79c69112dc
Since Clippy uses the `let_chains` feature, there are many occasions to collapse `if` and `if let` statements.
112 lines
4.3 KiB
Rust
112 lines
4.3 KiB
Rust
use crate::reference::DEREF_ADDROF;
|
|
use clippy_utils::diagnostics::span_lint_and_then;
|
|
use clippy_utils::source::SpanRangeExt;
|
|
use clippy_utils::ty::implements_trait;
|
|
use clippy_utils::{get_parent_expr, is_from_proc_macro, is_lint_allowed, is_mutable};
|
|
use rustc_errors::Applicability;
|
|
use rustc_hir::{BorrowKind, ExprKind, UnOp};
|
|
use rustc_lint::{LateContext, LateLintPass};
|
|
use rustc_middle::mir::Mutability;
|
|
use rustc_middle::ty;
|
|
use rustc_session::declare_lint_pass;
|
|
|
|
declare_clippy_lint! {
|
|
/// ### What it does
|
|
/// Checks for `&*(&T)`.
|
|
///
|
|
/// ### Why is this bad?
|
|
/// Dereferencing and then borrowing a reference value has no effect in most cases.
|
|
///
|
|
/// ### Known problems
|
|
/// False negative on such code:
|
|
/// ```no_run
|
|
/// let x = &12;
|
|
/// let addr_x = &x as *const _ as usize;
|
|
/// let addr_y = &&*x as *const _ as usize; // assert ok now, and lint triggered.
|
|
/// // But if we fix it, assert will fail.
|
|
/// assert_ne!(addr_x, addr_y);
|
|
/// ```
|
|
///
|
|
/// ### Example
|
|
/// ```no_run
|
|
/// let s = &String::new();
|
|
///
|
|
/// let a: &String = &* s;
|
|
/// ```
|
|
///
|
|
/// Use instead:
|
|
/// ```no_run
|
|
/// # let s = &String::new();
|
|
/// let a: &String = s;
|
|
/// ```
|
|
#[clippy::version = "1.63.0"]
|
|
pub BORROW_DEREF_REF,
|
|
complexity,
|
|
"deref on an immutable reference returns the same type as itself"
|
|
}
|
|
|
|
declare_lint_pass!(BorrowDerefRef => [BORROW_DEREF_REF]);
|
|
|
|
impl<'tcx> LateLintPass<'tcx> for BorrowDerefRef {
|
|
fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &rustc_hir::Expr<'tcx>) {
|
|
if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, addrof_target) = e.kind
|
|
&& let ExprKind::Unary(UnOp::Deref, deref_target) = addrof_target.kind
|
|
&& !matches!(deref_target.kind, ExprKind::Unary(UnOp::Deref, ..))
|
|
&& !e.span.from_expansion()
|
|
&& !deref_target.span.from_expansion()
|
|
&& !addrof_target.span.from_expansion()
|
|
&& let ref_ty = cx.typeck_results().expr_ty(deref_target)
|
|
&& let ty::Ref(_, inner_ty, Mutability::Not) = ref_ty.kind()
|
|
&& get_parent_expr(cx, e).is_none_or(|parent| {
|
|
match parent.kind {
|
|
// `*&*foo` should lint `deref_addrof` instead.
|
|
ExprKind::Unary(UnOp::Deref, _) => is_lint_allowed(cx, DEREF_ADDROF, parent.hir_id),
|
|
// `&*foo` creates a distinct temporary from `foo`
|
|
ExprKind::AddrOf(_, Mutability::Mut, _) => !matches!(
|
|
deref_target.kind,
|
|
ExprKind::Path(..)
|
|
| ExprKind::Field(..)
|
|
| ExprKind::Index(..)
|
|
| ExprKind::Unary(UnOp::Deref, ..)
|
|
),
|
|
_ => true,
|
|
}
|
|
})
|
|
&& !is_from_proc_macro(cx, e)
|
|
&& let e_ty = cx.typeck_results().expr_ty_adjusted(e)
|
|
// check if the reference is coercing to a mutable reference
|
|
&& (!matches!(e_ty.kind(), ty::Ref(_, _, Mutability::Mut)) || is_mutable(cx, deref_target))
|
|
&& let Some(deref_text) = deref_target.span.get_source_text(cx)
|
|
{
|
|
span_lint_and_then(
|
|
cx,
|
|
BORROW_DEREF_REF,
|
|
e.span,
|
|
"deref on an immutable reference",
|
|
|diag| {
|
|
diag.span_suggestion(
|
|
e.span,
|
|
"if you would like to reborrow, try removing `&*`",
|
|
deref_text.as_str(),
|
|
Applicability::MachineApplicable,
|
|
);
|
|
|
|
// has deref trait -> give 2 help
|
|
// doesn't have deref trait -> give 1 help
|
|
if let Some(deref_trait_id) = cx.tcx.lang_items().deref_trait()
|
|
&& !implements_trait(cx, *inner_ty, deref_trait_id, &[])
|
|
{
|
|
return;
|
|
}
|
|
|
|
diag.span_suggestion(
|
|
e.span,
|
|
"if you would like to deref, try using `&**`",
|
|
format!("&**{deref_text}"),
|
|
Applicability::MaybeIncorrect,
|
|
);
|
|
},
|
|
);
|
|
}
|
|
}
|
|
}
|