Fix #6253: Handle repeated args in quoted patterns

* Handle repeated args in quoted patterns in typer
* Handle repeated args in quoted patterns in Matcher
* Add Repeated extractor to get Seq[Expr[T]] from a Expr[Seq[T]]

Author: nicolasstucki

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

@@ -580,7 +580,10 @@ class Typer extends Namer
 
     if (untpd.isWildcardStarArg(tree)) {
       def typedWildcardStarArgExpr = {
-        val tpdExpr = typedExpr(tree.expr)
+        val ptArg =
+          if (ctx.mode.is(Mode.QuotedPattern)) pt.subst(defn.RepeatedParamClass :: Nil, defn.SeqType :: Nil)
+          else WildcardType
+        val tpdExpr = typedExpr(tree.expr, ptArg)
         tpdExpr.tpe.widenDealias match {
           case defn.ArrayOf(_) =>
             val starType = defn.ArrayType.appliedTo(WildcardType)
@@ -1960,12 +1963,15 @@ class Typer extends Namer
     object splitter extends tpd.TreeMap {
       val patBuf = new mutable.ListBuffer[Tree]
       override def transform(tree: Tree)(implicit ctx: Context) = tree match {
-        case Typed(Splice(pat), tpt) =>
+        case Typed(Splice(pat), tpt) if !tpt.tpe.derivesFrom(defn.RepeatedParamClass) =>
           val exprTpt = AppliedTypeTree(TypeTree(defn.QuotedExprType), tpt :: Nil)
           transform(Splice(Typed(pat, exprTpt)))
         case Splice(pat) =>
           try patternHole(tree)
-          finally patBuf += pat
+          finally {
+            val pat1 = pat.subst(defn.RepeatedParamClass :: Nil, defn.SeqClass :: Nil)
+            patBuf += pat1
+          }
         case _ =>
           super.transform(tree)
       }

library/src-bootstrapped/scala/internal/quoted/Matcher.scala

@@ -67,6 +67,9 @@ object Matcher {
         // Match a scala.internal.Quoted.patternHole and return the scrutinee tree
         case (IsTerm(scrutinee), TypeApply(patternHole, tpt :: Nil))
             if patternHole.symbol == kernel.Definitions_InternalQuoted_patternHole && scrutinee.tpe <:< tpt.tpe =>
+//          scrutinee match {
+//            case Repeated(args, _) =>
+//          }
           Some(Tuple1(scrutinee.seal))
 
         //
@@ -85,7 +88,7 @@ object Matcher {
         case (Select(qual1, _), Select(qual2, _)) if scrutinee.symbol == pattern.symbol =>
           treeMatches(qual1, qual2)
 
-        case (IsRef(_), IsRef(_, _)) if scrutinee.symbol == pattern.symbol =>
+        case (IsRef(_), IsRef(_)) if scrutinee.symbol == pattern.symbol =>
           Some(())
 
         case (Apply(fn1, args1), Apply(fn2, args2)) if fn1.symbol == fn2.symbol =>

library/src/scala/quoted/matching/Repeated.scala

@@ -0,0 +1,21 @@
+package scala.quoted.matching
+
+import scala.quoted.Expr
+
+import scala.tasty.Reflection // TODO do not depend on reflection directly
+
+/** Matches a literal sequence of expressions */
+object Repeated {
+
+  def unapply[T](expr: Expr[Seq[T]])(implicit reflect: Reflection): Option[Seq[Expr[T]]] = {
+    import reflect.{Repeated => RepeatedTree, _} // TODO rename to avoid clash
+    def repeated(tree: Term): Option[Seq[Expr[T]]] = tree match {
+      case RepeatedTree(elems, _) => Some(elems.map(x => x.seal.asInstanceOf[Expr[T]]))
+      case Block(Nil, e) => repeated(e)
+      case Inlined(_, Nil, e) => repeated(e)
+      case _  => None
+    }
+    repeated(expr.unseal)
+  }
+
+}

tests/pos/i6253.scala

@@ -0,0 +1,10 @@
+import scala.quoted._
+import scala.tasty.Reflection
+object Macros {
+  def impl(self: Expr[StringContext]) given Reflection: Expr[String] = self match {
+    case '{ StringContext() } => '{""}
+    case '{ StringContext($part1) } => part1
+    case '{ StringContext($part1, $part2) } => '{ $part1 + $part2 }
+    case '{ StringContext($parts: _*) } => '{ $parts.mkString }
+  }
+}

tests/run-with-compiler/i6253.check

@@ -0,0 +1,18 @@
+import scala.quoted._
+import scala.quoted.matching._
+
+import scala.tasty.Reflection
+
+object Macros {
+
+  inline def (self: => StringContext) xyz(args: => String*): String = ${impl('self, 'args)}
+
+  private def impl(self: Expr[StringContext], args: Expr[Seq[String]])(implicit reflect: Reflection): Expr[String] = {
+    self match {
+      case '{ StringContext($parts: _*) } =>
+        '{ StringContext($parts: _*).s($args: _*) }
+      case _ =>
+        '{ "ERROR" }
+    }
+  }
+}

tests/run-with-compiler/i6253/quoted_1.scala

@@ -0,0 +1,10 @@
+import Macros._
+
+object Test {
+
+  def main(args: Array[String]): Unit = {
+    println(xyz"Hello World")
+    println(xyz"Hello ${"World"}")
+  }
+
+}

tests/run-with-compiler/i6253/quoted_2.scala

@@ -0,0 +1,2 @@
+dlroW olleH
+ olleHWorld

tests/run-with-compiler/quote-matcher-string-interpolator.check

@@ -0,0 +1,21 @@
+import scala.quoted._
+import scala.quoted.matching._
+
+import scala.tasty.Reflection
+
+object Macros {
+
+  inline def (self: => StringContext) xyz(args: => String*): String = ${impl('self, 'args)}
+
+  private def impl(self: Expr[StringContext], args: Expr[Seq[String]])(implicit reflect: Reflection): Expr[String] = {
+    self match {
+      case '{ StringContext(${Repeated(parts)}: _*) } =>
+        val parts2 = parts.map(x => '{ $x.reverse }).toList.toExprOfList
+        '{ StringContext($parts2: _*).s($args: _*) }
+      case _ =>
+        '{ "ERROR" }
+    }
+
+  }
+
+}

tests/run-with-compiler/quote-matcher-string-interpolator/quoted_1.scala

@@ -0,0 +1,10 @@
+import Macros._
+
+object Test {
+
+  def main(args: Array[String]): Unit = {
+    println(xyz"Hello World")
+    println(xyz"Hello ${"World"}")
+  }
+
+}