Remove regex hack

Author: Jentsch

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -2838,7 +2838,7 @@ object Parsers {
      */
     def namedPattern(location: Location = Location.InPattern): Tree =
       // TODO: Figure out the performance impact of this lookahead
-      if (in.token == IDENTIFIER && in.lookahead.token == EQUALS)
+      if ((in.token == IDENTIFIER || in.token == BACKQUOTED_IDENT) && in.lookahead.token == EQUALS) then
         val ident = termIdent()
         accept(EQUALS)
         NamedArg(ident.name, pattern(location))

compiler/src/dotty/tools/dotc/typer/Applications.scala

@@ -1413,10 +1413,15 @@ trait Applications extends Compatibility {
 
           val positionOfStringNames: Map[String, Int] =
             if names.exists then
-              // TODO: Don't use regular expression to deconstruct tuples
-              val reg = "\"([^\"]+)\"".r
-              reg.findAllMatchIn(names.showDcl)
-                .map(_.group(1))
+              // TODO: why doesn't names.info.dealias works?
+              def dealias(typ: Type): Type = typ match
+                case alias: TypeAlias => alias.alias
+                case other => other
+
+              dealias(names.info)
+                // TODO: Error handling if Names is malformed
+                .tupleElementTypes.getOrElse(Nil)
+                .map { case ConstantType(Constant(name: String)) => name }
                 .zipWithIndex
                 .toMap
             // TODO: The test should actually be: is unapplyFn generated by the compiler because we have a case class?

tests/pos/namedPatternMatching.scala

@@ -10,7 +10,7 @@ object Age:
     Some(age.hidden.asInstanceOf)
 
 object StringExample:
-  def unapply(str: String): Option[(Char, Char) & { type Names = "first" *: "last" *: EmptyTuple }]  =
+  def unapply(str: String): (Char, Char) & { type Names = "first" *: "\"" *: EmptyTuple }  =
     Some((str.head, str.last)).asInstanceOf
 
 case class User(name: String, age: Age, city: String)
@@ -27,7 +27,7 @@ val User(name = name, age = Age(years = years)) = user
 
 // partial function
 val maybeTom = Some(user).collect {
-  case u @ User(name = StringExample(last = 'm')) => u
+  case u @ User(name = StringExample(`"` = 'm')) => u
 }
 
 val berlinerNames = for