Move SelfAssignment into Operators lint pass

Author: Jarcho

clippy_lints/src/lib.register_all.rs

@@ -254,6 +254,7 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
     LintId::of(operators::MODULO_ONE),
     LintId::of(operators::OP_REF),
     LintId::of(operators::PTR_EQ),
+    LintId::of(operators::SELF_ASSIGNMENT),
     LintId::of(option_env_unwrap::OPTION_ENV_UNWRAP),
     LintId::of(overflow_check_conditional::OVERFLOW_CHECK_CONDITIONAL),
     LintId::of(partialeq_ne_impl::PARTIALEQ_NE_IMPL),
@@ -278,7 +279,6 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
     LintId::of(repeat_once::REPEAT_ONCE),
     LintId::of(returns::LET_AND_RETURN),
     LintId::of(returns::NEEDLESS_RETURN),
-    LintId::of(self_assignment::SELF_ASSIGNMENT),
     LintId::of(self_named_constructors::SELF_NAMED_CONSTRUCTORS),
     LintId::of(serde_api::SERDE_API_MISUSE),
     LintId::of(significant_drop_in_scrutinee::SIGNIFICANT_DROP_IN_SCRUTINEE),

clippy_lints/src/lib.register_correctness.rs

@@ -51,12 +51,12 @@ store.register_group(true, "clippy::correctness", Some("clippy_correctness"), ve
     LintId::of(operators::ERASING_OP),
     LintId::of(operators::INEFFECTIVE_BIT_MASK),
     LintId::of(operators::MODULO_ONE),
+    LintId::of(operators::SELF_ASSIGNMENT),
     LintId::of(option_env_unwrap::OPTION_ENV_UNWRAP),
     LintId::of(ptr::INVALID_NULL_PTR_USAGE),
     LintId::of(ptr::MUT_FROM_REF),
     LintId::of(ranges::REVERSED_EMPTY_RANGES),
     LintId::of(regex::INVALID_REGEX),
-    LintId::of(self_assignment::SELF_ASSIGNMENT),
     LintId::of(serde_api::SERDE_API_MISUSE),
     LintId::of(size_of_in_element_count::SIZE_OF_IN_ELEMENT_COUNT),
     LintId::of(swap::ALMOST_SWAPPED),

clippy_lints/src/lib.register_lints.rs

@@ -425,6 +425,7 @@ store.register_lints(&[
     operators::NEEDLESS_BITWISE_BOOL,
     operators::OP_REF,
     operators::PTR_EQ,
+    operators::SELF_ASSIGNMENT,
     operators::VERBOSE_BIT_MASK,
     option_env_unwrap::OPTION_ENV_UNWRAP,
     option_if_let_else::OPTION_IF_LET_ELSE,
@@ -470,7 +471,6 @@ store.register_lints(&[
     returns::LET_AND_RETURN,
     returns::NEEDLESS_RETURN,
     same_name_method::SAME_NAME_METHOD,
-    self_assignment::SELF_ASSIGNMENT,
     self_named_constructors::SELF_NAMED_CONSTRUCTORS,
     semicolon_if_nothing_returned::SEMICOLON_IF_NOTHING_RETURNED,
     serde_api::SERDE_API_MISUSE,

clippy_lints/src/lib.rs

@@ -351,7 +351,6 @@ mod repeat_once;
 mod return_self_not_must_use;
 mod returns;
 mod same_name_method;
-mod self_assignment;
 mod self_named_constructors;
 mod semicolon_if_nothing_returned;
 mod serde_api;
@@ -805,7 +804,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(|| Box::new(stable_sort_primitive::StableSortPrimitive));
     store.register_late_pass(|| Box::new(repeat_once::RepeatOnce));
     store.register_late_pass(|| Box::new(unwrap_in_result::UnwrapInResult));
-    store.register_late_pass(|| Box::new(self_assignment::SelfAssignment));
     store.register_late_pass(|| Box::new(manual_unwrap_or::ManualUnwrapOr));
     store.register_late_pass(|| Box::new(manual_ok_or::ManualOkOr));
     store.register_late_pass(|| Box::new(semicolon_if_nothing_returned::SemicolonIfNothingReturned));

clippy_lints/src/operators/mod.rs

@@ -22,6 +22,7 @@ mod modulo_one;
 mod needless_bitwise_bool;
 mod op_ref;
 mod ptr_eq;
+mod self_assignment;
 mod verbose_bit_mask;
 
 declare_clippy_lint! {
@@ -686,6 +687,37 @@ declare_clippy_lint! {
     "use `std::ptr::eq` when comparing raw pointers"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for explicit self-assignments.
+    ///
+    /// ### Why is this bad?
+    /// Self-assignments are redundant and unlikely to be
+    /// intentional.
+    ///
+    /// ### Known problems
+    /// If expression contains any deref coercions or
+    /// indexing operations they are assumed not to have any side effects.
+    ///
+    /// ### Example
+    /// ```rust
+    /// struct Event {
+    ///     id: usize,
+    ///     x: i32,
+    ///     y: i32,
+    /// }
+    ///
+    /// fn copy_position(a: &mut Event, b: &Event) {
+    ///     a.x = b.x;
+    ///     a.y = a.y;
+    /// }
+    /// ```
+    #[clippy::version = "1.48.0"]
+    pub SELF_ASSIGNMENT,
+    correctness,
+    "explicit self-assignment"
+}
+
 pub struct Operators {
     arithmetic_context: arithmetic::Context,
     verbose_bit_mask_threshold: u64,
@@ -715,6 +747,7 @@ impl_lint_pass!(Operators => [
     MODULO_ARITHMETIC,
     NEEDLESS_BITWISE_BOOL,
     PTR_EQ,
+    SELF_ASSIGNMENT,
 ]);
 impl Operators {
     pub fn new(verbose_bit_mask_threshold: u64) -> Self {
@@ -760,6 +793,7 @@ impl<'tcx> LateLintPass<'tcx> for Operators {
             },
             ExprKind::Assign(lhs, rhs, _) => {
                 assign_op_pattern::check(cx, e, lhs, rhs);
+                self_assignment::check(cx, e, lhs, rhs);
             },
             ExprKind::Unary(op, arg) => {
                 if op == UnOp::Neg {

clippy_lints/src/operators/self_assignment.rs

@@ -0,0 +1,20 @@
+use clippy_utils::diagnostics::span_lint;
+use clippy_utils::eq_expr_value;
+use clippy_utils::source::snippet;
+use rustc_hir::Expr;
+use rustc_lint::LateContext;
+
+use super::SELF_ASSIGNMENT;
+
+pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>, lhs: &'tcx Expr<'_>, rhs: &'tcx Expr<'_>) {
+    if eq_expr_value(cx, lhs, rhs) {
+        let lhs = snippet(cx, lhs.span, "<lhs>");
+        let rhs = snippet(cx, rhs.span, "<rhs>");
+        span_lint(
+            cx,
+            SELF_ASSIGNMENT,
+            e.span,
+            &format!("self-assignment of `{}` to `{}`", rhs, lhs),
+        );
+    }
+}