Merge pull request #13700 from ghostbuster91/fix-12465

Do not perform completion on higher kinded trees

Author: prolativ

compiler/src/dotty/tools/dotc/interactive/Completion.scala

@@ -114,11 +114,12 @@ object Completion {
     val completions = path match {
         // Ignore synthetic select from `This` because in code it was `Ident`
         // See example in dotty.tools.languageserver.CompletionTest.syntheticThis
-        case Select(qual @ This(_), _) :: _ if qual.span.isSynthetic => completer.scopeCompletions
-        case Select(qual, _) :: _                                    => completer.selectionCompletions(qual)
-        case Import(expr, _) :: _                                    => completer.directMemberCompletions(expr)
-        case (_: untpd.ImportSelector) :: Import(expr, _) :: _       => completer.directMemberCompletions(expr)
-        case _                                                       => completer.scopeCompletions
+        case Select(qual @ This(_), _) :: _ if qual.span.isSynthetic  => completer.scopeCompletions
+        case Select(qual, _) :: _           if qual.tpe.hasSimpleKind => completer.selectionCompletions(qual)
+        case Select(qual, _) :: _                                     => Map.empty
+        case Import(expr, _) :: _                                     => completer.directMemberCompletions(expr)
+        case (_: untpd.ImportSelector) :: Import(expr, _) :: _        => completer.directMemberCompletions(expr)
+        case _                                                        => completer.scopeCompletions
       }
 
     val describedCompletions = describeCompletions(completions)

compiler/test/dotty/tools/dotc/interactive/CustomCompletionTests.scala

@@ -169,3 +169,4 @@ class CustomCompletionTests extends DottyTest:
 
       assert(offset == prefix.length)
       assert(labels.contains("scala.Function2"))
+

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

@@ -887,4 +887,12 @@ class CompletionTest {
           )
         )
   }
+
+  @Test def i12465_hkt: Unit =
+    code"""???.asInstanceOf[scala.collection.Seq].${m1}""".withSource
+      .completion(m1, Set())
+
+  @Test def i12465_hkt_alias: Unit =
+    code"""???.asInstanceOf[Seq].${m1}""".withSource
+      .completion(m1, Set())
 }