Fix #1457: Three incompatbilities with scalac

Two of these are unavoidable. I moved the tests to diabled/not-representable
and added in each case a comment to the main scala file detailing why there
is a deviation.

The last one (import-rewrite) is fixed.

Author: odersky

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

@@ -64,6 +64,7 @@ class ImportInfo(symf: => Symbol, val selectors: List[untpd.Tree], val isRootImp
             myExcluded += name
           case Pair(Ident(from: TermName), Ident(to: TermName)) =>
             myMapped = myMapped.updated(to, from)
+            myExcluded += from
             myOriginals += from
           case Ident(nme.WILDCARD) =>
             myWildcardImport = true

tests/pending/hkt/compiler.error renamed to tests/disabled/not-representable/hkt/compiler.error

@@ -1,3 +1,6 @@
+// This one is unavoidable. Dotty does not allow several overloaded
+// parameterless methods, so it picks the one in the subclass.
+
 import scala.language.higherKinds
 // Minimal reproduction for:
 // scala.collection.mutable.ArrayStack.empty[Int]

tests/pending/hkt/hkt.scala renamed to tests/disabled/not-representable/hkt/hkt.scala

@@ -0,0 +1,10 @@
+// This one should be rejected according to spec. The import takes precedence
+// over the type in the same package because the typeis declared in a
+// different compilation unit. scalac does not conform to spec here.
+package naming.resolution
+
+import java.nio.file._ // Imports `Files`
+
+object Resolution {
+  def gimmeFiles: Files = Files.list(Paths.get("."))
+}

tests/disabled/not-representable/naming-resolution/callsite.scala

@@ -0,0 +1,8 @@
+$ scalac tests/pending/naming-resolution/*.scala
+$ ./bin/dotc tests/pending/naming-resolution/*.scala
+tests/pending/naming-resolution/callsite.scala:6: error: type mismatch:
+ found   : java.util.stream.Stream[java.nio.file.Path]
+ required: java.nio.file.Files
+  def gimmeFiles: Files = Files.list(Paths.get("."))
+                                    ^
+one error found

tests/disabled/not-representable/naming-resolution/compiler.error

@@ -0,0 +1,5 @@
+package naming
+
+package object resolution {
+  type Files = java.util.stream.Stream[java.nio.file.Path]
+}