Add assigning_clones lint

tests/ui/assigning_clones.fixed

@@ -0,0 +1,211 @@
+// run-rustfix
+#![allow(unused)]
+#![allow(clippy::redundant_clone)]
+#![allow(clippy::ptr_arg)] // https://github.com/rust-lang/rust-clippy/issues/10612
+#![allow(clippy::needless_late_init)]
+#![allow(clippy::box_collection)]
+#![warn(clippy::assigning_clones)]
+
+use std::borrow::ToOwned;
+use std::ops::{Add, Deref, DerefMut};
+
+// Clone
+pub struct HasCloneFrom;
+
+impl Clone for HasCloneFrom {
+    fn clone(&self) -> Self {
+        Self
+    }
+    fn clone_from(&mut self, source: &Self) {
+        *self = HasCloneFrom;
+    }
+}
+
+fn clone_method_rhs_val(mut_thing: &mut HasCloneFrom, value_thing: HasCloneFrom) {
+    mut_thing.clone_from(&value_thing);
+}
+
+fn clone_method_rhs_ref(mut_thing: &mut HasCloneFrom, ref_thing: &HasCloneFrom) {
+    mut_thing.clone_from(ref_thing);
+}
+
+fn clone_method_lhs_val(mut mut_thing: HasCloneFrom, ref_thing: &HasCloneFrom) {
+    mut_thing.clone_from(ref_thing);
+}
+
+fn clone_function_lhs_mut_ref(mut_thing: &mut HasCloneFrom, ref_thing: &HasCloneFrom) {
+    ::std::clone::Clone::clone_from(mut_thing, ref_thing);
+}
+
+fn clone_function_lhs_val(mut mut_thing: HasCloneFrom, ref_thing: &HasCloneFrom) {
+    ::std::clone::Clone::clone_from(&mut mut_thing, ref_thing);
+}
+
+fn clone_function_through_trait(mut_thing: &mut HasCloneFrom, ref_thing: &HasCloneFrom) {
+    ::std::clone::Clone::clone_from(mut_thing, ref_thing);
+}
+
+fn clone_function_through_type(mut_thing: &mut HasCloneFrom, ref_thing: &HasCloneFrom) {
+    ::std::clone::Clone::clone_from(mut_thing, ref_thing);
+}
+
+fn clone_function_fully_qualified(mut_thing: &mut HasCloneFrom, ref_thing: &HasCloneFrom) {
+    ::std::clone::Clone::clone_from(mut_thing, ref_thing);
+}
+
+fn clone_method_lhs_complex(mut_thing: &mut HasCloneFrom, ref_thing: &HasCloneFrom) {
+    // These parens should be kept as necessary for a receiver
+    (mut_thing + &mut HasCloneFrom).clone_from(ref_thing);
+}
+
+fn clone_method_rhs_complex(mut_thing: &mut HasCloneFrom, ref_thing: &HasCloneFrom) {
+    // These parens should be removed since they are not needed in a function argument
+    mut_thing.clone_from(ref_thing + ref_thing);
+}
+
+fn assign_to_init_mut_var(b: HasCloneFrom) -> HasCloneFrom {
+    let mut a = HasCloneFrom;
+    for _ in 1..10 {
+        a.clone_from(&b);
+    }
+    a
+}
+
+fn assign_to_late_init_mut_var(b: HasCloneFrom) {
+    let mut a;
+    a = HasCloneFrom;
+    a = b.clone();
+}
+
+fn assign_to_uninit_var(b: HasCloneFrom) {
+    let a;
+    a = b.clone();
+}
+
+fn assign_to_uninit_mut_var(b: HasCloneFrom) {
+    let mut a;
+    a = b.clone();
+}
+
+#[derive(Clone)]
+pub struct HasDeriveClone;
+
+fn ignore_derive_clone(a: &mut HasDeriveClone, b: &HasDeriveClone) {
+    // Should not be linted, since the Clone impl is derived
+    *a = b.clone();
+}
+
+pub struct HasCloneImpl;
+
+impl Clone for HasCloneImpl {
+    fn clone(&self) -> Self {
+        Self
+    }
+}
+
+fn ignore_missing_clone_from(a: &mut HasCloneImpl, b: &HasCloneImpl) {
+    // Should not be linted, since the Clone impl doesn't override clone_from
+    *a = b.clone();
+}
+
+struct FakeClone;
+
+impl FakeClone {
+    /// This looks just like `Clone::clone`
+    fn clone(&self) -> Self {
+        FakeClone
+    }
+}
+
+fn ignore_fake_clone() {
+    let mut a = FakeClone;
+    let b = FakeClone;
+    // Should not be linted, since the Clone impl doesn't come from std
+    a = b.clone();
+}
+
+fn ignore_generic_clone<T: Clone>(a: &mut T, b: &T) {
+    // Should not be linted, since we don't know the actual clone impl
+    *a = b.clone();
+}
+
+// ToOwned
+fn owned_method_mut_ref(mut_string: &mut String, ref_str: &str) {
+    ref_str.clone_into(mut_string);
+}
+
+fn owned_method_val(mut mut_string: String, ref_str: &str) {
+    ref_str.clone_into(&mut mut_string);
+}
+
+struct HasDeref {
+    a: String
+}
+
+impl Deref for HasDeref {
+    type Target = String;
+    fn deref(&self) -> &Self::Target {
+        &self.a
+    }
+}
+
+impl DerefMut for HasDeref {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.a
+    }
+}
+
+fn owned_method_box(mut_box_string: &mut Box<String>, ref_str: &str) {
+    ref_str.clone_into(&mut (*mut_box_string));
+}
+
+fn owned_method_deref(mut_box_string: &mut HasDeref, ref_str: &str) {
+    ref_str.clone_into(&mut (*mut_box_string));
+}
+
+fn owned_function_mut_ref(mut_thing: &mut String, ref_str: &str) {
+    ::std::borrow::ToOwned::clone_into(ref_str, mut_thing);
+}
+
+fn owned_function_val(mut mut_thing: String, ref_str: &str) {
+    ::std::borrow::ToOwned::clone_into(ref_str, &mut mut_thing);
+}
+
+struct FakeToOwned;
+impl FakeToOwned {
+    /// This looks just like `ToOwned::to_owned`
+    fn to_owned(&self) -> Self {
+        FakeToOwned
+    }
+}
+
+fn fake_to_owned() {
+    let mut a = FakeToOwned;
+    let b = FakeToOwned;
+    // Should not be linted, since the ToOwned impl doesn't come from std
+    a = b.to_owned();
+}
+
+fn main() {}
+
+/// Trait implementation to allow producing a `Thing` with a low-precedence expression.
+impl Add for HasCloneFrom {
+    type Output = Self;
+    fn add(self, _: HasCloneFrom) -> Self {
+        self
+    }
+}
+/// Trait implementation to allow producing a `&Thing` with a low-precedence expression.
+impl<'a> Add for &'a HasCloneFrom {
+    type Output = Self;
+    fn add(self, _: &'a HasCloneFrom) -> Self {
+        self
+    }
+}
+/// Trait implementation to allow producing a `&mut Thing` with a low-precedence expression.
+impl<'a> Add for &'a mut HasCloneFrom {
+    type Output = Self;
+    fn add(self, _: &'a mut HasCloneFrom) -> Self {
+        self
+    }
+}

tests/ui/assigning_clones.rs

@@ -0,0 +1,211 @@
+// run-rustfix
+#![allow(unused)]
+#![allow(clippy::redundant_clone)]
+#![allow(clippy::ptr_arg)] // https://github.com/rust-lang/rust-clippy/issues/10612
+#![allow(clippy::needless_late_init)]
+#![allow(clippy::box_collection)]
+#![warn(clippy::assigning_clones)]
+
+use std::borrow::ToOwned;
+use std::ops::{Add, Deref, DerefMut};
+
+// Clone
+pub struct HasCloneFrom;
+
+impl Clone for HasCloneFrom {
+    fn clone(&self) -> Self {
+        Self
+    }
+    fn clone_from(&mut self, source: &Self) {
+        *self = HasCloneFrom;
+    }
+}
+
+fn clone_method_rhs_val(mut_thing: &mut HasCloneFrom, value_thing: HasCloneFrom) {
+    *mut_thing = value_thing.clone();
+}
+
+fn clone_method_rhs_ref(mut_thing: &mut HasCloneFrom, ref_thing: &HasCloneFrom) {
+    *mut_thing = ref_thing.clone();
+}
+
+fn clone_method_lhs_val(mut mut_thing: HasCloneFrom, ref_thing: &HasCloneFrom) {
+    mut_thing = ref_thing.clone();
+}
+
+fn clone_function_lhs_mut_ref(mut_thing: &mut HasCloneFrom, ref_thing: &HasCloneFrom) {
+    *mut_thing = Clone::clone(ref_thing);
+}
+
+fn clone_function_lhs_val(mut mut_thing: HasCloneFrom, ref_thing: &HasCloneFrom) {
+    mut_thing = Clone::clone(ref_thing);
+}
+
+fn clone_function_through_trait(mut_thing: &mut HasCloneFrom, ref_thing: &HasCloneFrom) {
+    *mut_thing = Clone::clone(ref_thing);
+}
+
+fn clone_function_through_type(mut_thing: &mut HasCloneFrom, ref_thing: &HasCloneFrom) {
+    *mut_thing = HasCloneFrom::clone(ref_thing);
+}
+
+fn clone_function_fully_qualified(mut_thing: &mut HasCloneFrom, ref_thing: &HasCloneFrom) {
+    *mut_thing = <HasCloneFrom as Clone>::clone(ref_thing);
+}
+
+fn clone_method_lhs_complex(mut_thing: &mut HasCloneFrom, ref_thing: &HasCloneFrom) {
+    // These parens should be kept as necessary for a receiver
+    *(mut_thing + &mut HasCloneFrom) = ref_thing.clone();
+}
+
+fn clone_method_rhs_complex(mut_thing: &mut HasCloneFrom, ref_thing: &HasCloneFrom) {
+    // These parens should be removed since they are not needed in a function argument
+    *mut_thing = (ref_thing + ref_thing).clone();
+}
+
+fn assign_to_init_mut_var(b: HasCloneFrom) -> HasCloneFrom {
+    let mut a = HasCloneFrom;
+    for _ in 1..10 {
+        a = b.clone();
+    }
+    a
+}
+
+fn assign_to_late_init_mut_var(b: HasCloneFrom) {
+    let mut a;
+    a = HasCloneFrom;
+    a = b.clone();
+}
+
+fn assign_to_uninit_var(b: HasCloneFrom) {
+    let a;
+    a = b.clone();
+}
+
+fn assign_to_uninit_mut_var(b: HasCloneFrom) {
+    let mut a;
+    a = b.clone();
+}
+
+#[derive(Clone)]
+pub struct HasDeriveClone;
+
+fn ignore_derive_clone(a: &mut HasDeriveClone, b: &HasDeriveClone) {
+    // Should not be linted, since the Clone impl is derived
+    *a = b.clone();
+}
+
+pub struct HasCloneImpl;
+
+impl Clone for HasCloneImpl {
+    fn clone(&self) -> Self {
+        Self
+    }
+}
+
+fn ignore_missing_clone_from(a: &mut HasCloneImpl, b: &HasCloneImpl) {
+    // Should not be linted, since the Clone impl doesn't override clone_from
+    *a = b.clone();
+}
+
+struct FakeClone;
+
+impl FakeClone {
+    /// This looks just like `Clone::clone`
+    fn clone(&self) -> Self {
+        FakeClone
+    }
+}
+
+fn ignore_fake_clone() {
+    let mut a = FakeClone;
+    let b = FakeClone;
+    // Should not be linted, since the Clone impl doesn't come from std
+    a = b.clone();
+}
+
+fn ignore_generic_clone<T: Clone>(a: &mut T, b: &T) {
+    // Should not be linted, since we don't know the actual clone impl
+    *a = b.clone();
+}
+
+// ToOwned
+fn owned_method_mut_ref(mut_string: &mut String, ref_str: &str) {
+    *mut_string = ref_str.to_owned();
+}
+
+fn owned_method_val(mut mut_string: String, ref_str: &str) {
+    mut_string = ref_str.to_owned();
+}
+
+struct HasDeref {
+    a: String,
+}
+
+impl Deref for HasDeref {
+    type Target = String;
+    fn deref(&self) -> &Self::Target {
+        &self.a
+    }
+}
+
+impl DerefMut for HasDeref {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.a
+    }
+}
+
+fn owned_method_box(mut_box_string: &mut Box<String>, ref_str: &str) {
+    **mut_box_string = ref_str.to_owned();
+}
+
+fn owned_method_deref(mut_box_string: &mut HasDeref, ref_str: &str) {
+    **mut_box_string = ref_str.to_owned();
+}
+
+fn owned_function_mut_ref(mut_thing: &mut String, ref_str: &str) {
+    *mut_thing = ToOwned::to_owned(ref_str);
+}
+
+fn owned_function_val(mut mut_thing: String, ref_str: &str) {
+    mut_thing = ToOwned::to_owned(ref_str);
+}
+
+struct FakeToOwned;
+impl FakeToOwned {
+    /// This looks just like `ToOwned::to_owned`
+    fn to_owned(&self) -> Self {
+        FakeToOwned
+    }
+}
+
+fn fake_to_owned() {
+    let mut a = FakeToOwned;
+    let b = FakeToOwned;
+    // Should not be linted, since the ToOwned impl doesn't come from std
+    a = b.to_owned();
+}
+
+fn main() {}
+
+/// Trait implementation to allow producing a `Thing` with a low-precedence expression.
+impl Add for HasCloneFrom {
+    type Output = Self;
+    fn add(self, _: HasCloneFrom) -> Self {
+        self
+    }
+}
+/// Trait implementation to allow producing a `&Thing` with a low-precedence expression.
+impl<'a> Add for &'a HasCloneFrom {
+    type Output = Self;
+    fn add(self, _: &'a HasCloneFrom) -> Self {
+        self
+    }
+}
+/// Trait implementation to allow producing a `&mut Thing` with a low-precedence expression.
+impl<'a> Add for &'a mut HasCloneFrom {
+    type Output = Self;
+    fn add(self, _: &'a mut HasCloneFrom) -> Self {
+        self
+    }
+}

tests/ui/assigning_clones.stderr

@@ -0,0 +1,107 @@
+error: assigning the result of `Clone::clone()` may be inefficient
+  --> $DIR/assigning_clones.rs:25:5
+   |
+LL |     *mut_thing = value_thing.clone();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `clone_from()`: `mut_thing.clone_from(&value_thing)`
+   |
+   = note: `-D clippy::assigning-clones` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::assigning_clones)]`
+
+error: assigning the result of `Clone::clone()` may be inefficient
+  --> $DIR/assigning_clones.rs:29:5
+   |
+LL |     *mut_thing = ref_thing.clone();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `clone_from()`: `mut_thing.clone_from(ref_thing)`
+
+error: assigning the result of `Clone::clone()` may be inefficient
+  --> $DIR/assigning_clones.rs:33:5
+   |
+LL |     mut_thing = ref_thing.clone();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `clone_from()`: `mut_thing.clone_from(ref_thing)`
+
+error: assigning the result of `Clone::clone()` may be inefficient
+  --> $DIR/assigning_clones.rs:37:5
+   |
+LL |     *mut_thing = Clone::clone(ref_thing);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `clone_from()`: `::std::clone::Clone::clone_from(mut_thing, ref_thing)`
+
+error: assigning the result of `Clone::clone()` may be inefficient
+  --> $DIR/assigning_clones.rs:41:5
+   |
+LL |     mut_thing = Clone::clone(ref_thing);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `clone_from()`: `::std::clone::Clone::clone_from(&mut mut_thing, ref_thing)`
+
+error: assigning the result of `Clone::clone()` may be inefficient
+  --> $DIR/assigning_clones.rs:45:5
+   |
+LL |     *mut_thing = Clone::clone(ref_thing);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `clone_from()`: `::std::clone::Clone::clone_from(mut_thing, ref_thing)`
+
+error: assigning the result of `Clone::clone()` may be inefficient
+  --> $DIR/assigning_clones.rs:49:5
+   |
+LL |     *mut_thing = HasCloneFrom::clone(ref_thing);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `clone_from()`: `::std::clone::Clone::clone_from(mut_thing, ref_thing)`
+
+error: assigning the result of `Clone::clone()` may be inefficient
+  --> $DIR/assigning_clones.rs:53:5
+   |
+LL |     *mut_thing = <HasCloneFrom as Clone>::clone(ref_thing);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `clone_from()`: `::std::clone::Clone::clone_from(mut_thing, ref_thing)`
+
+error: assigning the result of `Clone::clone()` may be inefficient
+  --> $DIR/assigning_clones.rs:58:5
+   |
+LL |     *(mut_thing + &mut HasCloneFrom) = ref_thing.clone();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `clone_from()`: `(mut_thing + &mut HasCloneFrom).clone_from(ref_thing)`
+
+error: assigning the result of `Clone::clone()` may be inefficient
+  --> $DIR/assigning_clones.rs:63:5
+   |
+LL |     *mut_thing = (ref_thing + ref_thing).clone();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `clone_from()`: `mut_thing.clone_from(ref_thing + ref_thing)`
+
+error: assigning the result of `Clone::clone()` may be inefficient
+  --> $DIR/assigning_clones.rs:69:9
+   |
+LL |         a = b.clone();
+   |         ^^^^^^^^^^^^^ help: use `clone_from()`: `a.clone_from(&b)`
+
+error: assigning the result of `ToOwned::to_owned()` may be inefficient
+  --> $DIR/assigning_clones.rs:134:5
+   |
+LL |     *mut_string = ref_str.to_owned();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `clone_into()`: `ref_str.clone_into(mut_string)`
+
+error: assigning the result of `ToOwned::to_owned()` may be inefficient
+  --> $DIR/assigning_clones.rs:138:5
+   |
+LL |     mut_string = ref_str.to_owned();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `clone_into()`: `ref_str.clone_into(&mut mut_string)`
+
+error: assigning the result of `ToOwned::to_owned()` may be inefficient
+  --> $DIR/assigning_clones.rs:159:5
+   |
+LL |     **mut_box_string = ref_str.to_owned();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `clone_into()`: `ref_str.clone_into(&mut (*mut_box_string))`
+
+error: assigning the result of `ToOwned::to_owned()` may be inefficient
+  --> $DIR/assigning_clones.rs:163:5
+   |
+LL |     **mut_box_string = ref_str.to_owned();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `clone_into()`: `ref_str.clone_into(&mut (*mut_box_string))`
+
+error: assigning the result of `ToOwned::to_owned()` may be inefficient
+  --> $DIR/assigning_clones.rs:167:5
+   |
+LL |     *mut_thing = ToOwned::to_owned(ref_str);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `clone_into()`: `::std::borrow::ToOwned::clone_into(ref_str, mut_thing)`
+
+error: assigning the result of `ToOwned::to_owned()` may be inefficient
+  --> $DIR/assigning_clones.rs:171:5
+   |
+LL |     mut_thing = ToOwned::to_owned(ref_str);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `clone_into()`: `::std::borrow::ToOwned::clone_into(ref_str, &mut mut_thing)`
+
+error: aborting due to 17 previous errors
+