Add resource drop source-map markers

Author: olwang

src/rust_lower.rs

@@ -526,6 +526,7 @@ impl<'a> RustLowerer<'a> {
                 ));
                 out.push_str(&format!("{pad}{{\n"));
                 self.lower_block(&stmt.body, out, indent + 1);
+                self.record_source_marker(out, indent + 1, "resource_drop", &stmt.span);
                 out.push_str(&format!("{pad}}}\n"));
             }
             Stmt::If(stmt) => {

tests/checker.rs

@@ -960,6 +960,33 @@ pub fn make_session(id: Int) -> Session {
     }));
 }
 
+#[test]
+fn rust_lowering_maps_with_resource_drop_points() {
+    let source = r#"
+fn copy(path: read Path) -> Result<Unit, FileError> {
+    with File.open_read(path: read path) as file {
+        File.read_all(file: mut file)?
+    }
+
+    return Ok(Unit)
+}
+"#;
+    let lowered =
+        lower_source_to_rust_with_map("resource.rss", source).expect("source should lower");
+
+    assert!(
+        lowered
+            .rust_source
+            .contains("// rss:span kind=resource_drop file=resource.rss")
+    );
+    assert!(
+        lowered
+            .source_map
+            .iter()
+            .any(|entry| entry.kind == "resource_drop" && entry.source.file == "resource.rss")
+    );
+}
+
 #[test]
 fn rustc_diagnostics_map_back_to_rsscript_source_spans() {
     let source = r#"