Fix #9829: Allow as in place of @ for pattern bindings

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

@@ -2631,7 +2631,10 @@ object Parsers {
     /**  Pattern2    ::=  [id `@'] InfixPattern
      */
     val pattern2: () => Tree = () => infixPattern() match {
-      case p @ Ident(name) if in.token == AT =>
+      case p @ Ident(name) if in.token == AT || in.isIdent(nme.as) =>
+        if in.token == AT && sourceVersion.isAtLeast(`3.1`) then
+          deprecationWarning(s"`@` bindings have been deprecated; use `as` instead", in.offset)
+
         val offset = in.skipToken()
 
         // compatibility for Scala2 `x @ _*` syntax
@@ -2659,7 +2662,8 @@ object Parsers {
     /**  InfixPattern ::= SimplePattern {id [nl] SimplePattern}
      */
     def infixPattern(): Tree =
-      infixOps(simplePattern(), in.canStartExprTokens, simplePattern, isOperator = in.name != nme.raw.BAR)
+      infixOps(simplePattern(), in.canStartExprTokens, simplePattern,
+        isOperator = in.name != nme.raw.BAR && in.name != nme.as)
 
     /** SimplePattern    ::= PatVar
      *                    |  Literal

docs/docs/internals/syntax.md

@@ -273,7 +273,7 @@ TypeCaseClause    ::=  ‘case’ InfixType ‘=>’ Type [nl]
 Pattern           ::=  Pattern1 { ‘|’ Pattern1 }                                Alternative(pats)
 Pattern1          ::=  Pattern2 [‘:’ RefinedType]                               Bind(name, Typed(Ident(wildcard), tpe))
                     |  ‘given’ PatVar ‘:’ RefinedType
-Pattern2          ::=  [id ‘@’] InfixPattern                                    Bind(name, pat)
+Pattern2          ::=  [id ‘as’] InfixPattern                                    Bind(name, pat)
 InfixPattern      ::=  SimplePattern { id [nl] SimplePattern }                  InfixOp(pat, op, pat)
 SimplePattern     ::=  PatVar                                                   Ident(wildcard)
                     |  Literal                                                  Bind(name, Ident(wildcard))

library/src-bootstrapped/dotty/internal/StringContextMacro.scala

@@ -62,7 +62,7 @@ object StringContextMacro {
     val sourceFile = strCtxExpr.unseal.pos.sourceFile
 
     val (partsExpr, parts) = strCtxExpr match {
-      case Expr.StringContext(p1 @ Consts(p2)) => (p1.toList, p2.toList)
+      case Expr.StringContext(p1 as Consts(p2)) => (p1.toList, p2.toList)
       case _ => report.throwError("Expected statically known String Context", strCtxExpr)
     }
 

library/src-bootstrapped/scala/internal/quoted/Matcher.scala

@@ -244,7 +244,7 @@ object Matcher {
 
           /* Term hole */
           // Match a scala.internal.Quoted.patternHole typed as a repeated argument and return the scrutinee tree
-          case (scrutinee @ Typed(s, tpt1), Typed(TypeApply(patternHole, tpt :: Nil), tpt2))
+          case (scrutinee as Typed(s, tpt1), Typed(TypeApply(patternHole, tpt :: Nil), tpt2))
               if patternHole.symbol == qctx.tasty.Definitions_InternalQuotedMatcher_patternHole &&
                  s.tpe <:< tpt.tpe &&
                  tpt2.tpe.derivesFrom(defn.RepeatedParamClass) =>
@@ -259,7 +259,7 @@ object Matcher {
 
           /* Higher order term hole */
           // Matches an open term and wraps it into a lambda that provides the free variables
-          case (scrutinee, pattern @ Apply(TypeApply(Ident("higherOrderHole"), List(Inferred())), Repeated(args, _) :: Nil))
+          case (scrutinee, pattern as Apply(TypeApply(Ident("higherOrderHole"), List(Inferred())), Repeated(args, _) :: Nil))
               if pattern.symbol == qctx.tasty.Definitions_InternalQuotedMatcher_higherOrderHole =>
 
             def bodyFn(lambdaArgs: List[Tree]): Tree = {

library/src-bootstrapped/scala/quoted/util/ExprMap.scala

@@ -51,7 +51,7 @@ trait ExprMap {
           tree
         case Super(qual, mix) =>
           tree
-        case tree @ Apply(fun, args) =>
+        case tree as Apply(fun, args) =>
           val MethodType(_, tpes, _) = fun.tpe.widen
           Apply.copy(tree)(transformTerm(fun, Type.of[Any]), transformTerms(args, tpes))
         case TypeApply(fun, args) =>

tests/init/crash/fors.scala

@@ -26,7 +26,7 @@ object Test extends App {
     var n = 0
     for (_ <- xs) n += 1; println(n)
     for ((x, y) <- xs zip ys) print(x + " "); println()
-    for (p @ (x, y) <- xs zip ys) print(p._1 + " "); println()
+    for (p as (x, y) <- xs zip ys) print(p._1 + " "); println()
 
     // iterators
     for (x <- it) print(x + " "); println()
@@ -53,7 +53,7 @@ object Test extends App {
     var n = 0
     for (_ <- xs) n += 1; println(n)
     for ((x, y) <- xs zip ys) print(x + " "); println()
-    for (p @ (x, y) <- xs zip ys) print(p._1 + " "); println()
+    for (p as (x, y) <- xs zip ys) print(p._1 + " "); println()
 
     // iterators
     for (x <- it) print(x + " "); println()

tests/neg/Iter3.scala

@@ -147,7 +147,7 @@ object Iter2 {
       flatten(map(f(_).buildIterator))
 
     override def ++[B >: A](that: IterableOnce[B]): ArrayIterator[B] = {
-      val thatIterator @ ArrayIterator(elems2, len2) = fromIterator(that.iterator)
+      val thatIterator as ArrayIterator(elems2, len2) = fromIterator(that.iterator)
       if (len == 0) thatIterator
       else if (len2 == 0) this.asInstanceOf[ArrayIterator[B]]
       else {

tests/neg/ensureReported.scala

@@ -1,6 +1,6 @@
 object AnonymousF {
   val f = {
-    case l @ List(1) => // error: missing parameter type
+    case l as List(1) => // error: missing parameter type
       Some(l)
   }
 }

tests/neg/i1716.scala

@@ -1,7 +1,7 @@
 object Fail {
   def f(m: Option[Int]): Unit = {
      m match {
-      case x @ Some[_] =>       // error: unbound wildcard type
+      case x as Some[_] =>       // error: unbound wildcard type
       case _           =>
     }
   }

tests/neg/i3200.scala

@@ -1,6 +1,6 @@
 object Test {
   case object Bob { override def equals(other: Any) = true }
   def main(args: Array[String]): Unit = {
-    val m : Bob.type = (5: Any) match { case x @ Bob => x }  // error
+    val m : Bob.type = (5: Any) match { case x as Bob => x }  // error
   }
 }

tests/neg/i3200b.scala

@@ -1,8 +1,8 @@
 object Test {
   def main(args: Array[String]): Unit = {
-    val a: Nil.type = (Vector(): Any) match { case n @ Nil => n } // error
-    val b: Nil.type = (Vector(): Any) match { case n @ (m @ Nil) => n } // error
-    val c: Int = (1.0: Any) match { case n @ 1 => n } // error
-    val d: Int = (1.0: Any) match { case n @ (m @ 1) => n } // error
+    val a: Nil.type = (Vector(): Any) match { case n as Nil => n } // error
+    val b: Nil.type = (Vector(): Any) match { case n as (m as Nil) => n } // error
+    val c: Int = (1.0: Any) match { case n as 1 => n } // error
+    val d: Int = (1.0: Any) match { case n as (m as 1) => n } // error
   }
 }

tests/neg/i3332.scala

@@ -16,6 +16,6 @@ object Test {
     case _ => println("nope")
   }
   def test(x: Any) = x match {
-    case _: String | _ @ A() => 1
+    case _: String | _ as A() => 1
   }
 }

tests/neg/i3812b.scala

@@ -19,9 +19,9 @@ object Test {
     Some(x) match { case Some(Z2.v)  => () } // ok
 
     Some(x) match { case Some(4) | Some(Z1.v) => () } // error
-    Some(x) match { case a @ Some(Z1.v)       => () } // error
+    Some(x) match { case a as Some(Z1.v)       => () } // error
 
     Some(x) match { case Some(4) | Some(Z2.v) => () } // ok
-    Some(x) match { case a @ Some(Z2.v)       => () } // ok
+    Some(x) match { case a as Some(Z2.v)       => () } // ok
   }
 }

tests/neg/i8407.scala

@@ -1,6 +1,6 @@
 object Test:
   val xs = List(1, 2, 3, 4, 5)
   xs match {
-    case List(1, 2, xs1 @ xs2: _*) => println(xs2) // error // error
+    case List(1, 2, xs1 as xs2: _*) => println(xs2) // error // error
     case _ => ()
   }

tests/neg/i8715.scala

@@ -1,2 +1,2 @@
 @main
-def Test = List(42) match { case List(xs @ (ys: _*)) => xs }  // error
+def Test = List(42) match { case List(xs as (ys: _*)) => xs }  // error

tests/neg/i9310.scala

@@ -1,5 +1,5 @@
 //AE-d101cfe6d25117a51897609e673f6c8e74d31e6e
-val foo @ this = 0
+val foo as this = 0
 class Foo {
   foo { } // error
 }

tests/neg/multi-patterns.scala

@@ -1,4 +1,4 @@
 object Test {
   val (a :: as), bs = List(1, 2, 3) // error
-  val B @ List(), C: List[Int] = List() // error
+  val B as List(), C: List[Int] = List() // error
 }

tests/neg/patternUnsoundness.scala

@@ -10,7 +10,7 @@ object patternUnsoundness extends App {
   val y: C[Object] = x
 
   y match {
-    case d @ D(x) => d.s = new Integer(1) // error
+    case d as D(x) => d.s = new Integer(1) // error
   }
 
   val z: String = x.s // used to throw ClassCast exception

tests/pos/Iter2.scala

@@ -193,7 +193,7 @@ object Iter2 {
       flatten(map(f(_).buildIterator))
 
     override def ++[B >: A](that: IterableOnce[B]): ArrayIterator[B] = {
-      val thatIterator @ ArrayIterator(elems2, len2) = fromIterator(that.iterator)
+      val thatIterator as ArrayIterator(elems2, len2) = fromIterator(that.iterator)
       if (len == 0) thatIterator
       else if (len2 == 0) this
       else {

tests/pos/i1540.scala

@@ -8,7 +8,7 @@ object Casey1 { def unapply(a: Casey1) = a }
 
 object Test {
   def main(args: Array[String]): Unit = {
-    val c @ Casey1(x) = new Casey1(0)
+    val c as Casey1(x) = new Casey1(0)
     assert(x == c.get)
   }
 }

tests/pos/i1540b.scala

@@ -8,7 +8,7 @@ object Casey1 { def unapply[T](a: Casey1[T]) = a }
 
 object Test {
   def main(args: Array[String]): Unit = {
-    val c @ Casey1(x) = new Casey1(0)
+    val c as Casey1(x) = new Casey1(0)
     assert(x == c.get)
   }
 }

tests/pos/i3412.scala

@@ -1,3 +1,3 @@
 class Test {
-  val A @ List() = List()
+  val A as List() = List()
 }

tests/pos/i4177.scala

@@ -6,7 +6,7 @@ class Test {
     val a: PartialFunction[Int, String] = { case Foo(x) => x }
     val b: PartialFunction[Int, String] = { case x => x.toString }
 
-    val e: PartialFunction[String, String] = { case x @ "abc" => x }
+    val e: PartialFunction[String, String] = { case x as "abc" => x }
     val f: PartialFunction[String, String] = x => x match { case "abc" => x }
     val g: PartialFunction[String, String] = x => x match { case "abc" if x.isEmpty => x }
 

tests/pos/i4564.scala

@@ -10,7 +10,7 @@ object ClashNoSig { // ok
   def unapply(x: ClashNoSig) = x
 
   ClashNoSig(2) match {
-    case c @ ClashNoSig(y) => c.copy(y + c._1)
+    case c as ClashNoSig(y) => c.copy(y + c._1)
   }
 }
 case class ClashNoSig private (x: Int) {

tests/pos/i5402.scala

@@ -9,7 +9,7 @@ object Main {
     case 1 => 1
     case 0 | 0 => 0
     case 2 | 2 | 2 | 3 | 2 | 3 => 0
-    case 4 | (_ @ 4) => 0
+    case 4 | (_ as 4) => 0
     case _ => -1
   }
 

tests/pos/simpleExtractors-2.scala

@@ -1,7 +1,7 @@
 class Foo {
   def bar(x: Any): Unit = x match {
     case Some(Some(i: Int)) => println(i)
-    case Some(s @ Some(i)) => println(s)
-    case s @ Some(r @ Some(i)) => println(s)
+    case Some(s as Some(i)) => println(s)
+    case s as Some(r as Some(i)) => println(s)
   }
 }

tests/pos/t10533.scala

@@ -1,5 +1,5 @@
 object Foo {
-  val b @ Bar(_) = Bar(1)(2)(3)
+  val b as Bar(_) = Bar(1)(2)(3)
 }
 
 case class Bar(a: Int)(b: Int)(c: Int)

tests/pos/t3136.scala

@@ -13,7 +13,7 @@ object NullaryMethodType {
 object Test {
   def TEST(tp: Type): String =
     tp match {
-      case PolyType(ps1, PolyType(ps2, res @ PolyType(a, b))) => "1" + tp // couldn't find a simpler version that still crashes
+      case PolyType(ps1, PolyType(ps2, res as PolyType(a, b))) => "1" + tp // couldn't find a simpler version that still crashes
       case NullaryMethodType(meh) => "2" + meh
     }
 }

tests/pos/t6675.scala

@@ -7,7 +7,7 @@ object LeftOrRight {
 
 object Test {
   (Left((0, 0)): Either[(Int, Int), (Int, Int)]) match {
-    case LeftOrRight(pair @ (a, b)) => a // false -Xlint warning: "extractor pattern binds a single value to a Product2 of type (Int, Int)"
+    case LeftOrRight(pair as (a, b)) => a // false -Xlint warning: "extractor pattern binds a single value to a Product2 of type (Int, Int)"
   }
 
   (Left((0, 0)): Either[(Int, Int), (Int, Int)]) match {

tests/pos/trailingCommas/trailingCommas.scala

@@ -114,7 +114,7 @@ trait SimplePattern {
 
   // test '@' syntax in patterns
   Some(1) match {
-    case Some(x @ 1,
+    case Some(x as 1,
     ) => x
   }
 

tests/pos/virtpatmat_alts_subst.scala

@@ -1,6 +1,6 @@
 case class Foo(s: String) {
   def appliedType(tycon: Any) =
     tycon match {
-        case Foo(sym @ ("NothingClass" | "AnyClass")) => println(sym)
+        case Foo(sym as ("NothingClass" | "AnyClass")) => println(sym)
     }
 }

tests/run/3179.scala

@@ -1,7 +1,7 @@
 object Test {
   def main(args: Array[String]): Unit = {
     ("": Any) match {
-      case a @ Test => 1
+      case a as Test => 1
       case _ => 2
     }
   }

tests/run/enums-serialization-compat.scala

@@ -31,19 +31,19 @@ extension (ref: AnyRef) def aliases(compare: AnyRef) = assert(ref eq compare, co
   val read = use(ByteArrayInputStream(buf.toByteArray))
   val in   = use(ObjectInputStream(read))
 
-  val Seq(Red @ _, Green @ _, Blue @ _, Indigo @ _) = (1 to 4).map(_ => in.readObject)
+  val Seq(Red as _, Green as _, Blue as _, Indigo as _) = (1 to 4).map(_ => in.readObject)
   Red    aliases JColor.Red
   Green  aliases SColor.Green
   Blue   aliases SColorTagged.Blue
   Indigo aliases SColorTagged.Indigo
 
-  val Seq(A @ _, C @ _, G @ _, T @ _) = (1 to 4).map(_ => in.readObject)
+  val Seq(A as _, C as _, G as _, T as _) = (1 to 4).map(_ => in.readObject)
   A aliases Nucleobase.A
   C aliases Nucleobase.C
   G aliases Nucleobase.G
   T aliases Nucleobase.T
 
-  val Seq(IntTag @ _, UnitTag @ _) = (1 to 2).map(_ => in.readObject)
+  val Seq(IntTag as _, UnitTag as _) = (1 to 2).map(_ => in.readObject)
   IntTag  aliases MyClassTag.IntTag
   UnitTag aliases MyClassTag.UnitTag
 

tests/run/fors.scala

@@ -26,7 +26,7 @@ object Test extends App {
     var n = 0
     for (_ <- xs) n += 1; println(n)
     for ((x, y) <- xs zip ys) print(x + " "); println()
-    for (p @ (x, y) <- xs zip ys) print(p._1 + " "); println()
+    for (p as (x, y) <- xs zip ys) print(p._1 + " "); println()
 
     // iterators
     for (x <- it) print(x + " "); println()
@@ -53,7 +53,7 @@ object Test extends App {
     var n = 0
     for (_ <- xs) n += 1; println(n)
     for ((x, y) <- xs zip ys) print(x + " "); println()
-    for (p @ (x, y) <- xs zip ys) print(p._1 + " "); println()
+    for (p as (x, y) <- xs zip ys) print(p._1 + " "); println()
 
     // iterators
     for (x <- it) print(x + " "); println()

tests/run/fully-abstract-interface.scala

@@ -20,7 +20,7 @@ object Test {
     const1 match {
       case AppliedOp(_, _, _) =>
         println("test1 fail")
-      case c @ Constant(n) =>
+      case c as Constant(n) =>
         println("test1 OK")
         println(s"$n = ${c.eval}")
     }
@@ -41,9 +41,9 @@ object Test {
     println(applied.eval)
 
     applied match {
-      case c @ Constant(n) =>
+      case c as Constant(n) =>
         println("test3 fail")
-      case a @ AppliedOp(op, x, y) =>
+      case a as AppliedOp(op, x, y) =>
         println("test3 OK")
         println(s"AppliedOp($op, $x, $y) = ${a.eval}")
     }
@@ -304,7 +304,7 @@ object ListImplementation extends Arithmetic {
   def opClassTag: ClassTag[Op] = new ClassTag[Constant] {
     def runtimeClass: Class[_] = classOf[List[_]]
     override def unapply(x: Any): Option[List[Any]] = x match {
-      case op @ (("+" | "*") :: Nil) =>
+      case op as (("+" | "*") :: Nil) =>
       // Test that it is:
       //   type Op <: List[Any] // List(id: "+" | "*")
       Some(op)

tests/run/fully-abstract-nat-1.scala

@@ -32,7 +32,7 @@ object Test {
     }
 
     def divOpt(a: Nat, b: Nat): Option[(Nat, Nat)] = b match {
-      case s @ Succ(_) =>
+      case s as Succ(_) =>
         // s is of type Nat though we know it is a Succ
         Some(safeDiv(a, s.asInstanceOf[Succ]))
       case _ => None

tests/run/fully-abstract-nat-2.scala

@@ -34,7 +34,7 @@ object Test {
     }
 
     def divOpt(a: Nat, b: Nat): Option[(Nat, Nat)] = b match {
-      case s @ Succ(_) => Some(safeDiv(a, s))
+      case s as Succ(_) => Some(safeDiv(a, s))
       case _ => None
     }