support ref-patterns

crates/ra_hir/src/code_model_impl/function/scope.rs

@@ -422,6 +422,9 @@ mod tests {
     fn do_check_local_name(code: &str, expected_offset: u32) {
         let (off, code) = extract_offset(code);
         let file = SourceFile::parse(&code);
+        let expected_name = find_node_at_offset::<ast::Name>(file.syntax(), expected_offset.into())
+            .expect("failed to find a name at the target offset");
+
         let fn_def: &ast::FnDef = find_node_at_offset(file.syntax(), off).unwrap();
         let name_ref: &ast::NameRef = find_node_at_offset(file.syntax(), off).unwrap();
 
@@ -431,11 +434,8 @@ mod tests {
             scopes: Arc::new(scopes),
             syntax_mapping: Arc::new(body_hir),
         };
-
         let local_name_entry = scopes.resolve_local_name(name_ref).unwrap();
         let local_name = local_name_entry.ptr();
-        let expected_name =
-            find_node_at_offset::<ast::Name>(file.syntax(), expected_offset.into()).unwrap();
         assert_eq!(local_name.range(), expected_name.syntax().range());
     }
 
@@ -470,11 +470,26 @@ mod tests {
     fn test_resolve_local_name_shadow() {
         do_check_local_name(
             r"
-        fn foo(x: String) {
+            fn foo(x: String) {
-            let x : &str = &x;
+                let x : &str = &x;
-            x<|>
+                x<|>
-        }",
+            }
-            46,
+            ",
+            53,
+        );
+    }
+
+    #[test]
+    fn ref_patterns_contribute_bindings() {
+        do_check_local_name(
+            r"
+            fn foo() {
+                if let Some(&from) = bar() {
+                    from<|>;
+                }
+            }
+            ",
+            53,
         );
     }
 }

crates/ra_hir/src/expr.rs

@@ -315,15 +315,20 @@ pub enum Pat {
         path: Option<Path>,
         args: Vec<PatId>,
     },
+    Ref {
+        pat: PatId,
+        mutability: Mutability,
+    },
 }
 
 impl Pat {
-    pub fn walk_child_pats(&self, f: impl FnMut(PatId)) {
+    pub fn walk_child_pats(&self, mut f: impl FnMut(PatId)) {
         match self {
             Pat::Missing | Pat::Bind { .. } => {}
             Pat::TupleStruct { args, .. } => {
                 args.iter().map(|pat| *pat).for_each(f);
             }
+            Pat::Ref { pat, .. } => f(*pat),
         }
     }
 }
@@ -684,6 +689,11 @@ impl ExprCollector {
                 let args = p.args().map(|p| self.collect_pat(p)).collect();
                 self.alloc_pat(Pat::TupleStruct { path, args }, syntax_ptr)
             }
+            ast::PatKind::RefPat(p) => {
+                let pat = self.collect_pat_opt(p.pat());
+                let mutability = Mutability::from_mutable(p.is_mut());
+                self.alloc_pat(Pat::Ref { pat, mutability }, syntax_ptr)
+            }
             _ => {
                 // TODO
                 self.alloc_pat(Pat::Missing, syntax_ptr)

crates/ra_syntax/src/ast.rs

@@ -348,6 +348,12 @@ impl UseTreeList {
     }
 }
 
+impl RefPat {
+    pub fn is_mut(&self) -> bool {
+        self.syntax().children().any(|n| n.kind() == MUT_KW)
+    }
+}
+
 fn child_opt<P: AstNode, C: AstNode>(parent: &P) -> Option<&C> {
     children(parent).next()
 }

crates/ra_syntax/src/ast/generated.rs

@@ -2456,7 +2456,11 @@ impl AstNode for RefPat {
 }
 
 
-impl RefPat {}
+impl RefPat {
+    pub fn pat(&self) -> Option<&Pat> {
+        super::child_opt(self)
+    }
+}
 
 // ReferenceType
 #[derive(Debug, PartialEq, Eq, Hash)]

crates/ra_syntax/src/grammar.ron

@@ -462,7 +462,7 @@ Grammar(
             ],
         ),
 
-        "RefPat": (),
+        "RefPat": ( options: [ "Pat" ]),
         "BindPat": ( traits: ["NameOwner"] ),
         "PlaceholderPat": (),
         "PathPat": (),