From 6282364f1f241053c05ff8f03c720ca8643dfa31 Mon Sep 17 00:00:00 2001
From: Ignacio Van Droogenbroeck <ignacio@vandroogenbroeck.net>
Date: Mon, 2 Mar 2026 19:03:48 -0600
Subject: [PATCH] perf(decode): replace goroutine-per-type value pool with
 sync.Pool
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Replaces the cachedValues mechanism (unbounded goroutine per type +
channel with buffer of 256) with sync.Pool per type stored in a
sync.Map. Eliminates goroutine leak — the old approach spawned a
goroutine for every unique decoded type that ran forever in an
infinite loop. No performance regression in benchmarks.
---
 decode_typgen.go | 36 +++++++++---------------------------
 1 file changed, 9 insertions(+), 27 deletions(-)

diff --git a/decode_typgen.go b/decode_typgen.go
index 0b4c1d0..e453bce 100644
--- a/decode_typgen.go
+++ b/decode_typgen.go
@@ -5,36 +5,18 @@ import (
 	"sync"
 )
 
-var cachedValues struct {
-	m map[reflect.Type]chan reflect.Value
-	sync.RWMutex
-}
+var cachedPools sync.Map // map[reflect.Type]*sync.Pool
 
 func cachedValue(t reflect.Type) reflect.Value {
-	cachedValues.RLock()
-	ch := cachedValues.m[t]
-	cachedValues.RUnlock()
-	if ch != nil {
-		return <-ch
-	}
-
-	cachedValues.Lock()
-	defer cachedValues.Unlock()
-	if ch = cachedValues.m[t]; ch != nil {
-		return <-ch
-	}
-
-	ch = make(chan reflect.Value, 256)
-	go func() {
-		for {
-			ch <- reflect.New(t)
-		}
-	}()
-	if cachedValues.m == nil {
-		cachedValues.m = make(map[reflect.Type]chan reflect.Value, 8)
+	v, ok := cachedPools.Load(t)
+	if !ok {
+		v, _ = cachedPools.LoadOrStore(t, &sync.Pool{
+			New: func() interface{} {
+				return reflect.New(t)
+			},
+		})
 	}
-	cachedValues.m[t] = ch
-	return <-ch
+	return v.(*sync.Pool).Get().(reflect.Value)
 }
 
 func (d *Decoder) newValue(t reflect.Type) reflect.Value {