start token tree module

crates/ra_hir/src/macros.rs

@@ -1,3 +1,6 @@
+#[allow(unused)]
+mod token_tree;
+
 /// Machinery for macro expansion.
 ///
 /// One of the more complicated things about macros is managing the source code

crates/ra_hir/src/macros/token_tree.rs

@@ -0,0 +1,36 @@
+use ra_syntax::SmolStr;
+
+enum TokenTree {
+    Leaf(Leaf),
+    Subtree(Subtree),
+}
+
+enum Leaf {
+    Literal(Literal),
+    Punct(Punct),
+    Ident(Ident),
+}
+
+struct Subtree {
+    delimiter: Delimiter,
+    token_trees: Vec<TokenTree>,
+}
+
+enum Delimiter {
+    Parenthesis,
+    Brace,
+    Bracket,
+    None,
+}
+
+struct Literal {
+    text: SmolStr,
+}
+
+struct Punct {
+    char: char,
+}
+
+struct Ident {
+    text: SmolStr,
+}