Set zero span for synthetic enum import selector

Fixes #11683

Author: tgodzik

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

@@ -520,7 +520,14 @@ object desugar {
           enumCases.last.pushAttachment(DesugarEnums.DefinesEnumLookupMethods, ())
         val enumCompanionRef = TermRefTree()
         val enumImport =
-          Import(enumCompanionRef, enumCases.flatMap(caseIds).map(ImportSelector(_)))
+          Import(enumCompanionRef, enumCases.flatMap(caseIds).map{
+            enumCase => 
+              val zeroSpan = if enumCase.span.exists then
+                enumCase.span.endPos
+              else
+                enumCase.span
+              ImportSelector(enumCase.withSpan(zeroSpan)).withSpan(zeroSpan)
+          })
         (enumImport :: enumStats, enumCases, enumCompanionRef)
       }
       else (stats, Nil, EmptyTree)

language-server/test/dotty/tools/languageserver/HoverTest.scala

@@ -213,4 +213,13 @@ class HoverTest {
       // sp the top-level definitions should be enclosed in an object called `Source0$package`.
       .hover(m1 to m2, hoverContent("(hello.Source0$package : hello.Source0$package.type)"))
   }
+
+  @Test def enumsRepeated: Unit = {
+    code"""|package example
+           |object SimpleEnum:
+           |  enum Color:
+           |    case ${m1}Red${m2}, Green, Blue
+           |""".withSource
+      .hover(m1 to m2, hoverContent("example.SimpleEnum.Color"))
+  }
 }