From 6329d730113e6804a431c86ba2a92a5b3900b4af Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Sun, 19 Mar 2023 15:30:36 +0800
Subject: [PATCH] avoid allocating a objectAttributeKeyWriteMap lambda when
 writing case classes

---
 .../upickle/implicits/internal/Macros.scala   |  5 ++---
 .../src-3/upickle/implicits/macros.scala      |  3 +--
 .../implicits/CaseClassReadWriters.scala      | 19 ++++++++++++++-----
 3 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/implicits/src-2/upickle/implicits/internal/Macros.scala b/implicits/src-2/upickle/implicits/internal/Macros.scala
index 15a341ddb..db3b5b6dd 100644
--- a/implicits/src-2/upickle/implicits/internal/Macros.scala
+++ b/implicits/src-2/upickle/implicits/internal/Macros.scala
@@ -345,10 +345,9 @@ object Macros {
 
       def write(i: Int) = {
         val snippet = q"""
-          this.writeSnippet[R, ${argTypes(i)}](
-            ${c.prefix}.objectAttributeKeyWriteMap,
+          this.writeSnippetMappedName[R, ${argTypes(i)}](
              ctx,
-             ${mappedArgs(i)},
+             ${c.prefix}.objectAttributeKeyWriteMap(${mappedArgs(i)}),
              implicitly[${c.prefix}.Writer[${argTypes(i)}]],
              v.${TermName(rawArgs(i))}
            )
diff --git a/implicits/src-3/upickle/implicits/macros.scala b/implicits/src-3/upickle/implicits/macros.scala
index da4fdde64..adb5224e9 100644
--- a/implicits/src-3/upickle/implicits/macros.scala
+++ b/implicits/src-3/upickle/implicits/macros.scala
@@ -144,9 +144,8 @@ def writeSnippetsImpl[R, T, WS <: Tuple](thisOuter: Expr[upickle.core.Types with
           val select = Select.unique(v.asTerm, rawLabel.name).asExprOf[Any]
           val snippet = '{
             ${self}.writeSnippet[R, tpe](
-              ${thisOuter}.objectAttributeKeyWriteMap,
               ${ctx},
-              ${Expr(label)},
+              ${thisOuter}.objectAttributeKeyWriteMap(${Expr(label)}),
               summonInline[Tuple.Elem[WS, index]],
               ${select},
             )
diff --git a/implicits/src/upickle/implicits/CaseClassReadWriters.scala b/implicits/src/upickle/implicits/CaseClassReadWriters.scala
index 6fa0dd814..3226d3115 100644
--- a/implicits/src/upickle/implicits/CaseClassReadWriters.scala
+++ b/implicits/src/upickle/implicits/CaseClassReadWriters.scala
@@ -24,6 +24,7 @@ trait CaseClassReadWriters extends upickle.core.Types{
     @deprecated("Not used, left for binary compatibility")
     def writeToObject[R](ctx: ObjVisitor[_, R], v: V): Unit
 
+    @scala.annotation.nowarn
     def write0[R](out: Visitor[_, R], v: V): R = {
       if (v == null) out.visitNull(-1)
       else {
@@ -33,16 +34,24 @@ trait CaseClassReadWriters extends upickle.core.Types{
       }
     }
 
+    def writeSnippetMappedName[R, V](ctx: _root_.upickle.core.ObjVisitor[_, R],
+                                     mappedArgsI: CharSequence,
+                                     w: Any,
+                                     value: Any) = {
+      val keyVisitor = ctx.visitKey(-1)
+      ctx.visitKeyValue(
+        keyVisitor.visitString(mappedArgsI, -1)
+      )
+      ctx.narrow.visitValue(w.asInstanceOf[Writer[Any]].write(ctx.subVisitor, value), -1)
+    }
+
+    @deprecated("Not used, left for binary compatibility")
     def writeSnippet[R, V](objectAttributeKeyWriteMap: CharSequence => CharSequence,
                            ctx: _root_.upickle.core.ObjVisitor[_, R],
                            mappedArgsI: String,
                            w: Any,
                            value: Any) = {
-      val keyVisitor = ctx.visitKey(-1)
-      ctx.visitKeyValue(
-        keyVisitor.visitString(objectAttributeKeyWriteMap(mappedArgsI), -1)
-      )
-      ctx.narrow.visitValue(w.asInstanceOf[Writer[Any]].write(ctx.subVisitor, value), -1)
+      writeSnippetMappedName(ctx, objectAttributeKeyWriteMap(mappedArgsI), w, value)
     }
   }