diff --git a/clippy_lints/src/redundant_slicing.rs b/clippy_lints/src/redundant_slicing.rs index cd3aee55655..b492f944dc3 100644 --- a/clippy_lints/src/redundant_slicing.rs +++ b/clippy_lints/src/redundant_slicing.rs @@ -1,11 +1,12 @@ use clippy_utils::diagnostics::span_lint_and_sugg; use clippy_utils::get_parent_expr; use clippy_utils::source::snippet_with_context; -use clippy_utils::ty::is_type_lang_item; +use clippy_utils::ty::{is_type_lang_item, peel_mid_ty_refs}; use if_chain::if_chain; use rustc_errors::Applicability; use rustc_hir::{BorrowKind, Expr, ExprKind, LangItem, Mutability}; use rustc_lint::{LateContext, LateLintPass}; +use rustc_middle::ty::subst::GenericArg; use rustc_session::{declare_lint_pass, declare_tool_lint}; declare_clippy_lint! { @@ -53,25 +54,55 @@ impl<'tcx> LateLintPass<'tcx> for RedundantSlicing { 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 cx.typeck_results().expr_ty(expr) == cx.typeck_results().expr_ty(indexed); then { + let (expr_ty, expr_ref_count) = peel_mid_ty_refs(cx.typeck_results().expr_ty(expr)); + let (indexed_ty, indexed_ref_count) = peel_mid_ty_refs(cx.typeck_results().expr_ty(indexed)); let mut app = Applicability::MachineApplicable; - 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") + let (help, sugg) = if expr_ty == indexed_ty { + if expr_ref_count > indexed_ref_count { + return; + } + + 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 if expr_ref_count != indexed_ref_count { + ("", "dereference the original value instead") + } else { + ("", "use the original value instead") + }; + + let snip = snippet_with_context(cx, indexed.span, ctxt, "..", &mut app).0; + (help_str, format!("{}{}{}", reborrow_str, "*".repeat(indexed_ref_count - expr_ref_count), snip)) + } else if let Some(target_id) = cx.tcx.lang_items().deref_target() { + if let Ok(deref_ty) = cx.tcx.try_normalize_erasing_regions( + cx.param_env, + cx.tcx.mk_projection(target_id, cx.tcx.mk_substs([GenericArg::from(indexed_ty)].into_iter())), + ) { + if deref_ty == expr_ty { + let snip = snippet_with_context(cx, indexed.span, ctxt, "..", &mut app).0; + ( + "dereference the original value instead", + format!("&{}{}*{}", mutability.prefix_str(), "*".repeat(indexed_ref_count), snip), + ) + } else { + return; + } + } else { + return; + } } else { - ("", "use the original value instead") + return; }; span_lint_and_sugg( @@ -79,8 +110,8 @@ impl<'tcx> LateLintPass<'tcx> for RedundantSlicing { REDUNDANT_SLICING, expr.span, "redundant slicing of the whole range", - help_str, - format!("{}{}", reborrow_str, snip), + help, + sugg, app, ); } diff --git a/tests/ui/redundant_slicing.fixed b/tests/ui/redundant_slicing.fixed new file mode 100644 index 00000000000..9716a48be94 --- /dev/null +++ b/tests/ui/redundant_slicing.fixed @@ -0,0 +1,40 @@ +// run-rustfix + +#![allow(unused)] +#![warn(clippy::redundant_slicing)] + +fn main() { + let slice: &[u32] = &[0]; + let _ = slice; // Redundant slice + + let v = vec![0]; + let _ = &*v; // Deref instead of slice + let _ = (&*v); // Outer borrow is redundant + + static S: &[u8] = &[0, 1, 2]; + let err = &mut &*S; // Should reborrow instead of slice + + let mut vec = vec![0]; + let mut_slice = &mut *vec; // Deref instead of slice + let _ = &mut *mut_slice; // Should reborrow instead of slice + + let ref_vec = &vec; + let _ = &**ref_vec; // Deref instead of slice + + macro_rules! m { + ($e:expr) => { + $e + }; + } + let _ = slice; + + macro_rules! m2 { + ($e:expr) => { + &$e[..] + }; + } + let _ = m2!(slice); // Don't lint in a macro + + let slice_ref = &slice; + let _ = *slice_ref; // Deref instead of slice +} diff --git a/tests/ui/redundant_slicing.rs b/tests/ui/redundant_slicing.rs index 554b6ba36ae..a6902f7619b 100644 --- a/tests/ui/redundant_slicing.rs +++ b/tests/ui/redundant_slicing.rs @@ -1,21 +1,26 @@ +// run-rustfix + #![allow(unused)] #![warn(clippy::redundant_slicing)] fn main() { let slice: &[u32] = &[0]; - let _ = &slice[..]; + let _ = &slice[..]; // Redundant slice let v = vec![0]; - let _ = &v[..]; // Changes the type - let _ = &(&v[..])[..]; // Outer borrow is redundant + let _ = &v[..]; // Deref instead of slice + let _ = &(&*v)[..]; // Outer borrow is redundant static S: &[u8] = &[0, 1, 2]; let err = &mut &S[..]; // Should reborrow instead of slice let mut vec = vec![0]; - let mut_slice = &mut *vec; + let mut_slice = &mut vec[..]; // Deref instead of slice let _ = &mut mut_slice[..]; // Should reborrow instead of slice + let ref_vec = &vec; + let _ = &ref_vec[..]; // Deref instead of slice + macro_rules! m { ($e:expr) => { $e @@ -29,4 +34,7 @@ fn main() { }; } let _ = m2!(slice); // Don't lint in a macro + + let slice_ref = &slice; + let _ = &slice_ref[..]; // Deref instead of slice } diff --git a/tests/ui/redundant_slicing.stderr b/tests/ui/redundant_slicing.stderr index bbd10eafbbe..c2a5e9e1914 100644 --- a/tests/ui/redundant_slicing.stderr +++ b/tests/ui/redundant_slicing.stderr @@ -1,34 +1,58 @@ error: redundant slicing of the whole range - --> $DIR/redundant_slicing.rs:6:13 + --> $DIR/redundant_slicing.rs:8:13 | -LL | let _ = &slice[..]; +LL | let _ = &slice[..]; // Redundant slice | ^^^^^^^^^^ help: use the original value instead: `slice` | = note: `-D clippy::redundant-slicing` implied by `-D warnings` error: redundant slicing of the whole range - --> $DIR/redundant_slicing.rs:10:13 + --> $DIR/redundant_slicing.rs:11:13 | -LL | let _ = &(&v[..])[..]; // Outer borrow is redundant - | ^^^^^^^^^^^^^ help: use the original value instead: `(&v[..])` +LL | let _ = &v[..]; // Deref instead of slice + | ^^^^^^ help: dereference the original value instead: `&*v` error: redundant slicing of the whole range - --> $DIR/redundant_slicing.rs:13:20 + --> $DIR/redundant_slicing.rs:12:13 + | +LL | let _ = &(&*v)[..]; // Outer borrow is redundant + | ^^^^^^^^^^ help: use the original value instead: `(&*v)` + +error: redundant slicing of the whole range + --> $DIR/redundant_slicing.rs:15:20 | LL | let err = &mut &S[..]; // Should reborrow instead of slice | ^^^^^^ help: reborrow the original value instead: `&*S` error: redundant slicing of the whole range - --> $DIR/redundant_slicing.rs:17:13 + --> $DIR/redundant_slicing.rs:18:21 + | +LL | let mut_slice = &mut vec[..]; // Deref instead of slice + | ^^^^^^^^^^^^ help: dereference the original value instead: `&mut *vec` + +error: redundant slicing of the whole range + --> $DIR/redundant_slicing.rs:19:13 | LL | let _ = &mut mut_slice[..]; // Should reborrow instead of slice | ^^^^^^^^^^^^^^^^^^ help: reborrow the original value instead: `&mut *mut_slice` error: redundant slicing of the whole range - --> $DIR/redundant_slicing.rs:24:13 + --> $DIR/redundant_slicing.rs:22:13 + | +LL | let _ = &ref_vec[..]; // Deref instead of slice + | ^^^^^^^^^^^^ help: dereference the original value instead: `&**ref_vec` + +error: redundant slicing of the whole range + --> $DIR/redundant_slicing.rs:29:13 | LL | let _ = &m!(slice)[..]; | ^^^^^^^^^^^^^^ help: use the original value instead: `slice` -error: aborting due to 5 previous errors +error: redundant slicing of the whole range + --> $DIR/redundant_slicing.rs:39:13 + | +LL | let _ = &slice_ref[..]; // Deref instead of slice + | ^^^^^^^^^^^^^^ help: dereference the original value instead: `*slice_ref` + +error: aborting due to 9 previous errors