1 files changed, 90 insertions, 0 deletions
diff --git a/components/plugins/lints/inheritance_integrity.rs b/components/plugins/lints/inheritance_integrity.rs
new file mode 100644
index 00000000000..d3ea6ee280d
--- /dev/null
+++ b/components/plugins/lints/inheritance_integrity.rs
@@ -0,0 +1,90 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * 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};
+use rustc::lint::{Context, LintPass, LintArray, Level};
+use rustc::middle::{ty, def};
+use rustc::middle::typeck::astconv::AstConv;
+
+use utils::match_lang_ty;
+
+declare_lint!(INHERITANCE_INTEGRITY, Deny,
+              "Ensures that struct fields are properly laid out for inheritance to work")
+
+/// Lint for ensuring proper layout of DOM structs
+///
+/// A DOM struct must have one Reflector field or one field
+/// which itself is a DOM struct (in which case it must be the first field).
+pub struct InheritancePass;
+
+impl LintPass for InheritancePass {
+    fn get_lints(&self) -> LintArray {
+        lint_array!(INHERITANCE_INTEGRITY)
+    }
+
+    fn check_struct_def(&mut self, cx: &Context, def: &ast::StructDef, _i: ast::Ident, _gen: &ast::Generics, id: ast::NodeId) {
+        // Lints are run post expansion, so it's fine to use
+        // #[_dom_struct_marker] here without also checking for #[dom_struct]
+        if ty::has_attr(cx.tcx, ast_util::local_def(id), "_dom_struct_marker") {
+            // Find the reflector, if any
+            let reflector_span = def.fields.iter().enumerate()
+                                    .find(|&(ctr, f)| {
+                                        if match_lang_ty(cx, &*f.node.ty, "reflector") {
+                                            if ctr > 0 {
+                                                cx.span_lint(INHERITANCE_INTEGRITY, f.span,
+                                                             "The Reflector should be the first field of the DOM struct");
+                                            }
+                                            return true;
+                                        }
+                                        false
+                                    })
+                                    .map(|(_, f)| f.span);
+            // Find all #[dom_struct] fields
+            let dom_spans: Vec<_> = def.fields.iter().enumerate().filter_map(|(ctr, f)| {
+                if let ast::TyPath(_, _, ty_id) = f.node.ty.node {
+                    if let Some(def::DefTy(def_id, _)) = cx.tcx.def_map.borrow().get(&ty_id).cloned() {
+                        if ty::has_attr(cx.tcx, def_id, "_dom_struct_marker") {
+                            // If the field is not the first, it's probably
+                            // being misused (a)
+                            if ctr > 0 {
+                                cx.span_lint(INHERITANCE_INTEGRITY, f.span,
+                                             "Bare DOM structs should only be used as the first field of a \
+                                              DOM struct. Consider using JS<T> instead.");
+                            }
+                            return Some(f.span)
+                        }
+                    }
+                }
+                None
+            }).collect();
+
+            // We should not have both a reflector and a dom struct field
+            if let Some(sp) = reflector_span {
+                if dom_spans.len() > 0 {
+                    cx.span_lint(INHERITANCE_INTEGRITY, cx.tcx.map.expect_item(id).span,
+                                 "This DOM struct has both Reflector and bare DOM struct members");
+                    if cx.current_level(INHERITANCE_INTEGRITY) != Level::Allow {
+                        let sess = cx.sess();
+                        sess.span_note(sp, "Reflector found here");
+                        for span in dom_spans.iter() {
+                            sess.span_note(*span, "Bare DOM struct found here");
+                        }
+                    }
+                }
+            // Nor should we have more than one dom struct field
+            } else if dom_spans.len() > 1 {
+                cx.span_lint(INHERITANCE_INTEGRITY, cx.tcx.map.expect_item(id).span,
+                             "This DOM struct has multiple DOM struct members, only one is allowed");
+                if cx.current_level(INHERITANCE_INTEGRITY) != Level::Allow {
+                    for span in dom_spans.iter() {
+                        cx.sess().span_note(*span, "Bare DOM struct found here");
+                    }
+                }
+            } else if dom_spans.len() == 0 {
+                cx.span_lint(INHERITANCE_INTEGRITY, cx.tcx.map.expect_item(id).span,
+                             "This DOM struct has no reflector or parent DOM struct");
+            }
+        }
+    }
+}