use newtype parttern for langauge server id

helix-core/src/diagnostic.rs

@@ -1,4 +1,6 @@
 //! LSP diagnostic utility types.
+use std::fmt;
+
 use serde::{Deserialize, Serialize};
 
 /// Describes the severity level of a [`Diagnostic`].
@@ -47,8 +49,25 @@ pub struct Diagnostic {
     pub message: String,
     pub severity: Option<Severity>,
     pub code: Option<NumberOrString>,
-    pub language_server_id: usize,
+    pub provider: DiagnosticProvider,
     pub tags: Vec<DiagnosticTag>,
     pub source: Option<String>,
     pub data: Option<serde_json::Value>,
 }
+
+// TODO turn this into an enum + feature flag when lsp becomes optional
+pub type DiagnosticProvider = LanguageServerId;
+
+// while I would prefer having this in helix-lsp that necessitates a bunch of
+// conversions I would rather not add. I think its fine since this just a very
+// trivial newtype wrapper and we would need something similar once we define
+// completions in core
+slotmap::new_key_type! {
+    pub struct LanguageServerId;
+}
+
+impl fmt::Display for LanguageServerId {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{:?}", self.0)
+    }
+}