96 lines
3.3 KiB
Rust
96 lines
3.3 KiB
Rust
use clippy_utils::diagnostics::{span_lint, span_lint_hir};
|
|
use clippy_utils::higher;
|
|
use rustc_hir as hir;
|
|
use rustc_hir::intravisit;
|
|
use rustc_lint::{LateContext, LateLintPass, LintContext};
|
|
use rustc_middle::lint::in_external_macro;
|
|
use rustc_middle::ty;
|
|
use rustc_session::declare_lint_pass;
|
|
|
|
declare_clippy_lint! {
|
|
/// ### What it does
|
|
/// Checks for instances of `mut mut` references.
|
|
///
|
|
/// ### Why is this bad?
|
|
/// Multiple `mut`s don't add anything meaningful to the
|
|
/// source. This is either a copy'n'paste error, or it shows a fundamental
|
|
/// misunderstanding of references.
|
|
///
|
|
/// ### Example
|
|
/// ```no_run
|
|
/// # let mut y = 1;
|
|
/// let x = &mut &mut y;
|
|
/// ```
|
|
#[clippy::version = "pre 1.29.0"]
|
|
pub MUT_MUT,
|
|
pedantic,
|
|
"usage of double-mut refs, e.g., `&mut &mut ...`"
|
|
}
|
|
|
|
declare_lint_pass!(MutMut => [MUT_MUT]);
|
|
|
|
impl<'tcx> LateLintPass<'tcx> for MutMut {
|
|
fn check_block(&mut self, cx: &LateContext<'tcx>, block: &'tcx hir::Block<'_>) {
|
|
intravisit::walk_block(&mut MutVisitor { cx }, block);
|
|
}
|
|
|
|
fn check_ty(&mut self, cx: &LateContext<'tcx>, ty: &'tcx hir::Ty<'_>) {
|
|
if let hir::TyKind::Ref(_, mty) = ty.kind
|
|
&& mty.mutbl == hir::Mutability::Mut
|
|
&& let hir::TyKind::Ref(_, mty) = mty.ty.kind
|
|
&& mty.mutbl == hir::Mutability::Mut
|
|
&& !in_external_macro(cx.sess(), ty.span)
|
|
{
|
|
span_lint(
|
|
cx,
|
|
MUT_MUT,
|
|
ty.span,
|
|
"generally you want to avoid `&mut &mut _` if possible",
|
|
);
|
|
}
|
|
}
|
|
}
|
|
|
|
pub struct MutVisitor<'a, 'tcx> {
|
|
cx: &'a LateContext<'tcx>,
|
|
}
|
|
|
|
impl<'a, 'tcx> intravisit::Visitor<'tcx> for MutVisitor<'a, 'tcx> {
|
|
fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
|
|
if in_external_macro(self.cx.sess(), expr.span) {
|
|
return;
|
|
}
|
|
|
|
if let Some(higher::ForLoop { arg, body, .. }) = higher::ForLoop::hir(expr) {
|
|
// A `for` loop lowers to:
|
|
// ```rust
|
|
// match ::std::iter::Iterator::next(&mut iter) {
|
|
// // ^^^^
|
|
// ```
|
|
// Let's ignore the generated code.
|
|
intravisit::walk_expr(self, arg);
|
|
intravisit::walk_expr(self, body);
|
|
} else if let hir::ExprKind::AddrOf(hir::BorrowKind::Ref, hir::Mutability::Mut, e) = expr.kind {
|
|
if let hir::ExprKind::AddrOf(hir::BorrowKind::Ref, hir::Mutability::Mut, _) = e.kind {
|
|
span_lint_hir(
|
|
self.cx,
|
|
MUT_MUT,
|
|
expr.hir_id,
|
|
expr.span,
|
|
"generally you want to avoid `&mut &mut _` if possible",
|
|
);
|
|
} else if let ty::Ref(_, ty, hir::Mutability::Mut) = self.cx.typeck_results().expr_ty(e).kind() {
|
|
if ty.peel_refs().is_sized(self.cx.tcx, self.cx.param_env) {
|
|
span_lint_hir(
|
|
self.cx,
|
|
MUT_MUT,
|
|
expr.hir_id,
|
|
expr.span,
|
|
"this expression mutably borrows a mutable reference. Consider reborrowing",
|
|
);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|