Improve printing of encoded unicode chars

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

@@ -152,8 +152,7 @@ object Completion {
       nameToSymbols.map { case (name, symbols) =>
         val typesFirst = symbols.sortWith((s1, s2) => s1.isType && !s2.isType)
         val desc = description(typesFirst)
-        val label = NameTransformer.decodeIllegalChars(name.toString)
-        Completion(label, desc, typesFirst)
+        Completion(name.show, desc, typesFirst)
       }
     }
 

compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala

@@ -24,7 +24,7 @@ import scala.tasty.util.Chars.isOperatorPart
 import transform.TypeUtils._
 
 import language.implicitConversions
-import dotty.tools.dotc.util.SourcePosition
+import dotty.tools.dotc.util.{NameTransformer, SourcePosition}
 import dotty.tools.dotc.ast.untpd.{MemberDef, Modifiers, PackageDef, RefTree, Template, TypeDef, ValOrDefDef}
 
 class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
@@ -75,7 +75,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
   }.toCommonFlags
 
   override def nameString(name: Name): String =
-    if (ctx.settings.YdebugNames.value) name.debugString else name.toString
+    if (ctx.settings.YdebugNames.value) name.debugString else NameTransformer.decodeIllegalChars(name.toString)
 
   override protected def simpleNameString(sym: Symbol): String =
     nameString(if (ctx.property(XprintMode).isEmpty) sym.originalName else sym.name)

compiler/src/dotty/tools/dotc/util/NameTransformer.scala

@@ -62,7 +62,12 @@ object NameTransformer {
       var i = 0
       while (i < name.length) {
         if (i < name.length - 5 && name(i) == '$' && name(i + 1) == 'u') {
-          sb.append(Integer.valueOf(name.substring(i + 2, i + 6), 16).toChar)
+          val numbers = name.substring(i + 2, i + 6)
+          try sb.append(Integer.valueOf(name.substring(i + 2, i + 6), 16).toChar)
+          catch {
+            case _: java.lang.NumberFormatException =>
+              sb.append("$u").append(numbers)
+          }
           i += 6
         } else {
           sb.append(name(i))

compiler/test-resources/repl/unicodeChars

@@ -0,0 +1,9 @@
+scala> type →
+
+scala> def bar: → = ???
+def bar: →
+
+scala> type `🤪`
+
+scala> def baz: `🤪` = ???
+def baz: 🤪

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

@@ -188,4 +188,16 @@ class HoverTest {
       .hover(m1 to m2, hoverContent("Int(1)"))
       .hover(m3 to m4, hoverContent("Int(1) @annot1 @annot2 @annot3 @annot4 @annot5"))
   }
+
+  @Test def unicodeChar: Unit = {
+    code"""object Test {
+          |  type →
+          |  type `🤪`
+          |  def ${m1}bar${m2}: → = ???
+          |  def ${m3}baz${m4}: `🤪` = ???
+          |}""".withSource
+      .hover(m1 to m2, hoverContent("Test.→"))
+      .hover(m3 to m4, hoverContent("Test.🤪"))
+
+  }
 }