Merge pull request #6615 from dotty-staging/select-symbol

Add reflect API: Select.apply with a symbol

Author: nicolasstucki

compiler/src/dotty/tools/dotc/tastyreflect/KernelImpl.scala

@@ -282,6 +282,9 @@ class KernelImpl(val rootContext: core.Contexts.Context, val rootPosition: util.
     if (self.symbol.signature == core.Signature.NotAMethod) None
     else Some(self.symbol.signature)
 
+  def Select_apply(qualifier: Term, symbol: Symbol)(implicit ctx: Context): Select =
+    withDefaultPos(implicit ctx => tpd.Select(qualifier, Types.TermRef(qualifier.tpe, symbol)))
+
   def Select_unique(qualifier: Term, name: String)(implicit ctx: Context): Select = {
     val denot = qualifier.tpe.member(name.toTermName)
     assert(!denot.isOverloaded, s"The symbol `$name` is overloaded. The method Select.unique can only be used for non-overloaded symbols.")

library/src/scala/tasty/reflect/Kernel.scala

@@ -329,6 +329,7 @@ trait Kernel {
   def Select_name(self: Select)(implicit ctx: Context): String
   def Select_signature(self: Select)(implicit ctx: Context): Option[Signature]
 
+  def Select_apply(qualifier: Term, symbol: Symbol)(implicit ctx: Context): Select
   def Select_unique(qualifier: Term, name: String)(implicit ctx: Context): Select
   // TODO rename, this returns an Apply and not a Select
   def Select_overloaded(qualifier: Term, name: String, targs: List[Type], args: List[Term])(implicit ctx: Context): Apply

library/src/scala/tasty/reflect/TreeOps.scala

@@ -231,6 +231,10 @@ trait TreeOps extends Core {
 
   /** Scala term selection */
   object Select {
+    /** Select a term member by symbol */
+    def apply(qualifier: Term, symbol: Symbol)(implicit ctx: Context): Select =
+      kernel.Select_apply(qualifier, symbol)
+
     /** Select a field or a non-overloaded method by name
      *
      *  @note The method will produce an assertion error if the selected

tests/run-macros/reflect-select-symbol-constructor/assert_1.scala

@@ -0,0 +1,46 @@
+import scala.quoted._
+import scala.tasty._
+
+object scalatest {
+
+  inline def assert(condition: => Boolean): Unit = ${ assertImpl('condition, '{""}) }
+
+  def assertImpl(cond: Expr[Boolean], clue: Expr[Any])(implicit refl: Reflection): Expr[Unit] = {
+    import refl._
+    import util._
+
+    def isImplicitMethodType(tp: Type): Boolean =
+      Type.IsMethodType.unapply(tp).flatMap(tp => if tp.isImplicit then Some(true) else None).nonEmpty
+
+    cond.unseal.underlyingArgument match {
+      case t @ Apply(sel @ Select(lhs, op), rhs :: Nil) =>
+        let(lhs) { left =>
+          let(rhs) { right =>
+            val app = Apply(Select(left, sel.symbol), right :: Nil)
+            let(app) { result =>
+              val l = left.seal
+              val r = right.seal
+              val b = result.seal.cast[Boolean]
+              val code = '{ scala.Predef.assert($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 = Apply(Select(Apply(qual, left :: Nil), sel.symbol), right :: Nil)
+            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]
+    }
+  }
+
+}

tests/run-macros/reflect-select-symbol-constructor/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"))
+  }
+}