Auto merge of #6688 - Manishearth:smarter-root-lint, r=jdm

Handle type parameters in unused_must_root

fixes #6651

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components/plugins/lib.rs

@@ -27,6 +27,7 @@ use rustc::plugin::Registry;
 use syntax::ext::base::*;
 
 use syntax::parse::token::intern;
+use syntax::feature_gate::AttributeType::Whitelisted;
 
 // Public for documentation to show up
 /// Handles the auto-deriving for `#[derive(JSTraceable)]`
@@ -49,10 +50,13 @@ pub fn plugin_registrar(reg: &mut Registry) {
     reg.register_macro("to_lower", casing::expand_lower);
     reg.register_macro("to_upper", casing::expand_upper);
     reg.register_lint_pass(box lints::transmute_type::TransmutePass as LintPassObject);
-    reg.register_lint_pass(box lints::unrooted_must_root::UnrootedPass as LintPassObject);
+    reg.register_lint_pass(box lints::unrooted_must_root::UnrootedPass::new() as LintPassObject);
     reg.register_lint_pass(box lints::privatize::PrivatizePass as LintPassObject);
     reg.register_lint_pass(box lints::inheritance_integrity::InheritancePass as LintPassObject);
     reg.register_lint_pass(box lints::str_to_string::StrToStringPass as LintPassObject);
     reg.register_lint_pass(box lints::ban::BanPass as LintPassObject);
     reg.register_lint_pass(box tenacious::TenaciousPass as LintPassObject);
+    reg.register_attribute("must_root".to_string(), Whitelisted);
+    reg.register_attribute("servo_lang".to_string(), Whitelisted);
+    reg.register_attribute("allow_unrooted_interior".to_string(), Whitelisted);
 }

components/plugins/lints/unrooted_must_root.rs

@@ -6,8 +6,9 @@ use syntax::{ast, codemap, visit};
 use syntax::attr::AttrMetaMethods;
 use rustc::ast_map;
 use rustc::lint::{Context, LintPass, LintArray};
-use rustc::middle::{ty, def};
+use rustc::middle::ty;
-use utils::unsafe_context;
+use rustc::middle::astconv_util::ast_ty_to_prim_ty;
+use utils::{match_def_path, unsafe_context};
 
 declare_lint!(UNROOTED_MUST_ROOT, Deny,
               "Warn and report usage of unrooted jsmanaged objects");
@@ -25,27 +26,50 @@ declare_lint!(UNROOTED_MUST_ROOT, Deny,
 ///
 /// This helps catch most situations where pointers like `JS<T>` are used in a way that they can be invalidated by a
 /// GC pass.
-pub struct UnrootedPass;
+///
+/// Structs which have their own mechanism of rooting their unrooted contents (e.g. `ScriptTask`)
+/// can be marked as `#[allow(unrooted_must_root)]`. Smart pointers which root their interior type
+/// can be marked as `#[allow_unrooted_interior]`
+pub struct UnrootedPass {
+    in_new_function: bool
+}
 
-// Checks if a type has the #[must_root] annotation.
+impl UnrootedPass {
-// Unwraps pointers as well
+    pub fn new() -> UnrootedPass {
-// TODO (#3874, sort of): unwrap other types like Vec/Option/HashMap/etc
+        UnrootedPass {
-fn lint_unrooted_ty(cx: &Context, ty: &ast::Ty, warning: &str) {
+            in_new_function: true
-    match ty.node {
+        }
-        ast::TyVec(ref t) | ast::TyFixedLengthVec(ref t, _) =>
+    }
-            lint_unrooted_ty(cx, &**t, warning),
+}
-        ast::TyPath(..) => {
+
-                match cx.tcx.def_map.borrow()[&ty.id] {
+/// Checks if a type is unrooted or contains any owned unrooted types
-                    def::PathResolution{ base_def: def::DefTy(def_id, _), .. } => {
+fn is_unrooted_ty(cx: &Context, ty: &ty::TyS, in_new_function: bool) -> bool {
-                        if cx.tcx.has_attr(def_id, "must_root") {
+    let mut ret = false;
-                            cx.span_lint(UNROOTED_MUST_ROOT, ty.span, warning);
+    ty.maybe_walk(|t| {
-                        }
+        match t.sty {
-                    }
+            ty::TyStruct(did, _) |
-                    _ => (),
+            ty::TyEnum(did, _) => {
+                if cx.tcx.has_attr(did, "must_root") {
+                    ret = true;
+                    false
+                } else if cx.tcx.has_attr(did, "allow_unrooted_interior") {
+                    false
+                } else if match_def_path(cx, did, &["core", "cell", "Ref"])
+                        || match_def_path(cx, did, &["core", "cell", "RefMut"]) {
+                        // Ref and RefMut are borrowed pointers, okay to hold unrooted stuff
+                        // since it will be rooted elsewhere
+                    false
+                } else {
+                    true
                 }
-            }
+            },
-        _ => (),
+            ty::TyBox(..) if in_new_function => false, // box in new() is okay
-    };
+            ty::TyRef(..) => false, // don't recurse down &ptrs
+            ty::TyRawPtr(..) => false, // don't recurse down *ptrs
+            _ => true
+        }
+    });
+    ret
 }
 
 impl LintPass for UnrootedPass {
@@ -65,8 +89,10 @@ impl LintPass for UnrootedPass {
         };
         if item.attrs.iter().all(|a| !a.check_name("must_root")) {
             for ref field in def.fields.iter() {
-                lint_unrooted_ty(cx, &*field.node.ty,
+                if is_unrooted_ty(cx, cx.tcx.node_id_to_type(field.node.id), false) {
-                                 "Type must be rooted, use #[must_root] on the struct definition to propagate");
+                    cx.span_lint(UNROOTED_MUST_ROOT, field.span,
+                                 "Type must be rooted, use #[must_root] on the struct definition to propagate")
+                }
             }
         }
     }
@@ -77,8 +103,13 @@ impl LintPass for UnrootedPass {
             match var.node.kind {
                 ast::TupleVariantKind(ref vec) => {
                     for ty in vec.iter() {
-                        lint_unrooted_ty(cx, &*ty.ty,
+                        ast_ty_to_prim_ty(cx.tcx, &*ty.ty).map(|t| {
-                                         "Type must be rooted, use #[must_root] on the enum definition to propagate")
+                            if is_unrooted_ty(cx, t, false) {
+                                cx.span_lint(UNROOTED_MUST_ROOT, ty.ty.span,
+                                             "Type must be rooted, use #[must_root] on \
+                                              the enum definition to propagate")
+                            }
+                        });
                     }
                 }
                 _ => () // Struct variants already caught by check_struct_def
@@ -90,7 +121,10 @@ impl LintPass for UnrootedPass {
                 block: &ast::Block, _span: codemap::Span, id: ast::NodeId) {
         match kind {
             visit::FkItemFn(i, _, _, _, _, _) |
-            visit::FkMethod(i, _, _) if i.as_str() == "new" || i.as_str() == "new_inherited" => {
+            visit::FkMethod(i, _, _) if i.as_str() == "new"
+                                        || i.as_str() == "new_inherited"
+                                        || i.as_str() == "new_initialized" => {
+                self.in_new_function = true;
                 return;
             },
             visit::FkItemFn(_, _, style, _, _, _) => match style {
@@ -99,6 +133,7 @@ impl LintPass for UnrootedPass {
             },
             _ => ()
         }
+        self.in_new_function = false;
 
         if unsafe_context(&cx.tcx.map, id) {
             return;
@@ -107,8 +142,11 @@ impl LintPass for UnrootedPass {
         match block.rules {
             ast::DefaultBlock => {
                 for arg in decl.inputs.iter() {
-                    lint_unrooted_ty(cx, &*arg.ty,
+                    ast_ty_to_prim_ty(cx.tcx, &*arg.ty).map(|t| {
-                                     "Type must be rooted")
+                        if is_unrooted_ty(cx, t, false) {
+                            cx.span_lint(UNROOTED_MUST_ROOT, arg.ty.span, "Type must be rooted")
+                        }
+                    });
                 }
             }
             _ => () // fn is `unsafe`
@@ -120,7 +158,6 @@ impl LintPass for UnrootedPass {
     // Expressions which return out of blocks eventually end up in a `let` or assignment
     // statement or a function return (which will be caught when it is used elsewhere)
     fn check_stmt(&mut self, cx: &Context, s: &ast::Stmt) {
-
         match s.node {
             ast::StmtDecl(_, id) |
             ast::StmtExpr(_, id) |
@@ -155,16 +192,10 @@ impl LintPass for UnrootedPass {
             _ => return
         };
 
-        let t = cx.tcx.expr_ty(&*expr);
+        let ty = cx.tcx.expr_ty(&*expr);
-        match t.sty {
+        if is_unrooted_ty(cx, ty, self.in_new_function) {
-            ty::TyStruct(did, _) |
+            cx.span_lint(UNROOTED_MUST_ROOT, expr.span,
-            ty::TyEnum(did, _) => {
+                                     &format!("Expression of type {:?} must be rooted", ty))
-                if cx.tcx.has_attr(did, "must_root") {
-                    cx.span_lint(UNROOTED_MUST_ROOT, expr.span,
-                                 &format!("Expression of type {:?} must be rooted", t));
-                }
-            }
-            _ => {}
         }
     }
 }

components/plugins/utils.rs

@@ -49,7 +49,11 @@ pub fn match_lang_ty(cx: &Context, ty: &Ty, value: &str) -> bool {
         _ => return false,
     };
 
-    cx.tcx.get_attrs(def_id).iter().any(|attr| {
+    match_lang_did(cx, def_id, value)
+}
+
+pub fn match_lang_did(cx: &Context, did: ast::DefId, value: &str) -> bool {
+    cx.tcx.get_attrs(did).iter().any(|attr| {
         match attr.node.value.node {
             ast::MetaNameValue(ref name, ref val) if &**name == "servo_lang" => {
                 match val.node {
@@ -88,3 +92,11 @@ pub fn unsafe_context(map: &ast_map::Map, id: ast::NodeId) -> bool {
                    // to be added.
     }
 }
+
+/// check if a DefId's path matches the given absolute type path
+/// usage e.g. with
+/// `match_def_path(cx, id, &["core", "option", "Option"])`
+pub fn match_def_path(cx: &Context, def_id: ast::DefId, path: &[&str]) -> bool {
+    cx.tcx.with_path(def_id, |iter| iter.map(|elem| elem.name())
+        .zip(path.iter()).all(|(nm, p)| &nm.as_str() == p))
+}

components/script/dom/bindings/js.rs

@@ -81,6 +81,7 @@ impl<T: Reflectable> JS<T> {
 
 /// An unrooted reference to a DOM object for use in layout. `Layout*Helpers`
 /// traits must be implemented on this.
+#[allow_unrooted_interior]
 pub struct LayoutJS<T> {
     ptr: NonZero<*const T>
 }
@@ -270,6 +271,12 @@ impl<T: Reflectable> MutNullableHeap<JS<T>> {
     pub unsafe fn get_inner_as_layout(&self) -> Option<LayoutJS<T>> {
         self.ptr.get().map(|js| js.to_layout())
     }
+
+    /// Get a rooted value out of this object
+    // FIXME(#6684)
+    pub fn get_rooted(&self) -> Option<Root<T>> {
+        self.get().map(|o| o.root())
+    }
 }
 
 impl<T: HeapGCValue+Copy> Default for MutNullableHeap<T> {
@@ -382,6 +389,7 @@ pub unsafe fn trace_roots(tracer: *mut JSTracer) {
 /// are additive, so this object's destruction will not invalidate other roots
 /// for the same JS value. `Root`s cannot outlive the associated
 /// `RootCollection` object.
+#[allow_unrooted_interior]
 pub struct Root<T: Reflectable> {
     /// Reference to rooted value that must not outlive this container
     ptr: NonZero<*const T>,

components/script/dom/bindings/refcounted.rs

@@ -57,6 +57,7 @@ unsafe impl Send for TrustedReference {}
 /// shared among tasks for use in asynchronous operations. The underlying
 /// DOM object is guaranteed to live at least as long as the last outstanding
 /// `Trusted<T>` instance.
+#[allow_unrooted_interior]
 pub struct Trusted<T: Reflectable> {
     /// A pointer to the Rust DOM object of type T, but void to allow
     /// sending `Trusted<T>` between tasks, regardless of T's sendability.

components/script/dom/bindings/trace.rs

@@ -455,6 +455,7 @@ impl<'a, T: JSTraceable> Drop for RootedTraceable<'a, T> {
 #[allow(unrooted_must_root)]
 #[no_move]
 #[derive(JSTraceable)]
+#[allow_unrooted_interior]
 pub struct RootedVec<T: JSTraceable + Reflectable> {
     v: Vec<T>
 }

components/script/dom/bindings/utils.rs

@@ -413,8 +413,7 @@ pub fn reflect_dom_object<T: Reflectable>
 }
 
 /// A struct to store a reference to the reflector of a DOM object.
-// Allowing unused_attribute because the lint sometimes doesn't run in order
+#[allow(raw_pointer_derive, unrooted_must_root)]
-#[allow(raw_pointer_derive, unrooted_must_root, unused_attributes)]
 #[must_root]
 #[servo_lang = "reflector"]
 // If you're renaming or moving this field, update the path in plugins::reflector as well

components/script/dom/browsercontext.rs

@@ -30,6 +30,7 @@ use std::default::Default;
 #[derive(JSTraceable)]
 #[privatize]
 #[allow(raw_pointer_derive)]
+#[must_root]
 pub struct BrowsingContext {
     history: Vec<SessionHistoryEntry>,
     active_index: usize,

components/script/dom/node.rs

@@ -328,14 +328,14 @@ impl<'a> PrivateNodeHelpers for &'a Node {
         match before {
             Some(ref before) => {
                 assert!(before.parent_node.get().map(Root::from_rooted).r() == Some(self));
-                match before.prev_sibling.get() {
+                let prev_sibling = before.GetPreviousSibling();
+                match prev_sibling {
                     None => {
                         assert!(Some(*before) == self.first_child.get().map(Root::from_rooted).r());
                         self.first_child.set(Some(JS::from_ref(new_child)));
                     },
                     Some(ref prev_sibling) => {
-                        let prev_sibling = prev_sibling.root();
+                        prev_sibling.next_sibling.set(Some(JS::from_ref(new_child)));
-                        prev_sibling.r().next_sibling.set(Some(JS::from_ref(new_child)));
                         new_child.prev_sibling.set(Some(JS::from_ref(prev_sibling.r())));
                     },
                 }
@@ -343,11 +343,11 @@ impl<'a> PrivateNodeHelpers for &'a Node {
                 new_child.next_sibling.set(Some(JS::from_ref(before)));
             },
             None => {
-                match self.last_child.get() {
+                let last_child = self.GetLastChild();
+                match last_child {
                     None => self.first_child.set(Some(JS::from_ref(new_child))),
                     Some(ref last_child) => {
-                        let last_child = last_child.root();
+                        assert!(last_child.next_sibling.get().is_none());
-                        assert!(last_child.r().next_sibling.get().is_none());
                         last_child.r().next_sibling.set(Some(JS::from_ref(new_child)));
                         new_child.prev_sibling.set(Some(JS::from_rooted(&last_child)));
                     }
@@ -365,22 +365,22 @@ impl<'a> PrivateNodeHelpers for &'a Node {
     /// Fails unless `child` is a child of this node.
     fn remove_child(self, child: &Node) {
         assert!(child.parent_node.get().map(Root::from_rooted).r() == Some(self));
-
+        let prev_sibling = child.GetPreviousSibling();
-        match child.prev_sibling.get() {
+        match prev_sibling {
             None => {
                 self.first_child.set(child.next_sibling.get());
             }
             Some(ref prev_sibling) => {
-                prev_sibling.root().r().next_sibling.set(child.next_sibling.get());
+                prev_sibling.next_sibling.set(child.next_sibling.get());
             }
         }
-
+        let next_sibling = child.GetNextSibling();
-        match child.next_sibling.get() {
+        match next_sibling {
             None => {
                 self.last_child.set(child.prev_sibling.get());
             }
             Some(ref next_sibling) => {
-                next_sibling.root().r().prev_sibling.set(child.prev_sibling.get());
+                next_sibling.prev_sibling.set(child.prev_sibling.get());
             }
         }
 
@@ -1476,9 +1476,10 @@ impl Node {
     // https://dom.spec.whatwg.org/#concept-node-adopt
     pub fn adopt(node: &Node, document: &Document) {
         // Step 1.
-        match node.parent_node.get() {
+        let parent_node = node.GetParentNode();
+        match parent_node {
             Some(ref parent) => {
-                Node::remove(node, parent.root().r(), SuppressObserver::Unsuppressed);
+                Node::remove(node, parent, SuppressObserver::Unsuppressed);
             }
             None => (),
         }

components/script/page.rs

@@ -14,6 +14,7 @@ use std::rc::Rc;
 
 /// Encapsulates a handle to a frame in a frame tree.
 #[derive(JSTraceable)]
+#[allow(unrooted_must_root)] // FIXME(#6687) this is wrong
 pub struct Page {
     /// Pipeline id associated with this page.
     id: PipelineId,

components/script/script_task.rs

@@ -287,6 +287,8 @@ impl Drop for StackRootTLS {
 /// Information for an entire page. Pages are top-level browsing contexts and can contain multiple
 /// frames.
 #[derive(JSTraceable)]
+// ScriptTask instances are rooted on creation, so this is okay
+#[allow(unrooted_must_root)]
 pub struct ScriptTask {
     /// A handle to the information pertaining to page layout
     page: DOMRefCell<Option<Rc<Page>>>,