servo: Merge #4189 - Return early and decline analysis when linting within unsafe functions; fixes #3658 (from chmanchester:rootlint); r=jdm

I think this matches the intent of the issue, I'm a rust/servo novice; any suggestions for improvements are welcome. Thanks!

Source-Repo: https://github.com/servo/servo
Source-Revision: 2615be9bab984c8356bc053f90452d6f9fdaa241

servo/components/plugins/lints.rs

@@ -2,7 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use syntax::{ast, ast_util, codemap, visit};
+use syntax::{ast, ast_map, ast_util, codemap, visit};
 use syntax::ast::Public;
 use syntax::attr::AttrMetaMethods;
 use rustc::lint::{Context, LintPass, LintArray};
@@ -92,6 +92,35 @@ fn lint_unrooted_ty(cx: &Context, ty: &ast::Ty, warning: &str) {
     };
 }
 
+// Determines if a block is in an unsafe context so that an unhelpful
+// lint can be aborted.
+fn unsafe_context(map: &ast_map::Map, id: ast::NodeId) -> bool {
+    match map.get(map.get_parent(id)) {
+        ast_map::NodeImplItem(itm) => {
+            match *itm {
+                ast::MethodImplItem(ref meth) => match meth.node {
+                    ast::MethDecl(_, _, _, _, style, _, _, _) => match style {
+                        ast::UnsafeFn => true,
+                        _ => false,
+                    },
+                    _ => false,
+                },
+                _ => false,
+            }
+        },
+        ast_map::NodeItem(itm) => {
+            match itm.node {
+                ast::ItemFn(_, style, _, _, _) => match style {
+                    ast::UnsafeFn => true,
+                    _ => false,
+                },
+                _ => false,
+            }
+        }
+        _ => false // There are probably a couple of other unsafe cases we don't care to lint, those will need to be added.
+    }
+}
+
 impl LintPass for UnrootedPass {
     fn get_lints(&self) -> LintArray {
         lint_array!(UNROOTED_MUST_ROOT)
@@ -122,14 +151,23 @@ impl LintPass for UnrootedPass {
     }
     /// Function arguments that are #[must_root] types are not allowed
     fn check_fn(&mut self, cx: &Context, kind: visit::FnKind, decl: &ast::FnDecl,
-                block: &ast::Block, _span: codemap::Span, _id: ast::NodeId) {
+                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" => {
                 return;
-            }
+            },
+            visit::FkItemFn(_, _, style, _) => match style {
+                ast::UnsafeFn => return,
+                _ => ()
+            },
             _ => ()
         }
+
+        if unsafe_context(&cx.tcx.map, id) {
+            return;
+        }
+
         match block.rules {
             ast::DefaultBlock => {
                 for arg in decl.inputs.iter() {
@@ -146,6 +184,16 @@ 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) |
+            ast::StmtSemi(_, id) if unsafe_context(&cx.tcx.map, id) => {
+                return
+            },
+            _ => ()
+        };
+
         let expr = match s.node {
             // Catch a `let` binding
             ast::StmtDecl(ref decl, _) => match decl.node {

servo/components/script/dom/element.rs

@@ -206,7 +206,6 @@ pub trait RawLayoutElementHelpers {
 }
 
 #[inline]
-#[allow(unrooted_must_root)]
 unsafe fn get_attr_for_layout<'a>(elem: &'a Element, namespace: &Namespace, name: &Atom) -> Option<&'a JS<Attr>> {
     // cast to point to T in RefCell<T> directly
     let attrs: *const Vec<JS<Attr>> = mem::transmute(&elem.attrs);
@@ -219,7 +218,6 @@ unsafe fn get_attr_for_layout<'a>(elem: &'a Element, namespace: &Namespace, name
 
 impl RawLayoutElementHelpers for Element {
     #[inline]
-    #[allow(unrooted_must_root)]
     unsafe fn get_attr_val_for_layout<'a>(&'a self, namespace: &Namespace, name: &Atom)
                                           -> Option<&'a str> {
         get_attr_for_layout(self, namespace, name).map(|attr| {
@@ -229,7 +227,6 @@ impl RawLayoutElementHelpers for Element {
     }
 
     #[inline]
-    #[allow(unrooted_must_root)]
     unsafe fn get_attr_vals_for_layout<'a>(&'a self, name: &Atom) -> Vec<&'a str> {
         let attrs = self.attrs.borrow_for_layout();
         (*attrs).iter().filter_map(|attr: &JS<Attr>| {
@@ -243,7 +240,6 @@ impl RawLayoutElementHelpers for Element {
     }
 
     #[inline]
-    #[allow(unrooted_must_root)]
     unsafe fn get_attr_atom_for_layout(&self, namespace: &Namespace, name: &Atom)
                                       -> Option<Atom> {
         let attrs = self.attrs.borrow_for_layout();
@@ -258,7 +254,6 @@ impl RawLayoutElementHelpers for Element {
     }
 
     #[inline]
-    #[allow(unrooted_must_root)]
     unsafe fn has_class_for_layout(&self, name: &Atom) -> bool {
         let attrs = self.attrs.borrow_for_layout();
         (*attrs).iter().find(|attr: & &JS<Attr>| {
@@ -273,7 +268,6 @@ impl RawLayoutElementHelpers for Element {
     }
 
     #[inline]
-    #[allow(unrooted_must_root)]
     unsafe fn get_classes_for_layout(&self) -> Option<&'static [Atom]> {
         let attrs = self.attrs.borrow_for_layout();
         (*attrs).iter().find(|attr: & &JS<Attr>| {
@@ -286,7 +280,6 @@ impl RawLayoutElementHelpers for Element {
     }
 
     #[inline]
-    #[allow(unrooted_must_root)]
     unsafe fn get_length_attribute_for_layout(&self, length_attribute: LengthAttribute)
                                               -> LengthOrPercentageOrAuto {
         match length_attribute {
@@ -301,7 +294,6 @@ impl RawLayoutElementHelpers for Element {
     }
 
     #[inline]
-    #[allow(unrooted_must_root)]
     unsafe fn get_integer_attribute_for_layout(&self, integer_attribute: IntegerAttribute)
                                                -> Option<i32> {
         match integer_attribute {
@@ -347,7 +339,6 @@ pub trait LayoutElementHelpers {
 }
 
 impl LayoutElementHelpers for JS<Element> {
-    #[allow(unrooted_must_root)]
     #[inline]
     unsafe fn html_element_in_html_document_for_layout(&self) -> bool {
         if (*self.unsafe_get()).namespace != ns!(HTML) {