introduce #[clippy::ignore_interior_mutability]

Author: ada4a

clippy_lints/src/non_copy_const.rs

@@ -70,8 +70,9 @@ declare_clippy_lint! {
     /// no way to both create a value as a constant and modify any mutable field using the
     /// type's public interface (e.g. `bytes::Bytes`). As there is no reasonable way to
     /// scan a crate's interface to see if this is the case, all such types will be linted.
-    /// If this happens use the `ignore-interior-mutability` configuration option to allow
-    /// the type.
+    /// If this happens, use the `ignore-interior-mutability` configuration option or put
+    /// the `#[clippy::ignore_interior_mutability]` attribute onto a type to allow the
+    /// type.
     ///
     /// ### Example
     /// ```no_run
@@ -131,8 +132,9 @@ declare_clippy_lint! {
     /// no way to both create a value as a constant and modify any mutable field using the
     /// type's public interface (e.g. `bytes::Bytes`). As there is no reasonable way to
     /// scan a crate's interface to see if this is the case, all such types will be linted.
-    /// If this happens use the `ignore-interior-mutability` configuration option to allow
-    /// the type.
+    /// If this happens, use the `ignore-interior-mutability` configuration option or put
+    /// the `#[clippy::ignore_interior_mutability]` attribute onto a type to allow the
+    /// type.
     ///
     /// ### Example
     /// ```no_run

clippy_utils/src/attrs.rs

@@ -28,6 +28,7 @@ pub fn get_builtin_attr<'a, A: AttributeExt + 'a>(
                 sym::cyclomatic_complexity => Some("cognitive_complexity"),
                 sym::author
                 | sym::version
+                | sym::ignore_interior_mutability
                 | sym::cognitive_complexity
                 | sym::dump
                 | sym::msrv

clippy_utils/src/sym.rs

@@ -174,6 +174,7 @@ generate! {
     has_significant_drop,
     hidden_glob_reexports,
     hygiene,
+    ignore_interior_mutability,
     insert,
     inspect,
     int_roundings,

clippy_utils/src/ty/mod.rs

@@ -1121,6 +1121,17 @@ impl<'tcx> InteriorMut<'tcx> {
     /// this type to be interior mutable. False negatives may be expected for infinitely recursive
     /// types, and `None` will be returned there.
     pub fn interior_mut_ty_chain(&mut self, cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<&'tcx ty::List<Ty<'tcx>>> {
+        // Check if given type has a `#[clippy::ignore_interior_mutability]` attribute
+        if let Some(did) = ty.ty_adt_def().map(AdtDef::did)
+            && !self.ignored_def_ids.contains(&did)
+            && let attrs = cx.tcx.get_all_attrs(did)
+            && get_unique_builtin_attr(cx.sess(), attrs, sym::ignore_interior_mutability).is_some()
+        {
+            self.ignored_def_ids.insert(did);
+            // Small optimization: since we know that we're going to ignore interior mutability for
+            // this type anyway, running `self.interior_mut_ty_chain_inner` is unnecessary
+            return None;
+        }
         self.interior_mut_ty_chain_inner(cx, ty, 0)
     }
 

tests/ui/borrow_interior_mutable_const.rs

@@ -234,4 +234,11 @@ fn main() {
             }
         }
     }
+    fn issue13865() {
+        #[clippy::ignore_interior_mutability]
+        struct Foo(Cell<i32>);
+
+        const FOO: Foo = Foo(Cell::new(0));
+        let _ = &FOO;
+    }
 }

tests/ui/declare_interior_mutable_const.rs

@@ -198,3 +198,9 @@ impl WithGenericAssocCell for i32 {
 
 thread_local!(static THREAD_LOCAL_CELL: Cell<u32> = const { Cell::new(0) });
 thread_local!(static THREAD_LOCAL_CELL2: Cell<u32> = Cell::new(0));
+
+fn issue13865() {
+    #[clippy::ignore_interior_mutability]
+    struct IgnoreInteriorMut(Cell<u32>);
+    const IIM: IgnoreInteriorMut = IgnoreInteriorMut(Cell::new(0));
+}

tests/ui/ifs_same_cond.rs

@@ -1,6 +1,8 @@
 #![warn(clippy::ifs_same_cond)]
 #![allow(clippy::if_same_then_else, clippy::needless_if, clippy::needless_else)] // all empty blocks
 
+use std::cell::Cell;
+
 fn ifs_same_cond() {
     let a = 0;
     let b = false;
@@ -72,7 +74,7 @@ fn issue10272() {
     } else {
     }
 
-    let x = std::cell::Cell::new(true);
+    let x = Cell::new(true);
     if x.get() {
     } else if !x.take() {
     } else if x.get() {
@@ -81,4 +83,34 @@ fn issue10272() {
     }
 }
 
+fn issue13865() {
+    #[clippy::ignore_interior_mutability]
+    struct X<T>(Cell<T>);
+
+    // delegate some methods so that the test case works
+    impl<T> X<T> {
+        fn get(&self) -> T
+        where
+            T: Copy,
+        {
+            self.0.get()
+        }
+        fn take(&self) -> T
+        where
+            T: Default,
+        {
+            self.0.take()
+        }
+    }
+
+    let x = X(Cell::new(true));
+    if x.get() {
+        //~^ ifs_same_cond
+        // x is interior mutable type, but that should be ignored, so we lint
+    } else if !x.take() {
+    } else if x.get() {
+    } else {
+    }
+}
+
 fn main() {}

tests/ui/ifs_same_cond.stderr

@@ -1,5 +1,5 @@
 error: these `if` branches have the same condition
-  --> tests/ui/ifs_same_cond.rs:8:8
+  --> tests/ui/ifs_same_cond.rs:10:8
    |
 LL |     if b {
    |        ^
@@ -11,7 +11,7 @@ LL |     } else if b {
    = help: to override `-D warnings` add `#[allow(clippy::ifs_same_cond)]`
 
 error: these `if` branches have the same condition
-  --> tests/ui/ifs_same_cond.rs:13:8
+  --> tests/ui/ifs_same_cond.rs:15:8
    |
 LL |     if b {
    |        ^
@@ -22,7 +22,7 @@ LL |     } else if b {
    |               ^
 
 error: these `if` branches have the same condition
-  --> tests/ui/ifs_same_cond.rs:19:8
+  --> tests/ui/ifs_same_cond.rs:21:8
    |
 LL |     if a == 1 {
    |        ^^^^^^
@@ -31,7 +31,7 @@ LL |     } else if a == 1 {
    |               ^^^^^^
 
 error: these `if` branches have the same condition
-  --> tests/ui/ifs_same_cond.rs:24:8
+  --> tests/ui/ifs_same_cond.rs:26:8
    |
 LL |     if 2 * a == 1 {
    |        ^^^^^^^^^^
@@ -40,13 +40,22 @@ LL |     } else if 2 * a == 1 {
    |               ^^^^^^^^^^
 
 error: these `if` branches have the same condition
-  --> tests/ui/ifs_same_cond.rs:58:8
+  --> tests/ui/ifs_same_cond.rs:60:8
    |
 LL |     if a.contains("ah") {
    |        ^^^^^^^^^^^^^^^^
 LL |
 LL |     } else if a.contains("ah") {
    |               ^^^^^^^^^^^^^^^^
 
-error: aborting due to 5 previous errors
+error: these `if` branches have the same condition
+  --> tests/ui/ifs_same_cond.rs:105:8
+   |
+LL |     if x.get() {
+   |        ^^^^^^^
+...
+LL |     } else if x.get() {
+   |               ^^^^^^^
+
+error: aborting due to 6 previous errors
 

tests/ui/mut_key.rs

@@ -113,3 +113,14 @@ fn main() {
     let _map = HashMap::<&mut usize, usize>::new();
     let _map = HashMap::<Result<&mut usize, ()>, usize>::new();
 }
+
+fn issue13865() {
+    #[clippy::ignore_interior_mutability]
+    struct IgnoreMut {
+        cell: std::cell::Cell<&'static [u32]>,
+    }
+
+    fn main() {
+        let a: HashSet<IgnoreMut> = HashSet::new();
+    }
+}