Map attribute input tokens correctly

crates/mbe/src/token_map.rs

@@ -1,5 +1,7 @@
 //! Mapping between `TokenId`s and the token's position in macro definitions or inputs.
 
+use std::hash::Hash;
+
 use parser::{SyntaxKind, T};
 use syntax::{TextRange, TextSize};
 
@@ -24,6 +26,25 @@ impl TokenTextRange {
     }
 }
 
+#[derive(Debug, Clone, Default)]
+pub struct MappedSubTree {
+    pub tree: tt::Subtree,
+    pub map: TokenMap,
+}
+
+impl Eq for MappedSubTree {}
+impl PartialEq for MappedSubTree {
+    fn eq(&self, other: &Self) -> bool {
+        self.tree == other.tree && self.map == other.map
+    }
+}
+
+impl Hash for MappedSubTree {
+    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+        self.tree.hash(state);
+    }
+}
+
 /// Maps `tt::TokenId` to the relative range of the original token.
 #[derive(Debug, PartialEq, Eq, Clone, Default)]
 pub struct TokenMap {