use pattern matching and closureDef extractor

Author: Linyxus

compiler/src/dotty/tools/dotc/cc/CheckCaptures.scala

@@ -507,19 +507,6 @@ class CheckCaptures extends Recheck, SymTransformer:
       recheckFinish(result, arg, pt)
     */
 
-    extension (tree: Tree)
-      private def isFunctionLiteral(using Context): Boolean = tree match
-        case Block((defTree @ DefDef(_, _, _, _)) :: Nil, Closure(_, meth, _)) =>
-          val defSym = defTree.symbol
-          val methSym = meth.symbol
-          defSym.eq(methSym)
-        case _ =>
-          false
-
-      private def isRefTree: Boolean = tree match
-        case _: RefTree => true
-        case _          => false
-
     /** If expected type `pt` is boxed and the tree is a function or a reference,
      *  don't propagate free variables.
      *  Otherwise, if the result type is boxed, simulate an unboxing by
@@ -528,8 +515,12 @@ class CheckCaptures extends Recheck, SymTransformer:
     override def recheck(tree: Tree, pt: Type = WildcardType)(using Context): Type =
       if tree.isTerm && pt.isBoxedCapturing then
         val saved = curEnv
-        if tree.isRefTree || tree.isFunctionLiteral then
-          curEnv = Env(curEnv.owner, nestedInOwner = false, CaptureSet.Var(), isBoxed = true, curEnv)
+
+        tree match
+          case _: RefTree | closureDef(_) =>
+            curEnv = Env(curEnv.owner, nestedInOwner = false, CaptureSet.Var(), isBoxed = true, curEnv)
+          case _ =>
+
         try super.recheck(tree, pt)
         finally curEnv = saved
       else