Update to tengo v2 (#976)

vendor/github.com/d5/tengo/v2/parser/file.go

@@ -0,0 +1,29 @@
+package parser
+
+import (
+	"strings"
+)
+
+// File represents a file unit.
+type File struct {
+	InputFile *SourceFile
+	Stmts     []Stmt
+}
+
+// Pos returns the position of first character belonging to the node.
+func (n *File) Pos() Pos {
+	return Pos(n.InputFile.Base)
+}
+
+// End returns the position of first character immediately after the node.
+func (n *File) End() Pos {
+	return Pos(n.InputFile.Base + n.InputFile.Size)
+}
+
+func (n *File) String() string {
+	var stmts []string
+	for _, e := range n.Stmts {
+		stmts = append(stmts, e.String())
+	}
+	return strings.Join(stmts, "; ")
+}