Merge pull request #1826 from dotty-staging/fix-compile-stdlib

Make more parts of stdlib compile

12 files changed, 131 insertions, 47 deletions

diff --git a/compiler/src/dotty/tools/dotc/ast/Desugar.scala b/compiler/src/dotty/tools/dotc/ast/Desugar.scala
index 13ddff08c..211683c0a 100644
--- a/compiler/src/dotty/tools/dotc/ast/Desugar.scala
+++ b/compiler/src/dotty/tools/dotc/ast/Desugar.scala
@@ -7,6 +7,7 @@ import util.Positions._, Types._, Contexts._, Constants._, Names._, NameOps._, F
 import SymDenotations._, Symbols._, StdNames._, Annotations._, Trees._
 import Decorators._
 import language.higherKinds
+import typer.FrontEnd
 import collection.mutable.ListBuffer
 import util.Property
 import reporting.diagnostic.messages._
@@ -363,7 +364,7 @@ object desugar {
           if (mods.is(Abstract) || hasRepeatedParam) Nil  // cannot have default arguments for repeated parameters, hence copy method is not issued
           else {
             def copyDefault(vparam: ValDef) =
-              makeAnnotated(defn.UncheckedVarianceAnnot, refOfDef(vparam))
+              makeAnnotated("scala.annotation.unchecked.uncheckedVariance", refOfDef(vparam))
             val copyFirstParams = derivedVparamss.head.map(vparam =>
               cpy.ValDef(vparam)(rhs = copyDefault(vparam)))
             val copyRestParamss = derivedVparamss.tail.nestedMap(vparam =>
@@ -559,7 +560,7 @@ object desugar {
     case VarPattern(named, tpt) =>
       derivedValDef(original, named, tpt, rhs, mods)
     case _ =>
-      val rhsUnchecked = makeAnnotated(defn.UncheckedAnnot, rhs)
+      val rhsUnchecked = makeAnnotated("scala.unchecked", rhs)
       val vars = getVariables(pat)
       val isMatchingTuple: Tree => Boolean = {
         case Tuple(es) => es.length == vars.length
@@ -688,11 +689,28 @@ object desugar {
     new ImplicitFunction(params, body)
   }
 
-  /** Add annotation with class `cls` to tree:
-   *      tree @cls
+  /** Add annotation to tree:
+   *      tree @fullName
+   *
+   *  The annotation is usually represented as a TypeTree referring to the class
+   *  with the given name `fullName`. However, if the annotation matches a file name
+   *  that is still to be entered, the annotation is represented as a cascade of `Selects`
+   *  following `fullName`. This is necessary so that we avoid reading an annotation from
+   *  the classpath that is also compiled from source.
    */
-  def makeAnnotated(cls: Symbol, tree: Tree)(implicit ctx: Context) =
-    Annotated(tree, untpd.New(untpd.TypeTree(cls.typeRef), Nil))
+  def makeAnnotated(fullName: String, tree: Tree)(implicit ctx: Context) = {
+    val parts = fullName.split('.')
+    val ttree = ctx.typerPhase match {
+      case phase: FrontEnd if phase.stillToBeEntered(parts.last) =>
+        val prefix =
+          ((Ident(nme.ROOTPKG): Tree) /: parts.init)((qual, name) =>
+            Select(qual, name.toTermName))
+        Select(prefix, parts.last.toTypeName)
+      case _ =>
+        TypeTree(ctx.requiredClass(fullName).typeRef)
+    }
+    Annotated(tree, untpd.New(ttree, Nil))
+  }
 
   private def derivedValDef(original: Tree, named: NameTree, tpt: Tree, rhs: Tree, mods: Modifiers)(implicit ctx: Context) = {
     val vdef = ValDef(named.name.asTermName, tpt, rhs)
diff --git a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
index 334306f19..8930983f3 100644
--- a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
+++ b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
@@ -757,8 +757,14 @@ class TypeComparer(initctx: Context) extends DotClass with ConstraintHandling {
     if (args1.isEmpty) args2.isEmpty
     else args2.nonEmpty && {
       val v = tparams.head.paramVariance
-      (v > 0 || isSubType(args2.head, args1.head)) &&
-      (v < 0 || isSubType(args1.head, args2.head))
+      def isSub(tp1: Type, tp2: Type) = tp2 match {
+        case tp2: TypeBounds =>
+          tp2.contains(tp1)
+        case _ =>
+          (v > 0 || isSubType(tp2, tp1)) &&
+          (v < 0 || isSubType(tp1, tp2))
+      }
+      isSub(args1.head, args2.head)
     } && isSubArgs(args1.tail, args2.tail, tparams)
 
   /** Test whether `tp1` has a base type of the form `B[T1, ..., Tn]` where
diff --git a/compiler/src/dotty/tools/dotc/core/TypeOps.scala b/compiler/src/dotty/tools/dotc/core/TypeOps.scala
index db73daaa2..c2a7d7ea6 100644
--- a/compiler/src/dotty/tools/dotc/core/TypeOps.scala
+++ b/compiler/src/dotty/tools/dotc/core/TypeOps.scala
@@ -552,7 +552,7 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
   def dynamicsEnabled =
     featureEnabled(defn.LanguageModuleClass, nme.dynamics)
 
-  def testScala2Mode(msg: String, pos: Position) = {
+  def testScala2Mode(msg: => String, pos: Position) = {
     if (scala2Mode) migrationWarning(msg, pos)
     scala2Mode
   }
diff --git a/compiler/src/dotty/tools/dotc/core/Types.scala b/compiler/src/dotty/tools/dotc/core/Types.scala
index 64fa48071..636204f64 100644
--- a/compiler/src/dotty/tools/dotc/core/Types.scala
+++ b/compiler/src/dotty/tools/dotc/core/Types.scala
@@ -217,6 +217,14 @@ object Types {
       case _ => false
     }
 
+    /** Is this the type of a method with a leading empty parameter list?
+     */
+    def isNullaryMethod(implicit ctx: Context): Boolean = this match {
+      case MethodType(Nil, _) => true
+      case tp: PolyType => tp.resultType.isNullaryMethod
+      case _ => false
+    }
+
     /** Is this an alias TypeBounds? */
     def isAlias: Boolean = this.isInstanceOf[TypeAlias]
 
diff --git a/compiler/src/dotty/tools/dotc/transform/ElimByName.scala b/compiler/src/dotty/tools/dotc/transform/ElimByName.scala
index 192227261..71ced3175 100644
--- a/compiler/src/dotty/tools/dotc/transform/ElimByName.scala
+++ b/compiler/src/dotty/tools/dotc/transform/ElimByName.scala
@@ -71,7 +71,7 @@ class ElimByName extends MiniPhaseTransform with InfoTransformer { thisTransform
 
     def transformArg(arg: Tree, formal: Type): Tree = formal.dealias match {
       case formalExpr: ExprType =>
-        val argType = arg.tpe.widen
+        val argType = arg.tpe.widenIfUnstable
         val argFun = arg match {
           case Apply(Select(qual, nme.apply), Nil)
           if qual.tpe.derivesFrom(defn.FunctionClass(0)) && isPureExpr(qual) =>
diff --git a/compiler/src/dotty/tools/dotc/transform/LiftTry.scala b/compiler/src/dotty/tools/dotc/transform/LiftTry.scala
index 6a273b91e..d01195614 100644
--- a/compiler/src/dotty/tools/dotc/transform/LiftTry.scala
+++ b/compiler/src/dotty/tools/dotc/transform/LiftTry.scala
@@ -57,7 +57,7 @@ class LiftTry extends MiniPhase with IdentityDenotTransformer { thisTransform =>
         ctx.debuglog(i"lifting tree at ${tree.pos}, current owner = ${ctx.owner}")
         val fn = ctx.newSymbol(
           ctx.owner, ctx.freshName("liftedTree").toTermName, Synthetic | Method,
-          MethodType(Nil, tree.tpe), coord = tree.pos)
+          MethodType(Nil, tree.tpe.widenIfUnstable), coord = tree.pos)
         tree.changeOwnerAfter(ctx.owner, fn, thisTransform)
         Block(DefDef(fn, tree) :: Nil, ref(fn).appliedToNone)
       }
diff --git a/compiler/src/dotty/tools/dotc/transform/SuperAccessors.scala b/compiler/src/dotty/tools/dotc/transform/SuperAccessors.scala
index fea478c9b..3c11827fc 100644
--- a/compiler/src/dotty/tools/dotc/transform/SuperAccessors.scala
+++ b/compiler/src/dotty/tools/dotc/transform/SuperAccessors.scala
@@ -71,21 +71,24 @@ class SuperAccessors(thisTransformer: DenotTransformer) {
       val Select(qual, name) = sel
       val sym = sel.symbol
       val clazz = qual.symbol.asClass
-      var supername = name.superName
-      if (clazz is Trait) supername = supername.expandedName(clazz)
-
-      val superAcc = clazz.info.decl(supername).suchThat(_.signature == sym.signature).symbol orElse {
-        ctx.debuglog(s"add super acc ${sym.showLocated} to $clazz")
-        val deferredOrPrivate = if (clazz is Trait) Deferred | ExpandedName else Private
-        val acc = ctx.newSymbol(
-            clazz, supername, SuperAccessor | Artifact | Method | deferredOrPrivate,
-            sel.tpe.widenSingleton.ensureMethodic, coord = sym.coord).enteredAfter(thisTransformer)
-        // Diagnostic for SI-7091
-        if (!accDefs.contains(clazz))
-          ctx.error(s"Internal error: unable to store accessor definition in ${clazz}. clazz.hasPackageFlag=${clazz is Package}. Accessor required for ${sel} (${sel.show})", sel.pos)
-        else accDefs(clazz) += DefDef(acc, EmptyTree)
-        acc
-      }
+      var superName = name.superName
+      if (clazz is Trait) superName = superName.expandedName(clazz)
+      val superInfo = sel.tpe.widenSingleton.ensureMethodic
+
+      val superAcc = clazz.info.decl(superName)
+        .suchThat(_.signature == superInfo.signature).symbol
+        .orElse {
+          ctx.debuglog(s"add super acc ${sym.showLocated} to $clazz")
+          val deferredOrPrivate = if (clazz is Trait) Deferred | ExpandedName else Private
+          val acc = ctx.newSymbol(
+              clazz, superName, SuperAccessor | Artifact | Method | deferredOrPrivate,
+              superInfo, coord = sym.coord).enteredAfter(thisTransformer)
+          // Diagnostic for SI-7091
+          if (!accDefs.contains(clazz))
+            ctx.error(s"Internal error: unable to store accessor definition in ${clazz}. clazz.hasPackageFlag=${clazz is Package}. Accessor required for ${sel} (${sel.show})", sel.pos)
+          else accDefs(clazz) += DefDef(acc, EmptyTree)
+          acc
+        }
 
       This(clazz).select(superAcc).withPos(sel.pos)
     }
diff --git a/compiler/src/dotty/tools/dotc/typer/Applications.scala b/compiler/src/dotty/tools/dotc/typer/Applications.scala
index 8a18e63c0..42c24ffb7 100644
--- a/compiler/src/dotty/tools/dotc/typer/Applications.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Applications.scala
@@ -657,18 +657,20 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
         case err: ErrorType => untpd.cpy.Apply(tree)(fun1, tree.args).withType(err)
         case TryDynamicCallType => typedDynamicApply(tree, pt)
         case _ =>
-          tryEither {
-            implicit ctx => simpleApply(fun1, proto)
-          } {
-            (failedVal, failedState) =>
-              def fail = { failedState.commit(); failedVal }
-              // Try once with original prototype and once (if different) with tupled one.
-              // The reason we need to try both is that the decision whether to use tupled
-              // or not was already taken but might have to be revised when an implicit
-              // is inserted on the qualifier.
-              tryWithImplicitOnQualifier(fun1, originalProto).getOrElse(
-                if (proto eq originalProto) fail
-                else tryWithImplicitOnQualifier(fun1, proto).getOrElse(fail))
+          if (originalProto.isDropped) fun1
+          else
+            tryEither {
+              implicit ctx => simpleApply(fun1, proto)
+            } {
+              (failedVal, failedState) =>
+                def fail = { failedState.commit(); failedVal }
+                // Try once with original prototype and once (if different) with tupled one.
+                // The reason we need to try both is that the decision whether to use tupled
+                // or not was already taken but might have to be revised when an implicit
+                // is inserted on the qualifier.
+                tryWithImplicitOnQualifier(fun1, originalProto).getOrElse(
+                  if (proto eq originalProto) fail
+                  else tryWithImplicitOnQualifier(fun1, proto).getOrElse(fail))
           }
       }
     }
diff --git a/compiler/src/dotty/tools/dotc/typer/FrontEnd.scala b/compiler/src/dotty/tools/dotc/typer/FrontEnd.scala
index cd374e32c..6eff63e2b 100644
--- a/compiler/src/dotty/tools/dotc/typer/FrontEnd.scala
+++ b/compiler/src/dotty/tools/dotc/typer/FrontEnd.scala
@@ -19,6 +19,15 @@ class FrontEnd extends Phase {
   override def isTyper = true
   import ast.tpd
 
+  /** The contexts for compilation units that are parsed but not yet entered */
+  private var remaining: List[Context] = Nil
+
+  /** Does a source file ending with `<name>.scala` belong to a compilation unit
+   *  that is parsed but not yet entered?
+   */
+  def stillToBeEntered(name: String): Boolean =
+    remaining.exists(_.compilationUnit.toString.endsWith(name + ".scala"))
+
   def monitor(doing: String)(body: => Unit)(implicit ctx: Context) =
     try body
     catch {
@@ -75,7 +84,11 @@ class FrontEnd extends Phase {
     }
     unitContexts foreach (parse(_))
     record("parsedTrees", ast.Trees.ntrees)
-    unitContexts.foreach(enterSyms(_))
+    remaining = unitContexts
+    while (remaining.nonEmpty) {
+      enterSyms(remaining.head)
+      remaining = remaining.tail
+    }
     unitContexts.foreach(enterAnnotations(_))
     unitContexts.foreach(typeCheck(_))
     record("total trees after typer", ast.Trees.ntrees)
diff --git a/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala b/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala
index ed6b95c3b..eb46a131f 100644
--- a/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala
+++ b/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala
@@ -40,7 +40,9 @@ object ProtoTypes {
     /** Test compatibility after normalization in a fresh typerstate. */
     def normalizedCompatible(tp: Type, pt: Type)(implicit ctx: Context) = {
       val nestedCtx = ctx.fresh.setExploreTyperState
-      isCompatible(normalize(tp, pt)(nestedCtx), pt)(nestedCtx)
+      val normTp = normalize(tp, pt)(nestedCtx)
+      isCompatible(normTp, pt)(nestedCtx) ||
+        pt.isRef(defn.UnitClass) && normTp.isParameterless
     }
 
     private def disregardProto(pt: Type)(implicit ctx: Context): Boolean = pt.dealias match {
@@ -250,6 +252,22 @@ object ProtoTypes {
     /** Somebody called the `tupled` method of this prototype */
     def isTupled: Boolean = myTupled.isInstanceOf[FunProto]
 
+    /** If true, the application of this prototype was canceled. */
+    private var toDrop: Boolean = false
+
+    /** Cancel the application of this prototype. This can happen for a nullary
+     *  application `f()` if `f` refers to a symbol that exists both in parameterless
+     *  form `def f` and nullary method form `def f()`. A common example for such
+     *  a method is `toString`. If in that case the type in the denotation is
+     *  parameterless, we compensate by dropping the application.
+     */
+    def markAsDropped() = {
+      assert(args.isEmpty)
+      toDrop = true
+    }
+
+    def isDropped: Boolean = toDrop
+
     override def toString = s"FunProto(${args mkString ","} => $resultType)"
 
     def map(tm: TypeMap)(implicit ctx: Context): FunProto =
diff --git a/compiler/src/dotty/tools/dotc/typer/RefChecks.scala b/compiler/src/dotty/tools/dotc/typer/RefChecks.scala
index dcbd444f9..3192546cd 100644
--- a/compiler/src/dotty/tools/dotc/typer/RefChecks.scala
+++ b/compiler/src/dotty/tools/dotc/typer/RefChecks.scala
@@ -299,7 +299,9 @@ object RefChecks {
                  !member.isAnyOverride) {
         // (*) Exclusion for default getters, fixes SI-5178. We cannot assign the Override flag to
         // the default getter: one default getter might sometimes override, sometimes not. Example in comment on ticket.
-        if (autoOverride(member))
+        // Also excluded under Scala2 mode are overrides of default methods of Java traits.
+        if (autoOverride(member) ||
+            other.owner.is(JavaTrait) && ctx.testScala2Mode("`override' modifier required when a Java 8 default method is re-implemented", member.pos))
           member.setFlag(Override)
         else if (member.owner != clazz && other.owner != clazz && !(other.owner derivesFrom member.owner))
           emitOverrideError(
@@ -326,7 +328,8 @@ object RefChecks {
         overrideError("needs to be a stable, immutable value")
       } else if (member.is(ModuleVal) && !other.isRealMethod && !other.is(Deferred | Lazy)) {
         overrideError("may not override a concrete non-lazy value")
-      } else if (member.is(Lazy, butNot = Module) && !other.isRealMethod && !other.is(Lazy)) {
+      } else if (member.is(Lazy, butNot = Module) && !other.isRealMethod && !other.is(Lazy) &&
+                 !ctx.testScala2Mode("may not override a non-lazy value", member.pos)) {
         overrideError("may not override a non-lazy value")
       } else if (other.is(Lazy) && !other.isRealMethod && !member.is(Lazy)) {
         overrideError("must be declared lazy to override a lazy value")
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 07a27a498..fe158dfe2 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -1640,13 +1640,19 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
     case _                  => false
   }
 
-  /** Add apply node or implicit conversions. Two strategies are tried, and the first
-   *  that is successful is picked. If neither of the strategies are successful, continues with
-   *  `fallBack`.
+  /** Potentially add apply node or implicit conversions. Before trying either,
+   *  if the function is applied to an empty parameter list (), we try
+   *
+   *  0th strategy: If `tree` overrides a nullary method, mark the prototype
+   *                so that the argument is dropped and return `tree` itself.
+   *
+   *  After that, two strategies are tried, and the first that is successful is picked.
+   *  If neither of the strategies are successful, continues with`fallBack`.
    *
    *  1st strategy: Try to insert `.apply` so that the result conforms to prototype `pt`.
    *                This strategy is not tried if the prototype represents already
    *                another `.apply` or `.apply()` selection.
+   *
    *  2nd strategy: If tree is a select `qual.name`, try to insert an implicit conversion
    *    around the qualifier part `qual` so that the result conforms to the expected type
    *    with wildcard result type.
@@ -1661,8 +1667,15 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
     def tryImplicit =
       tryInsertImplicitOnQualifier(tree, pt).getOrElse(fallBack)
 
-    if (isApplyProto(pt)) tryImplicit
-    else tryEither(tryApply(_))((_, _) => tryImplicit)
+    pt match {
+      case pt @ FunProto(Nil, _, _)
+      if tree.symbol.allOverriddenSymbols.exists(_.info.isNullaryMethod) =>
+        pt.markAsDropped()
+        tree
+      case _ =>
+        if (isApplyProto(pt)) tryImplicit
+        else tryEither(tryApply(_))((_, _) => tryImplicit)
+     }
   }
 
   /** If this tree is a select node `qual.name`, try to insert an implicit conversion