servo: Merge #15649 - Rewrite the ban-type lint in Python (from zimio:issue-15591-rewrite-ban-type-lint); r=Wafflespeanut

<!-- Please describe your changes on the following line: -->
Rewrite the ban-type lint in Python.

Question: Should the old ban-type lint written in rust be deleted?

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [x ] `./mach build -d` does not report any errors
- [x ] `./mach test-tidy` does not report any errors
- [x ] These changes fix #15591

<!-- Either: -->
- [ x] There are tests for these changes

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

Source-Repo: https://github.com/servo/servo
Source-Revision: 261df34ced0bdcb8126994c8653ac101d1172085

--HG--
rename : servo/tests/compiletest/plugin/compile-fail/ban-domrefcell.rs => servo/python/tidy/servo_tidy_tests/ban-domrefcell.rs
rename : servo/tests/compiletest/plugin/compile-fail/ban.rs => servo/python/tidy/servo_tidy_tests/ban.rs
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : adf4a3a1bb9570e342bcd4233445178fcf107802

servo/components/script_plugins/ban.rs

@@ -1,53 +0,0 @@
-/* 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 rustc::lint::{EarlyContext, LintPass, LintArray, EarlyLintPass, LintContext};
-use syntax::ast::Ty;
-use utils::match_ty_unwrap;
-
-declare_lint!(BANNED_TYPE, Deny,
-              "Ban various unsafe type combinations");
-
-/// Lint for banning various unsafe types
-///
-/// Banned types:
-///
-/// - `Cell<JSVal>`
-/// - `Cell<JS<T>>`
-pub struct BanPass;
-
-impl LintPass for BanPass {
-    fn get_lints(&self) -> LintArray {
-        lint_array!(BANNED_TYPE)
-    }
-}
-
-impl EarlyLintPass for BanPass {
-    fn check_ty(&mut self, cx: &EarlyContext, ty: &Ty) {
-        if match_ty_unwrap(ty, &["std", "cell", "Cell"])
-            .and_then(|t| t.get(0))
-            .and_then(|t| match_ty_unwrap(&**t, &["dom", "bindings", "js", "JS"]))
-            .is_some() {
-            cx.span_lint(BANNED_TYPE, ty.span, "Banned type Cell<JS<T>> detected. Use MutJS<JS<T>> instead")
-        }
-        if match_ty_unwrap(ty, &["std", "cell", "Cell"])
-            .and_then(|t| t.get(0))
-            .and_then(|t| match_ty_unwrap(&**t, &["js", "jsval", "JSVal"]))
-            .is_some() {
-            cx.span_lint(BANNED_TYPE, ty.span, "Banned type Cell<JSVal> detected. Use MutJS<JSVal> instead")
-        }
-        if match_ty_unwrap(ty, &["dom", "bindings", "cell", "DOMRefCell"])
-            .and_then(|t| t.get(0))
-            .and_then(|t| match_ty_unwrap(&**t, &["dom", "bindings", "js", "JS"]))
-            .is_some() {
-            cx.span_lint(BANNED_TYPE, ty.span, "Banned type DOMRefCell<JS<T>> detected. Use MutJS<JS<T>> instead")
-        }
-        if match_ty_unwrap(ty, &["dom", "bindings", "cell", "DOMRefCell"])
-            .and_then(|t| t.get(0))
-            .and_then(|t| match_ty_unwrap(&**t, &["js", "jsapi", "Heap"]))
-            .is_some() {
-            cx.span_lint(BANNED_TYPE, ty.span, "Banned type DOMRefCell<Heap<T>> detected. Use Heap<T> directly instead")
-        }
-    }
-}

servo/components/script_plugins/lib.rs

@@ -25,7 +25,6 @@ extern crate syntax;
 use rustc_plugin::Registry;
 use syntax::feature_gate::AttributeType::Whitelisted;
 
-mod ban;
 mod unrooted_must_root;
 /// Utilities for writing plugins
 mod utils;
@@ -33,7 +32,6 @@ mod utils;
 #[plugin_registrar]
 pub fn plugin_registrar(reg: &mut Registry) {
     reg.register_late_lint_pass(box unrooted_must_root::UnrootedPass::new());
-    reg.register_early_lint_pass(box ban::BanPass);
     reg.register_attribute("allow_unrooted_interior".to_string(), Whitelisted);
     reg.register_attribute("must_root".to_string(), Whitelisted);
 }

servo/python/tidy/servo_tidy/tidy.py

@@ -549,6 +549,12 @@ def check_rust(file_name, lines):
             (r": &Vec<", "use &[T] instead of &Vec<T>", no_filter),
             # No benefit over using &str
             (r": &String", "use &str instead of &String", no_filter),
+            # There should be any use of banned types:
+            # Cell<JSVal>, Cell<JS<T>>, DOMRefCell<JS<T>>, DOMRefCell<HEAP<T>>
+            (r"(\s|:)+Cell<JSVal>", "Banned type Cell<JSVal> detected. Use MutJS<JSVal> instead", no_filter),
+            (r"(\s|:)+Cell<JS<.+>>", "Banned type Cell<JS<T>> detected. Use MutJS<JS<T>> instead", no_filter),
+            (r"DOMRefCell<JS<.+>>", "Banned type DOMRefCell<JS<T>> detected. Use MutJS<JS<T>> instead", no_filter),
+            (r"DOMRefCell<Heap<.+>>", "Banned type DOMRefCell<Heap<T>> detected. Use MutJS<JS<T>> instead", no_filter),
             # No benefit to using &Root<T>
             (r": &Root<", "use &T instead of &Root<T>", no_filter),
             (r"^&&", "operators should go at the end of the first line", no_filter),

servo/python/tidy/servo_tidy_tests/ban.rs

@@ -9,10 +9,13 @@ extern crate js;
 
 use js::jsval::JSVal;
 use std::cell::Cell;
+use std::cell::UnsafeCell;
 
 struct Foo {
-    bar: Cell<JSVal>
+    bar: Cell<JSVal>,
     //~^ ERROR Banned type Cell<JSVal> detected. Use MutJS<JSVal> instead
+    foo: UnsafeCell<JSVal>
+    //~^ NOT AN ERROR
 }
 
 fn main() {}

servo/python/tidy/servo_tidy_tests/test_tidy.py

@@ -140,6 +140,14 @@ class CheckTidiness(unittest.TestCase):
         self.assertTrue('feature attribute is not in alphabetical order' in feature_errors.next()[2])
         self.assertNoMoreErrors(feature_errors)
 
+        ban_errors = tidy.collect_errors_for_files(iterFile('ban.rs'), [], [tidy.check_rust], print_text=False)
+        self.assertEqual('Banned type Cell<JSVal> detected. Use MutJS<JSVal> instead', ban_errors.next()[2])
+        self.assertNoMoreErrors(ban_errors)
+
+        ban_errors = tidy.collect_errors_for_files(iterFile('ban-domrefcell.rs'), [], [tidy.check_rust], print_text=False)
+        self.assertEqual('Banned type DOMRefCell<JS<T>> detected. Use MutJS<JS<T>> instead', ban_errors.next()[2])
+        self.assertNoMoreErrors(ban_errors)
+
     def test_spec_link(self):
         tidy.SPEC_BASE_PATH = base_path
         errors = tidy.collect_errors_for_files(iterFile('speclink.rs'), [], [tidy.check_spec], print_text=False)