Merge branch 'main' into fix-unsafe-null

Author: SuperCl4sh

.github/ISSUE_TEMPLATE/bug.md

@@ -9,19 +9,33 @@ assignees: ''
 
 ## Compiler version
 
-If you're not sure what version you're using, run `print scalaVersion` from sbt
-(if you're running scalac manually, use `scalac -version` instead).
+If you're not sure which version you're using, run `print scalaVersion` from sbt.
+(If you're running scalac manually, use `scalac -version` instead.)
+
+If possible, check if your issue appears in the nightly version of the compiler! For example, in Scala CLI (the `scala`/`scala-cli` runner script), you can use `//> using scala 3.nightly` (or `-S 3.nightly` from the command line) to grab the latest one.
 
 ## Minimized code
 
 <!--
 This code should be self contained, compilable (with possible failures) and as small as possible.
 
-Ideally, we should be able to just copy this code in a file and run `scalac` (and maybe `scala`) to reproduce the issue.
+Ideally, we should be able to just copy this code to a file and run `scalac` (and maybe `scala`) to reproduce the issue.
+
+If the code has external dependencies, please provide the Scala CLI directives (or SBT/other build tool configuration) that describe them.
+Also note that it's easier and faster for the maintenance team to address issues minimised to reproduce bugs without external dependencies.
+
+It's most convenient to also include `using` directives for the Scala version that demonstrates the problem,
+any compiler command-line options, as well as dependencies. An example is provided.
+
+It's also fine to paste the transcript of a REPL session. Note that some bugs may be specific to the REPL.
 -->
 
-```Scala
-println("hello, world")
+```scala
+//> using scala 3.7.0
+//> using options -Wall -Werror
+//> using dep com.outr::scribe:3.16.1
+
+@main def test = println("hello, world")
 ```
 
 ## Output

compiler/src/dotty/tools/MainGenericRunner.scala

@@ -158,7 +158,7 @@ object MainGenericRunner {
         .withScriptArgs(tail*)
         .noSave // -save not useful here
     case arg :: tail =>
-      val line = Try(Source.fromFile(arg).getLines.toList).toOption.flatMap(_.headOption)
+      val line = Try(Source.fromFile(arg).getLines().toList).toOption.flatMap(_.headOption)
       lazy val hasScalaHashbang = { val s = line.getOrElse("") ; s.startsWith("#!") && s.contains("scala") }
       if arg.endsWith(".scala") || arg.endsWith(".sc") || hasScalaHashbang then
         settings

compiler/src/dotty/tools/backend/jvm/Primitives.scala

@@ -150,13 +150,12 @@ object Primitives {
   case object XOR extends LogicalOp
 
   /** Signals the beginning of a series of concatenations.
-    *  On the JVM platform, it should create a new StringBuffer
-    */
+   *  On the JVM platform, it should create a new StringBuilder.
+   */
   case object StartConcat extends Primitive
 
-  /**
-   * type: (buf) => STR
-   * jvm : It should turn the StringBuffer into a String.
+  /** type: (buf) => STR
+   *  jvm : It should turn the StringBuilder into a String.
    */
   case object EndConcat extends Primitive
 

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -703,7 +703,7 @@ object desugar {
     def isNonEnumCase = !isEnumCase && (isCaseClass || isCaseObject)
     val isValueClass = parents.nonEmpty && isAnyVal(parents.head)
       // This is not watertight, but `extends AnyVal` will be replaced by `inline` later.
-    val caseClassInScala2Library = isCaseClass && ctx.settings.YcompileScala2Library.value
+    val caseClassInScala2Library = isCaseClass && Feature.shouldBehaveAsScala2
 
     val originalTparams = constr1.leadingTypeParams
     val originalVparamss = asTermOnly(constr1.trailingParamss)
@@ -922,7 +922,7 @@ object desugar {
           val copyRestParamss = derivedVparamss.tail.nestedMap(vparam =>
             cpy.ValDef(vparam)(rhs = EmptyTree))
           var flags = Synthetic | constr1.mods.flags & copiedAccessFlags
-          if ctx.settings.YcompileScala2Library.value then flags &~= Private
+          if Feature.shouldBehaveAsScala2 then flags &~= Private
           DefDef(
             nme.copy,
             joinParams(derivedTparams, copyFirstParams :: copyRestParamss),
@@ -983,7 +983,7 @@ object desugar {
           else {
             val appMods =
               var flags = Synthetic | constr1.mods.flags & copiedAccessFlags
-              if ctx.settings.YcompileScala2Library.value then flags &~= Private
+              if Feature.shouldBehaveAsScala2 then flags &~= Private
               Modifiers(flags).withPrivateWithin(constr1.mods.privateWithin)
             val appParamss =
               derivedVparamss.nestedZipWithConserve(constrVparamss)((ap, cp) =>
@@ -1066,7 +1066,7 @@ object desugar {
             paramss // drop leading () that got inserted by class
                     // TODO: drop this once we do not silently insert empty class parameters anymore
           case paramss => paramss
-        val finalFlag = if ctx.settings.YcompileScala2Library.value then EmptyFlags else Final
+        val finalFlag = if Feature.shouldBehaveAsScala2 then EmptyFlags else Final
         // implicit wrapper is typechecked in same scope as constructor, so
         // we can reuse the constructor parameters; no derived params are needed.
         DefDef(
@@ -1868,18 +1868,18 @@ object desugar {
   /** Map n-ary function `(x1: T1, ..., xn: Tn) => body` where n != 1 to unary function as follows:
    *
    *    (x$1: (T1, ..., Tn)) => {
-   *      def x1: T1 = x$1._1
+   *      val x1: T1 = x$1._1
    *      ...
-   *      def xn: Tn = x$1._n
+   *      val xn: Tn = x$1._n
    *      body
    *    }
    *
    *  or if `isGenericTuple`
    *
    *    (x$1: (T1, ... Tn) => {
-   *      def x1: T1 = x$1.apply(0)
+   *      val x1: T1 = x$1.apply(0)
    *      ...
-   *      def xn: Tn = x$1.apply(n-1)
+   *      val xn: Tn = x$1.apply(n-1)
    *      body
    *    }
    *

compiler/src/dotty/tools/dotc/ast/TreeInfo.scala

@@ -9,6 +9,7 @@ import Annotations.Annotation
 import NameKinds.ContextBoundParamName
 import typer.ConstFold
 import reporting.trace
+import config.Feature
 
 import Decorators.*
 import Constants.Constant
@@ -264,6 +265,19 @@ trait TreeInfo[T <: Untyped] { self: Trees.Instance[T] =>
     case _                            => false
   }
 
+  /** Expression was written `e: Unit` to quell warnings. Looks into adapted tree. */
+  def isAscribedToUnit(tree: Tree): Boolean =
+    import typer.Typer.AscribedToUnit
+       tree.hasAttachment(AscribedToUnit)
+    || {
+      def loop(tree: Tree): Boolean = tree match
+        case Apply(fn, _)     => fn.hasAttachment(AscribedToUnit) || loop(fn)
+        case TypeApply(fn, _) => fn.hasAttachment(AscribedToUnit) || loop(fn)
+        case Block(_, expr)   => expr.hasAttachment(AscribedToUnit) || loop(expr)
+        case _                => false
+      loop(tree)
+    }
+
   /** Does this CaseDef catch Throwable? */
   def catchesThrowable(cdef: CaseDef)(using Context): Boolean =
     catchesAllOf(cdef, defn.ThrowableType)
@@ -466,7 +480,7 @@ trait UntypedTreeInfo extends TreeInfo[Untyped] { self: Trees.Instance[Untyped]
    */
   private def defKind(tree: Tree)(using Context): FlagSet = unsplice(tree) match {
     case EmptyTree | _: Import => NoInitsInterface
-    case tree: TypeDef if ctx.settings.YcompileScala2Library.value =>
+    case tree: TypeDef if Feature.shouldBehaveAsScala2 =>
       if (tree.isClassDef) EmptyFlags else NoInitsInterface
     case tree: TypeDef => if (tree.isClassDef) NoInits else NoInitsInterface
     case tree: DefDef =>
@@ -479,7 +493,7 @@ trait UntypedTreeInfo extends TreeInfo[Untyped] { self: Trees.Instance[Untyped]
         NoInitsInterface
       else if tree.mods.is(Given) && tree.paramss.isEmpty then
         EmptyFlags // might become a lazy val: TODO: check whether we need to suppress NoInits once we have new lazy val impl
-      else if ctx.settings.YcompileScala2Library.value then
+      else if Feature.shouldBehaveAsScala2 then
         EmptyFlags
       else
         NoInits

compiler/src/dotty/tools/dotc/cc/CCState.scala

@@ -118,7 +118,7 @@ class CCState:
 
   private var capIsRoot: Boolean = false
 
-  private var ignoreFreshLevels: Boolean = false
+  private var collapseFresh: Boolean = false
 
 object CCState:
 
@@ -164,20 +164,21 @@ object CCState:
   /** Is `caps.cap` a root capability that is allowed to subsume other capabilities? */
   def capIsRoot(using Context): Boolean = ccState.capIsRoot
 
-  /** Run `op` under the assumption that all root.Fresh instances are equal.
+  /** Run `op` under the assumption that all FreshCap instances are equal
+   *  to each other and to GlobalCap.
    *  Needed to make override checking of types containing fresh work.
    *  Asserted in override checking, tested in maxSubsumes.
    *  Is this sound? Test case is neg-custom-args/captures/leaked-curried.scala.
    */
-  inline def ignoringFreshLevels[T](op: => T)(using Context): T =
+  inline def withCollapsedFresh[T](op: => T)(using Context): T =
     if isCaptureCheckingOrSetup then
       val ccs = ccState
-      val saved = ccs.ignoreFreshLevels
-      ccs.ignoreFreshLevels = true
-      try op finally ccs.ignoreFreshLevels = saved
+      val saved = ccs.collapseFresh
+      ccs.collapseFresh = true
+      try op finally ccs.collapseFresh = saved
     else op
 
-  /** Should all root.Fresh instances be treated equal? */
-  def ignoreFreshLevels(using Context): Boolean = ccState.ignoreFreshLevels
+  /** Should all FreshCap instances be treated as equal to GlobalCap? */
+  def collapseFresh(using Context): Boolean = ccState.collapseFresh
 
 end CCState