33 +0100
Subject: [PATCH 16/17] Fix layout of released SDK archives, restore
 intermiediete top-level directory  (#22199)

Fixes #22194

Restores top-level directory `scala3-${version}` that is present in
artifacts published before Scala 3.6, removed during hotfix 3.6.1
release.
We now follow the [Well formed SDK archives
layout](https://github.com/sdkman/sdkman-cli/wiki/Well-formed-SDK-archives).
Removing the top-level directory even though at first glance looked like
an improvement was in fact introducing problems to multiple package
managers and build tools.
---
 .github/workflows/ci.yaml | 12 +++---------
 project/Build.scala       |  9 ++++++++-
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index a2006e16c7e8..cc1eb5d40d97 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -801,19 +801,13 @@ jobs:
             distDir="$3"
 
             # Build binaries
-            ./project/scripts/sbt "${sbtProject}/Universal/stage"
+            ./project/scripts/sbt "all ${sbtProject}/Universal/packageBin ${sbtProject}/Universal/packageZipTarball"
 
-            outputPath="${distDir}/target/universal/stage"
             artifactName="scala3-${{ env.RELEASE_TAG }}${distroSuffix}"
-            zipArchive="${artifactName}.zip"
-            tarGzArchive="${artifactName}.tar.gz"
-
-            cwd=$(pwd)
-            (cd $outputPath && zip -r ${zipArchive} . && mv ${zipArchive} "${cwd}/")
-            tar -czf ${tarGzArchive} -C "$outputPath" .
 
             # Caluclate SHA for each of archive files
-            for file in "${zipArchive}" "${tarGzArchive}"; do
+            for file in "${artifactName}.zip" "${artifactName}.tar.gz"; do
+              mv ${distDir}/target/universal/$file $file
               sha256sum "${file}" > "${file}.sha256"
             done
           }
diff --git a/project/Build.scala b/project/Build.scala
index db3f149cbab6..5aec4a4231a6 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -2257,7 +2257,14 @@ object Build {
     // ========
     Universal / stage := (Universal / stage).dependsOn(republish).value,
     Universal / packageBin := (Universal / packageBin).dependsOn(republish).value,
-    Universal / packageZipTarball := (Universal / packageZipTarball).dependsOn(republish).value,
+    Universal / packageZipTarball := (Universal / packageZipTarball).dependsOn(republish)
+      .map { archiveFile =>
+        // Rename .tgz to .tar.gz for consistency with previous versions
+        val renamedFile = archiveFile.getParentFile() / archiveFile.getName.replaceAll("\\.tgz$", ".tar.gz")
+        IO.move(archiveFile, renamedFile)
+        renamedFile
+      }
+      .value,
     // ========
     Universal / mappings ++= directory(dist.base / "bin"),
     Universal / mappings ++= directory(republishRepo.value / "maven2"),

From 6b9f9f797e78f32b135b7cc6bc941e10d073dd7f Mon Sep 17 00:00:00 2001
From: kasiaMarek <kasia@marek.net>
Date: Fri, 6 Dec 2024 18:37:53 +0100
Subject: [PATCH 17/17] Add type parameters derived from enum to default param
 getters of enum cases

---
 .../src/dotty/tools/dotc/ast/Desugar.scala    | 19 ++++++++++++-------
 tests/pos/i22137.scala                        |  5 +++++
 2 files changed, 17 insertions(+), 7 deletions(-)
 create mode 100644 tests/pos/i22137.scala

diff --git a/compiler/src/dotty/tools/dotc/ast/Desugar.scala b/compiler/src/dotty/tools/dotc/ast/Desugar.scala
index 56c153498f87..a95e64e24b85 100644
--- a/compiler/src/dotty/tools/dotc/ast/Desugar.scala
+++ b/compiler/src/dotty/tools/dotc/ast/Desugar.scala
@@ -694,15 +694,15 @@ object desugar {
     val originalTparams = constr1.leadingTypeParams
     val originalVparamss = asTermOnly(constr1.trailingParamss)
     lazy val derivedEnumParams = enumClass.typeParams.map(derivedTypeParamWithVariance)
-    val impliedTparams =
-      if (isEnumCase) {
+    val enumTParams =
+      if isEnumCase then
         val tparamReferenced = typeParamIsReferenced(
-            enumClass.typeParams, originalTparams, originalVparamss, parents)
-        if (originalTparams.isEmpty && (parents.isEmpty || tparamReferenced))
+          enumClass.typeParams, originalTparams, originalVparamss, parents)
+        if originalTparams.isEmpty && (parents.isEmpty || tparamReferenced) then
           derivedEnumParams.map(tdef => tdef.withFlags(tdef.mods.flags | PrivateLocal))
-        else originalTparams
-      }
-      else originalTparams
+        else Nil
+      else Nil
+    val impliedTparams = enumTParams ++ originalTparams
 
     if mods.is(Trait) then
       for vparams <- originalVparamss; vparam <- vparams do
@@ -735,6 +735,11 @@ object desugar {
         derived.withAnnotations(Nil)
 
     val constr = cpy.DefDef(constr1)(paramss = joinParams(constrTparams, constrVparamss))
+    if enumTParams.nonEmpty then
+      defaultGetters = defaultGetters.map:
+        case ddef: DefDef =>
+          val tParams = enumTParams.map(tparam => toMethParam(tparam, KeepAnnotations.All))
+          cpy.DefDef(ddef)(paramss = joinParams(tParams, ddef.trailingParamss))
 
     val (normalizedBody, enumCases, enumCompanionRef) = {
       // Add constructor type parameters and evidence implicit parameters
diff --git a/tests/pos/i22137.scala b/tests/pos/i22137.scala
new file mode 100644
index 000000000000..b52dd9171146
--- /dev/null
+++ b/tests/pos/i22137.scala
@@ -0,0 +1,5 @@
+enum Parser[+Value]:
+  case Success(value: Value, issues: Seq[Failure] = Seq.empty) extends Parser[Value]
+  case Failure(exception: Throwable)                           extends Parser[Nothing]
+
+val v = Parser.Success(1)
\ No newline at end of file