Add extractor for function literals

Author: liufengyun

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

@@ -574,6 +574,25 @@ trait TreeOps extends Core {
     def tpeOpt(implicit ctx: Context): Option[Type] = kernel.Closure_tpeOpt(self)
   }
 
+  /** A lambda `(...) => ...` in the source code is represented as
+   *  a local method and a closure:
+   *
+   *  {
+   *    def m(...) = ...
+   *    closure(m)
+   *  }
+   *
+   */
+  object Lambda {
+    def unapply(tree: Tree)(implicit ctx: Context): Option[(List[ValDef], Term)] = tree match {
+      case Block((ddef @ DefDef(_, _, params :: Nil, _, Some(body))) :: Nil, Closure(meth, _))
+      if ddef.symbol == meth.symbol =>
+        Some(params, body)
+
+      case _ => None
+    }
+  }
+
   object IsIf {
     /** Matches any If and returns it */
     def unapply(tree: Tree)(implicit ctx: Context): Option[If] = kernel.matchIf(tree)

tests/run-macros/reflect-lambda/assert_1.scala

@@ -0,0 +1,18 @@
+import scala.quoted._
+import scala.tasty._
+
+object lib {
+
+  inline def assert(condition: => Boolean): Unit = ${ assertImpl('condition, '{""}) }
+
+  def assertImpl(cond: Expr[Boolean], clue: Expr[Any])(implicit refl: Reflection): Expr[Unit] = {
+    import refl._
+    import util._
+
+    cond.unseal.underlyingArgument match {
+      case t @ Apply(Select(lhs, op), Lambda(param :: Nil, Apply(Select(a, "=="), b :: Nil)) :: Nil)
+      if a.symbol == param.symbol || b.symbol == param.symbol =>
+        '{ scala.Predef.assert($cond) }
+    }
+  }
+}

tests/run-macros/reflect-lambda/test_2.scala

@@ -0,0 +1,14 @@
+object Test {
+  import lib._
+
+  case class IntList(args: Int*) {
+    def exists(f: Int => Boolean): Boolean = args.exists(f)
+  }
+
+  def main(args: Array[String]): Unit = {
+    assert(IntList(3, 5).exists(_ == 3))
+    assert(IntList(3, 5).exists(5 == _))
+    assert(IntList(3, 5).exists(x => x == 3))
+    assert(IntList(3, 5).exists(x => 5 == x))
+  }
+}