Avoid accidental captures of Context

compiler/src/dotty/tools/dotc/core/Annotations.scala

@@ -117,11 +117,17 @@ object Annotations {
       }
 
     /** Create an annotation where the symbol and the tree are computed lazily. */
-    def deferredSymAndTree(sym: => Symbol, treeFn: Context => Tree)(implicit ctx: Context): Annotation =
+    def deferredSymAndTree(symf: Context => Symbol, treeFn: Context => Tree)(implicit ctx: Context): Annotation =
       new LazyAnnotation {
-        lazy val symf = sym
-
-        override def symbol(implicit ctx: Context): Symbol = symf
+        private[this] var mySym: Symbol = _
+
+        override def symbol(implicit ctx: Context): Symbol = {
+          if (mySym == null || mySym.defRunId != ctx.runId) {
+            mySym = symf(ctx)
+            assert(mySym != null)
+          }
+          mySym
+        }
         def complete(implicit ctx: Context) = treeFn(ctx)
       }
 

compiler/src/dotty/tools/dotc/core/TypeOps.scala

@@ -401,12 +401,12 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
     def forwardRefs(from: Symbol, to: Type, prefs: List[TypeRef]) = to match {
       case to @ TypeBounds(lo1, hi1) if lo1 eq hi1 =>
         for (pref <- prefs) {
-          def forward(): Unit =
+          def forward()(implicit ctx: Context): Unit =
             for (argSym <- pref.decls)
               if (argSym is BaseTypeArg)
                 forwardRef(argSym, from, to, cls, decls)
           pref.info match {
-            case info: TempClassInfo => info.addSuspension(forward)
+            case info: TempClassInfo => info.addSuspension(implicit ctx => forward())
             case _ => forward()
           }
         }

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -3089,14 +3089,14 @@ object Types {
      *  be no longer temporary. These actions will be performed once `cls` gets a real
      *  ClassInfo.
      */
-    private var suspensions: List[() => Unit] = Nil
+    private var suspensions: List[Context => Unit] = Nil
 
-    def addSuspension(suspension: () => Unit): Unit = suspensions ::= suspension
+    def addSuspension(suspension: Context => Unit): Unit = suspensions ::= suspension
 
     /** Install classinfo with known parents in `denot` and resume all suspensions */
     def finalize(denot: SymDenotation, parents: List[TypeRef])(implicit ctx: Context) = {
       denot.info = derivedClassInfo(classParents = parents)
-      suspensions.foreach(_())
+      suspensions.foreach(_(ctx))
     }
   }
 

compiler/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala

@@ -806,7 +806,7 @@ class ClassfileParser(
     def classSymbol(externalName: Name)(implicit ctx: Context): Symbol = {
       /** Return the symbol of `innerName`, having the given `externalName`. */
       def innerSymbol(externalName: Name, innerName: Name, static: Boolean): Symbol = {
-        def getMember(sym: Symbol, name: Name): Symbol =
+        def getMember(sym: Symbol, name: Name)(implicit ctx: Context): Symbol =
           if (static)
             if (sym == classRoot.symbol) staticScope.lookup(name)
             else sym.companionModule.info.member(name).symbol

compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -554,7 +554,9 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table, posUnpickle
             val end = readEnd()
             val tp = readType()
             val lazyAnnotTree = readLater(end, rdr => ctx => rdr.readTerm()(ctx))
-            annots += Annotation.deferredSymAndTree(tp.typeSymbol, _ => lazyAnnotTree.complete)
+            annots += Annotation.deferredSymAndTree(
+              implicit ctx => tp.typeSymbol,
+              implicit ctx => lazyAnnotTree.complete)
           case tag =>
             assert(false, s"illegal modifier tag $tag at $currentAddr, end = $end")
         }
@@ -769,7 +771,7 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table, posUnpickle
       cls.setApplicableFlags(fork.indexStats(end))
       val constr = readIndexedDef().asInstanceOf[DefDef]
 
-      def mergeTypeParamsAndAliases(tparams: List[TypeDef], stats: List[Tree]): (List[Tree], List[Tree]) =
+      def mergeTypeParamsAndAliases(tparams: List[TypeDef], stats: List[Tree])(implicit ctx: Context): (List[Tree], List[Tree]) =
         (tparams, stats) match {
           case (tparam :: tparams1, (alias: TypeDef) :: stats1)
           if tparam.name == alias.name.expandedName(cls) =>

compiler/src/dotty/tools/dotc/core/unpickleScala2/Scala2Unpickler.scala

@@ -932,9 +932,10 @@ class Scala2Unpickler(bytes: Array[Byte], classRoot: ClassDenotation, moduleClas
   protected def deferredAnnot(end: Int)(implicit ctx: Context): Annotation = {
     val start = readIndex
     val atp = readTypeRef()
+    val phase = ctx.phase
     Annotation.deferred(
-      atp.typeSymbol, implicit ctx1 =>
-        atReadPos(start, () => readAnnotationContents(end)(ctx1.withPhase(ctx.phase))))
+      atp.typeSymbol, implicit ctx =>
+        atReadPos(start, () => readAnnotationContents(end)(ctx.withPhase(phase))))
   }
 
   /* Read an abstract syntax tree */

compiler/src/dotty/tools/dotc/printing/PlainPrinter.scala

@@ -7,6 +7,7 @@ import Contexts.Context, Scopes.Scope, Denotations.Denotation, Annotations.Annot
 import StdNames.{nme, tpnme}
 import ast.Trees._, ast._
 import typer.Implicits._
+import typer.ImportInfo
 import config.Config
 import java.lang.Integer.toOctalString
 import config.Config.summarizeDepth
@@ -502,6 +503,17 @@ class PlainPrinter(_ctx: Context) extends Printer {
       "?Unknown Implicit Result?"
   }
 
+  def toText(importInfo: ImportInfo): Text = {
+    val siteStr = importInfo.site.show
+    val exprStr = if (siteStr endsWith ".type") siteStr dropRight 5 else siteStr
+    val selectorStr = importInfo.selectors match {
+      case Ident(name) :: Nil => name.show
+      case _ => "{...}"
+    }
+    s"import $exprStr.$selectorStr"
+  }
+
+
   private var maxSummarized = Int.MaxValue
 
   def summarized[T](depth: Int)(op: => T): T = {

compiler/src/dotty/tools/dotc/printing/Printer.scala

@@ -6,6 +6,7 @@ import Texts._, ast.Trees._
 import Types.Type, Symbols.Symbol, Contexts.Context, Scopes.Scope, Constants.Constant,
        Names.Name, Denotations._, Annotations.Annotation
 import typer.Implicits.SearchResult
+import typer.ImportInfo
 
 /** The base class of all printers
  */
@@ -98,6 +99,9 @@ abstract class Printer {
   /** Textual representation of implicit search result */
   def toText(result: SearchResult): Text
 
+  /** Textual representation of info relating to an import clause */
+  def toText(result: ImportInfo): Text
+
       /** Perform string or text-producing operation `op` so that only a
    *  summarized text with given recursion depth is shown
    */

compiler/src/dotty/tools/dotc/transform/TailRec.scala

@@ -119,7 +119,7 @@ class TailRec extends MiniPhaseTransform with DenotTransformer with FullParamete
             // now this speculatively transforms tree and throws away result in many cases
             val rhsSemiTransformed = {
               val transformer = new TailRecElimination(origMeth, dd.tparams, owner, thisTpe, mandatory, label, abstractOverClass = defIsTopLevel)
-              val rhs = atGroupEnd(transformer.transform(dd.rhs)(_))
+              val rhs = atGroupEnd(implicit ctx => transformer.transform(dd.rhs))
               rewrote = transformer.rewrote
               rhs
             }

compiler/src/dotty/tools/dotc/typer/Applications.scala

@@ -683,7 +683,7 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
      *
      *     { val xs = es; e' = e' + args }
      */
-    def typedOpAssign: Tree = track("typedOpAssign") {
+    def typedOpAssign(implicit ctx: Context): Tree = track("typedOpAssign") {
       val Apply(Select(lhs, name), rhss) = tree
       val lhs1 = typedExpr(lhs)
       val liftedDefs = new mutable.ListBuffer[Tree]
@@ -805,16 +805,16 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
      *  whereas overloaded variants need to have a conforming variant.
      */
     def trySelectUnapply(qual: untpd.Tree)(fallBack: Tree => Tree): Tree = {
-      val genericProto = new UnapplyFunProto(WildcardType, this)
-      def specificProto = new UnapplyFunProto(selType, this)
       // try first for non-overloaded, then for overloaded ocurrences
       def tryWithName(name: TermName)(fallBack: Tree => Tree)(implicit ctx: Context): Tree =
-        tryEither {
-          implicit ctx => typedExpr(untpd.Select(qual, name), specificProto)
+        tryEither { implicit ctx =>
+          val specificProto = new UnapplyFunProto(selType, this)
+          typedExpr(untpd.Select(qual, name), specificProto)
         } {
           (sel, _) =>
-            tryEither {
-              implicit ctx => typedExpr(untpd.Select(qual, name), genericProto)
+            tryEither { implicit ctx =>
+              val genericProto = new UnapplyFunProto(WildcardType, this)
+              typedExpr(untpd.Select(qual, name), genericProto)
             } {
               (_, _) => fallBack(sel)
             }

compiler/src/dotty/tools/dotc/typer/ImportInfo.scala

@@ -5,6 +5,7 @@ package typer
 import ast.{tpd, untpd}
 import ast.Trees._
 import core._
+import printing.{Printer, Showable}
 import util.SimpleMap
 import Symbols._, Names._, Denotations._, Types._, Contexts._, StdNames._, Flags._
 import Decorators.StringInterpolators
@@ -13,9 +14,9 @@ object ImportInfo {
   /** The import info for a root import from given symbol `sym` */
   def rootImport(refFn: () => TermRef)(implicit ctx: Context) = {
     val selectors = untpd.Ident(nme.WILDCARD) :: Nil
-    def expr = tpd.Ident(refFn())
-    def imp = tpd.Import(expr, selectors)
-    new ImportInfo(imp.symbol, selectors, None, isRootImport = true)
+    def expr(implicit ctx: Context) = tpd.Ident(refFn())
+    def imp(implicit ctx: Context) = tpd.Import(expr, selectors)
+    new ImportInfo(implicit ctx => imp.symbol, selectors, None, isRootImport = true)
   }
 }
 
@@ -27,14 +28,14 @@ object ImportInfo {
  *  @param   isRootImport true if this is one of the implicit imports of scala, java.lang,
  *                        scala.Predef or dotty.DottyPredef in the start context, false otherwise.
  */
-class ImportInfo(symf: => Symbol, val selectors: List[untpd.Tree],
-                 symNameOpt: Option[TermName], val isRootImport: Boolean = false)(implicit ctx: Context) {
+class ImportInfo(symf: Context => Symbol, val selectors: List[untpd.Tree],
+                 symNameOpt: Option[TermName], val isRootImport: Boolean = false) extends Showable {
 
   // Dotty deviation: we cannot use a lazy val here for the same reason
   // that we cannot use one for `DottyPredefModuleRef`.
-  def sym = {
+  def sym(implicit ctx: Context) = {
     if (mySym == null) {
-      mySym = symf
+      mySym = symf(ctx)
       assert(mySym != null)
     }
     mySym
@@ -91,7 +92,7 @@ class ImportInfo(symf: => Symbol, val selectors: List[untpd.Tree],
   }
 
   /** The implicit references imported by this import clause */
-  def importedImplicits: List[TermRef] = {
+  def importedImplicits(implicit ctx: Context): List[TermRef] = {
     val pre = site
     if (isWildcardImport) {
       val refs = pre.implicitMembers
@@ -115,23 +116,21 @@ class ImportInfo(symf: => Symbol, val selectors: List[untpd.Tree],
    *      override import Predef.{any2stringAdd => _, StringAdd => _, _} // disables String +
    *      override import java.lang.{}                                   // disables all imports
    */
-  lazy val unimported: Symbol = {
-    lazy val sym = site.termSymbol
-    def maybeShadowsRoot = symNameOpt match {
-      case Some(symName) => defn.ShadowableImportNames.contains(symName)
-      case None => false
+  def unimported(implicit ctx: Context): Symbol = {
+    if (myUnimported == null) {
+      lazy val sym = site.termSymbol
+      def maybeShadowsRoot = symNameOpt match {
+        case Some(symName) => defn.ShadowableImportNames.contains(symName)
+        case None => false
+      }
+      myUnimported =
+        if (maybeShadowsRoot && defn.RootImportTypes.exists(_.symbol == sym)) sym
+        else NoSymbol
+      assert(myUnimported != null)
     }
-    if (maybeShadowsRoot && defn.RootImportTypes.exists(_.symbol == sym)) sym
-    else NoSymbol
+    myUnimported
   }
+  private[this] var myUnimported: Symbol = _
 
-  override def toString = {
-    val siteStr = site.show
-    val exprStr = if (siteStr endsWith ".type") siteStr dropRight 5 else siteStr
-    val selectorStr = selectors match {
-      case Ident(name) :: Nil => name.show
-      case _ => "{...}"
-    }
-    i"import $exprStr.$selectorStr"
-  }
+  def toText(printer: Printer) = printer.toText(this)
 }

compiler/src/dotty/tools/dotc/typer/Namer.scala

@@ -24,6 +24,7 @@ import language.implicitConversions
 import reporting.diagnostic.messages._
 
 trait NamerContextOps { this: Context =>
+  import NamerContextOps._
 
   /** Enter symbol into current class, if current class is owner of current context,
    *  or into current scope, if not. Should always be called instead of scope.enter
@@ -119,22 +120,25 @@ trait NamerContextOps { this: Context =>
     else monotpe
   }
 
-  /** Find moduleClass/sourceModule in effective scope */
-  private def findModuleBuddy(name: Name)(implicit ctx: Context) = {
-    val scope = effectiveScope
-    val it = scope.lookupAll(name).filter(_ is Module)
-    assert(it.hasNext, s"no companion $name in $scope")
-    it.next
-  }
-
   /** Add moduleClass or sourceModule functionality to completer
    *  for a module or module class
    */
-  def adjustModuleCompleter(completer: LazyType, name: Name) =
+  def adjustModuleCompleter(completer: LazyType, name: Name) = {
+    val scope = this.effectiveScope
     if (name.isTermName)
-      completer withModuleClass (_ => findModuleBuddy(name.moduleClassName))
+      completer withModuleClass (implicit ctx => findModuleBuddy(name.moduleClassName, scope))
     else
-      completer withSourceModule (_ => findModuleBuddy(name.sourceModuleName))
+      completer withSourceModule (implicit ctx => findModuleBuddy(name.sourceModuleName, scope))
+  }
+}
+
+object NamerContextOps {
+  /** Find moduleClass/sourceModule in effective scope */
+  private def findModuleBuddy(name: Name, scope: Scope)(implicit ctx: Context) = {
+    val it = scope.lookupAll(name).filter(_ is Module)
+    assert(it.hasNext, s"no companion $name in $scope")
+    it.next
+  }
 }
 
 /** This class creates symbols from definitions and imports and gives them
@@ -378,7 +382,7 @@ class Namer { typer: Typer =>
       case ref: RefTree => Some(ref.name.asTermName)
       case _            => None
     }
-    ctx.fresh.setImportInfo(new ImportInfo(sym, imp.selectors, impNameOpt))
+    ctx.fresh.setImportInfo(new ImportInfo(implicit ctx => sym, imp.selectors, impNameOpt))
   }
 
   /** A new context for the interior of a class */

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -145,7 +145,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
        */
       def bindingString(prec: Int, whereFound: Context, qualifier: String = "") =
         if (prec == wildImport || prec == namedImport) {
-          ex"""imported$qualifier by ${hl"${whereFound.importInfo.toString}"}"""
+          ex"""imported$qualifier by ${hl"${whereFound.importInfo}"}"""
         } else
           ex"""defined$qualifier in ${hl"${whereFound.owner.toString}"}"""
 

tests/repl/imports.check

@@ -11,7 +11,7 @@ scala> buf += xs
 11 |buf += xs
    |       ^^
    |       found:    scala.collection.immutable.List[Int](o.xs)
-   |       required: String
+   |       required: Int
    |       
 scala> buf ++= xs
 val res1: scala.collection.mutable.ListBuffer[Int] = ListBuffer(1, 2, 3)