Start on a DiagnosticProvider implementation for Rust

Co-Authored-By: Nathan Sobo <nathan@zed.dev>

crates/language/src/buffer.rs

@@ -805,10 +805,13 @@ impl Buffer {
                     }
                 }
 
+                let start_overshoot = start - last_edit_old_end;
                 start = last_edit_new_end;
-                start.add_assign(&(start - last_edit_old_end));
+                start.add_assign(&start_overshoot);
+
+                let end_overshoot = end - last_edit_old_end;
                 end = last_edit_new_end;
-                end.add_assign(&(end - last_edit_old_end));
+                end.add_assign(&end_overshoot);
             }
 
             let range = start.clip(Bias::Left, content)..end.clip(Bias::Right, content);

crates/language/src/language.rs

@@ -9,18 +9,14 @@ use anyhow::{anyhow, Result};
 use async_trait::async_trait;
 pub use buffer::Operation;
 pub use buffer::*;
-use collections::HashSet;
+use collections::{HashMap, HashSet};
 pub use diagnostic_set::DiagnosticEntry;
 use gpui::AppContext;
 use highlight_map::HighlightMap;
 use lazy_static::lazy_static;
 use parking_lot::Mutex;
 use serde::Deserialize;
-use std::{
-    path::{Path, PathBuf},
-    str,
-    sync::Arc,
-};
+use std::{path::Path, str, sync::Arc};
 use theme::SyntaxTheme;
 use tree_sitter::{self, Query};
 pub use tree_sitter::{Parser, Tree};
@@ -69,7 +65,7 @@ pub trait DiagnosticProvider: 'static + Send + Sync {
     async fn diagnose(
         &self,
         path: Arc<Path>,
-    ) -> Result<Vec<(PathBuf, Vec<DiagnosticEntry<usize>>)>>;
+    ) -> Result<HashMap<Arc<Path>, Vec<DiagnosticEntry<usize>>>>;
 }
 
 pub struct Language {