From 7bed8912057b1bd32e7c6a1eb6a84a04a1398140 Mon Sep 17 00:00:00 2001
From: Liu Fengyun <liu@fengy.me>
Date: Mon, 29 Mar 2021 14:10:00 +0200
Subject: [PATCH] Performance tweak for initialization check

Propagate visited set properly.
---
 .../tools/dotc/transform/init/Checking.scala  | 38 ++++++++++++-------
 tests/init/neg/function1.scala                |  2 +-
 2 files changed, 25 insertions(+), 15 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/transform/init/Checking.scala b/compiler/src/dotty/tools/dotc/transform/init/Checking.scala
index e47c3b08d264..cc8f95b20e8c 100644
--- a/compiler/src/dotty/tools/dotc/transform/init/Checking.scala
+++ b/compiler/src/dotty/tools/dotc/transform/init/Checking.scala
@@ -39,7 +39,18 @@ object Checking {
     safePromoted: mutable.Set[Potential],      // Potentials that can be safely promoted
     env: Env
   ) {
-    def withOwner(sym: Symbol): State = copy(env = env.withOwner(sym))
+    def withOwner[T](sym: Symbol)(op: State ?=> T): T =
+      val state = this.copy(env = env.withOwner(sym))
+      val res = op(using state)
+      this.visited = state.visited
+      res
+
+
+    def visit[T](eff: Effect)(op: State ?=> T): T =
+      val state: State = this.copy(path = path :+ eff.source, visited = this.visited + eff)
+      val res = op(using state)
+      this.visited = state.visited
+      res
 
     def test(op: State ?=> Errors): Errors = {
       val savedVisited = visited
@@ -58,15 +69,14 @@ object Checking {
         traceIndented("Already checked " + eff.show, init)
         Errors.empty
       }
-      else {
-        state.visited = state.visited + eff
-        val state2: State = state.copy(path = state.path :+ eff.source)
-        eff match {
-          case eff: Promote      => Checking.checkPromote(eff)(using state2)
-          case eff: FieldAccess  => Checking.checkFieldAccess(eff)(using state2)
-          case eff: MethodCall   => Checking.checkMethodCall(eff)(using state2)
+      else
+        state.visit(eff) {
+          eff match {
+            case eff: Promote      => Checking.checkPromote(eff)
+            case eff: FieldAccess  => Checking.checkFieldAccess(eff)
+            case eff: MethodCall   => Checking.checkMethodCall(eff)
+          }
         }
-      }
     }
   }
 
@@ -118,11 +128,11 @@ object Checking {
     def checkConstructor(ctor: Symbol, tp: Type, source: Tree)(using state: State): Unit = traceOp("checking " + ctor.show, init) {
       val cls = ctor.owner
       val classDef = cls.defTree
-      if (!classDef.isEmpty) {
-        given State = state.withOwner(cls)
-        if (ctor.isPrimaryConstructor) checkClassBody(classDef.asInstanceOf[TypeDef])
-        else checkSecondaryConstructor(ctor)
-      }
+      if (!classDef.isEmpty)
+        state.withOwner(cls) {
+          if (ctor.isPrimaryConstructor) checkClassBody(classDef.asInstanceOf[TypeDef])
+          else checkSecondaryConstructor(ctor)
+        }
     }
 
     def checkSecondaryConstructor(ctor: Symbol)(using state: State): Unit = traceOp("checking " + ctor.show, init) {
diff --git a/tests/init/neg/function1.scala b/tests/init/neg/function1.scala
index 15427f3de750..e01864ae1f47 100644
--- a/tests/init/neg/function1.scala
+++ b/tests/init/neg/function1.scala
@@ -4,7 +4,7 @@ class Foo {
   val fun2: Int => Int = n => 1 + n + list.size
   fun2(5)
 
-  List(5, 9).map(n => 2 + n + list.size)         // error
+  List(5, 9).map(n => 2 + n + list.size)
 
   final val list = List(1, 2, 3)                 // error