From 43a267325c5f6af1c48597d0ff5ba73f6f08115a Mon Sep 17 00:00:00 2001
From: Nicolas Stucki <nicolas.stucki@gmail.com>
Date: Wed, 17 Nov 2021 09:00:16 +0100
Subject: [PATCH] Add regression test

ConstructExpr and DestructExpr are used to construct and destruct
case classes into and from tuples containing the expressions of their
elements.
---
 .../contruct-desturct/ConstructExpr.scala     | 45 ++++++++++++++++++
 .../contruct-desturct/DestructExpr.scala      | 47 +++++++++++++++++++
 tests/pos-macros/contruct-desturct/Test.scala |  7 +++
 3 files changed, 99 insertions(+)
 create mode 100644 tests/pos-macros/contruct-desturct/ConstructExpr.scala
 create mode 100644 tests/pos-macros/contruct-desturct/DestructExpr.scala
 create mode 100644 tests/pos-macros/contruct-desturct/Test.scala

diff --git a/tests/pos-macros/contruct-desturct/ConstructExpr.scala b/tests/pos-macros/contruct-desturct/ConstructExpr.scala
new file mode 100644
index 000000000000..6a2a6f40f0c5
--- /dev/null
+++ b/tests/pos-macros/contruct-desturct/ConstructExpr.scala
@@ -0,0 +1,45 @@
+package scala.quoted
+package util
+
+trait ConstructExpr[T] {
+
+  type Elems <: Tuple
+
+  def from(x: Elems)(using Quotes): Expr[T]
+  // def from(x: Tuple.Map[Elems, Expr])(using Quotes): Expr[T] // alternative
+
+}
+
+object ConstructExpr {
+
+  def apply[T](using ce: ConstructExpr[T]): ce.type = ce
+
+    /** Default implementation of `ConstructExpr[Tuple1[T]]` */
+  given EmptyTupleConstructExpr[T: Type]: ConstructExpr[EmptyTuple] with {
+    type Elems = EmptyTuple
+    def from(x: Elems)(using Quotes): Expr[EmptyTuple] =
+      '{ EmptyTuple }
+  }
+
+  /** Default implementation of `ConstructExpr[Tuple1[T]]` */
+  given Tuple1ConstructExpr[T: Type]: ConstructExpr[Tuple1[T]] with {
+    type Elems = Tuple1[Expr[T]]
+    def from(x: Elems)(using Quotes): Expr[Tuple1[T]] =
+      '{ Tuple1[T](${x._1}) }
+  }
+
+  /** Default implementation of `ConstructExpr[Tuple2[T1, T2]]` */
+  given Tuple2ConstructExpr[T1: Type, T2: Type]: ConstructExpr[Tuple2[T1, T2]] with {
+    type Elems = (Expr[T1], Expr[T2])
+    def from(x: Elems)(using Quotes): Expr[Tuple2[T1, T2]] =
+      '{ Tuple2[T1, T2](${x._1}, ${x._2}) }
+  }
+
+  /** Default implementation of `ConstructExpr[Tuple3[T1, T2, T3]]` */
+  given Tuple3ConstructExpr[T1: Type, T2: Type, T3: Type]: ConstructExpr[Tuple3[T1, T2, T3]] with {
+    type Elems = (Expr[T1], Expr[T2], Expr[T3])
+    def from(x: Elems)(using Quotes): Expr[Tuple3[T1, T2, T3]] =
+      '{ Tuple3[T1, T2, T3](${x._1}, ${x._2}, ${x._3}) }
+  }
+
+}
diff --git a/tests/pos-macros/contruct-desturct/DestructExpr.scala b/tests/pos-macros/contruct-desturct/DestructExpr.scala
new file mode 100644
index 000000000000..b54be5e1116a
--- /dev/null
+++ b/tests/pos-macros/contruct-desturct/DestructExpr.scala
@@ -0,0 +1,47 @@
+package scala.quoted
+package util
+
+trait DestructExpr[T] {
+
+  type Elems <: Tuple
+
+  def unapply(x: Expr[T])(using Quotes): Option[Elems]
+  // def unapply(x: Expr[T])(using Quotes): Option[Tuple.Map[Elems, Expr]] // alternative
+
+}
+
+/** Default given instances of `DestructExpr` */
+object DestructExpr {
+
+  def unapply[T](x: Expr[T])(using de: DestructExpr[T])(using Quotes): Option[de.Elems] =
+    de.unapply(x)
+
+
+  /** Default implementation of `DestructExpr[Tuple1[...]]`
+   *  - Transform `'{Tuple1(x1)}` into `Some(Tuple1('{x1}))`
+   *  - Otherwise returns `None`
+   */
+  given DestructTuple1[T1](using Type[T1]): DestructExpr[Tuple1[T1]] with {
+    type Elems = Tuple1[Expr[T1]]
+    def unapply(x: Expr[Tuple1[T1]])(using Quotes) = x match {
+      case '{ new Tuple1[T1]($y) } => Some(Tuple1(y))
+      case '{     Tuple1[T1]($y) } => Some(Tuple1(y))
+      case _ => None
+    }
+  }
+
+  /** Default implementation of `DestructExpr[Tuple2[...]]`
+   *  - Transform `'{Tuple2(x1, x2)}` into `Some(Tuple2('{x1}, '{x2}))`
+   *  - Otherwise returns `None`
+   */
+  given DestructTuple2[T1, T2](using Type[T1], Type[T2]): DestructExpr[Tuple2[T1, T2]] with {
+    type Elems = (Expr[T1], Expr[T2])
+    def unapply(x: Expr[Tuple2[T1, T2]])(using Quotes) = x match {
+      case '{ new Tuple2[T1, T2]($y1, $y2) } => Some(Tuple2(y1, y2))
+      case '{     Tuple2[T1, T2]($y1, $y2) } => Some(Tuple2(y1, y2))
+      case '{ ($y1: T1) -> ($y2: T2) } => Some(Tuple2(y1, y2))
+      case _ => None
+    }
+  }
+
+}
diff --git a/tests/pos-macros/contruct-desturct/Test.scala b/tests/pos-macros/contruct-desturct/Test.scala
new file mode 100644
index 000000000000..a4d159ed7d35
--- /dev/null
+++ b/tests/pos-macros/contruct-desturct/Test.scala
@@ -0,0 +1,7 @@
+import scala.quoted.*
+import scala.quoted.util.*
+
+def test(using Quotes) =
+  '{ Tuple2(1, 2) } match
+    case DestructExpr((a, b)) =>
+      ConstructExpr[(Int, Int)].from((a, b))