Merge pull request #10519 from dotty-staging/move-quotes-as-last-parameter

Move `Quotes` as last parameter in `ExprMap.transform`

Author: nicolasstucki

library/src/scala/quoted/ExprMap.scala

@@ -3,10 +3,10 @@ package scala.quoted
 trait ExprMap:
 
   /** Map an expression `e` with a type `T` */
-  def transform[T](e: Expr[T])(using Quotes, Type[T]): Expr[T]
+  def transform[T](e: Expr[T])(using Type[T])(using Quotes): Expr[T]
 
   /** Map subexpressions an expression `e` with a type `T` */
-  def transformChildren[T](e: Expr[T])(using Quotes, Type[T]): Expr[T] = {
+  def transformChildren[T](e: Expr[T])(using Type[T])(using Quotes): Expr[T] = {
     import quotes.reflect._
     final class MapChildren() {
 
@@ -99,10 +99,13 @@ trait ExprMap:
           case _: Inlined =>
             transformTermChildren(tree, tpe)(owner)
           case _ if tree.isExpr =>
+            // WARNING: Never do a cast like this in user code (accepable within the stdlib).
+            // In theory we should use `tree.asExpr match { case '{ $expr: t } => Term.of(transform(expr)) }`
+            // This is to avoid conflicts when re-boostrapping the library.
             type X
             val expr = tree.asExpr.asInstanceOf[Expr[X]]
             val t = tpe.asType.asInstanceOf[Type[X]]
-            val transformedExpr = transform(expr)(using quotes, t)
+            val transformedExpr = transform(expr)(using t)
             Term.of(transformedExpr)
           case _ =>
             transformTermChildren(tree, tpe)(owner)

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

@@ -8,7 +8,7 @@ private def stringRewriter(e: Expr[Any])(using Quotes): Expr[Any] =
 
 private object StringRewriter extends ExprMap {
 
-  def transform[T](e: Expr[T])(using Quotes, Type[T]): Expr[T] = e match
+  def transform[T](e: Expr[T])(using Type[T])(using Quotes): Expr[T] = e match
     case Const(s: String) =>
       Expr(s.reverse) match
         case '{ $x: T } => x

tests/run-macros/expr-map-2/Macro_1.scala

@@ -8,7 +8,7 @@ private def stringRewriter(e: Expr[Any])(using Quotes): Expr[Any] =
 
 private object StringRewriter extends ExprMap {
 
-  def transform[T](e: Expr[T])(using Quotes, Type[T]): Expr[T] = e match
+  def transform[T](e: Expr[T])(using Type[T])(using Quotes): Expr[T] = e match
     case '{ ($x: Foo).x } =>
       '{ new Foo(4).x } match
         case '{ $e: T } => e

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

@@ -64,7 +64,7 @@ private object Rewriter {
 }
 
 private class Rewriter(preTransform: List[Transformation[_]] = Nil, postTransform: List[Transformation[_]] = Nil, fixPoint: Boolean) extends ExprMap {
-  def transform[T](e: Expr[T])(using Quotes, Type[T]): Expr[T] = {
+  def transform[T](e: Expr[T])(using Type[T])(using Quotes): Expr[T] = {
     val e2 = preTransform.foldLeft(e)((ei, transform) => transform(ei))
     val e3 = transformChildren(e2)
     val e4 = postTransform.foldLeft(e3)((ei, transform) => transform(ei))

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

@@ -101,7 +101,7 @@ private class Rewriter private (preTransform: List[Transformation] = Nil, postTr
   def withPost(transform: Transformation): Rewriter =
     new Rewriter(preTransform, transform :: postTransform, fixPoint)
 
-  def transform[T](e: Expr[T])(using Quotes, Type[T]): Expr[T] = {
+  def transform[T](e: Expr[T])(using Type[T])(using Quotes): Expr[T] = {
     val e2 = preTransform.foldLeft(e)((ei, transform) => transform(ei))
     val e3 = transformChildren(e2)
     val e4 = postTransform.foldLeft(e3)((ei, transform) => transform(ei))

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

@@ -29,7 +29,7 @@ private object Rewriter {
 }
 
 private class Rewriter(preTransform: Expr[Any] => Expr[Any], postTransform: Expr[Any] => Expr[Any], fixPoint: Boolean) extends ExprMap {
-  def transform[T](e: Expr[T])(using Quotes, Type[T]): Expr[T] = {
+  def transform[T](e: Expr[T])(using Type[T])(using Quotes): Expr[T] = {
     val e2 = checkedTransform(e, preTransform)
     val e3 = transformChildren(e2)
     val e4 = checkedTransform(e3, postTransform)