From 7f3efa1eb53f0fc1e1b1c496e1b73c4d5b46ad78 Mon Sep 17 00:00:00 2001
From: Michael McLoughlin <mmcloughlin@gmail.com>
Date: Mon, 17 Dec 2018 21:20:21 -0800
Subject: [PATCH] fix nil pointer dereference

---
 build/context.go | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/build/context.go b/build/context.go
index 84353ee..3dbdbf4 100644
--- a/build/context.go
+++ b/build/context.go
@@ -2,6 +2,7 @@ package build
 
 import (
 	"errors"
+	"go/types"
 
 	"github.com/mmcloughlin/avo"
 	"github.com/mmcloughlin/avo/gotypes"
@@ -53,7 +54,7 @@ func (c *Context) Signature(s *gotypes.Signature) {
 }
 
 func (c *Context) SignatureExpr(expr string) {
-	s, err := gotypes.ParseSignatureInPackage(c.pkg.Types, expr)
+	s, err := gotypes.ParseSignatureInPackage(c.types(), expr)
 	if err != nil {
 		c.AddError(err)
 		return
@@ -61,6 +62,13 @@ func (c *Context) SignatureExpr(expr string) {
 	c.Signature(s)
 }
 
+func (c *Context) types() *types.Package {
+	if c.pkg == nil {
+		return nil
+	}
+	return c.pkg.Types
+}
+
 func (c *Context) Instruction(i *avo.Instruction) {
 	c.activefunc().AddNode(i)
 }