Fix panic trying to get substs on unknown type

Fixes #585.

3 files changed, 27 insertions, 3 deletions

diff --git a/crates/ra_hir/src/ty.rs b/crates/ra_hir/src/ty.rs
index c602450e1..e690ae158 100644
--- a/crates/ra_hir/src/ty.rs
+++ b/crates/ra_hir/src/ty.rs
@@ -1134,7 +1134,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
         self.unify(&ty, expected);
 
-        let substs = ty.substs().expect("adt should have substs");
+        let substs = ty.substs().unwrap_or_else(Substs::empty);
 
         for (i, &subpat) in subpats.iter().enumerate() {
             let expected_ty = fields
@@ -1155,7 +1155,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
         self.unify(&ty, expected);
 
-        let substs = ty.substs().expect("adt should have substs");
+        let substs = ty.substs().unwrap_or_else(Substs::empty);
 
         for subpat in subpats {
             let matching_field = fields.iter().find(|field| field.name() == &subpat.name);
@@ -1403,7 +1403,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 spread,
             } => {
                 let (ty, def_id) = self.resolve_variant(path.as_ref());
-                let substs = ty.substs().expect("adt should have substs");
+                let substs = ty.substs().unwrap_or_else(Substs::empty);
                 for field in fields {
                     let field_ty = if let Some(def_id) = def_id {
                         self.db
diff --git a/crates/ra_hir/src/ty/tests.rs b/crates/ra_hir/src/ty/tests.rs
index 5aa24a29b..dc9b626dc 100644
--- a/crates/ra_hir/src/ty/tests.rs
+++ b/crates/ra_hir/src/ty/tests.rs
@@ -521,6 +521,22 @@ fn test(x: X) {
     );
 }
 
+#[test]
+fn bug_585() {
+    check_inference(
+        r#"
+fn test() {
+    X {};
+    match x {
+        A::B {} => (),
+        A::Y() => (),
+    }
+}
+"#,
+        "bug_585.txt",
+    );
+}
+
 fn infer(content: &str) -> String {
     let (db, _, file_id) = MockDatabase::with_single_file(content);
     let source_file = db.source_file(file_id);
diff --git a/crates/ra_hir/src/ty/tests/data/bug_585.txt b/crates/ra_hir/src/ty/tests/data/bug_585.txt
new file mode 100644
index 000000000..627702a38
--- /dev/null
+++ b/crates/ra_hir/src/ty/tests/data/bug_585.txt
@@ -0,0 +1,8 @@
+[11; 89) '{     ...   } }': ()
+[17; 21) 'X {}': [unknown]
+[27; 87) 'match ...     }': ()
+[33; 34) 'x': [unknown]
+[45; 52) 'A::B {}': [unknown]
+[56; 58) '()': ()
+[68; 74) 'A::Y()': [unknown]
+[78; 80) '()': ()