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/tastyreflect/KernelImpl.scala

@@ -1,6 +1,7 @@
 package dotty.tools.dotc
 package tastyreflect
 
+import dotty.tools.dotc.ast.Trees.SeqLiteral
 import dotty.tools.dotc.ast.{Trees, tpd, untpd}
 import dotty.tools.dotc.ast.tpd.TreeOps
 import dotty.tools.dotc.typer.Typer
@@ -1055,6 +1056,9 @@ class KernelImpl(val rootContext: core.Contexts.Context, val rootPosition: util.
   def Type_memberType(self: Type)(member: Symbol)(implicit ctx: Context): Type =
     member.info.asSeenFrom(self, member.owner)
 
+  def Type_derivesFrom(self: Type)(cls: ClassDefSymbol)(implicit ctx: Context): Boolean =
+    self.derivesFrom(cls)
+
   type ConstantType = Types.ConstantType
 
   def matchConstantType(tpe: TypeOrBounds)(implicit ctx: Context): Option[ConstantType] = tpe match {
@@ -1774,7 +1778,7 @@ class KernelImpl(val rootContext: core.Contexts.Context, val rootPosition: util.
   def Definitions_Array_length: Symbol = defn.Array_length.asTerm
   def Definitions_Array_update: Symbol = defn.Array_update.asTerm
 
-  def Definitions_RepeatedParamClass: Symbol = defn.RepeatedParamClass
+  def Definitions_RepeatedParamClass: ClassDefSymbol = defn.RepeatedParamClass
 
   def Definitions_OptionClass: Symbol = defn.OptionClass
   def Definitions_NoneModule: Symbol = defn.NoneClass.companionModule.asTerm

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

@@ -64,9 +64,17 @@ object Matcher {
 
       (normalize(scrutinee), normalize(pattern)) match {
 
+        // Match a scala.internal.Quoted.patternHole typed as a repeated argument and return the scrutinee tree
+        case (IsTerm(scrutinee @ Typed(s, tpt1)), Typed(TypeApply(patternHole, tpt :: Nil), tpt2))
+            if patternHole.symbol == kernel.Definitions_InternalQuoted_patternHole &&
+               s.tpe <:< tpt.tpe &&
+               tpt2.tpe.derivesFrom(definitions.RepeatedParamClass) =>
+          Some(Tuple1(scrutinee.seal))
+
         // 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 =>
+            if patternHole.symbol == kernel.Definitions_InternalQuoted_patternHole &&
+               scrutinee.tpe <:< tpt.tpe =>
           Some(Tuple1(scrutinee.seal))
 
         //
@@ -85,7 +93,7 @@ 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 Typed(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)
+  }
+
+}

library/src/scala/tasty/reflect/Kernel.scala

@@ -844,6 +844,9 @@ trait Kernel {
 
   def Type_memberType(self: Type)(member: Symbol)(implicit ctx: Context): Type
 
+  /** Is this type an instance of a non-bottom subclass of the given class `cls`? */
+  def Type_derivesFrom(self: Type)(cls: ClassDefSymbol)(implicit ctx: Context): Boolean
+
   /** A singleton type representing a known constant value */
   type ConstantType <: Type
 
@@ -1434,7 +1437,7 @@ trait Kernel {
   def Definitions_Array_length: Symbol
   def Definitions_Array_update: Symbol
 
-  def Definitions_RepeatedParamClass: Symbol
+  def Definitions_RepeatedParamClass: ClassDefSymbol
 
   def Definitions_OptionClass: Symbol
   def Definitions_NoneModule: Symbol

library/src/scala/tasty/reflect/StandardDefinitions.scala

@@ -106,7 +106,7 @@ trait StandardDefinitions extends Core {
     /** A dummy class symbol that is used to indicate repeated parameters
       *  compiled by the Scala compiler.
       */
-    def RepeatedParamClass: Symbol = kernel.Definitions_RepeatedParamClass
+    def RepeatedParamClass: ClassDefSymbol = kernel.Definitions_RepeatedParamClass
 
     /** The class symbol of class `scala.Option`. */
     def OptionClass: Symbol = kernel.Definitions_OptionClass

library/src/scala/tasty/reflect/TypeOrBoundsOps.scala

@@ -22,6 +22,11 @@ trait TypeOrBoundsOps extends Core {
     def typeSymbol(implicit ctx: Context): Symbol = kernel.Type_typeSymbol(self)
     def isSingleton(implicit ctx: Context): Boolean = kernel.Type_isSingleton(self)
     def memberType(member: Symbol)(implicit ctx: Context): Type = kernel.Type_memberType(self)(member)
+
+    /** Is this type an instance of a non-bottom subclass of the given class `cls`? */
+    def derivesFrom(cls: ClassDefSymbol)(implicit ctx: Context): Boolean =
+      kernel.Type_derivesFrom(self)(cls)
+
   }
 
   object IsType {

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-b.check

@@ -0,0 +1,2 @@
+Hello World
+Hello World

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

@@ -0,0 +1,22 @@
+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: _*) } =>
+        '{
+          val p: Seq[String] = $parts
+          val a: Seq[Any] = $args ++ Seq("")
+          p.zip(a).map(_ + _.toString).mkString
+        }
+      case _ =>
+        '{ "ERROR" }
+    }
+  }
+}