--- print.go.orig	2020-08-26 14:49:30.396184000 +0200
+++ print.go	2020-08-26 14:50:29.330829000 +0200
@@ -1,3 +1,6 @@
+// Code generated from print.go.orig. DO NOT EDIT
+// GENERATED FILE DO NOT EDIT
+//
 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
@@ -5,12 +8,16 @@
 package fmt
 
 import (
-	"internal/fmtsort"
+	// CUSTOM: needed to avoid a type mismatch on Formatter.
+	origFmt "fmt"
 	"io"
 	"os"
 	"reflect"
 	"sync"
 	"unicode/utf8"
+
+	// CUSTOM: our own import since we can't use internal from go stdlib.
+	"github.com/cockroachdb/redact/internal/fmtsort"
 )
 
 // Strings for use with buffer.WriteString.
@@ -51,7 +58,8 @@
 // The implementation of Format may call Sprint(f) or Fprint(f) etc.
 // to generate its output.
 type Formatter interface {
-	Format(f State, c rune)
+	// CUSTOM: refer to the original type, not the one defined here.
+	Format(f origFmt.State, c rune)
 }
 
 // Stringer is implemented by any value that has a String method,
@@ -105,6 +113,10 @@
 type pp struct {
 	buf buffer
 
+	// CUSTOM: hook fn for the redact package.
+	printArgSubstituteFn func(p *pp, a interface{}, verb rune) (newState int)
+	substituteState      int
+
 	// arg holds the current item, as an interface{}.
 	arg interface{}
 
@@ -635,7 +647,8 @@
 	return false
 }
 
-func (p *pp) printArg(arg interface{}, verb rune) {
+// CUSTOM: printArg() renamed to printArgOrig().
+func (p *pp) printArgOrig(arg interface{}, verb rune) {
 	p.arg = arg
 	p.value = reflect.Value{}