3 files changed, 58 insertions, 7 deletions

diff --git a/crates/ra_hir/src/ty.rs b/crates/ra_hir/src/ty.rs
index 854d3e3d9..324df5ef9 100644
--- a/crates/ra_hir/src/ty.rs
+++ b/crates/ra_hir/src/ty.rs
@@ -36,7 +36,7 @@ use crate::{
     db::HirDatabase,
     type_ref::{TypeRef, Mutability},
     name::KnownName,
-    expr::{Body, Expr, Literal, ExprId, PatId, UnaryOp, BinaryOp, Statement},
+    expr::{Body, Expr, Literal, ExprId, Pat, PatId, UnaryOp, BinaryOp, Statement},
 };
 
 /// The ID of a type variable.
@@ -872,6 +872,35 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         }
     }
 
+    // FIXME: Expectation should probably contain a reference to a Ty instead of
+    // a Ty itself
+    fn infer_pat(&mut self, pat: PatId, expected: &Expectation) -> Ty {
+        let body = Arc::clone(&self.body); // avoid borrow checker problem
+        match (&body[pat], &expected.ty) {
+            (Pat::Tuple(ref args), &Ty::Tuple(ref tuple_args))
+                if args.len() == tuple_args.len() =>
+            {
+                for (&pat, ty) in args.iter().zip(tuple_args.iter()) {
+                    // FIXME: can we do w/o cloning?
+                    self.infer_pat(pat, &Expectation::has_type(ty.clone()));
+                }
+            }
+            (&Pat::Ref { pat, mutability }, &Ty::Ref(ref sub_ty, ty_mut))
+                if mutability == ty_mut =>
+            {
+                self.infer_pat(pat, &Expectation::has_type((&**sub_ty).clone()));
+            }
+            // TODO: implement more
+            (_, ref _expected_ty) => {}
+        };
+        // use a new type variable if we got Ty::Unknown here
+        let ty = self.insert_type_vars_shallow(expected.ty.clone());
+        self.unify(&ty, &expected.ty);
+        let ty = self.resolve_ty_as_possible(ty);
+        self.write_pat_ty(pat, ty.clone());
+        ty
+    }
+
     fn infer_expr(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
         let body = Arc::clone(&self.body); // avoid borrow checker problem
         let ty = match &body[expr] {
@@ -1168,9 +1197,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                         decl_ty
                     };
 
-                    // TODO: walk the pattern here?
-
-                    self.write_pat_ty(*pat, ty);
+                    self.infer_pat(*pat, &Expectation::has_type(ty))?;
                 }
                 Statement::Expr(expr) => {
                     self.infer_expr(*expr, &Expectation::none());
@@ -1191,9 +1218,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             let ty = self.make_ty(type_ref);
             let ty = self.insert_type_vars(ty);
 
-            // TODO: walk pattern?
-
-            self.write_pat_ty(*pat, ty);
+            self.infer_pat(*pat, &Expectation::has_type(ty))?;
         }
         self.return_ty = {
             let ty = self.make_ty(signature.ret_type());
diff --git a/crates/ra_hir/src/ty/tests.rs b/crates/ra_hir/src/ty/tests.rs
index fc1e5b09c..a55551cbb 100644
--- a/crates/ra_hir/src/ty/tests.rs
+++ b/crates/ra_hir/src/ty/tests.rs
@@ -362,11 +362,22 @@ fn test(x: &str, y: isize) {
 fn infer_pattern() {
     check_inference(
         r#"
+enum E { A { x: usize }, B }
+
 fn test(x: &i32) {
     let y = x;
     let &z = x;
     let a = z;
     let (c, d) = (1, "hello");
+
+    let e = E::A { x: 3 };
+    if let E::A { x: x } = e {
+        x
+    };
+    match e {
+        E::A { x } => x,
+        E::B => 1,
+    };
 }
 "#,
         "pattern.txt",
diff --git a/crates/ra_hir/src/ty/tests/data/pattern.txt b/crates/ra_hir/src/ty/tests/data/pattern.txt
new file mode 100644
index 000000000..cca521833
--- /dev/null
+++ b/crates/ra_hir/src/ty/tests/data/pattern.txt
@@ -0,0 +1,15 @@
+[9; 10) 'x': &i32
+[18; 98) '{     ...o"); }': ()
+[28; 29) 'y': &i32
+[32; 33) 'x': &i32
+[43; 45) '&z': &i32
+[44; 45) 'z': i32
+[48; 49) 'x': &i32
+[59; 60) 'a': i32
+[63; 64) 'z': i32
+[74; 80) '(c, d)': (i32, &str)
+[75; 76) 'c': i32
+[78; 79) 'd': &str
+[83; 95) '(1, "hello")': (i32, &str)
+[84; 85) '1': i32
+[87; 94) '"hello"': &str