errfoundreturnnil.patch

diff --git a/ruleguard.rules.go b/ruleguard.rules.go
index 5d4c4fe..8d2f8c1 100644
--- a/ruleguard.rules.go
+++ b/ruleguard.rules.go
@@ -130,6 +130,34 @@ func errnoterror(m fluent.Matcher) {
                Report("err variable not error type")
 }

+// err found but return nil
+func errfoundreturnnil(m fluent.Matcher) {
+       m.Match(
+               "if $*_, err := $x; $err != nil { return nil } else if $_ { $*_ }",
+               "if $*_, err := $x; $err != nil { return nil } else { $*_ }",
+               "if $*_, err := $x; $err != nil { return nil }",
+
+               "if $*_, err = $x; $err != nil { return nil } else if $_ { $*_ }",
+               "if $*_, err = $x; $err != nil { return $*_, nil } else { $*_ }",
+               "if $*_, err = $x; $err != nil { return $*_, nil }",
+
+               "if err := $x; $err != nil { return nil } else if $_ { $*_ }",
+               "if err := $x; $err != nil { return $*_, nil } else { $*_ }",
+               "if err := $x; $err != nil { return $*_, nil }",
+
+               "if err := $x; $err != nil { return $*_, nil } else { $*_ }",
+               "if err := $x; $err != nil { return $*_, nil }",
+
+               "if err = $x; $err != nil { return $*_, nil } else { $*_ }",
+               "if err = $x; $err != nil { return $*_, nil }",
+
+               "if $err != nil { return nil }",
+               "if $err != nil { return $*_, nil }",
+       ).
+               Where(m["err"].Type.Is("error")).
+               Report("err value found but return value was nil")
+}
+
 // Identical if and else bodies
 func ifbodythenbody(m fluent.Matcher) {
        m.Match("if $*_ { $body } else { $body }").