2 files changed, 39 insertions, 8 deletions

diff --git a/crates/ra_hir_ty/src/method_resolution.rs b/crates/ra_hir_ty/src/method_resolution.rs
index 69c059ac8..533c6ccfb 100644
--- a/crates/ra_hir_ty/src/method_resolution.rs
+++ b/crates/ra_hir_ty/src/method_resolution.rs
@@ -95,14 +95,14 @@ impl Ty {
         // Types like slice can have inherent impls in several crates, (core and alloc).
         // The corresponding impls are marked with lang items, so we can use them to find the required crates.
         macro_rules! lang_item_crate {
-        ($($name:expr),+ $(,)?) => {{
-            let mut v = ArrayVec::<[LangItemTarget; 2]>::new();
-            $(
-                v.extend(db.lang_item(cur_crate, $name.into()));
-            )+
-            v
-        }};
-    }
+            ($($name:expr),+ $(,)?) => {{
+                let mut v = ArrayVec::<[LangItemTarget; 2]>::new();
+                $(
+                    v.extend(db.lang_item(cur_crate, $name.into()));
+                )+
+                v
+            }};
+        }
 
         let lang_item_targets = match self {
             Ty::Apply(a_ty) => match a_ty.ctor {
diff --git a/crates/ra_hir_ty/src/tests/regression.rs b/crates/ra_hir_ty/src/tests/regression.rs
index 14c8ed3a9..a02e3ee05 100644
--- a/crates/ra_hir_ty/src/tests/regression.rs
+++ b/crates/ra_hir_ty/src/tests/regression.rs
@@ -453,3 +453,34 @@ pub mod str {
     // should be Option<char>, but currently not because of Chalk ambiguity problem
     assert_eq!("(Option<{unknown}>, Option<{unknown}>)", super::type_at_pos(&db, pos));
 }
+
+#[test]
+fn issue_3642_bad_macro_stackover() {
+    let (db, pos) = TestDB::with_position(
+        r#"
+//- /main.rs
+#[macro_export]
+macro_rules! match_ast {
+    (match $node:ident { $($tt:tt)* }) => { match_ast!(match ($node) { $($tt)* }) };
+
+    (match ($node:expr) {
+        $( ast::$ast:ident($it:ident) => $res:expr, )*
+        _ => $catch_all:expr $(,)?
+    }) => {{
+        $( if let Some($it) = ast::$ast::cast($node.clone()) { $res } else )*
+        { $catch_all }
+    }};
+}
+
+fn main() {
+    let anchor<|> = match_ast! {
+        match parent {
+            as => {},
+            _ => return None
+        }
+    };
+}"#,
+    );
+
+    assert_eq!("()", super::type_at_pos(&db, pos));
+}