Restrict syntax of typed patterns

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -1287,11 +1287,14 @@ object Types {
      *  then the top-level union isn't widened. This is needed so that type inference can infer nullable types.
      */
     def widenUnion(using Context): Type = widen match
-      case tp @ OrNull(tp1): OrType =>
-        // Don't widen `T|Null`, since otherwise we wouldn't be able to infer nullable unions.
-        val tp1Widen = tp1.widenUnionWithoutNull
-        if (tp1Widen.isRef(defn.AnyClass)) tp1Widen
-        else tp.derivedOrType(tp1Widen, defn.NullType)
+      case tp: OrType => tp match
+        case OrNull(tp1) =>
+          // Don't widen `T|Null`, since otherwise we wouldn't be able to infer nullable unions.
+          val tp1Widen = tp1.widenUnionWithoutNull
+          if (tp1Widen.isRef(defn.AnyClass)) tp1Widen
+          else tp.derivedOrType(tp1Widen, defn.NullType)
+        case _ =>
+          tp.widenUnionWithoutNull
       case tp =>
         tp.widenUnionWithoutNull
 

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

@@ -2809,11 +2809,14 @@ object Parsers {
       if (isIdent(nme.raw.BAR)) { in.nextToken(); pattern1(location) :: patternAlts(location) }
       else Nil
 
-    /**  Pattern1     ::= Pattern2 [Ascription]
+    /**  Pattern1     ::= PatVar Ascription
+     *                  | [‘-’] integerLiteral Ascription
+     *                  | [‘-’] floatingPointLiteral Ascription
+     *                  | Pattern2
      */
     def pattern1(location: Location = Location.InPattern): Tree =
       val p = pattern2()
-      if in.isColon then
+      if (isVarPattern(p) || p.isInstanceOf[Number]) && in.isColon then
         in.nextToken()
         ascription(p, location)
       else p

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

@@ -476,13 +476,15 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
    *  (x: T | Null) => x.$asInstanceOf$[x.type & T]
    */
   def toNotNullTermRef(tree: Tree, pt: Type)(using Context): Tree = tree.tpe match
-    case ref @ OrNull(tpnn) : TermRef
+    case ref: TermRef
     if pt != AssignProto && // Ensure it is not the lhs of Assign
     ctx.notNullInfos.impliesNotNull(ref) &&
     // If a reference is in the context, it is already trackable at the point we add it.
     // Hence, we don't use isTracked in the next line, because checking use out of order is enough.
     !ref.usedOutOfOrder =>
-      tree.cast(AndType(ref, tpnn))
+      ref match
+        case OrNull(tpnn) => tree.cast(AndType(ref, tpnn))
+        case _            => tree
     case _ =>
       tree
 

docs/_docs/internals/syntax.md

@@ -318,7 +318,10 @@ TypeCaseClauses   ::=  TypeCaseClause { TypeCaseClause }
 TypeCaseClause    ::=  ‘case’ (InfixType | ‘_’) ‘=>’ Type [semi]
 
 Pattern           ::=  Pattern1 { ‘|’ Pattern1 }                                Alternative(pats)
-Pattern1          ::=  Pattern2 [‘:’ RefinedType]                               Bind(name, Typed(Ident(wildcard), tpe))
+Pattern1          ::=  PatVar ‘:’ RefinedType                                   Bind(name, Typed(Ident(wildcard), tpe))
+                    | [‘-’] integerLiteral ‘:’ RefinedType                      Typed(pat, tpe)
+                    | [‘-’] floatingPointLiteral ‘:’ RefinedType                Typed(pat, tpe)
+                    |  Pattern2
 Pattern2          ::=  [id ‘@’] InfixPattern [‘*’]                              Bind(name, pat)
 InfixPattern      ::=  SimplePattern { id [nl] SimplePattern }                  InfixOp(pat, op, pat)
 SimplePattern     ::=  PatVar                                                   Ident(wildcard)

docs/_docs/reference/syntax.md

@@ -306,7 +306,10 @@ TypeCaseClauses   ::=  TypeCaseClause { TypeCaseClause }
 TypeCaseClause    ::=  ‘case’ (InfixType | ‘_’) ‘=>’ Type [semi]
 
 Pattern           ::=  Pattern1 { ‘|’ Pattern1 }
-Pattern1          ::=  Pattern2 [‘:’ RefinedType]
+Pattern1          ::=  PatVar ‘:’ RefinedType
+                    | [‘-’] integerLiteral ‘:’ RefinedType
+                    | [‘-’] floatingPointLiteral ‘:’ RefinedType
+                    |  Pattern2
 Pattern2          ::=  [id ‘@’] InfixPattern [‘*’]
 InfixPattern      ::=  SimplePattern { id [nl] SimplePattern }
 SimplePattern     ::=  PatVar

tests/neg/i10994.scala

@@ -0,0 +1,2 @@
+def foo = true match
+  case (b: Boolean): Boolean => ()  // error

tests/neg/i15893.scala

@@ -0,0 +1,61 @@
+sealed trait NatT
+case class Zero() extends NatT
+case class Succ[+N <: NatT](n: N) extends NatT
+
+type Mod2[N <: NatT] <: NatT = N match
+  case Zero => Zero
+  case Succ[Zero] => Succ[Zero]
+  case Succ[Succ[predPredN]] => Mod2[predPredN]
+
+def mod2(n: NatT):  NatT = n match
+  case Zero() => Zero()
+  case Succ(Zero()) => Succ(Zero())
+  case Succ(Succ(predPredN)) => mod2(predPredN)
+
+inline def inlineMod2(inline n: NatT):  NatT = inline n match
+  case Zero() => Zero()
+  case Succ(Zero()) => Succ(Zero())
+  case Succ(Succ(predPredN)) => inlineMod2(predPredN)
+
+transparent inline def transparentInlineMod2(inline n: NatT):  NatT = inline n match
+  case Zero() => Zero()
+  case Succ(Zero()) => Succ(Zero())
+  case Succ(Succ(predPredN)) => transparentInlineMod2(predPredN)
+
+def dependentlyTypedMod2[N <: NatT](n: N): Mod2[N] = n match // exhaustivity warning; unexpected
+  case Zero(): Zero => Zero() // error
+  case Succ(Zero()): Succ[Zero] => Succ(Zero()) // error
+  case Succ(Succ(predPredN)): Succ[Succ[_]] => dependentlyTypedMod2(predPredN) // error
+
+inline def inlineDependentlyTypedMod2[N <: NatT](inline n: N): Mod2[N] = inline n match
+  case Zero(): Zero => Zero() // error
+  case Succ(Zero()): Succ[Zero] => Succ(Zero()) // error
+  case Succ(Succ(predPredN)): Succ[Succ[_]] => inlineDependentlyTypedMod2(predPredN) // error
+
+transparent inline def transparentInlineDependentlyTypedMod2[N <: NatT](inline n: N): Mod2[N] = inline n match
+  case Zero(): Zero => Zero() // error
+  case Succ(Zero()): Succ[Zero] => Succ(Zero()) // error
+  case Succ(Succ(predPredN)): Succ[Succ[_]] => transparentInlineDependentlyTypedMod2(predPredN) // error
+
+def foo(n: NatT): NatT = mod2(n) match
+  case Succ(Zero()) => Zero()
+  case _ => n
+
+inline def inlineFoo(inline n: NatT): NatT = inline inlineMod2(n) match
+  case Succ(Zero()) => Zero()
+  case _ => n
+
+inline def transparentInlineFoo(inline n: NatT): NatT = inline transparentInlineMod2(n) match
+  case Succ(Zero()) => Zero()
+  case _ => n
+
+@main def main(): Unit =
+  println(mod2(Succ(Succ(Succ(Zero()))))) // prints Succ(Zero()), as expected
+  println(foo(Succ(Succ(Succ(Zero()))))) // prints Zero(), as expected
+  println(inlineMod2(Succ(Succ(Succ(Zero()))))) // prints Succ(Zero()), as expected
+  println(inlineFoo(Succ(Succ(Succ(Zero()))))) // prints Succ(Succ(Succ(Zero()))); unexpected
+  println(transparentInlineMod2(Succ(Succ(Succ(Zero()))))) // prints Succ(Zero()), as expected
+  println(transparentInlineFoo(Succ(Succ(Succ(Zero()))))) // prints Zero(), as expected
+  println(dependentlyTypedMod2(Succ(Succ(Succ(Zero()))))) // runtime error; unexpected
+//  println(inlineDependentlyTypedMod2(Succ(Succ(Succ(Zero()))))) // doesn't compile; unexpected
+//  println(transparentInlineDependentlyTypedMod2(Succ(Succ(Succ(Zero()))))) // doesn't compile; unexpected

tests/neg/t5702-neg-bad-and-wild.check

@@ -10,10 +10,10 @@
    |                       pattern expected
    |
    | longer explanation available when compiling with `-explain`
--- [E040] Syntax Error: tests/neg/t5702-neg-bad-and-wild.scala:13:23 ---------------------------------------------------
+-- [E040] Syntax Error: tests/neg/t5702-neg-bad-and-wild.scala:13:22 ---------------------------------------------------
 13 |      case List(1, _*3:) =>  // error // error
-   |                       ^
-   |                       an identifier expected, but ')' found
+   |                      ^
+   |                      ')' expected, but ':' found
 -- [E032] Syntax Error: tests/neg/t5702-neg-bad-and-wild.scala:15:18 ---------------------------------------------------
 15 |      case List(x*, 1) => // error: pattern expected
    |                  ^

tests/pos-macros/i11211.scala

@@ -12,7 +12,7 @@ def takeOptionImpl2[T](using Quotes, Type[T]): Unit = '{
 def takeOptionImpl[T](o: Expr[Option[T]], default: Expr[T])(using Quotes, Type[T]): Expr[T] = '{
  $o match {
    case Some(t1) => t1
-   case None: Option[T] => $default
+   case None => $default
  }
 }
 

tests/pos/patmat.scala

@@ -16,7 +16,7 @@ object Test {
   }
 
   (xs.length, xs) match {
-    case (0, Nil: List[Int]) => println("1")
+    case (0, Nil) => println("1")
     case (_, Nil) => println("2")
     case (0, _)   => println("3")
     case (x, y)   => println("4")
@@ -46,9 +46,4 @@ object Test {
     case Some(s) => println(s)
     case None => println("nothing")
   }
-
-  type IntPair = (Int, Int)
-  ??? match {
-    case (x, y): IntPair => x * y
-  }
 }

tests/semanticdb/expect/ValPattern.expect.scala

@@ -6,7 +6,7 @@ class ValPattern/*<-example::ValPattern#*/ {
   val Some/*->scala::Some.*/(number1/*<-example::ValPattern#number1.*/) =
     Some/*->scala::Some.*/(1)
 
-  val List/*->scala::package.List.*/(Some/*->scala::Some.*/(q1/*<-example::ValPattern#q1.*/), None/*->scala::None.*/: None/*->scala::None.*/.type, None/*->scala::None.*/) = ???/*->scala::Predef.`???`().*/
+  val List/*->scala::package.List.*/(Some/*->scala::Some.*/(q1/*<-example::ValPattern#q1.*/), None/*->scala::None.*/) = ???/*->scala::Predef.`???`().*/
 
   var (leftVar/*<-example::ValPattern#leftVar().*/, rightVar/*<-example::ValPattern#rightVar().*/) = (1, 2)
   var Some/*->scala::Some.*/(number1Var/*<-example::ValPattern#number1Var().*/) =

tests/semanticdb/expect/ValPattern.scala

@@ -6,7 +6,7 @@ class ValPattern {
   val Some(number1) =
     Some(1)
 
-  val List(Some(q1), None: None.type, None) = ???
+  val List(Some(q1), None) = ???
 
   var (leftVar, rightVar) = (1, 2)
   var Some(number1Var) =

tests/semanticdb/metac.expect

@@ -3493,7 +3493,7 @@ Uri => ValPattern.scala
 Text => empty
 Language => Scala
 Symbols => 22 entries
-Occurrences => 46 entries
+Occurrences => 44 entries
 Synthetics => 11 entries
 
 Symbols:
@@ -3532,9 +3532,7 @@ Occurrences:
 [8:11..8:15): Some -> scala/Some.
 [8:16..8:18): q1 <- example/ValPattern#q1.
 [8:21..8:25): None -> scala/None.
-[8:27..8:31): None -> scala/None.
-[8:38..8:42): None -> scala/None.
-[8:46..8:49): ??? -> scala/Predef.`???`().
+[8:29..8:32): ??? -> scala/Predef.`???`().
 [10:7..10:14): leftVar <- example/ValPattern#leftVar().
 [10:16..10:24): rightVar <- example/ValPattern#rightVar().
 [11:6..11:10): Some -> scala/Some.