4f4abf4e06
Warn about assignments where left-hand side place expression is the same
as right-hand side value expression. For example, warn about assignment in:
```rust
pub struct Event {
id: usize,
x: i32,
y: i32,
}
pub fn copy_position(a: &mut Event, b: &Event) {
a.x = b.x;
a.y = a.y;
}
```
52 lines
1.5 KiB
Rust
52 lines
1.5 KiB
Rust
use crate::utils::{eq_expr_value, snippet, span_lint};
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use rustc_hir::{Expr, ExprKind};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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declare_clippy_lint! {
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/// **What it does:** Checks for explicit self-assignments.
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///
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/// **Why is this bad?** Self-assignments are redundant and unlikely to be
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/// intentional.
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///
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/// **Known problems:** If expression contains any deref coercions or
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/// indexing operations they are assumed not to have any side effects.
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///
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/// **Example:**
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///
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/// ```rust
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/// struct Event {
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/// id: usize,
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/// x: i32,
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/// y: i32,
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/// }
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///
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/// fn copy_position(a: &mut Event, b: &Event) {
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/// a.x = b.x;
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/// a.y = a.y;
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/// }
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/// ```
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pub SELF_ASSIGNMENT,
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correctness,
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"explicit self-assignment"
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}
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declare_lint_pass!(SelfAssignment => [SELF_ASSIGNMENT]);
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impl<'tcx> LateLintPass<'tcx> for SelfAssignment {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if let ExprKind::Assign(lhs, rhs, _) = &expr.kind {
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if eq_expr_value(cx, lhs, rhs) {
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let lhs = snippet(cx, lhs.span, "<lhs>");
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let rhs = snippet(cx, rhs.span, "<rhs>");
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span_lint(
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cx,
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SELF_ASSIGNMENT,
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expr.span,
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&format!("self-assignment of `{}` to `{}`", rhs, lhs),
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);
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}
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}
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}
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}
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