Merge #1328

1328: Change TokenSource to iteration based r=matklad a=edwin0cheng

This PR change the `TokenSource` trait from random access to be an iteration based trait:
```rust

/// `TokenSource` abstracts the source of the tokens parser operates one.
///
/// Hopefully this will allow us to treat text and token trees in the same way!
pub trait TokenSource {
    fn current(&self) -> Token;

    /// Lookahead n token
    fn lookahead_nth(&self, n: usize) -> Token;

    /// bump cursor to next token
    fn bump(&mut self);

    /// Is the current token a specified keyword?
    fn is_keyword(&self, kw: &str) -> bool;
}

/// `TokenCursor` abstracts the cursor of `TokenSource` operates one.
#[derive(Debug, Copy, Clone, Eq, PartialEq)]
pub struct Token {
    /// What is the current token?
    pub kind: SyntaxKind,

    /// Is the current token joined to the next one (`> >` vs `>>`).
    pub is_jointed_to_next: bool,
}
```

Note that the refactoring based on this new trait will be separated to incoming PRs

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

1 files changed, 2 insertions, 2 deletions

diff --git a/crates/ra_syntax/src/parsing/reparsing.rs b/crates/ra_syntax/src/parsing/reparsing.rs
index 6de02a15a..3b6687f61 100644
--- a/crates/ra_syntax/src/parsing/reparsing.rs
+++ b/crates/ra_syntax/src/parsing/reparsing.rs
@@ -85,9 +85,9 @@ fn reparse_block<'node>(
     if !is_balanced(&tokens) {
         return None;
     }
-    let token_source = TextTokenSource::new(&text, &tokens);
+    let mut token_source = TextTokenSource::new(&text, &tokens);
     let mut tree_sink = TextTreeSink::new(&text, &tokens);
-    reparser.parse(&token_source, &mut tree_sink);
+    reparser.parse(&mut token_source, &mut tree_sink);
     let (green, new_errors) = tree_sink.finish();
     Some((node.replace_with(green), new_errors, node.range()))
 }