From 9c2d83a4c809b0b11ca389bb454e197859e5116c Mon Sep 17 00:00:00 2001
From: Marcus Klaas de Vries <mail@marcusklaas.nl>
Date: Wed, 16 Jan 2019 17:47:59 +0100
Subject: Add crude implementation of tuplestruct pattern inference

---
 crates/ra_hir/src/ty.rs                         | 81 +++++++++++++++++--------
 crates/ra_hir/src/ty/tests.rs                   | 36 ++++++-----
 crates/ra_hir/src/ty/tests/data/adt_pattern.txt | 12 ++++
 3 files changed, 89 insertions(+), 40 deletions(-)
 create mode 100644 crates/ra_hir/src/ty/tests/data/adt_pattern.txt

diff --git a/crates/ra_hir/src/ty.rs b/crates/ra_hir/src/ty.rs
index a13356714..cdecbd064 100644
--- a/crates/ra_hir/src/ty.rs
+++ b/crates/ra_hir/src/ty.rs
@@ -877,7 +877,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
     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) {
+        let ty = match (&body[pat], &expected.ty) {
             (Pat::Tuple(ref args), &Ty::Tuple(ref tuple_args))
                 if args.len() == tuple_args.len() =>
             {
@@ -885,42 +885,71 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                     // FIXME: can we do w/o cloning?
                     self.infer_pat(pat, &Expectation::has_type(ty.clone()));
                 }
+                expected.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()));
+                expected.ty.clone()
             }
-            (pattern, &Ty::Adt { def_id, .. }) => {
-                let adt_def = def_id.resolve(self.db);
-                match (pattern, adt_def) {
-                    (&Pat::Struct, Def::Struct(s)) => {}
-                    (
-                        &Pat::TupleStruct {
-                            path: ref p,
-                            args: ref sub_pats,
-                        },
-                        Def::Enum(ref e),
-                    ) => {
-                        // TODO: resolve enum
-                    }
-                    (
-                        &Pat::TupleStruct {
-                            path: ref p,
-                            args: ref sub_pats,
-                        },
-                        Def::EnumVariant(ref e),
-                    ) => {
-                        let variant_data = self.db.enum_variant_data(e.def_id);
+            (
+                &Pat::TupleStruct {
+                    path: ref p,
+                    args: ref sub_pats,
+                },
+                _expected,
+            ) => {
+                let def = p
+                    .as_ref()
+                    .and_then(|path| self.module.resolve_path(self.db, &path).take_types())
+                    .map(|def_id| def_id.resolve(self.db));
+
+                if let Some(def) = def {
+                    let (ty, fields) = match def {
+                        Def::Struct(s) => {
+                            let fields: Vec<_> = self
+                                .db
+                                .struct_data(s.def_id())
+                                .variant_data
+                                .fields()
+                                .iter()
+                                .cloned()
+                                .collect();
+                            (type_for_struct(self.db, s), fields)
+                        }
+                        Def::EnumVariant(ev) => {
+                            let fields: Vec<_> =
+                                ev.variant_data(self.db).fields().iter().cloned().collect();
+                            (type_for_enum_variant(self.db, ev), fields)
+                        }
+                        _ => unreachable!(),
+                    };
+                    // walk subpats
+                    if fields.len() == sub_pats.len() {
+                        for (&sub_pat, field) in sub_pats.iter().zip(fields.iter()) {
+                            let sub_ty = Ty::from_hir(
+                                self.db,
+                                &self.module,
+                                self.impl_block.as_ref(),
+                                &field.type_ref,
+                            );
+
+                            self.infer_pat(sub_pat, &Expectation::has_type(sub_ty));
+                        }
+
+                        ty
+                    } else {
+                        expected.ty.clone()
                     }
-                    _ => {}
+                } else {
+                    expected.ty.clone()
                 }
             }
-            // TODO: implement more
-            (_, ref _expected_ty) => {}
+            (_, ref _expected_ty) => expected.ty.clone(),
         };
         // use a new type variable if we got Ty::Unknown here
-        let ty = self.insert_type_vars_shallow(expected.ty.clone());
+        let ty = self.insert_type_vars_shallow(ty);
         self.unify(&ty, &expected.ty);
         let ty = self.resolve_ty_as_possible(ty);
         self.write_pat_ty(pat, ty.clone());
diff --git a/crates/ra_hir/src/ty/tests.rs b/crates/ra_hir/src/ty/tests.rs
index ff2c8b0d4..75fe2cc6e 100644
--- a/crates/ra_hir/src/ty/tests.rs
+++ b/crates/ra_hir/src/ty/tests.rs
@@ -359,31 +359,39 @@ fn test(x: &str, y: isize) {
 }
 
 #[test]
-fn infer_pattern() {
+fn infer_simple_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");
+}
+"#,
+        "pattern.txt",
+    );
+}
+
+#[test]
+fn infer_adt_pattern() {
+    check_inference(
+        r#"
+enum E {
+    A { x: usize },
+    B
+}
+
+struct S(u32, E);
 
+fn test() {
     let e = E::A { x: 3 };
-    if let E::A { x: x } = e {
-        x
-    };
-    match e {
-        E::A { x } => x,
-        E::B => 1,
-    };
+
+    let S(y, z) = foo;
+    let E::A { x: new_var } = e;
 }
 "#,
-        "pattern.txt",
+        "adt_pattern.txt",
     );
 }
 
diff --git a/crates/ra_hir/src/ty/tests/data/adt_pattern.txt b/crates/ra_hir/src/ty/tests/data/adt_pattern.txt
new file mode 100644
index 000000000..d23b865a0
--- /dev/null
+++ b/crates/ra_hir/src/ty/tests/data/adt_pattern.txt
@@ -0,0 +1,12 @@
+[49; 192) '{     ...  }; }': ()
+[59; 60) 'e': E
+[63; 76) 'E::A { x: 3 }': E
+[73; 74) '3': usize
+[82; 124) 'if let...     }': [unknown]
+[105; 106) 'e': E
+[107; 124) '{     ...     }': [unknown]
+[117; 118) 'x': [unknown]
+[130; 189) 'match ...     }': [unknown]
+[136; 137) 'e': E
+[162; 163) 'x': [unknown]
+[181; 182) '1': i32
-- 
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