Ignore associated types in traits when considering type complexity

[rust.git] / clippy_lints / src / types / mod.rs

diff --git a/clippy_lints/src/types/mod.rs b/clippy_lints/src/types/mod.rs
index 9588de8459cfe3f337b2351cc6afc5b6c6e8b800..69cd49d884cc00ae91674369eeae38cf86c5ac5d 100644 (file)
--- a/clippy_lints/src/types/mod.rs
+++ b/clippy_lints/src/types/mod.rs
@@ -1,5 +1,5 @@
 mod borrowed_box;
-mod box_vec;
+mod box_collection;
 mod linked_list;
 mod option_option;
 mod rc_buffer;
@@ -21,12 +21,12 @@
 
 declare_clippy_lint! {
     /// ### What it does
-    /// Checks for use of `Box<Vec<_>>` anywhere in the code.
+    /// Checks for use of `Box<T>` where T is a collection such as Vec anywhere in the code.
     /// Check the [Box documentation](https://doc.rust-lang.org/std/boxed/index.html) for more information.
     ///
     /// ### Why is this bad?
-    /// `Vec` already keeps its contents in a separate area on
-    /// the heap. So if you `Box` it, you just add another level of indirection
+    /// Collections already keeps their contents in a separate area on
+    /// the heap. So if you `Box` them, you just add another level of indirection
     /// without any benefit whatsoever.
     ///
     /// ### Example
@@ -43,7 +43,8 @@
     ///     values: Vec<Foo>,
     /// }
     /// ```
-    pub BOX_VEC,
+    #[clippy::version = "1.57.0"]
+    pub BOX_COLLECTION,
     perf,
     "usage of `Box<Vec<T>>`, vector elements are already on the heap"
 }
@@ -75,6 +76,7 @@
     ///     values: Vec<i32>,
     /// }
     /// ```
+    #[clippy::version = "1.33.0"]
     pub VEC_BOX,
     complexity,
     "usage of `Vec<Box<T>>` where T: Sized, vector elements are already on the heap"
@@ -113,6 +115,7 @@
     ///     Contents::None
     /// }
     /// ```
+    #[clippy::version = "pre 1.29.0"]
     pub OPTION_OPTION,
     pedantic,
     "usage of `Option<Option<T>>`"
@@ -152,6 +155,7 @@
     /// # use std::collections::LinkedList;
     /// let x: LinkedList<usize> = LinkedList::new();
     /// ```
+    #[clippy::version = "pre 1.29.0"]
     pub LINKEDLIST,
     pedantic,
     "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a `VecDeque`"
@@ -176,6 +180,7 @@
     /// ```rust,ignore
     /// fn foo(bar: &T) { ... }
     /// ```
+    #[clippy::version = "pre 1.29.0"]
     pub BORROWED_BOX,
     complexity,
     "a borrow of a boxed type"
@@ -200,6 +205,7 @@
     /// ```rust
     /// fn foo(bar: &usize) {}
     /// ```
+    #[clippy::version = "1.44.0"]
     pub REDUNDANT_ALLOCATION,
     perf,
     "redundant allocation"
@@ -234,6 +240,7 @@
     /// ```rust,ignore
     /// fn foo(interned: Rc<str>) { ... }
     /// ```
+    #[clippy::version = "1.48.0"]
     pub RC_BUFFER,
     restriction,
     "shared ownership of a buffer type"
@@ -255,6 +262,7 @@
     ///     inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
     /// }
     /// ```
+    #[clippy::version = "pre 1.29.0"]
     pub TYPE_COMPLEXITY,
     complexity,
     "usage of very complex types that might be better factored into `type` definitions"
@@ -287,6 +295,7 @@
     /// use std::cell::RefCell
     /// fn foo(interned: Rc<RefCell<i32>>) { ... }
     /// ```
+    #[clippy::version = "1.55.0"]
     pub RC_MUTEX,
     restriction,
     "usage of `Rc<Mutex<T>>`"
@@ -298,7 +307,7 @@ pub struct Types {
     avoid_breaking_exported_api: bool,
 }
 
-impl_lint_pass!(Types => [BOX_VEC, VEC_BOX, OPTION_OPTION, LINKEDLIST, BORROWED_BOX, REDUNDANT_ALLOCATION, RC_BUFFER, RC_MUTEX, TYPE_COMPLEXITY]);
+impl_lint_pass!(Types => [BOX_COLLECTION, VEC_BOX, OPTION_OPTION, LINKEDLIST, BORROWED_BOX, REDUNDANT_ALLOCATION, RC_BUFFER, RC_MUTEX, TYPE_COMPLEXITY]);
 
 impl<'tcx> LateLintPass<'tcx> for Types {
     fn check_fn(&mut self, cx: &LateContext<'_>, _: FnKind<'_>, decl: &FnDecl<'_>, _: &Body<'_>, _: Span, id: HirId) {
@@ -341,7 +350,7 @@ fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
 
     fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx ImplItem<'_>) {
         match item.kind {
-            ImplItemKind::Const(ty, _) | ImplItemKind::TyAlias(ty) => self.check_ty(
+            ImplItemKind::Const(ty, _) => self.check_ty(
                 cx,
                 ty,
                 CheckTyContext {
@@ -349,8 +358,10 @@ fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx ImplItem<'_>)
                     ..CheckTyContext::default()
                 },
             ),
-            // methods are covered by check_fn
-            ImplItemKind::Fn(..) => (),
+            // Methods are covered by check_fn.
+            // Type aliases are ignored because oftentimes it's impossible to
+            // make type alias declaration in trait simpler, see #1013
+            ImplItemKind::Fn(..) | ImplItemKind::TyAlias(..) => (),
         }
     }
 
@@ -447,7 +458,7 @@ fn check_ty(&mut self, cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>, mut context:
                         // in `clippy_lints::utils::conf.rs`
 
                         let mut triggered = false;
-                        triggered |= box_vec::check(cx, hir_ty, qpath, def_id);
+                        triggered |= box_collection::check(cx, hir_ty, qpath, def_id);
                         triggered |= redundant_allocation::check(cx, hir_ty, qpath, def_id);
                         triggered |= rc_buffer::check(cx, hir_ty, qpath, def_id);
                         triggered |= vec_box::check(cx, hir_ty, qpath, def_id, self.vec_box_size_threshold);