REPL completion for idents starting with number

This relaxes some of the completion result filtering to allow backticked
identifiers such as the following to show up in completion results.

   object Test {
     def `1 world` = ""
   }

The pathological builtin names to guard against all start with `<`,
even in their encoded forms (backticked `<` would start with a `$`).

Fixes scala/bug#13076

Author: harpocrates

src/interactive/scala/tools/nsc/interactive/Global.scala

@@ -21,7 +21,6 @@ import scala.collection.mutable
 import scala.collection.mutable.{HashSet, LinkedHashMap}
 import scala.jdk.javaapi.CollectionConverters
 import scala.language.implicitConversions
-import scala.reflect.internal.Chars.isIdentifierStart
 import scala.reflect.internal.util.SourceFile
 import scala.tools.nsc.io.AbstractFile
 import scala.tools.nsc.reporters.Reporter
@@ -1191,7 +1190,7 @@ class Global(settings: Settings, _reporter: Reporter, projectName: String = "")
       results.filter { (member: Member) =>
         val symbol = member.sym
         def isStable = member.tpe.isStable || member.sym.isStable || member.sym.getterIn(member.sym.owner).isStable
-        def isJunk = !symbol.exists || symbol.name.isEmpty || !isIdentifierStart(member.sym.name.charAt(0)) // e.g. <byname>
+        def isJunk = !symbol.exists || symbol.name.isEmpty || symbol.encodedName.charAt(0) == '<' // e.g. <byname>
         def nameTypeOk: Boolean = {
           forImport || // Completing an import: keep terms and types.
             symbol.name.isTermName == name.isTermName || // Keep names of the same type
@@ -1202,7 +1201,7 @@ class Global(settings: Settings, _reporter: Reporter, projectName: String = "")
           matcher(member.aliasInfo.map(_.sym.name).getOrElse(NoSymbol.name)) && !forImport && symbol.name.isTermName == name.isTermName
         }
 
-        !isJunk && member.accessible && !symbol.isConstructor && (name.isEmpty || (matcher(member.sym.name) || aliasTypeOk)
+        !isJunk && member.accessible && (name.isEmpty || (matcher(member.sym.name) || aliasTypeOk)
           && nameTypeOk)
 
       }

test/junit/scala/tools/nsc/interpreter/CompletionTest.scala

@@ -94,6 +94,9 @@ class CompletionTest {
     checkExact(completer, "object O { private def x_y_z = 1; x_y", "}")("x_y_z")
     checkExact(completer, "object x_y_z; import x_y")("x_y_z")
 
+    checkExact(completer, "object O { def `1 thing` = 1 }; O.")("1 thing")
+    checkExact(completer, "object O { def `<x>` = 1 }; O.")("<x>")
+
     checkExact(completer, "object x_y_z { def a_b_c }; import x_y_z.a_b")("a_b_c")
 
     checkExact(completer, "object X { private[this] def definition = 0; def")("definition")