From ff006982c355bef55fb7b36944a1cc661bacf287 Mon Sep 17 00:00:00 2001
From: Josh Bleecher Snyder <josharian@gmail.com>
Date: Mon, 30 Dec 2013 17:17:19 -0800
Subject: [PATCH] text/template: don't panic when using AddParseTree with an
 unparsed template

Fixes #7032.

R=golang-codereviews, r
CC=golang-codereviews
https://golang.org/cl/43960045
---
 src/pkg/text/template/multi_test.go | 12 ++++++++++++
 src/pkg/text/template/template.go   |  2 +-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/pkg/text/template/multi_test.go b/src/pkg/text/template/multi_test.go
index 1f6ed5d8e22..e4e804880a4 100644
--- a/src/pkg/text/template/multi_test.go
+++ b/src/pkg/text/template/multi_test.go
@@ -259,6 +259,18 @@ func TestAddParseTree(t *testing.T) {
 	}
 }
 
+// Issue 7032
+func TestAddParseTreeToUnparsedTemplate(t *testing.T) {
+	master := "{{define \"master\"}}{{end}}"
+	tmpl := New("master")
+	tree, err := parse.Parse("master", master, "", "", nil)
+	if err != nil {
+		t.Fatalf("unexpected parse err: %v", err)
+	}
+	masterTree := tree["master"]
+	tmpl.AddParseTree("master", masterTree) // used to panic
+}
+
 func TestRedefinition(t *testing.T) {
 	var tmpl *Template
 	var err error
diff --git a/src/pkg/text/template/template.go b/src/pkg/text/template/template.go
index a2b9062ad14..249d0cbfb90 100644
--- a/src/pkg/text/template/template.go
+++ b/src/pkg/text/template/template.go
@@ -105,7 +105,7 @@ func (t *Template) copy(c *common) *Template {
 // AddParseTree creates a new template with the name and parse tree
 // and associates it with t.
 func (t *Template) AddParseTree(name string, tree *parse.Tree) (*Template, error) {
-	if t.tmpl[name] != nil {
+	if t.common != nil && t.tmpl[name] != nil {
 		return nil, fmt.Errorf("template: redefinition of template %q", name)
 	}
 	nt := t.New(name)