Represent untyped operators as Ident instead of Name

This has two advantages:
- We can distinguish BackquotedIdent from Ident, allowing the user to
  use a defined "type `&`", see testcase.
- We get better positions for the operators. This is useful in IDEs, for
  example to get the type at point.

9 files changed, 44 insertions, 43 deletions

diff --git a/compiler/src/dotty/tools/dotc/ast/Desugar.scala b/compiler/src/dotty/tools/dotc/ast/Desugar.scala
index 2e471e046..3835355e3 100644
--- a/compiler/src/dotty/tools/dotc/ast/Desugar.scala
+++ b/compiler/src/dotty/tools/dotc/ast/Desugar.scala
@@ -353,7 +353,7 @@ object desugar {
           for (i <- 0 until arity if nme.selectorName(i) `ne` caseParams(i).name)
           yield syntheticProperty(nme.selectorName(i), Select(This(EmptyTypeIdent), caseParams(i).name))
         def isRepeated(tree: Tree): Boolean = tree match {
-          case PostfixOp(_, nme.raw.STAR) => true
+          case PostfixOp(_, Ident(nme.raw.STAR)) => true
           case ByNameTypeTree(tree1) => isRepeated(tree1)
           case _ => false
         }
@@ -739,23 +739,23 @@ object desugar {
 
     /** Translate infix operation expression  left op right
      */
-    def makeBinop(left: Tree, op: Name, right: Tree): Tree = {
+    def makeBinop(left: Tree, op: Ident, right: Tree): Tree = {
       def assignToNamedArg(arg: Tree) = arg match {
         case Assign(Ident(name), rhs) => cpy.NamedArg(arg)(name, rhs)
         case _ => arg
       }
-      if (isLeftAssoc(op)) {
+      if (isLeftAssoc(op.name)) {
         val args: List[Tree] = right match {
           case Parens(arg) => assignToNamedArg(arg) :: Nil
           case Tuple(args) => args mapConserve assignToNamedArg
           case _ => right :: Nil
         }
-        Apply(Select(left, op), args)
+        Apply(Select(left, op.name), args)
       } else {
         val x = ctx.freshName().toTermName
         new InfixOpBlock(
           ValDef(x, TypeTree(), left).withMods(synthetic),
-          Apply(Select(right, op), Ident(x)))
+          Apply(Select(right, op.name), Ident(x)))
       }
     }
 
@@ -956,25 +956,25 @@ object desugar {
         Apply(Select(Apply(Ident(nme.StringContext), strs), id), elems)
       case InfixOp(l, op, r) =>
         if (ctx.mode is Mode.Type)
-          if (op == tpnme.raw.AMP) AndTypeTree(l, r)     // l & r
-          else if (op == tpnme.raw.BAR) OrTypeTree(l, r) // l | r
-          else AppliedTypeTree(Ident(op), l :: r :: Nil) // op[l, r]
+          if (!op.isBackquoted && op.name == tpnme.raw.AMP) AndTypeTree(l, r)     // l & r
+          else if (!op.isBackquoted && op.name == tpnme.raw.BAR) OrTypeTree(l, r) // l | r
+          else AppliedTypeTree(op, l :: r :: Nil) // op[l, r]
         else if (ctx.mode is Mode.Pattern)
-          Apply(Ident(op), l :: r :: Nil) // op(l, r)
+          Apply(op, l :: r :: Nil) // op(l, r)
         else // l.op(r), or val x = r; l.op(x), plus handle named args specially
           makeBinop(l, op, r)
       case PostfixOp(t, op) =>
-        if ((ctx.mode is Mode.Type) && op == nme.raw.STAR) {
+        if ((ctx.mode is Mode.Type) && !op.isBackquoted && op.name == nme.raw.STAR) {
           val seqType = if (ctx.compilationUnit.isJava) defn.ArrayType else defn.SeqType
           Annotated(
             AppliedTypeTree(ref(seqType), t),
             New(ref(defn.RepeatedAnnotType), Nil :: Nil))
         } else {
           assert(ctx.mode.isExpr || ctx.reporter.hasErrors, ctx.mode)
-          Select(t, op)
+          Select(t, op.name)
         }
       case PrefixOp(op, t) =>
-        Select(t, nme.UNARY_PREFIX ++ op)
+        Select(t, nme.UNARY_PREFIX ++ op.name)
       case Parens(t) =>
         t
       case Tuple(ts) =>
diff --git a/compiler/src/dotty/tools/dotc/ast/Trees.scala b/compiler/src/dotty/tools/dotc/ast/Trees.scala
index 6dc2c9a13..7ab8de39f 100644
--- a/compiler/src/dotty/tools/dotc/ast/Trees.scala
+++ b/compiler/src/dotty/tools/dotc/ast/Trees.scala
@@ -334,10 +334,15 @@ object Trees {
     extends RefTree[T] {
     type ThisTree[-T >: Untyped] = Ident[T]
     def qualifier: Tree[T] = genericEmptyTree
+
+    /** Is this a `BackquotedIdent` ? */
+    def isBackquoted: Boolean = false
   }
 
   class BackquotedIdent[-T >: Untyped] private[ast] (name: Name)
     extends Ident[T](name) {
+    override def isBackquoted: Boolean = true
+
     override def toString = s"BackquotedIdent($name)"
   }
 
diff --git a/compiler/src/dotty/tools/dotc/ast/untpd.scala b/compiler/src/dotty/tools/dotc/ast/untpd.scala
index 37dc32c0e..99bc3240f 100644
--- a/compiler/src/dotty/tools/dotc/ast/untpd.scala
+++ b/compiler/src/dotty/tools/dotc/ast/untpd.scala
@@ -15,9 +15,9 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
   // ----- Tree cases that exist in untyped form only ------------------
 
   trait OpTree extends Tree {
-    def op: Name
-    override def isTerm = op.isTermName
-    override def isType = op.isTypeName
+    def op: Ident
+    override def isTerm = op.name.isTermName
+    override def isType = op.name.isTypeName
   }
 
   /** A typed subtree of an untyped tree needs to be wrapped in a TypedSlice
@@ -66,9 +66,9 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
    */
   class WildcardFunction(placeholderParams: List[ValDef], body: Tree) extends Function(placeholderParams, body)
 
-  case class InfixOp(left: Tree, op: Name, right: Tree) extends OpTree
-  case class PostfixOp(od: Tree, op: Name) extends OpTree
-  case class PrefixOp(op: Name, od: Tree) extends OpTree
+  case class InfixOp(left: Tree, op: Ident, right: Tree) extends OpTree
+  case class PostfixOp(od: Tree, op: Ident) extends OpTree
+  case class PrefixOp(op: Ident, od: Tree) extends OpTree
   case class Parens(t: Tree) extends ProxyTree {
     def forwardTo = t
   }
@@ -357,7 +357,7 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
    *  parameter, the reference will be a repeated argument.
    */
   def refOfDef(tree: MemberDef)(implicit ctx: Context) = tree match {
-    case ValDef(_, PostfixOp(_, nme.raw.STAR), _) => repeated(Ident(tree.name))
+    case ValDef(_, PostfixOp(_, Ident(nme.raw.STAR)), _) => repeated(Ident(tree.name))
     case _ => Ident(tree.name)
   }
 
@@ -409,15 +409,15 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
       case tree: Function if (args eq tree.args) && (body eq tree.body) => tree
       case _ => untpd.Function(args, body).withPos(tree.pos)
     }
-    def InfixOp(tree: Tree)(left: Tree, op: Name, right: Tree) = tree match {
+    def InfixOp(tree: Tree)(left: Tree, op: Ident, right: Tree) = tree match {
       case tree: InfixOp if (left eq tree.left) && (op eq tree.op) && (right eq tree.right) => tree
       case _ => untpd.InfixOp(left, op, right).withPos(tree.pos)
     }
-    def PostfixOp(tree: Tree)(od: Tree, op: Name) = tree match {
+    def PostfixOp(tree: Tree)(od: Tree, op: Ident) = tree match {
       case tree: PostfixOp if (od eq tree.od) && (op eq tree.op) => tree
       case _ => untpd.PostfixOp(od, op).withPos(tree.pos)
     }
-    def PrefixOp(tree: Tree)(op: Name, od: Tree) = tree match {
+    def PrefixOp(tree: Tree)(op: Ident, od: Tree) = tree match {
       case tree: PrefixOp if (op eq tree.op) && (od eq tree.od) => tree
       case _ => untpd.PrefixOp(op, od).withPos(tree.pos)
     }
diff --git a/compiler/src/dotty/tools/dotc/parsing/JavaParsers.scala b/compiler/src/dotty/tools/dotc/parsing/JavaParsers.scala
index 92ab10db9..d35594823 100644
--- a/compiler/src/dotty/tools/dotc/parsing/JavaParsers.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/JavaParsers.scala
@@ -448,7 +448,7 @@ object JavaParsers {
       if (in.token == DOTDOTDOT) {
         in.nextToken()
         t = atPos(t.pos.start) {
-          PostfixOp(t, nme.raw.STAR)
+          PostfixOp(t, Ident(nme.raw.STAR))
         }
       }
       atPos(start, in.offset) {
diff --git a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
index f62093db0..5ed4fbdd7 100644
--- a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
@@ -30,7 +30,7 @@ object Parsers {
   import reporting.diagnostic.Message
   import reporting.diagnostic.messages._
 
-  case class OpInfo(operand: Tree, operator: Name, offset: Offset)
+  case class OpInfo(operand: Tree, operator: Ident, offset: Offset)
 
   class ParensCounters {
     private var parCounts = new Array[Int](lastParen - firstParen)
@@ -414,18 +414,17 @@ object Parsers {
           "left- and right-associative operators with same precedence may not be mixed", offset)
 
     def reduceStack(base: List[OpInfo], top: Tree, prec: Int, leftAssoc: Boolean): Tree = {
-      if (opStack != base && precedence(opStack.head.operator) == prec)
-        checkAssoc(opStack.head.offset, opStack.head.operator, leftAssoc)
+      if (opStack != base && precedence(opStack.head.operator.name) == prec)
+        checkAssoc(opStack.head.offset, opStack.head.operator.name, leftAssoc)
       def recur(top: Tree): Tree = {
         if (opStack == base) top
         else {
           val opInfo = opStack.head
-          val opPrec = precedence(opInfo.operator)
+          val opPrec = precedence(opInfo.operator.name)
           if (prec < opPrec || leftAssoc && prec == opPrec) {
             opStack = opStack.tail
             recur {
-              val opPos = Position(opInfo.offset, opInfo.offset + opInfo.operator.length, opInfo.offset)
-              atPos(opPos union opInfo.operand.pos union top.pos) {
+              atPos(opInfo.operator.pos union opInfo.operand.pos union top.pos) {
                 InfixOp(opInfo.operand, opInfo.operator, top)
               }
             }
@@ -449,10 +448,9 @@ object Parsers {
       val base = opStack
       var top = first
       while (isIdent && in.name != notAnOperator) {
-        val op = if (isType) in.name.toTypeName else in.name
-        top = reduceStack(base, top, precedence(op), isLeftAssoc(op))
+        val op = if (isType) typeIdent() else termIdent()
+        top = reduceStack(base, top, precedence(op.name), isLeftAssoc(op.name))
         opStack = OpInfo(top, op, in.offset) :: opStack
-        ident()
         newLineOptWhenFollowing(canStartOperand)
         if (maybePostfix && !canStartOperand(in.token)) {
           val topInfo = opStack.head
@@ -870,7 +868,7 @@ object Parsers {
       val t = toplevelTyp()
       if (isIdent(nme.raw.STAR)) {
         in.nextToken()
-        atPos(startOffset(t)) { PostfixOp(t, nme.raw.STAR) }
+        atPos(startOffset(t)) { PostfixOp(t, Ident(nme.raw.STAR)) }
       } else t
     }
 
@@ -1189,11 +1187,11 @@ object Parsers {
     val prefixExpr = () =>
       if (isIdent && nme.raw.isUnary(in.name)) {
         val start = in.offset
-        val name = ident()
-        if (name == nme.raw.MINUS && isNumericLit)
+        val op = termIdent()
+        if (op.name == nme.raw.MINUS && isNumericLit)
           simpleExprRest(literal(start), canApply = true)
         else
-          atPos(start) { PrefixOp(name, simpleExpr()) }
+          atPos(start) { PrefixOp(op, simpleExpr()) }
       }
       else simpleExpr()
 
@@ -1260,7 +1258,7 @@ object Parsers {
           val app = atPos(startOffset(t), in.offset) { Apply(t, argumentExprs()) }
           simpleExprRest(app, canApply = true)
         case USCORE =>
-          atPos(startOffset(t), in.skipToken()) { PostfixOp(t, nme.WILDCARD) }
+          atPos(startOffset(t), in.skipToken()) { PostfixOp(t, Ident(nme.WILDCARD)) }
         case _ =>
           t
       }
diff --git a/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala b/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala
index 7f124563d..5b75df6b2 100644
--- a/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala
+++ b/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala
@@ -516,7 +516,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
           argsText ~ " => " ~ toText(body)
         }
       case InfixOp(l, op, r) =>
-        val opPrec = parsing.precedence(op)
+        val opPrec = parsing.precedence(op.name)
         changePrec(opPrec) { toText(l) ~ " " ~ toText(op) ~ " " ~ toText(r) }
       case PostfixOp(l, op) =>
         changePrec(InfixPrec) { toText(l) ~ " " ~ toText(op) }
diff --git a/compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala b/compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala
index 181dfccd9..7c49e68dd 100644
--- a/compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala
+++ b/compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala
@@ -1077,8 +1077,6 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {
 
   trait MatchTranslator extends TreeMakers with ScalacPatternExpanders {
 
-    def isBackquoted(x: Ident) = x.isInstanceOf[BackquotedIdent]
-
     def isVarPattern(pat: Tree): Boolean = pat match {
       case x: BackquotedIdent => false
       case x: Ident => x.name.isVariableName
diff --git a/compiler/src/dotty/tools/dotc/typer/EtaExpansion.scala b/compiler/src/dotty/tools/dotc/typer/EtaExpansion.scala
index c390ae808..e7e7ece78 100644
--- a/compiler/src/dotty/tools/dotc/typer/EtaExpansion.scala
+++ b/compiler/src/dotty/tools/dotc/typer/EtaExpansion.scala
@@ -144,7 +144,7 @@ object EtaExpansion {
       ids = ids.init :+ repeated(ids.last)
     var body: Tree = Apply(lifted, ids)
     mt.resultType match {
-      case rt: MethodType if !rt.isImplicit => body = PostfixOp(body, nme.WILDCARD)
+      case rt: MethodType if !rt.isImplicit => body = PostfixOp(body, Ident(nme.WILDCARD))
       case _ =>
     }
     val fn = untpd.Function(params, body)
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 59df98a93..5ea36986f 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -1440,7 +1440,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
 
 
   def typedAsFunction(tree: untpd.PostfixOp, pt: Type)(implicit ctx: Context): Tree = {
-    val untpd.PostfixOp(qual, nme.WILDCARD) = tree
+    val untpd.PostfixOp(qual, Ident(nme.WILDCARD)) = tree
     val pt1 = if (defn.isFunctionType(pt)) pt else AnyFunctionProto
     var res = typed(qual, pt1)
     if (pt1.eq(AnyFunctionProto) && !defn.isFunctionClass(res.tpe.classSymbol)) {
@@ -1541,7 +1541,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
           case tree: untpd.Annotated => typedAnnotated(tree, pt)
           case tree: untpd.TypedSplice => typedTypedSplice(tree)
           case tree:  untpd.UnApply => typedUnApply(tree, pt)
-          case tree @ untpd.PostfixOp(qual, nme.WILDCARD) => typedAsFunction(tree, pt)
+          case tree @ untpd.PostfixOp(qual, Ident(nme.WILDCARD)) => typedAsFunction(tree, pt)
           case untpd.EmptyTree => tpd.EmptyTree
           case _ => typedUnadapted(desugar(tree), pt)
         }