fix(check): Propagate metadata through parens

check/src/metadata.rs

@@ -65,7 +65,7 @@ impl ArcMetadata for MaybeMetadata {
     }
 }
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 enum MaybeMetadata {
     Empty,
     Data(Arc<Metadata>),
@@ -371,6 +371,7 @@ pub fn metadata(
                 Expr::MacroExpansion {
                     ref replacement, ..
                 } => self.metadata_expr(replacement),
+                Expr::Tuple { ref elems, .. } if elems.len() == 1 => self.metadata_expr(&elems[0]),
                 _ => {
                     ast::walk_expr(self, expr);
                     Default::default()

check/tests/metadata.rs

@@ -116,6 +116,31 @@ type Test = Int
     );
 }
 
+#[test]
+fn propagate_metadata_parens() {
+    let _ = env_logger::try_init();
+
+    let text = r#"
+/// The identity function
+let id x = x
+id
+"#;
+    let (mut expr, result) = support::typecheck_expr(text);
+
+    assert!(result.is_ok(), "{}", result.unwrap_err());
+
+    let metadata = metadata(&MockEnv, &mut expr);
+    assert_eq!(
+        metadata,
+        Metadata {
+            definition: Some(intern("id:32")),
+            comment: Some(line_comment("The identity function")),
+            args: vec![Argument::explicit(intern("x:35"))],
+            ..Metadata::default()
+        }
+    );
+}
+
 #[test]
 fn propagate_metadata_record_field_comment() {
     let _ = env_logger::try_init();