text/template: catch unmatched right delimiter
It was simply a missing error case: when scanning plain text
outside of an action, a right delimiter should be an error.

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/13468045

src/pkg/text/template/parse/lex.go

diff --git a/src/pkg/text/template/parse/lex.go b/src/pkg/text/template/parse/lex.go
index 1674aaf..690497d 100644
--- a/src/pkg/text/template/parse/lex.go
+++ b/src/pkg/text/template/parse/lex.go
@@ -217,6 +217,10 @@
 			}
 			return lexLeftDelim
 		}
+		// Check for right after left in case they're the same.
+		if strings.HasPrefix(l.input[l.pos:], l.rightDelim) {
+			return l.errorf("unmatched right delimiter")
+		}
 		if l.next() == eof {
 			break
 		}

src/pkg/text/template/parse/lex_test.go

diff --git a/src/pkg/text/template/parse/lex_test.go b/src/pkg/text/template/parse/lex_test.go
index ae90ae4..e72e07f 100644
--- a/src/pkg/text/template/parse/lex_test.go
+++ b/src/pkg/text/template/parse/lex_test.go
@@ -340,6 +340,9 @@
 		{itemText, 0, "hello-"},
 		{itemError, 0, `comment ends before closing delimiter`},
 	}},
+	{"unmatched right delimiter", "hello-{.}}-world", []item{
+		{itemError, 0, `unmatched right delimiter`},
+	}},
 }
 
 // collect gathers the emitted items into a slice.

src/pkg/text/template/parse/parse_test.go

diff --git a/src/pkg/text/template/parse/parse_test.go b/src/pkg/text/template/parse/parse_test.go
index c35f4ac..049e65c 100644
--- a/src/pkg/text/template/parse/parse_test.go
+++ b/src/pkg/text/template/parse/parse_test.go
@@ -312,7 +312,7 @@
 	{"spaces only", " \t\n \t\n", true},
 	{"definition", `{{define "x"}}something{{end}}`, true},
 	{"definitions and space", "{{define `x`}}something{{end}}\n\n{{define `y`}}something{{end}}\n\n", true},
-	{"definitions and text", "{{define `x`}}something{{end}}\nx\n{{define `y`}}something{{end}}\ny\n}}", false},
+	{"definitions and text", "{{define `x`}}something{{end}}\nx\n{{define `y`}}something{{end}}\ny\n", false},
 	{"definition and action", "{{define `x`}}something{{end}}{{if 3}}foo{{end}}", false},
 }