From 789471d9c38994b43d3efdf858fcfa24296be82f Mon Sep 17 00:00:00 2001
From: Liu Fengyun <liu@fengy.me>
Date: Fri, 7 Jun 2019 14:56:03 +0200
Subject: [PATCH] Add Dotty-style tree constructor DSL to reflect

---
 library/src/scala/tasty/reflect/TreeOps.scala | 37 +++++++++++++++
 tests/run-macros/reflect-dsl/assert_1.scala   | 46 +++++++++++++++++++
 tests/run-macros/reflect-dsl/test_2.scala     | 29 ++++++++++++
 3 files changed, 112 insertions(+)
 create mode 100644 tests/run-macros/reflect-dsl/assert_1.scala
 create mode 100644 tests/run-macros/reflect-dsl/test_2.scala

diff --git a/library/src/scala/tasty/reflect/TreeOps.scala b/library/src/scala/tasty/reflect/TreeOps.scala
index e2c28c98d070..1d3dd5863d60 100644
--- a/library/src/scala/tasty/reflect/TreeOps.scala
+++ b/library/src/scala/tasty/reflect/TreeOps.scala
@@ -179,6 +179,43 @@ trait TreeOps extends Core {
     def pos(implicit ctx: Context): Position = kernel.Term_pos(self)
     def underlyingArgument(implicit ctx: Context): Term = kernel.Term_underlyingArgument(self)
     def underlying(implicit ctx: Context): Term = kernel.Term_underlying(self)
+
+    /** A unary apply node with given argument: `tree(arg)` */
+    def appliedTo(arg: Term)(implicit ctx: Context): Term =
+      appliedToArgs(arg :: Nil)
+
+    /** An apply node with given arguments: `tree(arg, args0, ..., argsN)` */
+    def appliedTo(arg: Term, args: Term*)(implicit ctx: Context): Term =
+      appliedToArgs(arg :: args.toList)
+
+    /** An apply node with given argument list `tree(args(0), ..., args(args.length - 1))` */
+    def appliedToArgs(args: List[Term])(implicit ctx: Context): Apply =
+      Apply(self, args)
+
+    /** The current tree applied to given argument lists:
+     *  `tree (argss(0)) ... (argss(argss.length -1))`
+     */
+    def appliedToArgss(argss: List[List[Term]])(implicit ctx: Context): Term =
+      ((self: Term) /: argss)(Apply(_, _))
+
+    /** The current tree applied to (): `tree()` */
+    def appliedToNone(implicit ctx: Context): Apply = appliedToArgs(Nil)
+
+    /** The current tree applied to given type argument: `tree[targ]` */
+    def appliedToType(targ: Type)(implicit ctx: Context): Term =
+      appliedToTypes(targ :: Nil)
+
+    /** The current tree applied to given type arguments: `tree[targ0, ..., targN]` */
+    def appliedToTypes(targs: List[Type])(implicit ctx: Context): Term =
+      appliedToTypeTrees(targs map (Inferred(_)))
+
+    /** The current tree applied to given type argument list: `tree[targs(0), ..., targs(targs.length - 1)]` */
+    def appliedToTypeTrees(targs: List[TypeTree])(implicit ctx: Context): Term =
+      if (targs.isEmpty) self else TypeApply(self, targs)
+
+    /** A select node that selects the given symbol.
+     */
+    def select(sym: Symbol)(implicit ctx: Context): Select = Select(self, sym)
   }
 
   object IsTerm {
diff --git a/tests/run-macros/reflect-dsl/assert_1.scala b/tests/run-macros/reflect-dsl/assert_1.scala
new file mode 100644
index 000000000000..f1e60b925e0b
--- /dev/null
+++ b/tests/run-macros/reflect-dsl/assert_1.scala
@@ -0,0 +1,46 @@
+import scala.quoted._
+import scala.tasty._
+
+object scalatest {
+
+  inline def assert(condition: => Boolean): Unit = ${ assertImpl('condition, '{""}) }
+
+  def assertImpl(cond: Expr[Boolean], clue: Expr[Any])(implicit refl: Reflection): Expr[Unit] = {
+    import refl._
+    import util._
+
+    def isImplicitMethodType(tp: Type): Boolean =
+      Type.IsMethodType.unapply(tp).flatMap(tp => if tp.isImplicit then Some(true) else None).nonEmpty
+
+    cond.unseal.underlyingArgument match {
+      case t @ Apply(sel @ Select(lhs, op), rhs :: Nil) =>
+        let(lhs) { left =>
+          let(rhs) { right =>
+            val app = left.select(sel.symbol).appliedTo(right)
+            let(app) { result =>
+              val l = left.seal
+              val r = right.seal
+              val b = result.seal.cast[Boolean]
+              val code = '{ scala.Predef.assert($b) }
+              code.unseal
+            }
+          }
+        }.seal.cast[Unit]
+      case Apply(f @ Apply(sel @ Select(Apply(qual, lhs :: Nil), op), rhs :: Nil), implicits)
+      if isImplicitMethodType(f.tpe) =>
+        let(lhs) { left =>
+          let(rhs) { right =>
+            val app = qual.appliedTo(left).select(sel.symbol).appliedTo(right)
+            let(Apply(app, implicits)) { result =>
+              val l = left.seal
+              val r = right.seal
+              val b = result.seal.cast[Boolean]
+              val code = '{ scala.Predef.assert($b) }
+              code.unseal
+            }
+          }
+        }.seal.cast[Unit]
+    }
+  }
+
+}
diff --git a/tests/run-macros/reflect-dsl/test_2.scala b/tests/run-macros/reflect-dsl/test_2.scala
new file mode 100644
index 000000000000..1525360a71f7
--- /dev/null
+++ b/tests/run-macros/reflect-dsl/test_2.scala
@@ -0,0 +1,29 @@
+object Test {
+  import scalatest._
+
+  case class Box[T](v: T) {
+    def >(that: Box[T]): Boolean = this == that
+  }
+
+  trait EqInt
+  implicit val eq: EqInt = new EqInt {}
+
+  implicit class AnyOps[T](x: T) {
+    def === (y: T)(implicit c: EqInt) = x == y
+  }
+
+  def main(args: Array[String]): Unit = {
+    val a = Box(Some(10))
+    val five: Float = 5.0f
+    val six: Double = 6.0
+    val ten: Int = 10
+    assert(a.v === Some(10))
+    assert(five < six)
+    assert(five > 4)
+    assert(ten > 5)
+    assert(six < 7)
+    assert(six > 5L)
+    assert(Box(6) > Box(6))
+    assert(Box("h") > Box("h"))
+  }
+}