Add missing spans in closures

Previously they where infered from the mods.

Author: nicolasstucki

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -933,11 +933,14 @@ object desugar {
    *      def $anonfun(params) = body
    *      Closure($anonfun)
    */
-  def makeClosure(params: List[ValDef], body: Tree, tpt: Tree = null, isImplicit: Boolean)(implicit ctx: Context): Block =
+  def makeClosure(params: List[ValDef], body: Tree, tpt: Tree = null, isImplicit: Boolean)(implicit ctx: Context): Block = {
+    val span = params.headOption.fold(body.span)(_.span.union(body.span))
     Block(
       DefDef(nme.ANON_FUN, Nil, params :: Nil, if (tpt == null) TypeTree() else tpt, body)
+        .withSpan(span)
         .withMods(synthetic | Artifact),
-      Closure(Nil, Ident(nme.ANON_FUN), if (isImplicit) ImplicitEmptyTree else EmptyTree))
+      Closure(Nil, Ident(nme.ANON_FUN), if (isImplicit) ImplicitEmptyTree else EmptyTree)).withSpan(span)
+  }
 
   /** If `nparams` == 1, expand partial function
    *

compiler/test/dotty/tools/repl/TabcompleteTests.scala

@@ -91,6 +91,12 @@ class TabcompleteTests extends ReplTest {
       assertEquals(expected, tabComplete("val foo: Rena"))
     }
 
+  @Test def tabClosureComplete = fromInitialState { implicit s =>
+    assertEquals(List("map", "mapConserve"), tabComplete("Nil.map"))
+    assertEquals(List("map", "mapConserve"), tabComplete("(x: Int => Int) => Nil.map"))
+    assertEquals(List("apply"), tabComplete("(x: Int => Int) => x.ap"))
+  }
+
   @Test def importScala = fromInitialState { implicit s =>
     val comp = tabComplete("import scala.")
     // check that there are no special symbols leaked: <byname>, <special-ops>, ...