bugfix: Print backticks when identifier should not be printed as is

presentation-compiler/src/main/dotty/tools/pc/printer/ShortenedTypePrinter.scala

@@ -32,6 +32,7 @@ import dotty.tools.pc.Params
 import dotty.tools.pc.utils.InteractiveEnrichments.*
 
 import org.eclipse.lsp4j.TextEdit
+import scala.meta.internal.mtags.KeywordWrapper
 
 /**
  * A type printer that shortens types by replacing fully qualified names with shortened versions.
@@ -48,7 +49,9 @@ class ShortenedTypePrinter(
 )(using indexedCtx: IndexedContext, reportCtx: ReportContext) extends RefinedPrinter(indexedCtx.ctx):
   private val missingImports: mutable.Set[ImportSel] = mutable.LinkedHashSet.empty
   private val defaultWidth = 1000
-
+  private val keywordWrapper = new KeywordWrapper {
+    override def keywords: Set[String] = KeywordWrapper.Scala3HardKeywords
+  }
   private val methodFlags =
     Flags.commonFlags(
       Private,
@@ -205,6 +208,12 @@ class ShortenedTypePrinter(
       case tp if tp.isError => super.toText(indexedCtx.ctx.definitions.AnyType)
       case _ => super.toText(tp)
 
+  override def nameString(name: Name): String =
+    val nameStr = super.nameString(name)
+    if nameStr.nonEmpty then
+      keywordWrapper.backtickWrap(nameStr)
+    else nameStr
+
   override def toTextSingleton(tp: SingletonType): Text =
     tp match
       case ConstantType(const) => toText(const)

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

@@ -1138,7 +1138,7 @@ class CompletionSuite extends BaseCompletionSuite:
           |  scala@@
           |}
           |""".stripMargin,
-      """|scala <root>
+      """|scala `<root>`
          |""".stripMargin
     )
 
@@ -1725,8 +1725,8 @@ class CompletionSuite extends BaseCompletionSuite:
     check(
       """|import @@
          |""".stripMargin,
-      """|java <root>
-         |javax <root>
+      """|java `<root>`
+         |javax `<root>`
          |""".stripMargin,
       filter = _.startsWith("java")
     )
@@ -1744,8 +1744,8 @@ class CompletionSuite extends BaseCompletionSuite:
     check(
       """|export @@
          |""".stripMargin,
-      """|java <root>
-         |javax <root>
+      """|java `<root>`
+         |javax `<root>`
          |""".stripMargin,
       filter = _.startsWith("java")
     )
@@ -2090,7 +2090,7 @@ class CompletionSuite extends BaseCompletionSuite:
          |""".stripMargin
     )
 
-  @Test def `conflict-3` = 
+  @Test def `conflict-3` =
    check(
      """|package a
         |object A {

presentation-compiler/test/dotty/tools/pc/tests/edit/InsertInferredTypeSuite.scala

@@ -597,6 +597,76 @@ class InsertInferredTypeSuite extends BaseCodeActionSuite:
          |""".stripMargin
     )
 
+  @Test def `backticks-4` =
+    checkEdit(
+      """|case class `Foo-Foo`(i: Int)
+         |object O{
+         |  val <<foo>> = `Foo-Foo`(1)
+         |}""".stripMargin,
+      """|case class `Foo-Foo`(i: Int)
+         |object O{
+         |  val foo: `Foo-Foo` = `Foo-Foo`(1)
+         |}
+         |""".stripMargin
+    )
+
+  @Test def `backticks-5` =
+    checkEdit(
+      """|object A{
+         |  case class `Foo-Foo`(i: Int)
+         |}
+         |object O{
+         |  val <<foo>> = A.`Foo-Foo`(1)
+         |}""".stripMargin,
+      """|import A.`Foo-Foo`
+         |object A{
+         |  case class `Foo-Foo`(i: Int)
+         |}
+         |object O{
+         |  val foo: `Foo-Foo` = A.`Foo-Foo`(1)
+         |}
+         |""".stripMargin
+  )
+
+  @Test def `backticks-6` =
+    checkEdit(
+    """|object A{
+       |  case class `Foo-Foo`[A](i: A)
+       |}
+       |object O{
+       |  val <<foo>> = A.`Foo-Foo`(1)
+       |}""".stripMargin,
+    """|import A.`Foo-Foo`
+       |object A{
+       |  case class `Foo-Foo`[A](i: A)
+       |}
+       |object O{
+       |  val foo: `Foo-Foo`[Int] = A.`Foo-Foo`(1)
+       |}
+       |""".stripMargin
+  )
+
+  @Test def `backticks-7` =
+    checkEdit(
+    """|object A{
+       |  class `x-x`
+       |  case class Foo[A](i: A)
+       |}
+       |object O{
+       |  val <<foo>> = A.Foo(new A.`x-x`)
+       |}""".stripMargin,
+    """|import A.Foo
+       |import A.`x-x`
+       |object A{
+       |  class `x-x`
+       |  case class Foo[A](i: A)
+       |}
+       |object O{
+       |  val foo: Foo[`x-x`] = A.Foo(new A.`x-x`)
+       |}
+       |""".stripMargin
+  )
+
   @Test def `literal-types1` =
     checkEdit(
       """|object O {