Add BackquotedValDef to keep track of backquotes in val names

Author: nicolasstucki

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -166,7 +166,7 @@ object desugar {
   }
 
   def transformQuotedPatternName(vdef: ValDef)(implicit ctx: Context): ValDef = {
-    if (ctx.mode.is(Mode.QuotedPattern) && vdef.name.startsWith("$")) {
+    if (ctx.mode.is(Mode.QuotedPattern) && !vdef.isBackquoted && vdef.name.startsWith("$")) {
       val name = vdef.name.toString.substring(1).toTermName
       val mods = vdef.mods.withAddedAnnotation(New(ref(defn.InternalQuoted_patternBindHoleAnnot.typeRef)).withSpan(vdef.span))
       cpy.ValDef(vdef)(name).withMods(mods)

compiler/src/dotty/tools/dotc/ast/Trees.scala

@@ -704,6 +704,15 @@ object Trees {
     assert(isEmpty || tpt != genericEmptyTree)
     def unforced: LazyTree = preRhs
     protected def force(x: AnyRef): Unit = preRhs = x
+
+    /** Is this a `BackquotedValDef` ? */
+    def isBackquoted: Boolean = false
+  }
+
+  class BackquotedValDef[-T >: Untyped] private[ast] (name: TermName, tpt: Tree[T], preRhs: LazyTree)(implicit @constructorOnly src: SourceFile)
+    extends ValDef[T](name, tpt, preRhs) {
+    override def isBackquoted: Boolean = true
+    override def productPrefix: String = "BackquotedValDef"
   }
 
   /** mods def name[tparams](vparams_1)...(vparams_n): tpt = rhs */
@@ -932,6 +941,7 @@ object Trees {
     type Alternative = Trees.Alternative[T]
     type UnApply = Trees.UnApply[T]
     type ValDef = Trees.ValDef[T]
+    type BackquotedValDef = Trees.BackquotedValDef[T]
     type DefDef = Trees.DefDef[T]
     type TypeDef = Trees.TypeDef[T]
     type Template = Trees.Template[T]
@@ -1125,6 +1135,9 @@ object Trees {
         case _ => finalize(tree, untpd.UnApply(fun, implicits, patterns)(sourceFile(tree)))
       }
       def ValDef(tree: Tree)(name: TermName, tpt: Tree, rhs: LazyTree)(implicit ctx: Context): ValDef = tree match {
+        case tree: BackquotedValDef =>
+          if ((name == tree.name) && (tpt eq tree.tpt) && (rhs eq tree.unforcedRhs)) tree
+          else finalize(tree, untpd.BackquotedValDef(name, tpt, rhs)(sourceFile(tree)))
         case tree: ValDef if (name == tree.name) && (tpt eq tree.tpt) && (rhs eq tree.unforcedRhs) => tree
         case _ => finalize(tree, untpd.ValDef(name, tpt, rhs)(sourceFile(tree)))
       }

compiler/src/dotty/tools/dotc/ast/untpd.scala

@@ -321,6 +321,7 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
   def Alternative(trees: List[Tree])(implicit src: SourceFile): Alternative = new Alternative(trees)
   def UnApply(fun: Tree, implicits: List[Tree], patterns: List[Tree])(implicit src: SourceFile): UnApply = new UnApply(fun, implicits, patterns)
   def ValDef(name: TermName, tpt: Tree, rhs: LazyTree)(implicit src: SourceFile): ValDef = new ValDef(name, tpt, rhs)
+  def BackquotedValDef(name: TermName, tpt: Tree, rhs: LazyTree)(implicit src: SourceFile): ValDef = new BackquotedValDef(name, tpt, rhs)
   def DefDef(name: TermName, tparams: List[TypeDef], vparamss: List[List[ValDef]], tpt: Tree, rhs: LazyTree)(implicit src: SourceFile): DefDef = new DefDef(name, tparams, vparamss, tpt, rhs)
   def TypeDef(name: TypeName, rhs: Tree)(implicit src: SourceFile): TypeDef = new TypeDef(name, rhs)
   def Template(constr: DefDef, parents: List[Tree], derived: List[Tree], self: ValDef, body: LazyTreeList)(implicit src: SourceFile): Template =
@@ -406,8 +407,12 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
   def makeAndType(left: Tree, right: Tree)(implicit ctx: Context): AppliedTypeTree =
     AppliedTypeTree(ref(defn.andType.typeRef), left :: right :: Nil)
 
-  def makeParameter(pname: TermName, tpe: Tree, mods: Modifiers = EmptyModifiers)(implicit ctx: Context): ValDef =
-    ValDef(pname, tpe, EmptyTree).withMods(mods | Param)
+  def makeParameter(pname: TermName, tpe: Tree, mods: Modifiers = EmptyModifiers, isBackquoted: Boolean = false)(implicit ctx: Context): ValDef = {
+    val vdef =
+      if (isBackquoted) BackquotedValDef(pname, tpe, EmptyTree)
+      else ValDef(pname, tpe, EmptyTree)
+    vdef.withMods(mods | Param)
+  }
 
   def makeSyntheticParameter(n: Int = 1, tpt: Tree = null, flags: FlagSet = EmptyFlags)(implicit ctx: Context): ValDef =
     ValDef(nme.syntheticParamName(n), if (tpt == null) TypeTree() else tpt, EmptyTree)

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

@@ -403,10 +403,10 @@ object Parsers {
     /** Convert tree to formal parameter
     */
     def convertToParam(tree: Tree, expected: String = "formal parameter"): ValDef = tree match {
-      case Ident(name) =>
-        makeParameter(name.asTermName, TypeTree()).withSpan(tree.span)
-      case Typed(Ident(name), tpt) =>
-        makeParameter(name.asTermName, tpt).withSpan(tree.span)
+      case id @ Ident(name) =>
+        makeParameter(name.asTermName, TypeTree(), isBackquoted = id.isBackquoted).withSpan(tree.span)
+      case Typed(id @ Ident(name), tpt) =>
+        makeParameter(name.asTermName, tpt, isBackquoted = id.isBackquoted).withSpan(tree.span)
       case Typed(Splice(Ident(name)), tpt) =>
         makeParameter(("$" + name).toTermName, tpt).withSpan(tree.span)
       case _ =>
@@ -2369,7 +2369,9 @@ object Parsers {
           }
         } else EmptyTree
       lhs match {
-        case (id @ Ident(name: TermName)) :: Nil => {
+        case (id: BackquotedIdent) :: Nil if id.name.isTermName =>
+          finalizeDef(BackquotedValDef(id.name.asTermName, tpt, rhs), mods, start)
+        case Ident(name: TermName) :: Nil => {
           finalizeDef(ValDef(name, tpt, rhs), mods, start)
         } case _ =>
           PatDef(mods, lhs, tpt, rhs)

tests/neg/quotedPatterns-2.scala

@@ -1,10 +1,6 @@
 object Test {
   def test(x: quoted.Expr[Int]) given tasty.Reflection = x match {
-//    case '{ val a = 4; '{ a }; $y } => y // error: access to value a from wrong staging level
-    case '{ val `$y`: Int = 2; 1 } =>
-      y // error
-    case '{ ((`$y`: Int) => 3); 2 } =>
-      y // error
+    case '{ val a = 4; '{ a }; $y } => y // error: access to value a from wrong staging level
     case _ =>
   }
 }

tests/neg/quotedPatterns-3.scala

@@ -0,0 +1,9 @@
+object Test {
+  def test(x: quoted.Expr[Int]) given tasty.Reflection = x match {
+    case '{ val `$y`: Int = 2; 1 } =>
+      y // error: Not found: y
+    case '{ ((`$y`: Int) => 3); 2 } =>
+      y // error: Not found: y
+    case _ =>
+  }
+}

tests/run-with-compiler/quote-matcher-symantics-2/quoted_1.scala

@@ -34,7 +34,7 @@ object Macros {
     }
 
     def liftFun(e: Expr[DSL => DSL])(implicit env: Map[Binding[DSL], Expr[T]]): Expr[T => T] = e match {
-      case '{ (`$x`: DSL) => ($body: DSL) } =>
+      case '{ ($x: DSL) => ($body: DSL) } =>
         sym.lam((y: Expr[T]) => lift(body)(env + (x -> y)))
 
       case _ =>