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, 6 insertions, 0 deletions

diff --git a/crates/ra_syntax/src/ast/make.rs b/crates/ra_syntax/src/ast/make.rs
index 53d6fa562..ae8829807 100644
--- a/crates/ra_syntax/src/ast/make.rs
+++ b/crates/ra_syntax/src/ast/make.rs
@@ -267,6 +267,12 @@ pub mod tokens {
         sf.syntax().first_child_or_token().unwrap().into_token().unwrap()
     }
 
+    pub fn doc_comment(text: &str) -> SyntaxToken {
+        assert!(!text.trim().is_empty());
+        let sf = SourceFile::parse(text).ok().unwrap();
+        sf.syntax().first_child_or_token().unwrap().into_token().unwrap()
+    }
+
     pub fn literal(text: &str) -> SyntaxToken {
         assert_eq!(text.trim(), text);
         let lit: ast::Literal = super::ast_from_text(&format!("fn f() {{ let _ = {}; }}", text));