Factor out common code

Author: nicolasstucki

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

@@ -140,8 +140,7 @@ object desugar {
    *    def x_=($1: <TypeTree()>): Unit = ()
    */
   def valDef(vdef0: ValDef)(implicit ctx: Context): Tree = {
-    val vdef = transformQuotedPatternName(vdef0)
-    val ValDef(name, tpt, rhs) = vdef
+    val vdef @ ValDef(name, tpt, rhs) = transformQuotedPatternName(vdef0)
     val mods = vdef.mods
     val setterNeeded =
       (mods is Mutable) && ctx.owner.isClass && (!(mods is PrivateLocal) || (ctx.owner is Trait))
@@ -165,14 +164,6 @@ object desugar {
     else vdef
   }
 
-  def transformQuotedPatternName(vdef: ValDef)(implicit ctx: Context): ValDef = {
-    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)
-    } else vdef
-  }
-
   def makeImplicitParameters(tpts: List[Tree], contextualFlag: FlagSet = EmptyFlags, forPrimaryConstructor: Boolean = false)(implicit ctx: Context): List[ValDef] =
     for (tpt <- tpts) yield {
        val paramFlags: FlagSet = if (forPrimaryConstructor) PrivateLocalParamAccessor else Param
@@ -207,9 +198,7 @@ object desugar {
    *      inline def f(x: Boolean): Any = (if (x) 1 else ""): Any
    */
   private def defDef(meth0: DefDef, isPrimaryConstructor: Boolean = false)(implicit ctx: Context): Tree = {
-    val meth = transformQuotedPatternName(meth0)
-
-    val DefDef(_, tparams, vparamss, tpt, rhs) = meth
+    val meth @ DefDef(_, tparams, vparamss, tpt, rhs) = transformQuotedPatternName(meth0)
     val methName = normalizeName(meth, tpt).asTermName
     val mods = meth.mods
     val epbuf = new ListBuffer[ValDef]
@@ -283,12 +272,30 @@ object desugar {
     }
   }
 
-  def transformQuotedPatternName(ddef: DefDef)(implicit ctx: Context): DefDef = {
-    if (ctx.mode.is(Mode.QuotedPattern) && !ddef.isBackquoted && ddef.name != nme.ANON_FUN && ddef.name.startsWith("$")) {
-      val name = ddef.name.toString.substring(1).toTermName
-      val mods = ddef.mods.withAddedAnnotation(New(ref(defn.InternalQuoted_patternBindHoleAnnot.typeRef)).withSpan(ddef.span))
-      cpy.DefDef(ddef)(name).withMods(mods)
-    } else ddef
+  /** Transforms a definition with a name starting with a `$` in a quoted pattern into a `quoted.binding.Binding` splice.
+   *
+   *  The desugaring consists in renaming the the definition and adding the `@patternBindHole` annotation. This
+   *  annotation is used during typing to perform the full transformation.
+   *
+   *  A definition
+   *  ```scala
+   *    case '{ def $a(...) = ... a() ...; ... a() ... }
+   *  ```
+   *  into
+   *  ```scala
+   *    case '{ @patternBindHole def a(...) = ... a() ...; ... a() ... }
+   *  ```
+   */
+  def transformQuotedPatternName(tree: ValOrDefDef)(implicit ctx: Context): ValOrDefDef = {
+    if (ctx.mode.is(Mode.QuotedPattern) && !tree.isBackquoted && tree.name != nme.ANON_FUN && tree.name.startsWith("$")) {
+      val name = tree.name.toString.substring(1).toTermName
+      val newTree: ValOrDefDef = tree match {
+        case tree: ValDef => cpy.ValDef(tree)(name)
+        case tree: DefDef => cpy.DefDef(tree)(name)
+      }
+      val mods = tree.mods.withAddedAnnotation(New(ref(defn.InternalQuoted_patternBindHoleAnnot.typeRef)).withSpan(tree.span))
+      newTree.withMods(mods)
+    } else tree
   }
 
   // Add all evidence parameters in `params` as implicit parameters to `meth` */

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

@@ -357,6 +357,7 @@ object Trees {
 
   /** A ValDef or DefDef tree */
   abstract class ValOrDefDef[-T >: Untyped](implicit @constructorOnly src: SourceFile) extends MemberDef[T] with WithLazyField[Tree[T]] {
+    type ThisTree[-T >: Untyped] <: ValOrDefDef[T]
     def name: TermName
     def tpt: Tree[T]
     def unforcedRhs: LazyTree = unforced