Do not publish Scala 3 parsing errors

Let's unify the parsing errors are presented to the user, the Scalameta parser is much better now and it should make it a bit faster.

Also, this would cause issues in sbt files if the build was not imported and the fallback version set to Scala 3.0.0.

metals/src/main/scala/scala/meta/internal/metals/MetalsLanguageServer.scala

@@ -268,10 +268,7 @@ class MetalsLanguageServer(
   def parseTreesAndPublishDiags(paths: Seq[AbsolutePath]): Future[Seq[Unit]] = {
     Future.traverse(paths.distinct) { path =>
       if (path.isScalaFilename) {
-        // diagnostics from the compiler are still needed for Scala 3
-        compilers.didChange(path).map { diags =>
-          diagnostics.onSyntaxError(path, diags ++ trees.didChange(path))
-        }
+        Future(diagnostics.onSyntaxError(path, trees.didChange(path)))
       } else {
         Future.successful(())
       }

metals/src/main/scala/scala/meta/internal/parsing/Trees.scala

@@ -75,17 +75,14 @@ final class Trees(
   }
 
   /**
-   * Parse file at the given path and return a list of errors if there are any and
-   * the file belongs to a Scala 2 target.
-   *
+   * Parse file at the given path and return a list of errors if there are any.
    * @param path file to parse
    * @return list of errors if the file failed to parse
    */
   def didChange(path: AbsolutePath): List[Diagnostic] = {
     val dialect = getDialect(path)
     parse(path, dialect) match {
-      // only publish parser diagnostics for Scala 2, which does not support significant indentation
-      case Some(parsed) if !dialect.allowSignificantIndentation =>
+      case Some(parsed) =>
         parsed match {
           case Parsed.Error(pos, message, _) =>
             List(
@@ -100,9 +97,7 @@ final class Trees(
             trees(path) = tree
             List()
         }
-      // don't publish diagnostics
-      case _ =>
-        List()
+      case _ => List()
     }
   }
 

mtags/src/main/scala-3/scala/meta/internal/pc/ScalaPresentationCompiler.scala

@@ -395,16 +395,8 @@ case class ScalaPresentationCompiler(
 
   override def didChange(
       params: VirtualFileParams
-  ): CompletableFuture[ju.List[Diagnostic]] = {
-    compilerAccess.withNonInterruptableCompiler(
-      Nil.asJava,
-      params.token
-    ) { access =>
-      val driver = access.compiler()
-      val uri = params.uri
-      CompilerInterfaces.parseErrors(driver, uri, params.text)
-    }
-  }
+  ): CompletableFuture[ju.List[Diagnostic]] =
+    CompletableFuture.completedFuture(Nil.asJava)
 
   override def didClose(uri: URI): Unit = {
     compilerAccess.withNonInterruptableCompiler(