SI-6844 restrict splicing in parameter position

Previously were a bit too permissive on how splicing in function
parameter position worked. This made confusing things like
possible:

   val x = TermName(“x”)
   q”def foo($x)”

Now you can either splice trees in that position (ValDefs) or
you have to provide type if you splice a name.

3 files changed, 23 insertions, 3 deletions

diff --git a/src/compiler/scala/tools/reflect/quasiquotes/Parsers.scala b/src/compiler/scala/tools/reflect/quasiquotes/Parsers.scala
index 6e6b617e5c..7604f779d6 100644
--- a/src/compiler/scala/tools/reflect/quasiquotes/Parsers.scala
+++ b/src/compiler/scala/tools/reflect/quasiquotes/Parsers.scala
@@ -80,8 +80,20 @@ trait Parsers { self: Quasiquotes =>
       }
       import treeBuilder.{global => _, unit => _, _}
 
+      def quasiquoteParam(name: Name, flags: FlagSet = NoFlags) =
+        ValDef(Modifiers(flags), name.toTermName, Ident(tpnme.QUASIQUOTE_PARAM), EmptyTree)
+
       // q"def foo($x)"
-      override def allowTypelessParams = true
+      override def param(owner: Name, implicitmod: Int, caseParam: Boolean): ValDef =
+        if (isHole && lookingAhead { in.token == COMMA || in.token == RPAREN }) {
+          quasiquoteParam(ident(), implicitmod)
+        } else super.param(owner, implicitmod, caseParam)
+
+      // q"($x) => ..." && q"class X { selfie => }
+      override def convertToParam(tree: Tree): ValDef = tree match {
+        case Ident(name) if isHole(name) => quasiquoteParam(name)
+        case _ => super.convertToParam(tree)
+      }
 
       // q"foo match { case $x }"
       override def caseClause(): CaseDef =
@@ -193,4 +205,4 @@ trait Parsers { self: Quasiquotes =>
   }
 
   object FreshName extends FreshNameExtractor(nme.QUASIQUOTE_PREFIX)
-}
\ No newline at end of file
+}
diff --git a/src/compiler/scala/tools/reflect/quasiquotes/Placeholders.scala b/src/compiler/scala/tools/reflect/quasiquotes/Placeholders.scala
index bdb44ad9a2..5669ec731f 100644
--- a/src/compiler/scala/tools/reflect/quasiquotes/Placeholders.scala
+++ b/src/compiler/scala/tools/reflect/quasiquotes/Placeholders.scala
@@ -95,7 +95,6 @@ trait Placeholders { self: Quasiquotes =>
       case Ident(name) => name
       case Bind(name, Ident(nme.WILDCARD)) => name
       case TypeDef(_, name, List(), TypeBoundsTree(EmptyTree, EmptyTree)) => name
-      case ValDef(_, name, TypeTree(), EmptyTree) => name
     }
   }
 
@@ -111,6 +110,12 @@ trait Placeholders { self: Quasiquotes =>
     }
   }
 
+  object ParamPlaceholder extends HolePlaceholder {
+    def matching = {
+      case ValDef(_, name, Ident(tpnme.QUASIQUOTE_PARAM), EmptyTree) => name
+    }
+  }
+
   object TuplePlaceholder {
     def unapply(tree: Tree): Option[List[Tree]] = tree match {
       case Apply(Ident(nme.QUASIQUOTE_TUPLE), args) => Some(args)
diff --git a/src/compiler/scala/tools/reflect/quasiquotes/Reifiers.scala b/src/compiler/scala/tools/reflect/quasiquotes/Reifiers.scala
index 87ab52414c..58baad01a1 100644
--- a/src/compiler/scala/tools/reflect/quasiquotes/Reifiers.scala
+++ b/src/compiler/scala/tools/reflect/quasiquotes/Reifiers.scala
@@ -137,6 +137,7 @@ trait Reifiers { self: Quasiquotes =>
       case RefineStatPlaceholder(hole) => reifyRefineStat(hole)
       case EarlyDefPlaceholder(hole) => reifyEarlyDef(hole)
       case PackageStatPlaceholder(hole) => reifyPackageStat(hole)
+      case ParamPlaceholder(hole) => hole.tree
       // for enumerators are checked not during splicing but during
       // desugaring of the for loop in SyntacticFor & SyntacticForYield
       case ForEnumPlaceholder(hole) => hole.tree
@@ -311,6 +312,8 @@ trait Reifiers { self: Quasiquotes =>
       case EarlyDefPlaceholder(h @ Hole(_, DotDot)) => reifyEarlyDef(h)
       case PackageStatPlaceholder(h @ Hole(_, DotDot)) => reifyPackageStat(h)
       case ForEnumPlaceholder(Hole(tree, DotDot)) => tree
+      case ParamPlaceholder(Hole(tree, DotDot)) => tree
+      case List(ParamPlaceholder(Hole(tree, DotDotDot))) => tree
       case List(Placeholder(Hole(tree, DotDotDot))) => tree
     } {
       reify(_)