Fix missing code-completion on standalone annotations

Co-authored-by: Stefan Pavikevik <[email protected]>
Co-authored-by: Tomasz Godzik <[email protected]>
Co-authored-by: Anatolii Kmetiuk <[email protected]>

Author: 4 people

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -3472,7 +3472,11 @@ object Parsers {
           givenDef(start, mods, atSpan(in.skipToken()) { Mod.Given() })
         case _ =>
           syntaxErrorOrIncomplete(ExpectedStartOfTopLevelDefinition())
-          EmptyTree
+          mods.annotations match {
+            case head :: Nil => head
+            case Nil => EmptyTree
+            case all => Block(all, errorTermTree)
+          }
       }
 
     /** ClassDef ::= id ClassConstr TemplateOpt

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

@@ -138,4 +138,8 @@ class TabcompleteTests extends ReplTest {
       tabComplete("import quoted.* ; def fooImpl(using Quotes): Expr[Int] = { import quotes.reflect.* ; TypeRepr.of[Int].s"))
   }
 
+  @Test def i13624 = fromInitialState { implicit s =>
+    assertEquals(List("implicitNotFound"), tabComplete("@annotation.implicitNot"))
+    assertEquals(List("main"), tabComplete("@annotation.implicitNotFound @mai"))
+  }
 }