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Improve redundant_slicing

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Fix bad suggestion when a reborrow might be required
Fix bad suggestion when the value being sliced is a macro call
Don't lint inside of a macro due to the previous context sensitive changes
This commit is contained in:
Jason Newcomb 2021-03-25 22:30:14 -04:00
parent f41d68faa6
commit 0ff68bb151
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GPG key ID: DA59E8643A37ED06
3 changed files with 78 additions and 20 deletions
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37
clippy_lints/src/redundant_slicing.rs
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@ -1,11 +1,12 @@
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet_with_applicability;
use clippy_utils::source::snippet_with_context;
use clippy_utils::ty::is_type_lang_item;
use clippy_utils::{get_parent_expr, in_macro};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind, LangItem};
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_middle::{lint::in_external_macro, ty::TyS};
use rustc_hir::{BorrowKind, Expr, ExprKind, LangItem, Mutability};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty::TyS;
use rustc_session::{declare_lint_pass, declare_tool_lint};
declare_clippy_lint! {
@ -40,26 +41,44 @@ declare_lint_pass!(RedundantSlicing => [REDUNDANT_SLICING]);
impl LateLintPass<'_> for RedundantSlicing {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if in_external_macro(cx.sess(), expr.span) {
if in_macro(expr.span) {
return;
}
let ctxt = expr.span.ctxt();
if_chain! {
if let ExprKind::AddrOf(_, _, addressee) = expr.kind;
if let ExprKind::AddrOf(BorrowKind::Ref, mutability, addressee) = expr.kind;
if addressee.span.ctxt() == ctxt;
if let ExprKind::Index(indexed, range) = addressee.kind;
if is_type_lang_item(cx, cx.typeck_results().expr_ty_adjusted(range), LangItem::RangeFull);
if TyS::same_type(cx.typeck_results().expr_ty(expr), cx.typeck_results().expr_ty(indexed));
then {
let mut app = Applicability::MachineApplicable;
let hint = snippet_with_applicability(cx, indexed.span, "..", &mut app).into_owned();
let snip = snippet_with_context(cx, indexed.span, ctxt, "..", &mut app).0;
let (reborrow_str, help_str) = if mutability == Mutability::Mut {
// The slice was used to reborrow the mutable reference.
("&mut *", "reborrow the original value instead")
} else if matches!(
get_parent_expr(cx, expr),
Some(Expr {
kind: ExprKind::AddrOf(BorrowKind::Ref, Mutability::Mut, _),
..
})
) {
// The slice was used to make a temporary reference.
("&*", "reborrow the original value instead")
} else {
("", "use the original value instead")
};
span_lint_and_sugg(
cx,
REDUNDANT_SLICING,
expr.span,
"redundant slicing of the whole range",
"use the original slice instead",
hint,
help_str,
format!("{}{}", reborrow_str, snip),
app,
);
}