const: n < iota support

consts.go

@@ -35,7 +35,12 @@ func (c *ConstsValidator) Validate(v *ast.GenDecl, fset *token.FileSet) error {
 		}
 
 		for _, vss := range s.Values {
-			_, ok := vss.(*ast.Ident)
+			bexpr, ok := vss.(*ast.BinaryExpr)
+			if ok {
+				vss = bexpr.Y
+			}
+
+			_, ok = vss.(*ast.Ident)
 			if ok {
 				return nil // iota
 			}

testdata/consts_iota.go

@@ -4,5 +4,6 @@ const (
 	Bla          = "iota"
 	Consts_iota  = iota
 	Consts_iota2 = iota + 1
+	Consts_iota0 = 1 << iota
 	Consts_iota1
 )