75 lines
2.4 KiB
Rust
75 lines
2.4 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_help;
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use clippy_utils::{path_def_id, peel_middle_ty_refs};
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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;
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use rustc_span::sym;
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declare_clippy_lint! {
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/// ### What it does
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///
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/// Checks for calls to `std::mem::size_of_val()` where the argument is
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/// a reference to a reference.
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///
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/// ### Why is this bad?
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///
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/// Calling `size_of_val()` with a reference to a reference as the argument
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/// yields the size of the reference-type, not the size of the value behind
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/// the reference.
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///
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/// ### Example
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/// ```no_run
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/// struct Foo {
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/// buffer: [u8],
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/// }
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///
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/// impl Foo {
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/// fn size(&self) -> usize {
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/// // Note that `&self` as an argument is a `&&Foo`: Because `self`
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/// // is already a reference, `&self` is a double-reference.
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/// // The return value of `size_of_val()` therefore is the
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/// // size of the reference-type, not the size of `self`.
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/// std::mem::size_of_val(&self)
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/// }
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/// }
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/// ```
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/// Use instead:
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/// ```no_run
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/// struct Foo {
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/// buffer: [u8],
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/// }
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///
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/// impl Foo {
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/// fn size(&self) -> usize {
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/// // Correct
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/// std::mem::size_of_val(self)
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/// }
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/// }
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/// ```
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#[clippy::version = "1.68.0"]
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pub SIZE_OF_REF,
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suspicious,
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"Argument to `std::mem::size_of_val()` is a double-reference, which is almost certainly unintended"
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}
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declare_lint_pass!(SizeOfRef => [SIZE_OF_REF]);
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impl LateLintPass<'_> for SizeOfRef {
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fn check_expr(&mut self, cx: &LateContext<'_>, expr: &'_ Expr<'_>) {
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if let ExprKind::Call(path, [arg]) = expr.kind
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&& let Some(def_id) = path_def_id(cx, path)
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&& cx.tcx.is_diagnostic_item(sym::mem_size_of_val, def_id)
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&& let arg_ty = cx.typeck_results().expr_ty(arg)
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&& peel_middle_ty_refs(arg_ty).1 > 1
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{
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span_lint_and_help(
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cx,
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SIZE_OF_REF,
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expr.span,
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"argument to `std::mem::size_of_val()` is a reference to a reference",
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None,
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"dereference the argument to `std::mem::size_of_val()` to get the size of the value instead of the size of the reference-type",
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);
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}
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}
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}
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