From a9907c15845e8273e99fd14a9f1641020ffd5cac Mon Sep 17 00:00:00 2001
From: Dave Collins <dave@davec.name>
Date: Sun, 20 Jan 2013 20:44:21 -0600
Subject: Improve invalid reflect value handling.

It was previously possible for an invalid reflect value to lead to a panic
in certain obscure cases.  Rather than adding multiple checks for the
invalid reflect value, handle invalid reflect values immediately.
---
 spew/format.go | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

(limited to 'spew/format.go')

diff --git a/spew/format.go b/spew/format.go
index f06cbdb..49ef854 100644
--- a/spew/format.go
+++ b/spew/format.go
@@ -197,8 +197,14 @@ func (f *formatState) formatPtr(v reflect.Value) {
 // dealing with and formats it appropriately.  It is a recursive function,
 // however circular data structures are detected and handled properly.
 func (f *formatState) format(v reflect.Value) {
-	// Handle pointers specially.
+	// Handle invalid reflect values immediately.
 	kind := v.Kind()
+	if kind == reflect.Invalid {
+		f.fs.Write(invalidAngleBytes)
+		return
+	}
+
+	// Handle pointers specially.
 	if kind == reflect.Ptr {
 		f.formatPtr(v)
 		return
@@ -224,7 +230,8 @@ func (f *formatState) format(v reflect.Value) {
 
 	switch kind {
 	case reflect.Invalid:
-		f.fs.Write(invalidAngleBytes)
+		// Do nothing.  We should never get here since invalid has already
+		// been handled above.
 
 	case reflect.Bool:
 		printBool(f.fs, v.Bool())
-- 
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