use rustc::lint::*;
use rustc::hir::{ExprAddrOf, Expr, MutImmutable, Pat, PatKind, BindingMode};
use rustc::ty::TyRef;
use utils::{span_lint, in_macro};
use rustc::ty::adjustment::AutoAdjustment::AdjustDerefRef;
declare_lint! {
pub NEEDLESS_BORROW,
Warn,
"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 LateLintPass for NeedlessBorrow {
fn check_expr(&mut self, cx: &LateContext, e: &Expr) {
if in_macro(cx, e.span) {
return;
}
if let ExprAddrOf(MutImmutable, ref inner) = e.node {
if let TyRef(..) = cx.tcx.expr_ty(inner).sty {
if let Some(&AdjustDerefRef(ref deref)) = cx.tcx.tables.borrow().adjustments.get(&e.id) {
if deref.autoderefs > 1 && deref.autoref.is_some() {
span_lint(cx,
NEEDLESS_BORROW,
e.span,
"this expression borrows a reference that is immediately dereferenced by the \
compiler");
}
}
}
}
}
fn check_pat(&mut self, cx: &LateContext, pat: &Pat) {
if in_macro(cx, pat.span) {
return;
}
if let PatKind::Binding(BindingMode::BindByRef(MutImmutable), _, _) = pat.node {
if let TyRef(_, ref tam) = cx.tcx.pat_ty(pat).sty {
if tam.mutbl == MutImmutable {
if let TyRef(..) = tam.ty.sty {
span_lint(cx,
NEEDLESS_BORROW,
pat.span,
"this pattern creates a reference to a reference")
}
}
}
}
}
}