Make generics work in struct patterns

3 files changed, 87 insertions, 17 deletions

diff --git a/crates/ra_hir/src/ty.rs b/crates/ra_hir/src/ty.rs
index 1d2d1b906..3608daae4 100644
--- a/crates/ra_hir/src/ty.rs
+++ b/crates/ra_hir/src/ty.rs
@@ -683,9 +683,9 @@ pub(super) fn type_for_def(db: &impl HirDatabase, def_id: DefId) -> Ty {
 
 pub(super) fn type_for_field(db: &impl HirDatabase, def_id: DefId, field: Name) -> Option<Ty> {
     let def = def_id.resolve(db);
-    let variant_data = match def {
-        Def::Struct(s) => s.variant_data(db),
-        Def::EnumVariant(ev) => ev.variant_data(db),
+    let (variant_data, generics) = match def {
+        Def::Struct(s) => (s.variant_data(db), s.generics(db)),
+        Def::EnumVariant(ev) => (ev.variant_data(db), ev.parent_enum(db).generics(db)),
         // TODO: unions
         _ => panic!(
             "trying to get type for field in non-struct/variant {:?}",
@@ -694,7 +694,6 @@ pub(super) fn type_for_field(db: &impl HirDatabase, def_id: DefId, field: Name)
     };
     let module = def_id.module(db);
     let impl_block = def_id.impl_block(db);
-    let generics = db.generics(def_id);
     let type_ref = variant_data.get_field_type_ref(&field)?;
     Some(Ty::from_hir(
         db,
@@ -893,6 +892,14 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         ty
     }
 
+    fn unify_substs(&mut self, substs1: &Substs, substs2: &Substs) -> bool {
+        substs1
+            .0
+            .iter()
+            .zip(substs2.0.iter())
+            .all(|(t1, t2)| self.unify(t1, t2))
+    }
+
     fn unify(&mut self, ty1: &Ty, ty2: &Ty) -> bool {
         // try to resolve type vars first
         let ty1 = self.resolve_ty_shallow(ty1);
@@ -913,12 +920,16 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             (Ty::Bool, _) | (Ty::Str, _) | (Ty::Never, _) | (Ty::Char, _) => ty1 == ty2,
             (
                 Ty::Adt {
-                    def_id: def_id1, ..
+                    def_id: def_id1,
+                    substs: substs1,
+                    ..
                 },
                 Ty::Adt {
-                    def_id: def_id2, ..
+                    def_id: def_id2,
+                    substs: substs2,
+                    ..
                 },
-            ) if def_id1 == def_id2 => true,
+            ) if def_id1 == def_id2 => self.unify_substs(substs1, substs2),
             (Ty::Slice(t1), Ty::Slice(t2)) => self.unify(t1, t2),
             (Ty::RawPtr(t1, m1), Ty::RawPtr(t2, m2)) if m1 == m2 => self.unify(t1, t2),
             (Ty::Ref(t1, m1), Ty::Ref(t2, m2)) if m1 == m2 => self.unify(t1, t2),
@@ -1088,49 +1099,65 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         }
     }
 
-    fn resolve_fields(&self, path: Option<&Path>) -> Option<(Ty, Vec<StructField>)> {
-        let def_id = self.module.resolve_path(self.db, path?).take_types()?;
+    fn resolve_fields(&mut self, path: Option<&Path>) -> Option<(Ty, Vec<StructField>)> {
+        let (ty, def_id) = self.resolve_variant(path);
+        let def_id = def_id?;
         let def = def_id.resolve(self.db);
 
         match def {
             Def::Struct(s) => {
                 let fields = s.fields(self.db);
-                Some((type_for_struct(self.db, s), fields))
+                Some((ty, fields))
             }
             Def::EnumVariant(ev) => {
                 let fields = ev.fields(self.db);
-                Some((type_for_enum_variant(self.db, ev), fields))
+                Some((ty, fields))
             }
             _ => None,
         }
     }
 
-    fn infer_tuple_struct_pat(&mut self, path: Option<&Path>, subpats: &[PatId]) -> Ty {
+    fn infer_tuple_struct_pat(
+        &mut self,
+        path: Option<&Path>,
+        subpats: &[PatId],
+        expected: &Ty,
+    ) -> Ty {
         let (ty, fields) = self
             .resolve_fields(path)
             .unwrap_or((Ty::Unknown, Vec::new()));
 
+        self.unify(&ty, expected);
+
+        let substs = ty.substs().expect("adt should have substs");
+
         for (i, &subpat) in subpats.iter().enumerate() {
             let expected_ty = fields
                 .get(i)
                 .and_then(|field| field.ty(self.db))
-                .unwrap_or(Ty::Unknown);
+                .unwrap_or(Ty::Unknown)
+                .subst(&substs);
             self.infer_pat(subpat, &expected_ty);
         }
 
         ty
     }
 
-    fn infer_struct_pat(&mut self, path: Option<&Path>, subpats: &[FieldPat]) -> Ty {
+    fn infer_struct_pat(&mut self, path: Option<&Path>, subpats: &[FieldPat], expected: &Ty) -> Ty {
         let (ty, fields) = self
             .resolve_fields(path)
             .unwrap_or((Ty::Unknown, Vec::new()));
 
+        self.unify(&ty, expected);
+
+        let substs = ty.substs().expect("adt should have substs");
+
         for subpat in subpats {
             let matching_field = fields.iter().find(|field| field.name() == &subpat.name);
             let expected_ty = matching_field
                 .and_then(|field| field.ty(self.db))
-                .unwrap_or(Ty::Unknown);
+                .unwrap_or(Ty::Unknown)
+                .subst(&substs);
             self.infer_pat(subpat.pat, &expected_ty);
         }
 
@@ -1175,11 +1202,11 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             Pat::TupleStruct {
                 path: ref p,
                 args: ref subpats,
-            } => self.infer_tuple_struct_pat(p.as_ref(), subpats),
+            } => self.infer_tuple_struct_pat(p.as_ref(), subpats, expected),
             Pat::Struct {
                 path: ref p,
                 args: ref fields,
-            } => self.infer_struct_pat(p.as_ref(), fields),
+            } => self.infer_struct_pat(p.as_ref(), fields, expected),
             Pat::Path(path) => self
                 .module
                 .resolve_path(self.db, &path)
diff --git a/crates/ra_hir/src/ty/tests.rs b/crates/ra_hir/src/ty/tests.rs
index c590a09db..06e32df59 100644
--- a/crates/ra_hir/src/ty/tests.rs
+++ b/crates/ra_hir/src/ty/tests.rs
@@ -439,6 +439,32 @@ fn test(a1: A<u32>, i: i32) {
 }
 
 #[test]
+fn infer_generics_in_patterns() {
+    check_inference(
+        r#"
+struct A<T> {
+    x: T,
+}
+
+enum Option<T> {
+    Some(T),
+    None,
+}
+
+fn test(a1: A<u32>, o: Option<u64>) {
+    let A { x: x2 } = a1;
+    let A::<i64> { x: x3 } = A { x: 1 };
+    match o {
+        Option::Some(t) => t,
+        _ => 1,
+    };
+}
+"#,
+        "generics_in_patterns.txt",
+    );
+}
+
+#[test]
 fn infer_function_generics() {
     check_inference(
         r#"
diff --git a/crates/ra_hir/src/ty/tests/data/generics_in_patterns.txt b/crates/ra_hir/src/ty/tests/data/generics_in_patterns.txt
new file mode 100644
index 000000000..1b01ef19e
--- /dev/null
+++ b/crates/ra_hir/src/ty/tests/data/generics_in_patterns.txt
@@ -0,0 +1,17 @@
+[79; 81) 'a1': A<u32>
+[91; 92) 'o': Option<u64>
+[107; 244) '{     ...  }; }': ()
+[117; 128) 'A { x: x2 }': A<u32>
+[124; 126) 'x2': u32
+[131; 133) 'a1': A<u32>
+[143; 161) 'A::<i6...: x3 }': A<i64>
+[157; 159) 'x3': i64
+[164; 174) 'A { x: 1 }': A<i64>
+[171; 172) '1': i64
+[180; 241) 'match ...     }': u64
+[186; 187) 'o': Option<u64>
+[198; 213) 'Option::Some(t)': Option<u64>
+[211; 212) 't': u64
+[217; 218) 't': u64
+[228; 229) '_': Option<u64>
+[233; 234) '1': u64