108 lines
3.6 KiB
Rust
108 lines
3.6 KiB
Rust
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use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::source::snippet_opt;
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use clippy_utils::{match_def_path, meets_msrv, msrvs, paths};
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use rustc_ast::ast::LitKind;
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use rustc_errors::Applicability;
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use rustc_hir::{BinOpKind, Expr, ExprKind, GenericArg, QPath};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::ty::{self, Ty};
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use rustc_semver::RustcVersion;
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use rustc_session::{declare_tool_lint, impl_lint_pass};
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for uses of `std::mem::size_of::<T>() * 8` when
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/// `T::BITS` is available.
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///
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/// ### Why is this bad?
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/// Can be written as the shorter `T::BITS`.
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///
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/// ### Example
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/// ```rust
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/// std::mem::size_of::<usize>() * 8;
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/// ```
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/// Use instead:
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/// ```rust
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/// usize::BITS;
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/// ```
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#[clippy::version = "1.60.0"]
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pub MANUAL_BITS,
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style,
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"manual implementation of `size_of::<T>() * 8` can be simplified with `T::BITS`"
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}
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#[derive(Clone)]
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pub struct ManualBits {
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msrv: Option<RustcVersion>,
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}
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impl ManualBits {
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#[must_use]
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pub fn new(msrv: Option<RustcVersion>) -> Self {
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Self { msrv }
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}
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}
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impl_lint_pass!(ManualBits => [MANUAL_BITS]);
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impl<'tcx> LateLintPass<'tcx> for ManualBits {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if !meets_msrv(self.msrv.as_ref(), &msrvs::MANUAL_BITS) {
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return;
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}
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if_chain! {
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if let ExprKind::Binary(bin_op, left_expr, right_expr) = expr.kind;
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if let BinOpKind::Mul = &bin_op.node;
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if let Some((real_ty, resolved_ty, other_expr)) = get_one_size_of_ty(cx, left_expr, right_expr);
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if matches!(resolved_ty.kind(), ty::Int(_) | ty::Uint(_));
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if let ExprKind::Lit(lit) = &other_expr.kind;
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if let LitKind::Int(8, _) = lit.node;
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then {
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span_lint_and_sugg(
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cx,
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MANUAL_BITS,
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expr.span,
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"usage of `mem::size_of::<T>()` to obtain the size of `T` in bits",
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"consider using",
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format!("{}::BITS", snippet_opt(cx, real_ty.span).unwrap()),
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Applicability::MachineApplicable,
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);
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}
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}
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}
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}
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fn get_one_size_of_ty<'tcx>(
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cx: &LateContext<'tcx>,
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expr1: &'tcx Expr<'_>,
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expr2: &'tcx Expr<'_>,
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) -> Option<(&'tcx rustc_hir::Ty<'tcx>, Ty<'tcx>, &'tcx Expr<'tcx>)> {
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match (get_size_of_ty(cx, expr1), get_size_of_ty(cx, expr2)) {
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(Some((real_ty, resolved_ty)), None) => Some((real_ty, resolved_ty, expr2)),
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(None, Some((real_ty, resolved_ty))) => Some((real_ty, resolved_ty, expr1)),
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_ => None,
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}
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}
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fn get_size_of_ty<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<(&'tcx rustc_hir::Ty<'tcx>, Ty<'tcx>)> {
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if_chain! {
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if let ExprKind::Call(count_func, _func_args) = expr.kind;
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if let ExprKind::Path(ref count_func_qpath) = count_func.kind;
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if let QPath::Resolved(_, count_func_path) = count_func_qpath;
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if let Some(segment_zero) = count_func_path.segments.get(0);
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if let Some(args) = segment_zero.args;
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if let Some(GenericArg::Type(real_ty)) = args.args.get(0);
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if let Some(def_id) = cx.qpath_res(count_func_qpath, count_func.hir_id).opt_def_id();
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if match_def_path(cx, def_id, &paths::MEM_SIZE_OF);
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then {
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cx.typeck_results().node_substs(count_func.hir_id).types().next().map(|resolved_ty| (real_ty, resolved_ty))
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} else {
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None
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}
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}
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}
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