Merge pull request #6930 from dotty-staging/add-type-quote-patterns

Add quoted type patterns

Author: nicolasstucki

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -642,9 +642,14 @@ class Definitions {
     @tu lazy val InternalQuoted_patternHole: Symbol = InternalQuotedModule.requiredMethod("patternHole")
     @tu lazy val InternalQuoted_patternBindHoleAnnot: ClassSymbol = InternalQuotedModule.requiredClass("patternBindHole")
     @tu lazy val InternalQuoted_QuoteTypeTagAnnot: ClassSymbol = InternalQuotedModule.requiredClass("quoteTypeTag")
+    @tu lazy val InternalQuoted_fromAboveAnnot: ClassSymbol = InternalQuotedModule.requiredClass("fromAbove")
 
-  @tu lazy val InternalQuotedMatcherModule: Symbol = ctx.requiredModule("scala.internal.quoted.Matcher")
-    @tu lazy val InternalQuotedMatcher_unapply: Symbol = InternalQuotedMatcherModule.requiredMethod(nme.unapply)
+
+  @tu lazy val InternalQuotedExprModule: Symbol = ctx.requiredModule("scala.internal.quoted.Expr")
+    @tu lazy val InternalQuotedExpr_unapply: Symbol = InternalQuotedExprModule.requiredMethod(nme.unapply)
+
+  @tu lazy val InternalQuotedTypeModule: Symbol = ctx.requiredModule("scala.internal.quoted.Type")
+    @tu lazy val InternalQuotedType_unapply: Symbol = InternalQuotedTypeModule.requiredMethod(nme.unapply)
 
   @tu lazy val QuotedTypeClass: ClassSymbol = ctx.requiredClass("scala.quoted.Type")
     @tu lazy val QuotedType_splice: Symbol = QuotedTypeClass.requiredType(tpnme.splice)

compiler/src/dotty/tools/dotc/core/quoted/PickledQuotes.scala

@@ -80,8 +80,13 @@ object PickledQuotes {
     val unpickled = unpickle(tastyBytes, args, isType = true)(ctx.addMode(Mode.ReadPositions))
     val tpt = unpickled match {
       case Block(aliases, tpt) =>
-        // `@quoteTypeTag type` aliasses are not required after unpickling
-        tpt
+        // `@quoteTypeTag type` aliases are not required after unpickling.
+        // Type definitions are placeholders for type holes in the pickled quote, at this point
+        // those holes have been filled. As we already dealias al references to them in `dealiasTypeTags`
+        // there is no need to keep their definitions in the tree. As artifacts of quote reification
+        // they also do not have a meaningful position in the source.
+        val aliases1 = aliases.filter(!_.symbol.hasAnnotation(defn.InternalQuoted_QuoteTypeTagAnnot))
+        seq(aliases1, tpt)
       case tpt => tpt
     }
     tpt.withType(dealiasTypeTags(tpt.tpe))

compiler/src/dotty/tools/dotc/tastyreflect/ReflectionCompilerInterface.scala

@@ -1809,6 +1809,7 @@ class ReflectionCompilerInterface(val rootContext: core.Contexts.Context) extend
 
   def Definitions_InternalQuoted_patternHole: Symbol = defn.InternalQuoted_patternHole
   def Definitions_InternalQuoted_patternBindHoleAnnot: Symbol = defn.InternalQuoted_patternBindHoleAnnot
+  def Definitions_InternalQuoted_fromAboveAnnot: Symbol = defn.InternalQuoted_fromAboveAnnot
 
   // Types
 

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

@@ -46,8 +46,8 @@ trait QuotesAndSplices {
       case _ =>
     }
     val tree1 =
-      if (tree.quoted.isType) typedTypeApply(untpd.TypeApply(untpd.ref(defn.InternalQuoted_typeQuote.termRef), tree.quoted :: Nil), pt)(quoteContext)
-      else if (ctx.mode.is(Mode.Pattern) && level == 0) typedQuotePattern(tree, pt)
+      if (ctx.mode.is(Mode.Pattern) && level == 0) typedQuotePattern(tree, pt)
+      else if (tree.quoted.isType) typedTypeApply(untpd.TypeApply(untpd.ref(defn.InternalQuoted_typeQuote.termRef), tree.quoted :: Nil), pt)(quoteContext)
       else typedApply(untpd.Apply(untpd.ref(defn.InternalQuoted_exprQuote.termRef), tree.quoted), pt)(quoteContext)
     tree1.withSpan(tree.span)
   }
@@ -163,6 +163,16 @@ trait QuotesAndSplices {
       })
 
     object splitter extends tpd.TreeMap {
+      private var variance: Int = 1
+
+      @forceInline private def atVariance[T](v: Int)(op: => T): T = {
+        val saved = variance
+        variance = v
+        val res = op
+        variance = saved
+        res
+      }
+
       val patBuf = new mutable.ListBuffer[Tree]
       val freshTypePatBuf = new mutable.ListBuffer[Tree]
       val freshTypeBindingsBuff = new mutable.ListBuffer[Tree]
@@ -206,11 +216,21 @@ trait QuotesAndSplices {
           super.transform(tree)
         case tdef: TypeDef if tdef.symbol.hasAnnotation(defn.InternalQuoted_patternBindHoleAnnot) =>
           transformTypeBindingTypeDef(tdef, typePatBuf)
+         case tree @ AppliedTypeTree(tpt, args) =>
+            val args1: List[Tree] = args.zipWithConserve(tpt.tpe.typeParams.map(_.paramVariance)) { (arg, v) =>
+              arg.tpe match {
+                case _: TypeBounds => transform(arg)
+                case _ => atVariance(variance * v)(transform(arg))
+              }
+            }
+            cpy.AppliedTypeTree(tree)(transform(tpt), args1)
         case _ =>
           super.transform(tree)
       }
 
-      def transformTypeBindingTypeDef(tdef: TypeDef, buff: mutable.Builder[Tree, List[Tree]]): Tree = {
+      private def transformTypeBindingTypeDef(tdef: TypeDef, buff: mutable.Builder[Tree, List[Tree]])(implicit ctx: Context): Tree = {
+        if (variance == -1)
+          tdef.symbol.addAnnotation(Annotation(New(ref(defn.InternalQuoted_fromAboveAnnot.typeRef)).withSpan(tdef.span)))
         val bindingType = getBinding(tdef.symbol).symbol.typeRef
         val bindingTypeTpe = AppliedType(defn.QuotedTypeClass.typeRef, bindingType :: Nil)
         assert(tdef.name.startsWith("$"))
@@ -248,7 +268,7 @@ trait QuotesAndSplices {
   }
 
   /** Type a quote pattern `case '{ <quoted> } =>` qiven the a current prototype. Typing the pattern
-   *  will also transform it into a call to `scala.internal.quoted.Matcher.unapply`.
+   *  will also transform it into a call to `scala.internal.quoted.Expr.unapply`.
    *
    *  Code directly inside the quote is typed as an expression using Mode.QuotedPattern. Splices
    *  within the quotes become patterns again and typed acordingly.
@@ -275,7 +295,7 @@ trait QuotesAndSplices {
    *  and the patterns in the splices. All these are recombined into a call to `Matcher.unapply`.
    *
    *  ```
-   *  case scala.internal.quoted.Matcher.unapply[
+   *  case scala.internal.quoted.Expr.unapply[
    *          Tuple1[$t @ _], // Type binging definition
    *          Tuple2[Type[$t], Expr[List[$t]]] // Typing the result of the pattern match
    *        ](
@@ -344,14 +364,16 @@ trait QuotesAndSplices {
 
     val splicePat = typed(untpd.Tuple(splices.map(x => untpd.TypedSplice(replaceBindingsInTree.transform(x)))).withSpan(quoted.span), patType)
 
+    val unapplySym = if (tree.quoted.isTerm) defn.InternalQuotedExpr_unapply else defn.InternalQuotedType_unapply
+    val quoteClass = if (tree.quoted.isTerm) defn.QuotedExprClass else defn.QuotedTypeClass
+    val quotedPattern =
+      if (tree.quoted.isTerm) ref(defn.InternalQuoted_exprQuote.termRef).appliedToType(defn.AnyType).appliedTo(shape).select(nme.apply).appliedTo(qctx)
+      else ref(defn.InternalQuoted_typeQuote.termRef).appliedToTypeTrees(shape :: Nil)
     UnApply(
-      fun = ref(defn.InternalQuotedMatcher_unapply.termRef).appliedToTypeTrees(typeBindingsTuple :: TypeTree(patType) :: Nil),
-      implicits =
-          ref(defn.InternalQuoted_exprQuote.termRef).appliedToType(defn.AnyType).appliedTo(shape).select(nme.apply).appliedTo(qctx) ::
-          Literal(Constant(typeBindings.nonEmpty)) ::
-          qctx :: Nil,
+      fun = ref(unapplySym.termRef).appliedToTypeTrees(typeBindingsTuple :: TypeTree(patType) :: Nil),
+      implicits = quotedPattern :: Literal(Constant(typeBindings.nonEmpty)) :: qctx :: Nil,
       patterns = splicePat :: Nil,
-      proto = defn.QuotedExprClass.typeRef.appliedTo(replaceBindings(quoted1.tpe) & quotedPt))
+      proto = quoteClass.typeRef.appliedTo(replaceBindings(quoted1.tpe) & quotedPt))
   }
 }
 

docs/docs/reference/other-new-features/quoted-pattern-spec.md

@@ -18,18 +18,18 @@ def foo(x: Expr[Int]) given tasty.Reflect: Expr[Int] = x match {
 ```
 In the example above we have `$a` which provides a `Bind[Int]`, `$x` which provides an `Expr[Int]` and `${Bind(`a`)}` which probides an `Expr[Int]` that is pattern matched against `Bind(`a`)` to check that it is a reference to `a`.
 
-Quoted patterns are transformed during typer to a call of `scala.internal.quoted.Matcher.unapply` which splits the quoted code into the patterns and a reifiable quote that will be used as witnesses at runtime.
+Quoted patterns are transformed during typer to a call of `scala.internal.quoted.Expr.unapply` which splits the quoted code into the patterns and a reifiable quote that will be used as witnesses at runtime.
 
 ```scala
 def foo(x: Expr[Int]) given tasty.Reflect: Expr[Int] = x match {
-  case scala.internal.quoted.Matcher.unapply[Tuple3[Bind[Int], Expr[Int], Expr[Int]]](Tuple3(a, x, Bind(`a`), y))('{ @patternBindHole val a: Int = patternHole[Int]; patternHole[Int] + 1 }) =>
+  case scala.internal.quoted.Expr.unapply[Tuple3[Bind[Int], Expr[Int], Expr[Int]]](Tuple3(a, x, Bind(`a`), y))('{ @patternBindHole val a: Int = patternHole[Int]; patternHole[Int] + 1 }) =>
 }
 ```
 
 
 ## Runtime semantics
 
-At runtime to a `quoted.Expr` can be matched to another using `scala.internal.quoted.Matcher.unapply`.
+At runtime to a `quoted.Expr` can be matched to another using `scala.internal.quoted.Expr.unapply`.
 
 ```scala
 def unapply[Tup <: Tuple](scrutineeExpr: Expr[_])(implicit patternExpr: Expr[_], reflection: Reflection): Option[Tup]
@@ -49,7 +49,7 @@ def matched[T](x: T) = Some(Tuple1(x))
 def (x: Matching) && (y: Matching) = if (x == None || y == None) None else Some(x.get ++ y.get)
 def fold[T](m: Mattching*) given Env: Matching = m.fold(matched)(_ && _)
 
-// `a =#= b` stands for `a` matches `b` 
+// `a =#= b` stands for `a` matches `b`
 def (scrutinee: Tree) =#= pattern: Tree) given Env: Matching // described by cases in the tables below
 
 def envWith(equiv: (Symbol, Symbol)*) given Env: Env // Adds to the current environment the fact that s1 from the scrutinee is equivalent to s2 in the pattern