Fix completions for named tuples (#24169)

fixes scalameta/metals#7764

This fix was partially implemented during the [Scala Tooling
Spree](https://scalameta.org/scala-tooling-spree/)

Co-authored-by: Jakub Kozłowski <[email protected]>

Author: KacperFKorban

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

@@ -187,6 +187,15 @@ object Completion:
           Some(qual)
         case _ => None
 
+  private object NamedTupleSelection:
+    def unapply(path: List[tpd.Tree])(using Context): Option[tpd.Tree] =
+      path match
+        case (tpd.Apply(tpd.Apply(tpd.TypeApply(fun, _), List(qual)), _)) :: _
+          if fun.symbol.exists && fun.symbol.name == nme.apply &&
+             fun.symbol.owner.exists && fun.symbol.owner == defn.NamedTupleModule.moduleClass =>
+          Some(qual)
+        case _ => None
+
 
   /** Inspect `path` to determine the offset where the completion result should be inserted. */
   def completionOffset(untpdPath: List[untpd.Tree]): Int =
@@ -195,7 +204,7 @@ object Completion:
       case _ => 0
 
   /** Handle case when cursor position is inside extension method construct.
-   *  The extension method construct is then desugared into methods, and consturct parameters
+   *  The extension method construct is then desugared into methods, and construct parameters
    *  are no longer a part of a typed tree, but instead are prepended to method parameters.
    *
    *  @param untpdPath The typed or untyped path to the tree that is being completed
@@ -242,6 +251,7 @@ object Completion:
         completer.scopeCompletions.names ++ completer.selectionCompletions(qual)
       case tpd.Select(qual, _) :: _                                             => completer.selectionCompletions(qual)
       case (tree: tpd.ImportOrExport) :: _                                      => completer.directMemberCompletions(tree.expr)
+      case NamedTupleSelection(qual)                                            => completer.selectionCompletions(qual)
       case _                                                                    => completer.scopeCompletions.names
 
     interactiv.println(i"""completion info with pos    = $pos,

presentation-compiler/test/dotty/tools/pc/tests/completion/CompletionSuite.scala

@@ -2053,6 +2053,28 @@ class CompletionSuite extends BaseCompletionSuite:
       """.stripMargin,
     )
 
+  @Test def `namedTuple completions-3` =
+    check(
+      """|import scala.NamedTuple.*
+         |
+         |val person = (name = "Jakub", city = "Wrocław")
+         |
+         |val n = person.@@name""".stripMargin,
+      "name: String",
+      filter = _ == "name: String"
+    )
+
+  @Test def `namedTuple completions-4` =
+    check(
+      """|import scala.NamedTuple.*
+         |
+         |val person = (name = "Jakub", city = "Wrocław")
+         |
+         |val n = person.n@@ame""".stripMargin,
+      "name: String",
+      filter = _ == "name: String"
+    )
+
   @Test def `Selectable with namedTuple Fields member` =
     check(
       """|import scala.NamedTuple.*
@@ -2285,7 +2307,7 @@ class CompletionSuite extends BaseCompletionSuite:
         |""".stripMargin,
       "asTerm: Term"
     )
-  
+
   @Test def `derives-no-square-brackets` =
     check(
       """