133 lines
4.2 KiB
Rust
133 lines
4.2 KiB
Rust
use rustc_ast::Mutability;
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use rustc_data_structures::fx::FxHashMap;
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use rustc_hir::{def::Res, Expr, ExprKind, HirId, Local, QPath, StmtKind, UnOp};
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use rustc_middle::ty::{self, TypeAndMut};
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use rustc_span::{sym, Span};
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use crate::{lints::InvalidReferenceCastingDiag, LateContext, LateLintPass, LintContext};
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declare_lint! {
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/// The `invalid_reference_casting` lint checks for casts of `&T` to `&mut T`
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/// without using interior mutability.
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///
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/// ### Example
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///
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/// ```rust,compile_fail
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/// fn x(r: &i32) {
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/// unsafe {
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/// *(r as *const i32 as *mut i32) += 1;
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/// }
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/// }
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/// ```
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///
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/// {{produces}}
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///
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/// ### Explanation
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///
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/// Casting `&T` to `&mut T` without using interior mutability is undefined behavior,
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/// as it's a violation of Rust reference aliasing requirements.
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///
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/// `UnsafeCell` is the only way to obtain aliasable data that is considered
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/// mutable.
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INVALID_REFERENCE_CASTING,
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Deny,
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"casts of `&T` to `&mut T` without interior mutability"
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}
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#[derive(Default)]
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pub struct InvalidReferenceCasting {
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casted: FxHashMap<HirId, Span>,
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}
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impl_lint_pass!(InvalidReferenceCasting => [INVALID_REFERENCE_CASTING]);
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impl<'tcx> LateLintPass<'tcx> for InvalidReferenceCasting {
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fn check_stmt(&mut self, cx: &LateContext<'tcx>, stmt: &'tcx rustc_hir::Stmt<'tcx>) {
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let StmtKind::Local(local) = stmt.kind else {
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return;
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};
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let Local { init: Some(init), els: None, .. } = local else {
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return;
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};
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if is_cast_from_const_to_mut(cx, init) {
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self.casted.insert(local.pat.hir_id, init.span);
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}
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}
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
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// &mut <expr>
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let inner = if let ExprKind::AddrOf(_, Mutability::Mut, expr) = expr.kind {
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expr
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// <expr> = ...
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} else if let ExprKind::Assign(expr, _, _) = expr.kind {
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expr
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// <expr> += ...
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} else if let ExprKind::AssignOp(_, expr, _) = expr.kind {
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expr
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} else {
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return;
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};
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let ExprKind::Unary(UnOp::Deref, e) = &inner.kind else {
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return;
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};
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let orig_cast = if is_cast_from_const_to_mut(cx, e) {
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None
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} else if let ExprKind::Path(QPath::Resolved(_, path)) = e.kind
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&& let Res::Local(hir_id) = &path.res
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&& let Some(orig_cast) = self.casted.get(hir_id) {
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Some(*orig_cast)
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} else {
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return;
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};
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cx.emit_spanned_lint(
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INVALID_REFERENCE_CASTING,
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expr.span,
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if matches!(expr.kind, ExprKind::AddrOf(..)) {
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InvalidReferenceCastingDiag::BorrowAsMut { orig_cast }
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} else {
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InvalidReferenceCastingDiag::AssignToRef { orig_cast }
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},
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);
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}
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}
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fn is_cast_from_const_to_mut<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'tcx>) -> bool {
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let e = e.peel_blocks();
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// <expr> as *mut ...
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let e = if let ExprKind::Cast(e, t) = e.kind
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&& let ty::RawPtr(TypeAndMut { mutbl: Mutability::Mut, .. }) = cx.typeck_results().node_type(t.hir_id).kind() {
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e
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// <expr>.cast_mut()
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} else if let ExprKind::MethodCall(_, expr, [], _) = e.kind
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&& let Some(def_id) = cx.typeck_results().type_dependent_def_id(e.hir_id)
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&& cx.tcx.is_diagnostic_item(sym::ptr_cast_mut, def_id) {
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expr
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} else {
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return false;
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};
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let e = e.peel_blocks();
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// <expr> as *const ...
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let e = if let ExprKind::Cast(e, t) = e.kind
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&& let ty::RawPtr(TypeAndMut { mutbl: Mutability::Not, .. }) = cx.typeck_results().node_type(t.hir_id).kind() {
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e
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// ptr::from_ref(<expr>)
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} else if let ExprKind::Call(path, [arg]) = e.kind
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&& let ExprKind::Path(ref qpath) = path.kind
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&& let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id()
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&& cx.tcx.is_diagnostic_item(sym::ptr_from_ref, def_id) {
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arg
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} else {
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return false;
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};
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let e = e.peel_blocks();
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matches!(cx.typeck_results().node_type(e.hir_id).kind(), ty::Ref(_, _, Mutability::Not))
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}
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