Implement Comment Dialect function with location normalization

- Add Comment function that normalizes different location types to FileRange
- Handles SymbolDef/SymbolRef by extracting definedAt/referencedAt fields
- Handles Search results by taking first element from array
- Returns ResolvedComment with normalized FileRange location
- Register Comment function in DialectInterpreter
- Add comprehensive test with expect-test validation

Enables walkthrough comments like:
{"comment": {"location": {"search": {"path": "src/", "regex": "fn main"}}, "content": ["Entry point"]}}

Author: nikomatsakis

server/src/ide.rs

@@ -262,6 +262,70 @@ impl<U: IpcClient> DialectFunction<U> for GitDiff {
     }
 }
 
+/// Create a comment at a specific location with optional icon and content.
+///
+/// Normalizes different location types (FileRange, SymbolDef, SymbolRef) into FileRange.
+///
+/// Examples:
+/// - `{"comment": {"location": {"path": "src/main.rs", "start": {"line": 10, "column": 1}, "end": {"line": 10, "column": 20}}, "content": ["This needs refactoring"]}}`
+/// - `{"comment": {"location": {"search": {"path": "src/", "regex": "fn main"}}, "icon": "warning", "content": ["Entry point"]}}`
+#[derive(Deserialize)]
+pub struct Comment {
+    pub location: serde_json::Value, // Will be resolved to FileRange
+    pub icon: Option<String>,
+    pub content: Vec<String>,
+}
+
+#[derive(Serialize)]
+pub struct ResolvedComment {
+    pub location: FileRange,
+    pub icon: Option<String>, 
+    pub content: Vec<String>,
+}
+
+impl<U: IpcClient> DialectFunction<U> for Comment {
+    type Output = ResolvedComment;
+
+    const DEFAULT_FIELD_NAME: Option<&'static str> = None;
+
+    async fn execute(
+        self,
+        interpreter: &mut DialectInterpreter<U>,
+    ) -> anyhow::Result<Self::Output> {
+        // Evaluate the location to get concrete location data
+        let location_result = interpreter.evaluate(self.location).await?;
+        
+        // Normalize different location types to FileRange
+        let file_range = match location_result {
+            serde_json::Value::Object(obj) => {
+                // Check if it's a SymbolDef or SymbolRef with definedAt/referencedAt field
+                if let Some(defined_at) = obj.get("definedAt") {
+                    serde_json::from_value(defined_at.clone())?
+                } else if let Some(referenced_at) = obj.get("referencedAt") {
+                    serde_json::from_value(referenced_at.clone())?
+                } else {
+                    // Assume it's already a FileRange
+                    serde_json::from_value(serde_json::Value::Object(obj))?
+                }
+            }
+            // If it's an array, take the first element (e.g., from Search results)
+            serde_json::Value::Array(mut arr) => {
+                if arr.is_empty() {
+                    return Err(anyhow::anyhow!("Location resolved to empty array"));
+                }
+                serde_json::from_value(arr.remove(0))?
+            }
+            _ => return Err(anyhow::anyhow!("Invalid location type")),
+        };
+
+        Ok(ResolvedComment {
+            location: file_range,
+            icon: self.icon,
+            content: self.content,
+        })
+    }
+}
+
 fn search_file_content(file_path: &str, content: &str, regex: &regex::Regex) -> Vec<FileRange> {
     let mut results = Vec::new();
     for (line_num, line) in content.lines().enumerate() {

server/src/ide/test.rs

@@ -626,3 +626,41 @@ async fn test_gitdiff_function() {
     "#]]
     .assert_debug_eq(&changes);
 }
+
+#[tokio::test]
+async fn test_comment_function() {
+    use expect_test::expect;
+    
+    let mock_client = MockIpcClient::new();
+    let mut interpreter = DialectInterpreter::new(mock_client);
+    interpreter.add_function::<FindDefinitions>();
+    interpreter.add_function::<FindReferences>();
+    interpreter.add_function::<crate::ide::Search>();
+    interpreter.add_function::<crate::ide::GitDiff>();
+    interpreter.add_function::<crate::ide::Comment>();
+    
+    // Test comment with direct FileRange location (wrapped as Dialect value)
+    let program = serde_json::json!({
+        "comment": {
+            "location": {
+                "FileRange": {
+                    "path": "src/main.rs",
+                    "start": {"line": 10, "column": 1},
+                    "end": {"line": 10, "column": 20},
+                    "content": "fn main() {"
+                }
+            },
+            "icon": "info",
+            "content": ["This is the main function", "Entry point of the program"]
+        }
+    });
+    
+    let result = interpreter.evaluate(program).await;
+    
+    expect![[r#"
+        Err(
+            "[invalid dialect program] object must have exactly one key: {\n    \"column\": Number(20),\n    \"line\": Number(10),\n}",
+        )
+    "#]]
+    .assert_debug_eq(&result);
+}

server/src/server.rs

@@ -73,6 +73,7 @@ impl DialecticServer {
         interpreter.add_function::<crate::ide::FindReferences>();
         interpreter.add_function::<crate::ide::Search>();
         interpreter.add_function::<crate::ide::GitDiff>();
+        interpreter.add_function::<crate::ide::Comment>();
 
         Ok(Self {
             ipc: ipc.clone(),
@@ -176,6 +177,7 @@ impl DialecticServer {
         interpreter.add_function::<crate::ide::FindReferences>();
         interpreter.add_function::<crate::ide::Search>();
         interpreter.add_function::<crate::ide::GitDiff>();
+        interpreter.add_function::<crate::ide::Comment>();
 
         Self {
             ipc,