Fix #1286: Error on inexistent imports that are not used.

Author: nicolasstucki

src/dotty/language.scala

@@ -4,6 +4,16 @@ object language {
 
   class Feature
 
+  /** Enable scala.Dynamic */
+  val dynamics = new Feature
+
   /** Keep union types */
   val keepUnions = new Feature
+
+  /** Disable auto tupling */
+  val noAutoTupling = new Feature
+
+  /** Enable Scala 2 compatibility mode */
+  val Scala2 = new Feature
+
 }

src/dotty/tools/dotc/transform/PostTyper.scala

@@ -271,6 +271,19 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer  { thisTran
               case tpe => tpe
             }
           )
+        case Import(expr, selectors) =>
+          val exprTpe = expr.tpe
+          def checkIdent(ident: Ident): Unit = {
+            val name = ident.name.asTermName.encode
+            if (name != nme.WILDCARD && !exprTpe.member(name).exists && !exprTpe.member(name.toTypeName).exists)
+              ctx.error(s"${ident.name} is not a member of ${expr.show}", ident.pos)
+          }
+          selectors.foreach {
+            case ident: Ident          => checkIdent(ident)
+            case Pair(ident: Ident, _) => checkIdent(ident)
+            case _                     =>
+          }
+          super.transform(tree)
         case tree =>
           super.transform(tree)
       }

tests/neg/i1286.scala

@@ -0,0 +1,12 @@
+import scala.idontexist // error
+import scala.io.Idontexist // error
+
+import scala.io
+import io.Idontexist2 // error
+
+import scala.io.{ AnsiColor, Idontexist3 } // error
+
+import scala.io.{ Idontexist4 => Foo } // error
+import scala.io.{ Idontexist5 => _ } // error
+
+object Test

tests/pos/t2913.scala

@@ -10,7 +10,7 @@ class RichA {
 }
 
 object TestNoAutoTupling {
-  import language.noAutoTupling // try with on and off
+  import dotty.language.noAutoTupling // try with on and off
 
   implicit def AToRichA(a: A): RichA = new RichA