Remove quoted.Const.unapply

This extractor was replaced with the more versatile extractor `quoted.Expr.unapply`.
Usually, it is better to use `expr.value`/`expr.valueOrError` when it is simpler to do so.

* Remove definition of `quoted.Const.unapply`
* Replace uses of `Const` with `Expr`

**Migration**

* Consider using `expr.value` and them match on `Option`
* Consider using `expr.valueOrError`
* Replace `Const(x)` with `Expr(x)` if the type is known
* Replace `Const(x: Int)` with `'{ ${Expr(x)}: Int }` if type of expression must be checked at runtime

Author: nicolasstucki

docs/docs/reference/metaprogramming/macros.md

@@ -634,15 +634,15 @@ It is possible to deconstruct or extract values out of `Expr` using pattern matc
 
 * `scala.quoted.Expr`/`scala.quoted.Exprs`: matches an expression of a value (or list of values) and returns the value (or list of values).
 * `scala.quoted.Const`/`scala.quoted.Consts`: Same as `Expr`/`Exprs` but only works on primitive values.
-* `scala.quoted.Varargs`: matches an explicit sequence of expressions and returns them. These sequences are useful to get individual `Expr[T]` out of a varargs expression of type `Expr[Seq[T]]`.
+* `scala.quoted.Varargs`: matches an explicit sequence of expresions and returns them. These sequences are useful to get individual `Expr[T]` out of a varargs expression of type `Expr[Seq[T]]`.
 
 
 These could be used in the following way to optimize any call to `sum` that has statically known values.
 ```scala
 inline def sum(inline args: Int*): Int = ${ sumExpr('args) }
 private def sumExpr(argsExpr: Expr[Seq[Int]])(using Quotes): Expr[Int] = argsExpr match {
-  case Varargs(args @ Exprs(argValues)) =>
-    // args is of type Seq[Expr[Int]]
+  case Varargs(argExprs @ Exprs(argValues)) =>
+    // argExprs is of type Seq[Expr[Int]]
     // argValues is of type Seq[Int]
     Expr(argValues.sum) // precompute result of sum
   case Varargs(argExprs) => // argExprs is of type Seq[Expr[Int]]

library/src-bootstrapped/scala/quoted/Expr.scala

@@ -32,7 +32,7 @@ object Expr {
     Block(statements.map(Term.of), Term.of(expr)).asExpr.asInstanceOf[Expr[T]]
   }
 
-  /** Creates an expression that will construct the value `x` */
+  /** Lift a value into an expression containing the construction of that value */
   def apply[T](x: T)(using ToExpr[T])(using Quotes): Expr[T] =
     scala.Predef.summon[ToExpr[T]].apply(x)
 

library/src-bootstrapped/scala/quoted/FromExpr.scala

@@ -136,8 +136,8 @@ object FromExpr {
    */
   given StringContextFromExpr: FromExpr[StringContext] with {
     def unapply(x: Expr[StringContext])(using Quotes) = x match {
-      case '{ new StringContext(${Varargs(Consts(args))}: _*) } => Some(StringContext(args: _*))
-      case '{     StringContext(${Varargs(Consts(args))}: _*) } => Some(StringContext(args: _*))
+      case '{ new StringContext(${Varargs(Exprs(args))}: _*) } => Some(StringContext(args: _*))
+      case '{     StringContext(${Varargs(Exprs(args))}: _*) } => Some(StringContext(args: _*))
       case _ => None
     }
   }

library/src-non-bootstrapped/scala/quoted/Expr.scala

@@ -1,3 +1,7 @@
 package scala.quoted
 
 abstract class Expr[+T] private[scala]
+
+object Expr:
+  def apply[T](x: T)(using ToExpr[T])(using Quotes): Expr[T] = ???
+  def unapply[T](x: Expr[T])(using FromExpr[T])(using Quotes): Option[T] = ???

library/src-non-bootstrapped/scala/quoted/ToExpr.scala

@@ -0,0 +1,4 @@
+package scala.quoted
+
+trait ToExpr[T]:
+  def apply(x: T)(using Quotes): T

library/src/scala/quoted/Const.scala

@@ -1,5 +1,6 @@
 package scala.quoted
 
+/** Value expressions */
 object Exprs:
 
   /** Matches literal sequence of literal constant value expressions and return a sequence of values.
@@ -9,7 +10,6 @@ object Exprs:
    *  inline def sum(args: Int*): Int = ${ sumExpr('args) }
    *  def sumExpr(argsExpr: Expr[Seq[Int]])(using Quotes): Expr[Int] = argsExpr match
    *    case Varargs(Exprs(args)) =>
-   *    case Varargs(Exprs(args)) =>
    *      // args: Seq[Int]
    *      ...
    *  }

library/src/scala/quoted/Consts.scala

@@ -9,7 +9,7 @@ object Macro {
     var res: Expr[String] = null
     for _ <- 0 to 5_000 do
       (strCtxExpr, argsExpr) match {
-        case ('{ StringContext(${Varargs(Consts(parts))}: _*) }, Varargs(Consts(args))) =>
+        case ('{ StringContext(${Varargs(Exprs(parts))}: _*) }, Varargs(Exprs(args))) =>
           res = Expr(StringContext(parts: _*).s(args: _*))
         case _ => ???
       }

library/src/scala/quoted/Exprs.scala

@@ -9,7 +9,7 @@ object Macro {
     import quotes.reflect._
     sc match {
       case '{ StringContext(${Varargs(parts)}: _*) } =>
-        for (part @ Const(s) <- parts)
+        for (part @ Expr(s) <- parts)
           report.error(s, Term.of(part).pos)
     }
     '{}

tests/bench/string-interpolation-macro/Macro.scala

@@ -9,7 +9,7 @@ object Macro {
     import quotes.reflect._
     sc match {
       case '{ StringContext(${Varargs(parts)}: _*) } =>
-        for (part @ Const(s) <- parts)
+        for (part @ Expr(s) <- parts)
           report.error(s, Term.of(part).pos)
     }
     '{}

tests/neg-macros/i6432/Macro_1.scala

@@ -10,7 +10,7 @@ object E {
 
   implicit def ev1[T: Type]: FromExpr[E[T]] = new FromExpr {
     def unapply(x: Expr[E[T]])(using Quotes) = x match {
-      case '{ I(${Const(n)}) } => Some(I(n).asInstanceOf[E[T]])
+      case '{ I(${Expr(n)}) } => Some(I(n).asInstanceOf[E[T]])
       case '{ Plus[T](${Value(x)}, ${Value(y)})(using $op) } if op.matches('{Plus2.IPlus}) => Some(Plus(x, y)(using Plus2.IPlus.asInstanceOf[Plus2[T]]).asInstanceOf[E[T]])
       case _ => None
     }

tests/neg-macros/i6432b/Macro_1.scala

@@ -4,8 +4,8 @@ import scala.quoted._
 import Even._
 
 object EvenFromDigitsImpl:
-  def apply(digits: Expr[String])(using Quotes): Expr[Even] = digits match {
-    case Const(ds) =>
+  def apply(digits: Expr[String])(using Quotes): Expr[Even] = digits.unlift match {
+    case Some(ds) =>
       val ev =
         try evenFromDigits(ds)
         catch {

tests/neg-macros/inline-macro-staged-interpreter/Macro_1.scala

@@ -9,7 +9,7 @@ private def stringRewriter(e: Expr[Any])(using Quotes): Expr[Any] =
 private object StringRewriter extends ExprMap {
 
   def transform[T](e: Expr[T])(using Type[T])(using Quotes): Expr[T] = e match
-    case Const(s: String) =>
+    case '{ ${Expr(s)}: String } =>
       Expr(s.reverse) match
         case '{ $x: T } => x
         case _ => e // e had a singlton String type

tests/neg-with-compiler/GenericNumLits/EvenFromDigitsImpl_1.scala

@@ -26,9 +26,9 @@ private def rewriteMacro[T: Type](x: Expr[T])(using Quotes): Expr[T] = {
             case (_, Some(_)) => '{ $y * $x }
             case _ => '{ $x * $y }
           }
-        case '{ power(${Const(x)}, ${Const(y)}) } =>
+        case '{ power(${Expr(x)}, ${Expr(y)}) } =>
           Expr(power(x, y))
-        case '{ power($x, ${Const(y)}) } =>
+        case '{ power($x, ${Expr(y)}) } =>
           if y == 0 then '{1}
           else '{ times($x, power($x, ${Expr(y-1)})) }
       }),

tests/run-macros/expr-map-1/Macro_1.scala

@@ -25,9 +25,9 @@ private def rewriteMacro[T: Type](x: Expr[T])(using Quotes): Expr[T] = {
           case (_, Some(_)) => '{ $y * $x }
           case _ => '{ $x * $y }
         }
-      case '{ power(${Const(x)}, ${Const(y)}) } =>
+      case '{ power(${Expr(x)}, ${Expr(y)}) } =>
         Expr(power(x, y))
-      case '{ power($x, ${Const(y)}) } =>
+      case '{ power($x, ${Expr(y)}) } =>
         if y == 0 then '{1}
         else '{ times($x, power($x, ${Expr(y-1)})) }
     }

tests/run-macros/flops-rewrite-2/Macro_1.scala

@@ -11,8 +11,8 @@ object E {
 
   implicit def ev1[T: Type]: FromExpr[E[T]] = new FromExpr { // TODO use type class derivation
     def unapply(x: Expr[E[T]])(using Quotes) = (x match {
-      case '{ I(${Const(n)}) } => Some(I(n))
-      case '{ D(${Const(n)}) } => Some(D(n))
+      case '{ I(${Expr(n)}) } => Some(I(n))
+      case '{ D(${Expr(n)}) } => Some(D(n))
       case '{ Plus[Int](${Value(x)}, ${Value(y)})(using $op) } => Some(Plus(x, y)(using Plus2.IPlus))
       case '{ Plus[Double](${Value(x)}, ${Value(y)})(using $op) } => Some(Plus(x, y)(using Plus2.DPlus))
       case '{ Times[Int](${Value(x)}, ${Value(y)})(using $op) } => Some(Times(x, y)(using Times2.ITimes))

tests/run-macros/flops-rewrite-3/Macro_1.scala

@@ -8,7 +8,7 @@ object Macros {
 
   private def impl(self: Expr[StringContext], args: Expr[Seq[String]])(using Quotes): Expr[String] = {
     self match {
-      case '{ StringContext(${Varargs(Consts(parts))}: _*) } =>
+      case '{ StringContext(${Varargs(Exprs(parts))}: _*) } =>
         val upprerParts: List[String] = parts.toList.map(_.toUpperCase)
         val upprerPartsExpr: Expr[List[String]] = Expr.ofList(upprerParts.map(Expr(_)))
         '{ StringContext($upprerPartsExpr: _*).s($args: _*) }

tests/run-macros/inline-macro-staged-interpreter/Macro_1.scala

@@ -10,7 +10,7 @@ object Macros {
 
     def lift(e: Expr[DSL]): Expr[T] = e match {
 
-      case '{ LitDSL(${ Const(c) }) } =>
+      case '{ LitDSL(${ Expr(c) }) } =>
         '{ $sym.value(${Expr(c)}) }
 
       case '{ ($x: DSL) + ($y: DSL) } =>

tests/run-macros/quote-matcher-string-interpolator-3/quoted_1.scala

@@ -21,7 +21,7 @@ object Macros {
 
     def lift(e: Expr[DSL])(implicit env: Map[Int, Expr[T]]): Expr[T] = e match {
 
-      case '{ LitDSL(${Const(c)}) } => sym.value(c)
+      case '{ LitDSL(${Expr(c)}) } => sym.value(c)
 
       case '{ ($x: DSL) + ($y: DSL) } => sym.plus(lift(x), lift(y))
 
@@ -35,7 +35,7 @@ object Macros {
           lift(close(body1)(nEnvVar))(env + (i -> lift(value)))
         }
 
-      case '{ envVar(${Const(i)}) } => env(i)
+      case '{ envVar(${Expr(i)}) } => env(i)
 
       case _ =>
         import quotes.reflect._

tests/run-macros/quote-matcher-symantics-1/quoted_1.scala

@@ -18,15 +18,15 @@ object Macros {
     object FromEnv {
       def unapply[T](e: Expr[Any])(using env: Env): Option[Expr[R[T]]] =
         e match
-          case '{envVar[t](${Const(id)})} =>
+          case '{envVar[t](${Expr(id)})} =>
             env.get(id).asInstanceOf[Option[Expr[R[T]]]] // We can only add binds that have the same type as the refs
           case _ =>
             None
     }
 
     def lift[T: Type](e: Expr[T])(using env: Env): Expr[R[T]] = ((e: Expr[Any]) match {
-      case Const(e: Int) => '{ $sym.int(${Expr(e)}).asInstanceOf[R[T]] }
-      case Const(e: Boolean) => '{ $sym.bool(${Expr(e)}).asInstanceOf[R[T]] }
+      case '{ ${Expr(e)}: Int } => '{ $sym.int(${Expr(e)}).asInstanceOf[R[T]] }
+      case '{ ${Expr(e)}: Boolean } => '{ $sym.bool(${Expr(e)}).asInstanceOf[R[T]] }
 
       case '{ ($x: Int) + ($y: Int) } =>
         '{ $sym.add(${lift(x)}, ${lift(y)}).asInstanceOf[R[T]] }

tests/run-macros/quote-matcher-symantics-2/quoted_1.scala

@@ -9,7 +9,7 @@ private def sumExprShow(argsExpr: Expr[Seq[Int]]) (using Quotes): Expr[String] =
 
 private def sumExpr(argsExpr: Expr[Seq[Int]])(using Quotes) : Expr[Int] = {
   UnsafeExpr.underlyingArgument(argsExpr) match {
-    case Varargs(Consts(args)) => // args is of type Seq[Int]
+    case Varargs(Exprs(args)) => // args is of type Seq[Int]
       Expr(args.sum) // precompute result of sum
     case Varargs(argExprs) => // argExprs is of type Seq[Expr[Int]]
       val staticSum: Int = argExprs.map(_.value.getOrElse(0)).sum

tests/run-macros/quote-matcher-symantics-3/quoted_1.scala

@@ -2,4 +2,3 @@
 4
 abc
 null
-OK

tests/run-macros/quoted-matching-docs/Macro_1.scala

@@ -11,12 +11,12 @@ object Macros {
     val buff = new StringBuilder
     def stagedPrintln(x: Any): Unit = buff append java.util.Objects.toString(x) append "\n"
 
-    Expr(3) match { case Const(n) => stagedPrintln(n) }
-    '{4} match { case Const(n) => stagedPrintln(n) }
-    '{"abc"} match { case Const(n) => stagedPrintln(n) }
+    Expr(3) match { case Expr(n) => stagedPrintln(n) }
+    '{4} match { case Expr(n) => stagedPrintln(n) }
+    '{"abc"} match { case Expr(n) => stagedPrintln(n) }
     '{null} match { case '{null} => stagedPrintln(null) }
 
-    '{new Object} match { case Const(n) => println(n); case _ => stagedPrintln("OK") }
+    // '{new Object} match { case Expr(n) => println(n); case _ => stagedPrintln("OK") }
 
     '{print(${Expr(buff.result())})}
   }