Make handling of tuples more consistent in quasi-quotes

On one hand we know that q"($expr)" is the same as q"$expr". On the
other if we wrap it into a list and splice as q"(..$expr)" we get a
Tuple1 constructor call which is inconsistent.

This pull request fixes this inconsistency by making q"(..$expr)" being
equivalent q"(${expr.head})" for single-element list.

We also add support for matching of expressions as single-element tuples
(similarly to blocks) and remove liftables and unliftables for Tuple1
(which aren't clearly defined any longer due to q"(foo)" == q"foo"
invariant).

2 files changed, 6 insertions, 8 deletions

diff --git a/src/reflect/scala/reflect/api/StandardLiftables.scala b/src/reflect/scala/reflect/api/StandardLiftables.scala
index 5a03996dd9..6c2c8ca618 100644
--- a/src/reflect/scala/reflect/api/StandardLiftables.scala
+++ b/src/reflect/scala/reflect/api/StandardLiftables.scala
@@ -53,9 +53,6 @@ trait StandardLiftables { self: Universe =>
       case right: Right[L, R] => lift(right)
     }
 
-    implicit def liftTuple1[T1](implicit liftT1: Liftable[T1]): Liftable[Tuple1[T1]] = Liftable { t =>
-      SyntacticTuple(liftT1(t._1) :: Nil)
-    }
     implicit def liftTuple2[T1, T2](implicit liftT1: Liftable[T1], liftT2: Liftable[T2]): Liftable[Tuple2[T1, T2]] = Liftable { t =>
       SyntacticTuple(liftT1(t._1) :: liftT2(t._2) :: Nil)
     }
@@ -147,9 +144,6 @@ trait StandardLiftables { self: Universe =>
     implicit def unliftType: Unliftable[Type]                    = Unliftable[Type] { case tt: TypeTree if tt.tpe != null => tt.tpe }
     implicit def unliftConstant: Unliftable[Constant]            = Unliftable[Constant] { case Literal(const) => const }
 
-    implicit def unliftTuple1[T1](implicit UnliftT1: Unliftable[T1]): Unliftable[Tuple1[T1]] = Unliftable {
-      case SyntacticTuple(UnliftT1(v1) :: Nil) => Tuple1(v1)
-    }
     implicit def unliftTuple2[T1, T2](implicit UnliftT1: Unliftable[T1], UnliftT2: Unliftable[T2]): Unliftable[Tuple2[T1, T2]] = Unliftable {
       case SyntacticTuple(UnliftT1(v1) :: UnliftT2(v2) :: Nil) => Tuple2(v1, v2)
     }
diff --git a/src/reflect/scala/reflect/internal/BuildUtils.scala b/src/reflect/scala/reflect/internal/BuildUtils.scala
index c5581601de..738eb316f0 100644
--- a/src/reflect/scala/reflect/internal/BuildUtils.scala
+++ b/src/reflect/scala/reflect/internal/BuildUtils.scala
@@ -350,7 +350,7 @@ trait BuildUtils { self: SymbolTable =>
     object SyntacticTuple extends SyntacticTupleExtractor {
       def apply(args: List[Tree]): Tree = {
         require(args.isEmpty || TupleClass(args.length).exists, s"Tuples with ${args.length} arity aren't supported")
-        gen.mkTuple(args, flattenUnary = false)
+        gen.mkTuple(args)
       }
 
       def unapply(tree: Tree): Option[List[Tree]] = tree match {
@@ -360,6 +360,8 @@ trait BuildUtils { self: SymbolTable =>
           if sym == TupleClass(args.length).companionModule
           && (targs.isEmpty || targs.length == args.length) =>
           Some(args)
+        case _ if tree.isTerm =>
+          Some(tree :: Nil)
         case _ =>
           None
       }
@@ -368,7 +370,7 @@ trait BuildUtils { self: SymbolTable =>
     object SyntacticTupleType extends SyntacticTupleExtractor {
       def apply(args: List[Tree]): Tree = {
         require(args.isEmpty || TupleClass(args.length).exists, s"Tuples with ${args.length} arity aren't supported")
-        gen.mkTupleType(args, flattenUnary = false)
+        gen.mkTupleType(args)
       }
 
       def unapply(tree: Tree): Option[List[Tree]] = tree match {
@@ -377,6 +379,8 @@ trait BuildUtils { self: SymbolTable =>
         case MaybeTypeTreeOriginal(AppliedTypeTree(TupleClassRef(sym), args))
           if sym == TupleClass(args.length) =>
           Some(args)
+        case _ if tree.isType =>
+          Some(tree :: Nil)
         case _ =>
           None
       }