Report member that doesn't support named arguments

Author: Jentsch

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

@@ -1393,29 +1393,31 @@ trait Applications extends Compatibility {
             .memberDenots(typeNameFilter, (name, buf) => if (name.toString == "Names") buf += typeInfoOfGetMethod.member(name).asSingleDenotation)
             .headOption
 
+          val positionOfStringNames: Map[String, Int] =
+            if names.isDefined then
+              // TODO: Don't use regular expression to deconstruct tuples
+              val reg = "\"([^\"]+)\"".r
+              reg.findAllMatchIn(names.get.showDcl)
+                .map(_.group(1))
+                .zipWithIndex
+                .toMap
+            // TODO: The test should actually be: is unapplyFn generated by the compiler because we have a case class?
+            else if unapplyFn.tpe.widen.paramInfoss.head.head.typeSymbol.is(CaseClass) then
+              unapplyFn.tpe.widen.paramInfoss.head.head.fields.map(_.name.toString).zipWithIndex.toMap
+            else
+              report.error(i"'${qual}' doesn't support named patterns", qual)
+              Map.empty
+
           val positionOfName: PartialFunction[Name, Int] =
-              if names.isDefined then
-                // TODO: Don't use regular expression to deconstruct tuples
-                val reg = "\"([^\"]+)\"".r
-                reg.findAllMatchIn(names.get.showDcl)
-                  .map(_.group(1))
-                  .zipWithIndex
-                  .toMap
-              // TODO: The test should actually be: is unapplyFn generated by the compiler because we have a case class?
-              else if unapplyFn.tpe.widen.paramInfoss.head.head.typeSymbol.is(CaseClass) then
-                unapplyFn.tpe.widen.paramInfoss.head.head.fields.map(_.name.toString).zipWithIndex.toMap
-              else
-                // TODO: Report member
-                report.error("Doesn't support named patterns")
-                Map.empty
             // TODO: Is is necessary to convert names to strings?
-            .compose{ case name: Name => name.show }
+            positionOfStringNames.compose(_.show)
 
           val namedArgs = bunchedArgs
             .flatMap {
               case pattern @ NamedArg(positionOfName(_), _) => Seq(pattern)
               case pattern @ NamedArg(unknownName, _) =>
-                report.error(s"'${unknownName.show}' is unknown", pattern)
+                if (positionOfStringNames.nonEmpty)
+                  report.error(s"'${unknownName.show}' is unknown", pattern)
                 Seq.empty
               case unnamedArgument =>
                 report.error("Only named arguments allowed here", unnamedArgument)

tests/neg/negNamedPatternMatching.check

@@ -1,16 +1,20 @@
--- Error: tests/neg/negNamedPatternMatching.scala:21:20 ----------------------------------------------------------------
-21 |  case User(names = "Tom", city = city) => ??? // error
+-- Error: tests/neg/negNamedPatternMatching.scala:18:20 ----------------------------------------------------------------
+18 |  case User(names = "Tom", city = city) => ??? // error
    |                    ^^^^^
    |                    'names' is unknown
--- Error: tests/neg/negNamedPatternMatching.scala:22:22 ----------------------------------------------------------------
-22 |  case User(city = _, 10) => null // error
+-- Error: tests/neg/negNamedPatternMatching.scala:19:22 ----------------------------------------------------------------
+19 |  case User(city = _, 10) => null // error
    |                      ^^
    |                      Only named arguments allowed here
--- Error: tests/neg/negNamedPatternMatching.scala:25:11 ----------------------------------------------------------------
-25 |    name = "Tom 2",  // error
+-- Error: tests/neg/negNamedPatternMatching.scala:20:18 ----------------------------------------------------------------
+20 |  case User(age = Age(years = 10)) => null // error
+   |                  ^^^
+   |                  'patterns.Age' doesn't support named patterns
+-- Error: tests/neg/negNamedPatternMatching.scala:23:11 ----------------------------------------------------------------
+23 |    name = "Tom 2",  // error
    |           ^^^^^^^
    |           'name' was already used before
--- Error: tests/neg/negNamedPatternMatching.scala:26:11 ----------------------------------------------------------------
-26 |    name = "Tom 3" // error
+-- Error: tests/neg/negNamedPatternMatching.scala:24:11 ----------------------------------------------------------------
+24 |    name = "Tom 3" // error
    |           ^^^^^^^
    |           'name' was already used before

tests/neg/negNamedPatternMatching.scala

@@ -1,17 +1,14 @@
 package patterns
 
-class Age(val hidden: Int)
+type Age = Age.Age
 
 object Age:
-  def apply(years: Int): Age = new Age(years)
+  opaque type Age = Int
 
-  // TODO: Describe alternative encoding with tagged tuples
-  def unapply(age: Age): Some[Int & { type Names = "years" *: EmptyTuple }] =
-    Some(age.hidden.asInstanceOf)
+  def apply(years: Int): Age = years
 
-object StringExample:
-  def unapply(str: String): Option[(Char, Char) & { type Names = "first" *: "last" *: EmptyTuple }]  =
-    Some((str.head, str.last)).asInstanceOf
+  def unapply(age: Age): Some[Int] =
+    Some(age)
 
 case class User(name: String, age: Age, city: String)
 
@@ -20,6 +17,7 @@ val user = User(name = "Anna", age = Age(10), city = "Berlin")
 val annasCity = user match
   case User(names = "Tom", city = city) => ??? // error
   case User(city = _, 10) => null // error
+  case User(age = Age(years = 10)) => null // error
   case User(
     name = "Tom",
     name = "Tom 2",  // error