Return an undefined Pos when an object list's Items are empty

hcl/ast/ast.go

@@ -25,6 +25,8 @@ func (ObjectType) node() {}
 func (LiteralType) node() {}
 func (ListType) node() {}
 
+var unknownPos token.Pos
+
 // File represents a single HCL file
 type File struct {
  Node Node // usually a *ObjectList
@@ -108,7 +110,12 @@ func (o *ObjectList) Elem() *ObjectList {
 }
 
 func (o *ObjectList) Pos() token.Pos {
- // always returns the uninitiliazed position
+ // If an Object has no members, it won't have a first item
+ // to use as position
+ if len(o.Items)==0 {
+ return unknownPos
+ }
+ // Return the uninitialized position
  return o.Items[0].Pos()
 }
 
@@ -133,10 +140,10 @@ type ObjectItem struct {
 }
 
 func (o *ObjectItem) Pos() token.Pos {
- // I'm not entirely sure what causes this, but removing this causes
- // a test failure. We should investigate at some point.
+ // If a parsed object has no keys, there is no position
+ // for its first element.
  if len(o.Keys) == 0 {
- return token.Pos{}
+ return unknownPos
  }
 
  return o.Keys[0].Pos()