101 lines
3.4 KiB
Rust
101 lines
3.4 KiB
Rust
//! Checks for needless address of operations (`&`)
|
|
//!
|
|
//! This lint is **warn** by default
|
|
|
|
use rustc::lint::*;
|
|
use rustc::hir::{BindingAnnotation, Expr, ExprAddrOf, MutImmutable, Pat, PatKind};
|
|
use rustc::ty;
|
|
use rustc::ty::adjustment::{Adjust, Adjustment};
|
|
use utils::{in_macro, snippet_opt, span_lint_and_then};
|
|
|
|
/// **What it does:** Checks for address of operations (`&`) that are going to
|
|
/// be dereferenced immediately by the compiler.
|
|
///
|
|
/// **Why is this bad?** Suggests that the receiver of the expression borrows
|
|
/// the expression.
|
|
///
|
|
/// **Known problems:** None.
|
|
///
|
|
/// **Example:**
|
|
/// ```rust
|
|
/// let x: &i32 = &&&&&&5;
|
|
/// ```
|
|
declare_clippy_lint! {
|
|
pub NEEDLESS_BORROW,
|
|
complexity,
|
|
"taking a reference that is going to be automatically dereferenced"
|
|
}
|
|
|
|
#[derive(Copy, Clone)]
|
|
pub struct NeedlessBorrow;
|
|
|
|
impl LintPass for NeedlessBorrow {
|
|
fn get_lints(&self) -> LintArray {
|
|
lint_array!(NEEDLESS_BORROW)
|
|
}
|
|
}
|
|
|
|
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NeedlessBorrow {
|
|
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
|
|
if in_macro(e.span) {
|
|
return;
|
|
}
|
|
if let ExprAddrOf(MutImmutable, ref inner) = e.node {
|
|
if let ty::TyRef(..) = cx.tables.expr_ty(inner).sty {
|
|
for adj3 in cx.tables.expr_adjustments(e).windows(3) {
|
|
if let [Adjustment {
|
|
kind: Adjust::Deref(_),
|
|
..
|
|
}, Adjustment {
|
|
kind: Adjust::Deref(_),
|
|
..
|
|
}, Adjustment {
|
|
kind: Adjust::Borrow(_),
|
|
..
|
|
}] = *adj3
|
|
{
|
|
span_lint_and_then(
|
|
cx,
|
|
NEEDLESS_BORROW,
|
|
e.span,
|
|
"this expression borrows a reference that is immediately dereferenced \
|
|
by the compiler",
|
|
|db| {
|
|
if let Some(snippet) = snippet_opt(cx, inner.span) {
|
|
db.span_suggestion(e.span, "change this to", snippet);
|
|
}
|
|
},
|
|
);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
fn check_pat(&mut self, cx: &LateContext<'a, 'tcx>, pat: &'tcx Pat) {
|
|
if in_macro(pat.span) {
|
|
return;
|
|
}
|
|
if_chain! {
|
|
if let PatKind::Binding(BindingAnnotation::Ref, _, name, _) = pat.node;
|
|
if let ty::TyRef(_, ref tam) = cx.tables.pat_ty(pat).sty;
|
|
if tam.mutbl == MutImmutable;
|
|
if let ty::TyRef(_, ref tam) = tam.ty.sty;
|
|
// only lint immutable refs, because borrowed `&mut T` cannot be moved out
|
|
if tam.mutbl == MutImmutable;
|
|
then {
|
|
span_lint_and_then(
|
|
cx,
|
|
NEEDLESS_BORROW,
|
|
pat.span,
|
|
"this pattern creates a reference to a reference",
|
|
|db| {
|
|
if let Some(snippet) = snippet_opt(cx, name.span) {
|
|
db.span_suggestion(pat.span, "change this to", snippet);
|
|
}
|
|
}
|
|
)
|
|
}
|
|
}
|
|
}
|
|
}
|