Add line and column number to MapItem instances

decode.go

@@ -586,7 +586,7 @@ func (d *decoder) mappingSlice(n *node, out reflect.Value) (good bool) {
 			d.merge(n.children[i+1], out)
 			continue
 		}
-		item := MapItem{}
+		item := MapItem{Line: n.line, Col: n.column}
 		k := reflect.ValueOf(&item.Key).Elem()
 		if d.unmarshal(n.children[i], k) {
 			v := reflect.ValueOf(&item.Value).Elem()

decode_test.go

@@ -529,7 +529,7 @@ var unmarshalTests = []struct {
 	// Ordered maps.
 	{
 		"{b: 2, a: 1, d: 4, c: 3, sub: {e: 5}}",
-		&yaml.MapSlice{{"b", 2}, {"a", 1}, {"d", 4}, {"c", 3}, {"sub", yaml.MapSlice{{"e", 5}}}},
+		&yaml.MapSlice{{"b", 2, 0, 0}, {"a", 1, 0, 0}, {"d", 4, 0, 0}, {"c", 3, 0, 0}, {"sub", yaml.MapSlice{{"e", 5, 0, 30}}, 0, 0}},
 	},
 
 	// Issue #39.

encode_test.go

@@ -287,7 +287,7 @@ var marshalTests = []struct {
 
 	// Ordered maps.
 	{
-		&yaml.MapSlice{{"b", 2}, {"a", 1}, {"d", 4}, {"c", 3}, {"sub", yaml.MapSlice{{"e", 5}}}},
+		&yaml.MapSlice{{"b", 2, 0, 0}, {"a", 1, 0, 0}, {"d", 4, 0, 0}, {"c", 3, 0, 0}, {"sub", yaml.MapSlice{{"e", 5, 0, 0}}, 0, 0}},
 		"b: 2\na: 1\nd: 4\nc: 3\nsub:\n  e: 5\n",
 	},
 

yaml.go

@@ -21,6 +21,7 @@ type MapSlice []MapItem
 // MapItem is an item in a MapSlice.
 type MapItem struct {
 	Key, Value interface{}
+	Line, Col int
 }
 
 // The Unmarshaler interface may be implemented by types to customize their