itroduce trait for ast tokens

crates/ra_syntax/src/validation/byte.rs

@@ -1,7 +1,7 @@
 //! Validation of byte literals
 
 use crate::{
-    ast::{self, AstNode},
+    ast::{self, AstNode, AstToken},
     string_lexing::{self, StringComponentKind},
     TextRange,
     validation::char,

crates/ra_syntax/src/validation/byte_string.rs

@@ -1,5 +1,5 @@
 use crate::{
-    ast::{self, AstNode},
+    ast::{self, AstNode, AstToken},
     string_lexing::{self, StringComponentKind},
     yellow::{
         SyntaxError,

crates/ra_syntax/src/validation/char.rs

@@ -5,7 +5,7 @@ use std::u32;
 use arrayvec::ArrayString;
 
 use crate::{
-    ast::{self, AstNode},
+    ast::{self, AstNode, AstToken},
     string_lexing::{self, StringComponentKind},
     TextRange,
     yellow::{

crates/ra_syntax/src/validation/string.rs

@@ -1,5 +1,5 @@
 use crate::{
-    ast::{self, AstNode},
+    ast::{self, AstNode, AstToken},
     string_lexing,
     yellow::{
         SyntaxError,