Avoid allocating tintError twice (#82)

* Avoid allocating tintError twice

Passing the type-asserted tintError value as an error causes a second allocation.

Since the helper method is only for tintError values, change the signature to specify the concrete type to elide the second allocation.

* added `tint.Err` benchmark

---------

Co-authored-by: lmittmann <lmittmann@users.noreply.github.com>

handler.go

@@ -417,7 +417,7 @@ func (h *handler) appendValue(buf *buffer, v slog.Value, quote bool) {
 	}
 }
 
-func (h *handler) appendTintError(buf *buffer, err error, attrKey, groupsPrefix string) {
+func (h *handler) appendTintError(buf *buffer, err tintError, attrKey, groupsPrefix string) {
 	buf.WriteStringIf(!h.noColor, ansiBrightRedFaint)
 	appendString(buf, groupsPrefix+attrKey, true)
 	buf.WriteByte('=')

handler_test.go

@@ -558,6 +558,14 @@ func BenchmarkLogAttrs(b *testing.B) {
 				)
 			},
 		},
+		{
+			"error",
+			func(logger *slog.Logger) {
+				logger.LogAttrs(context.TODO(), slog.LevelError, testMessage,
+					tint.Err(errTest),
+				)
+			},
+		},
 	}
 
 	for _, h := range handler {