Merge #3518

3518: Add parse_to_token_tree r=matklad a=edwin0cheng

This PR introduce a function for parsing `&str` to `tt::TokenTree`:

```rust
// Convert a string to a `TokenTree`
pub fn parse_to_token_tree(text: &str) -> Option<(tt::Subtree, TokenMap)> {
````

Co-authored-by: Edwin Cheng <[email protected]>

1 files changed, 2 insertions, 1 deletions

diff --git a/crates/ra_mbe/src/lib.rs b/crates/ra_mbe/src/lib.rs
index 2c6ae5658..43afe24cc 100644
--- a/crates/ra_mbe/src/lib.rs
+++ b/crates/ra_mbe/src/lib.rs
@@ -31,7 +31,8 @@ pub enum ExpandError {
 }
 
 pub use crate::syntax_bridge::{
-    ast_to_token_tree, syntax_node_to_token_tree, token_tree_to_syntax_node, TokenMap,
+    ast_to_token_tree, parse_to_token_tree, syntax_node_to_token_tree, token_tree_to_syntax_node,
+    TokenMap,
 };
 
 /// This struct contains AST for a single `macro_rules` definition. What might