Fix #941

src/dotty/tools/dotc/core/Denotations.scala

@@ -320,7 +320,7 @@ object Denotations {
                   try info1 & info2
                   catch {
                     case ex: MergeError =>
-                      if (pre.widen.classSymbol.is(Scala2x))
+                      if (pre.widen.classSymbol.is(Scala2x) || ctx.scala2Mode)
                         info1 // follow Scala2 linearization -
                               // compare with way merge is performed in SymDenotation#computeMembersNamed
                       else

src/dotty/tools/dotc/reporting/ConsoleReporter.scala

@@ -47,6 +47,8 @@ class ConsoleReporter(
         printMessageAndPos(s"error: ${d.msg}", d.pos)
         if (ctx.settings.prompt.value) displayPrompt()
       case d: ConditionalWarning if !d.enablingOption.value =>
+      case d: MigrationWarning =>
+        printMessageAndPos(s"migration warning: ${d.msg}", d.pos)
       case d: Warning =>
         printMessageAndPos(s"warning: ${d.msg}", d.pos)
       case _ =>

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

@@ -909,6 +909,13 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
     val DefDef(name, tparams, vparamss, tpt, _) = ddef
     completeAnnotations(ddef, sym)
     val tparams1 = tparams mapconserve (typed(_).asInstanceOf[TypeDef])
+    // for secondary constructors we need to use that their type parameters
+    // are aliases of the class type parameters. See pos/i941.scala
+    if (sym.isConstructor && !sym.isPrimaryConstructor)
+      (sym.owner.typeParams, tparams1).zipped.foreach {(tparam, tdef) =>
+        tdef.symbol.info = TypeAlias(tparam.typeRef)
+       }
+
     val vparamss1 = vparamss nestedMapconserve (typed(_).asInstanceOf[ValDef])
     if (sym is Implicit) checkImplicitParamsNotSingletons(vparamss1)
     val tpt1 = checkSimpleKinded(typedType(tpt))
@@ -1044,8 +1051,19 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
     }
   }
 
-  def typedAsFunction(tree: untpd.Tree, pt: Type)(implicit ctx: Context): Tree =
-    typed(tree, if (defn.isFunctionType(pt)) pt else AnyFunctionProto)
+  def typedAsFunction(tree: untpd.Tree, pt: Type)(implicit ctx: Context): Tree = {
+    val pt1 = if (defn.isFunctionType(pt)) pt else AnyFunctionProto
+    var res = typed(tree, pt1)
+    if (pt1.eq(AnyFunctionProto) && !defn.isFunctionClass(res.tpe.classSymbol)) {
+      def msg = i"not a function: ${res.tpe}; cannot be followed by `_'"
+      if (ctx.scala2Mode) {
+        ctx.migrationWarning(msg, tree.pos)
+        res = typed(untpd.Function(Nil, untpd.TypedSplice(res)))
+      }
+      else ctx.error(msg, tree.pos)
+    }
+    res
+  }
 
   /** Retrieve symbol attached to given tree */
   protected def retrieveSym(tree: untpd.Tree)(implicit ctx: Context) = tree.removeAttachment(SymOfTree) match {

test/dotc/scala-collections.whitelist

@@ -232,12 +232,12 @@
 ./scala-scala/src/library/scala/collection/immutable/SetProxy.scala
 
 # https://github.com/lampepfl/dotty/issues/942
-# ./scala-scala/src/library/scala/collection/immutable/SortedMap.scala
-#./scala-scala/src/library/scala/collection/immutable/SortedSet.scala
+./scala-scala/src/library/scala/collection/immutable/SortedMap.scala
+./scala-scala/src/library/scala/collection/immutable/SortedSet.scala
 
 # https://github.com/lampepfl/dotty/issues/941
-#./scala-scala/src/library/scala/collection/immutable/Stream.scala
-#./scala-scala/src/library/scala/collection/immutable/StreamView.scala
+./scala-scala/src/library/scala/collection/immutable/Stream.scala
+./scala-scala/src/library/scala/collection/immutable/StreamView.scala
 
 ./scala-scala/src/library/scala/collection/immutable/TreeMap.scala
 ./scala-scala/src/library/scala/collection/immutable/TreeSet.scala

test/dotc/tests.scala

@@ -151,6 +151,7 @@ class tests extends CompilerTest {
   @Test def neg_i0248_inherit_refined = compileFile(negDir, "i0248-inherit-refined", xerrors = 4)
   @Test def neg_i0281 = compileFile(negDir, "i0281-null-primitive-conforms", xerrors = 3)
   @Test def neg_i583 = compileFile(negDir, "i0583-skolemize", xerrors = 2)
+  @Test def neg_i941 = compileFile(negDir, "i941", xerrors = 3)
   @Test def neg_finalSealed = compileFile(negDir, "final-sealed", xerrors = 2)
   @Test def neg_i705 = compileFile(negDir, "i705-inner-value-class", xerrors = 7)
   @Test def neg_i866 = compileFile(negDir, "i866", xerrors = 2)

tests/neg/i941.scala

@@ -0,0 +1,9 @@
+object Test {
+
+  def bar(tl: => String) = {
+    val x = tl _ //error
+    val y = x _ // error
+    val s: String = x() // error
+  }
+
+}

tests/pos/i941.scala

@@ -0,0 +1,10 @@
+object Test {
+
+  class C[A] {
+
+    def this(y: A) = { this(); foo(y) }
+
+    def foo(x: A): Unit = ()
+
+  }
+}