Fix #6873: Extract quotes and splices typing logic into QuotesAndSplices

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

@@ -0,0 +1,359 @@
+package dotty.tools.dotc.typer
+
+import dotty.tools.dotc.ast._
+import dotty.tools.dotc.ast.Trees._
+import dotty.tools.dotc.core._
+import dotty.tools.dotc.core.Annotations._
+import dotty.tools.dotc.core.Constants._
+import dotty.tools.dotc.core.Contexts._
+import dotty.tools.dotc.core.Decorators._
+import dotty.tools.dotc.core.Flags._
+import dotty.tools.dotc.core.NameKinds.UniqueName
+import dotty.tools.dotc.core.Names._
+import dotty.tools.dotc.core.StagingContext._
+import dotty.tools.dotc.core.StdNames._
+import dotty.tools.dotc.core.Symbols._
+import dotty.tools.dotc.core.Types._
+import dotty.tools.dotc.reporting._
+import dotty.tools.dotc.typer.Implicits._
+import dotty.tools.dotc.typer.Inferencing._
+import dotty.tools.dotc.util.Spans._
+import dotty.tools.dotc.util.Stats.track
+
+import scala.collection.mutable
+
+import scala.annotation.tailrec
+import scala.annotation.internal.sharable
+import scala.annotation.threadUnsafe
+
+/** Type quotes `'{ ... }` and splices `${ ... }` */
+trait QuotesAndSplices { self: Typer =>
+
+  import tpd._
+
+  /** Translate `'{ t }` into `scala.quoted.Expr.apply(t)` and `'[T]` into `scala.quoted.Type.apply[T]`
+   *  while tracking the quotation level in the context.
+   */
+  def typedQuote(tree: untpd.Quote, pt: Type)(implicit ctx: Context): Tree = track("typedQuote") {
+    val qctx = inferImplicitArg(defn.QuoteContextType, tree.span)
+    if (level == 0 && qctx.tpe.isInstanceOf[SearchFailureType])
+      ctx.error(missingArgMsg(qctx, defn.QuoteContextType, ""), ctx.source.atSpan(tree.span))
+
+    tree.quoted match {
+      case untpd.Splice(innerExpr) if tree.isTerm =>
+        ctx.warning("Canceled splice directly inside a quote. '{ ${ XYZ } } is equivalent to XYZ.", tree.sourcePos)
+        typed(innerExpr, pt)
+      case untpd.TypSplice(innerType) if tree.isType =>
+        ctx.warning("Canceled splice directly inside a quote. '[ ${ XYZ } ] is equivalent to XYZ.", tree.sourcePos)
+        typed(innerType, pt)
+      case quoted =>
+        ctx.compilationUnit.needsStaging = true
+        val tree1 =
+          if (quoted.isType) typedTypeApply(untpd.TypeApply(untpd.ref(defn.InternalQuoted_typeQuoteR), quoted :: Nil), pt)(quoteContext)
+          else if (ctx.mode.is(Mode.Pattern) && level == 0) typedQuotePattern(quoted, pt, qctx)
+          else typedApply(untpd.Apply(untpd.ref(defn.InternalQuoted_exprQuoteR), quoted), pt)(quoteContext)
+        tree1.withSpan(tree.span)
+    }
+  }
+
+  /** Translate `${ t: Expr[T] }` into expression `t.splice` while tracking the quotation level in the context */
+  def typedSplice(tree: untpd.Splice, pt: Type)(implicit ctx: Context): Tree = track("typedSplice") {
+    checkSpliceOutsideQuote(tree)
+    tree.expr match {
+      case untpd.Quote(innerExpr) if innerExpr.isTerm =>
+        ctx.warning("Canceled quote directly inside a splice. ${ '{ XYZ } } is equivalent to XYZ.", tree.sourcePos)
+        typed(innerExpr, pt)
+      case expr =>
+        ctx.compilationUnit.needsStaging = true
+        if (ctx.mode.is(Mode.QuotedPattern) && level == 1) {
+          if (isFullyDefined(pt, ForceDegree.all)) {
+            def spliceOwner(ctx: Context): Symbol =
+              if (ctx.mode.is(Mode.QuotedPattern)) spliceOwner(ctx.outer) else ctx.owner
+            val pat = typedPattern(expr, defn.QuotedExprType.appliedTo(pt))(
+              spliceContext.retractMode(Mode.QuotedPattern).withOwner(spliceOwner(ctx)))
+            Splice(pat)
+          } else {
+            ctx.error(i"Type must be fully defined.\nConsider annotating the splice using a type ascription:\n  ($tree: XYZ).", expr.sourcePos)
+            tree.withType(UnspecifiedErrorType)
+          }
+        }
+        else {
+          if (StagingContext.level == 0) {
+            // Mark the first inline method from the context as a macro
+            def markAsMacro(c: Context): Unit =
+              if (c.owner eq c.outer.owner) markAsMacro(c.outer)
+              else if (c.owner.isInlineMethod) c.owner.setFlag(Macro)
+              else if (!c.outer.owner.is(Package)) markAsMacro(c.outer)
+            markAsMacro(ctx)
+          }
+          typedApply(untpd.Apply(untpd.ref(defn.InternalQuoted_exprSpliceR), tree.expr), pt)(spliceContext).withSpan(tree.span)
+        }
+    }
+  }
+
+  /** Translate ${ t: Type[T] }` into type `t.splice` while tracking the quotation level in the context */
+  def typedTypSplice(tree: untpd.TypSplice, pt: Type)(implicit ctx: Context): Tree = track("typedTypSplice") {
+    ctx.compilationUnit.needsStaging = true
+    checkSpliceOutsideQuote(tree)
+    tree.expr match {
+      case untpd.Quote(innerType) if innerType.isType =>
+        ctx.warning("Canceled quote directly inside a splice. ${ '[ XYZ ] } is equivalent to XYZ.", tree.sourcePos)
+        typed(innerType, pt)
+      case expr =>
+        if (ctx.mode.is(Mode.QuotedPattern) && level == 1) {
+          if (isFullyDefined(pt, ForceDegree.all)) {
+            ctx.error(i"Spliced type pattern must not be fully defined. Consider using $pt directly", tree.expr.sourcePos)
+            tree.withType(UnspecifiedErrorType)
+          } else {
+            def spliceOwner(ctx: Context): Symbol =
+              if (ctx.mode.is(Mode.QuotedPattern)) spliceOwner(ctx.outer) else ctx.owner
+            val name = expr match {
+              case Ident(name) => ("$" + name).toTypeName
+              case Typed(Ident(name), _) => ("$" + name).toTypeName
+              case Bind(name, _) => ("$" + name).toTypeName
+              case _ => NameKinds.UniqueName.fresh("$".toTypeName)
+            }
+            val typeSym = ctx.newSymbol(spliceOwner(ctx), name, EmptyFlags, TypeBounds.empty, NoSymbol, expr.span)
+            typeSym.addAnnotation(Annotation(New(ref(defn.InternalQuoted_patternBindHoleAnnot.typeRef)).withSpan(expr.span)))
+            val pat = typedPattern(expr, defn.QuotedTypeType.appliedTo(typeSym.typeRef))(
+                spliceContext.retractMode(Mode.QuotedPattern).withOwner(spliceOwner(ctx)))
+            pat.select(tpnme.splice)
+          }
+        } else {
+          typedSelect(untpd.Select(tree.expr, tpnme.splice), pt)(spliceContext).withSpan(tree.span)
+        }
+    }
+  }
+
+  private def checkSpliceOutsideQuote(tree: untpd.Tree)(implicit ctx: Context): Unit = {
+    if (level == 0 && !ctx.owner.ownersIterator.exists(_.is(Inline)))
+      ctx.error("Splice ${...} outside quotes '{...} or inline method", tree.sourcePos)
+    else if (level < 0)
+      ctx.error(
+        s"""Splice $${...} at level $level.
+          |
+          |Inline method may contain a splice at level 0 but the contents of this splice cannot have a splice.
+          |""".stripMargin, tree.sourcePos
+      )
+  }
+
+  /** Split a typed quoted pattern is split into its type bindings, pattern expression and inner patterns.
+   *  Type definitions with `@patternBindHole` will be inserted in the pattern expression for each type binding.
+   *
+   *  A quote pattern
+   *  ```
+   *  case '{ type ${given t: Type[$t @ _]}; ${ls: Expr[List[$t]]} } => ...
+   *  ```
+   *  will return
+   *  ```
+   *  (
+   *    Map(<$t>: Symbol -> <$t @ _>: Bind),
+   *    <'{
+   *       @scala.internal.Quoted.patternBindHole type $t
+   *       scala.internal.Quoted.patternHole[List[$t]]
+   *    }>: Tree,
+   *    List(<ls: Expr[List[$t]]>: Tree)
+   *  )
+   *  ```
+   */
+  private def splitQuotePattern(quoted: Tree)(implicit ctx: Context): (Map[Symbol, Bind], Tree, List[Tree]) = {
+    val ctx0 = ctx
+
+    val typeBindings: collection.mutable.Map[Symbol, Bind] = collection.mutable.Map.empty
+    def getBinding(sym: Symbol): Bind =
+      typeBindings.getOrElseUpdate(sym, {
+        val bindingBounds = sym.info
+        val bsym = ctx.newPatternBoundSymbol(sym.name.toTypeName, bindingBounds, quoted.span)
+        Bind(bsym, untpd.Ident(nme.WILDCARD).withType(bindingBounds)).withSpan(quoted.span)
+      })
+
+    object splitter extends tpd.TreeMap {
+      val patBuf = new mutable.ListBuffer[Tree]
+      val freshTypePatBuf = new mutable.ListBuffer[Tree]
+      val freshTypeBindingsBuff = new mutable.ListBuffer[Tree]
+      val typePatBuf = new mutable.ListBuffer[Tree]
+      override def transform(tree: Tree)(implicit ctx: Context) = tree match {
+        case Typed(Splice(pat), tpt) if !tpt.tpe.derivesFrom(defn.RepeatedParamClass) =>
+          val tpt1 = transform(tpt) // Transform type bindings
+          val exprTpt = AppliedTypeTree(TypeTree(defn.QuotedExprType), tpt1 :: Nil)
+          transform(Splice(Typed(pat, exprTpt)))
+        case Splice(pat) =>
+          try ref(defn.InternalQuoted_patternHoleR).appliedToType(tree.tpe).withSpan(tree.span)
+          finally {
+            val patType = pat.tpe.widen
+            val patType1 = patType.underlyingIfRepeated(isJava = false)
+            val pat1 = if (patType eq patType1) pat else pat.withType(patType1)
+            patBuf += pat1
+          }
+        case Select(pat, _) if tree.symbol == defn.QuotedType_splice =>
+          val sym = tree.tpe.dealias.typeSymbol.asType
+          val tdef = TypeDef(sym).withSpan(sym.span)
+          freshTypeBindingsBuff += transformTypeBindingTypeDef(tdef, freshTypePatBuf)
+          TypeTree(tree.tpe.dealias).withSpan(tree.span)
+
+        case ddef: ValOrDefDef =>
+          if (ddef.symbol.hasAnnotation(defn.InternalQuoted_patternBindHoleAnnot)) {
+            val bindingType = ddef.symbol.info match {
+              case t: ExprType => t.resType
+              case t: MethodType => t.toFunctionType()
+              case t: PolyType =>
+                HKTypeLambda(t.paramNames)(
+                    x => t.paramInfos.mapConserve(_.subst(t, x).asInstanceOf[TypeBounds]),
+                    x => t.resType.subst(t, x).toFunctionType())
+              case t => t
+            }
+            val bindingExprTpe = AppliedType(defn.QuotedMatchingBindingType, bindingType :: Nil)
+            assert(ddef.name.startsWith("$"))
+            val bindName = ddef.name.toString.stripPrefix("$").toTermName
+            val sym = ctx0.newPatternBoundSymbol(bindName, bindingExprTpe, ddef.span)
+            patBuf += Bind(sym, untpd.Ident(nme.WILDCARD).withType(bindingExprTpe)).withSpan(ddef.span)
+          }
+          super.transform(tree)
+        case tdef: TypeDef if tdef.symbol.hasAnnotation(defn.InternalQuoted_patternBindHoleAnnot) =>
+          transformTypeBindingTypeDef(tdef, typePatBuf)
+        case _ =>
+          super.transform(tree)
+      }
+
+      def transformTypeBindingTypeDef(tdef: TypeDef, buff: mutable.Builder[Tree, List[Tree]]): Tree = {
+        val bindingType = getBinding(tdef.symbol).symbol.typeRef
+        val bindingTypeTpe = AppliedType(defn.QuotedTypeType, bindingType :: Nil)
+        assert(tdef.name.startsWith("$"))
+        val bindName = tdef.name.toString.stripPrefix("$").toTermName
+        val sym = ctx0.newPatternBoundSymbol(bindName, bindingTypeTpe, tdef.span, flags = ImplicitTerm)
+        buff += Bind(sym, untpd.Ident(nme.WILDCARD).withType(bindingTypeTpe)).withSpan(tdef.span)
+        super.transform(tdef)
+      }
+    }
+    val shape0 = splitter.transform(quoted)
+    val patterns = (splitter.freshTypePatBuf.iterator ++ splitter.typePatBuf.iterator ++ splitter.patBuf.iterator).toList
+    val freshTypeBindings = splitter.freshTypeBindingsBuff.result()
+
+    val shape1 = seq(
+      freshTypeBindings,
+      shape0
+    )
+    val shape2 = {
+      if (freshTypeBindings.isEmpty) shape1
+      else {
+        val isFreshTypeBindings = freshTypeBindings.map(_.symbol).toSet
+        val typeMap = new TypeMap() {
+          def apply(tp: Type): Type = tp match {
+            case tp: TypeRef if tp.typeSymbol == defn.QuotedType_splice =>
+              val tp1 = tp.dealias
+              if (isFreshTypeBindings(tp1.typeSymbol)) tp1
+              else tp
+            case tp => mapOver(tp)
+          }
+        }
+        new TreeTypeMap(typeMap = typeMap).transform(shape1)
+      }
+    }
+
+    (typeBindings.toMap, shape2, patterns)
+  }
+
+   /** Type a quote pattern `case '{ <quoted> } =>` qiven the a current prototype. Typing the pattern
+   *  will also transform it into a call to `scala.internal.quoted.Matcher.unapply`.
+   *
+   *  Code directly inside the quote is typed as an expression using Mode.QuotedPattern. Splices
+   *  within the quotes become patterns again and typed acordingly.
+   *
+   *  ```
+   *  case '{ ($ls: List[$t]) } =>
+   *    // `t` is of type `Type[T$1]` for some unknown T$1
+   *    // `t` is implicitly available
+   *    // `l` is of type `Expr[List[T$1]]`
+   *    '{ val h: $t = $ls.head  }
+   *  ```
+   *
+   *  For each type splice we will create a new type binding in the pattern match ($t @ _ in this case)
+   *  and a corresponding type in the quoted pattern as a hole (@patternBindHole type $t in this case).
+   *  All these generated types are inserted at the start of the quoted code.
+   *
+   *  After typing the tree will resemble
+   *
+   *  ```
+   *  case '{ type ${given t: Type[$t @ _]}; ${ls: Expr[List[$t]]} } => ...
+   *  ```
+   *
+   *  Then the pattern is _split_ into the expression containd in the pattern replacing the splices by holes,
+   *  and the patterns in the splices. All these are recombined into a call to `Matcher.unapply`.
+   *
+   *  ```
+   *  case scala.internal.quoted.Matcher.unapply[
+   *          Tuple1[$t @ _], // Type binging definition
+   *          Tuple2[Type[$t], Expr[List[$t]]] // Typing the result of the pattern match
+   *        ](
+   *          Tuple2.unapply
+   *            [Type[$t], Expr[List[$t]]] //Propagated from the tuple above
+   *            (implict t @ _, ls @ _: Expr[List[$t]]) // from the spliced patterns
+   *        )(
+   *         '{ // Runtime quote Matcher.unapply uses to mach against. Expression directly inside the quoted pattern without the splices
+   *            @scala.internal.Quoted.patternBindHole type $t
+   *            scala.internal.Quoted.patternHole[List[$t]]
+   *          },
+   *          true, // If there is at least one type splice. Used to instantiate the context with or without GADT constraints
+   *          x$2 // tasty.Reflection instance
+   *        ) => ...
+   *  ```
+   */
+  private def typedQuotePattern(quoted: untpd.Tree, pt: Type, qctx: tpd.Tree)(implicit ctx: Context): Tree = {
+    val exprPt = pt.baseType(defn.QuotedExprClass)
+    val quotedPt = exprPt.argInfos.headOption match {
+      case Some(argPt: ValueType) => argPt // excludes TypeBounds
+      case _ => defn.AnyType
+    }
+    val quoted0 = desugar.quotedPattern(quoted, untpd.TypedSplice(TypeTree(quotedPt)))
+    val quoted1 = typedExpr(quoted0, WildcardType)(quoteContext.addMode(Mode.QuotedPattern))
+
+    val (typeBindings, shape, splices) = splitQuotePattern(quoted1)
+
+    class ReplaceBindings extends TypeMap() {
+      override def apply(tp: Type): Type = tp match {
+        case tp: TypeRef =>
+          val tp1 = if (tp.typeSymbol == defn.QuotedType_splice) tp.dealias else tp
+          typeBindings.get(tp1.typeSymbol).fold(tp)(_.symbol.typeRef)
+        case tp => mapOver(tp)
+      }
+    }
+    val replaceBindings = new ReplaceBindings
+    val patType = defn.tupleType(splices.tpes.map(tpe => replaceBindings(tpe.widen)))
+
+    val typeBindingsTuple = tpd.tupleTypeTree(typeBindings.values.toList)
+
+    val replaceBindingsInTree = new TreeMap {
+      private[this] var bindMap = Map.empty[Symbol, Symbol]
+      override def transform(tree: tpd.Tree)(implicit ctx: Context): tpd.Tree = {
+        tree match {
+          case tree: Bind =>
+            val sym = tree.symbol
+            val newInfo = replaceBindings(sym.info)
+            val newSym = ctx.newSymbol(sym.owner, sym.name, sym.flags, newInfo, sym.privateWithin, sym.coord)
+            bindMap += sym -> newSym
+            Bind(newSym, transform(tree.body)).withSpan(sym.span)
+          case _ =>
+            super.transform(tree).withType(replaceBindingsInType(tree.tpe))
+        }
+      }
+      private[this] val replaceBindingsInType = new ReplaceBindings {
+        override def apply(tp: Type): Type = tp match {
+          case tp: TermRef => bindMap.get(tp.termSymbol).fold[Type](tp)(_.typeRef)
+          case tp => super.apply(tp)
+        }
+      }
+    }
+
+    val splicePat = typed(untpd.Tuple(splices.map(x => untpd.TypedSplice(replaceBindingsInTree.transform(x)))).withSpan(quoted.span), patType)
+
+    UnApply(
+      fun = ref(defn.InternalQuotedMatcher_unapplyR).appliedToTypeTrees(typeBindingsTuple :: TypeTree(patType) :: Nil),
+      implicits =
+        ref(defn.InternalQuoted_exprQuoteR).appliedToType(shape.tpe).appliedTo(shape) ::
+          Literal(Constant(typeBindings.nonEmpty)) ::
+          qctx :: Nil,
+      patterns = splicePat :: Nil,
+      proto = defn.QuotedExprType.appliedTo(replaceBindings(quoted1.tpe) & quotedPt))
+  }
+
+}