Auto merge of rust-lang#94929 - flip1995:clippyup, r=Manishearth

Update Clippy

r? `@Manishearth`

A few days delayed, because I recovered from a cold last week and couldn't get myself to do the sync, sorry. 🙃

Author: bors

Cargo.lock

@@ -624,10 +624,10 @@ dependencies = [
  "futures 0.3.19",
  "if_chain",
  "itertools",
- "num_cpus",
  "parking_lot",
  "quote",
  "regex",
+ "rustc-semver",
  "rustc-workspace-hack",
  "rustc_tools_util 0.2.0",
  "semver",

src/tools/clippy/.github/workflows/clippy.yml

@@ -74,10 +74,3 @@ jobs:
       run: bash .github/driver.sh
       env:
         OS: ${{ runner.os }}
-
-    - name: Test cargo dev new lint
-      run: |
-        cargo dev new_lint --name new_early_pass --pass early
-        cargo dev new_lint --name new_late_pass --pass late
-        cargo check
-        git reset --hard HEAD

src/tools/clippy/.github/workflows/clippy_bors.yml

@@ -143,13 +143,6 @@ jobs:
       env:
         OS: ${{ runner.os }}
 
-    - name: Test cargo dev new lint
-      run: |
-        cargo dev new_lint --name new_early_pass --pass early
-        cargo dev new_lint --name new_late_pass --pass late
-        cargo check
-        git reset --hard HEAD
-
   integration_build:
     needs: changelog
     runs-on: ubuntu-latest

src/tools/clippy/.github/workflows/clippy_dev.yml

@@ -36,6 +36,13 @@ jobs:
     - name: Test fmt
       run: cargo dev fmt --check
 
+    - name: Test cargo dev new lint
+      run: |
+        cargo dev new_lint --name new_early_pass --pass early
+        cargo dev new_lint --name new_late_pass --pass late
+        cargo check
+        git reset --hard HEAD
+
   # These jobs doesn't actually test anything, but they're only used to tell
   # bors the build completed, as there is no practical way to detect when a
   # workflow is successful listening to webhooks only.

src/tools/clippy/CHANGELOG.md

@@ -3042,6 +3042,7 @@ Released 2018-09-13
 <!-- lint disable no-unused-definitions -->
 <!-- begin autogenerated links to lint list -->
 [`absurd_extreme_comparisons`]: https://rust-lang.github.io/rust-clippy/master/index.html#absurd_extreme_comparisons
+[`allow_attributes_without_reason`]: https://rust-lang.github.io/rust-clippy/master/index.html#allow_attributes_without_reason
 [`almost_swapped`]: https://rust-lang.github.io/rust-clippy/master/index.html#almost_swapped
 [`approx_constant`]: https://rust-lang.github.io/rust-clippy/master/index.html#approx_constant
 [`as_conversions`]: https://rust-lang.github.io/rust-clippy/master/index.html#as_conversions
@@ -3076,6 +3077,7 @@ Released 2018-09-13
 [`cast_ptr_alignment`]: https://rust-lang.github.io/rust-clippy/master/index.html#cast_ptr_alignment
 [`cast_ref_to_mut`]: https://rust-lang.github.io/rust-clippy/master/index.html#cast_ref_to_mut
 [`cast_sign_loss`]: https://rust-lang.github.io/rust-clippy/master/index.html#cast_sign_loss
+[`cast_slice_different_sizes`]: https://rust-lang.github.io/rust-clippy/master/index.html#cast_slice_different_sizes
 [`char_lit_as_u8`]: https://rust-lang.github.io/rust-clippy/master/index.html#char_lit_as_u8
 [`chars_last_cmp`]: https://rust-lang.github.io/rust-clippy/master/index.html#chars_last_cmp
 [`chars_next_cmp`]: https://rust-lang.github.io/rust-clippy/master/index.html#chars_next_cmp
@@ -3225,6 +3227,7 @@ Released 2018-09-13
 [`iter_nth_zero`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_nth_zero
 [`iter_overeager_cloned`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_overeager_cloned
 [`iter_skip_next`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_skip_next
+[`iter_with_drain`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_with_drain
 [`iterator_step_by_zero`]: https://rust-lang.github.io/rust-clippy/master/index.html#iterator_step_by_zero
 [`just_underscores_and_digits`]: https://rust-lang.github.io/rust-clippy/master/index.html#just_underscores_and_digits
 [`large_const_arrays`]: https://rust-lang.github.io/rust-clippy/master/index.html#large_const_arrays
@@ -3297,6 +3300,7 @@ Released 2018-09-13
 [`missing_inline_in_public_items`]: https://rust-lang.github.io/rust-clippy/master/index.html#missing_inline_in_public_items
 [`missing_panics_doc`]: https://rust-lang.github.io/rust-clippy/master/index.html#missing_panics_doc
 [`missing_safety_doc`]: https://rust-lang.github.io/rust-clippy/master/index.html#missing_safety_doc
+[`missing_spin_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#missing_spin_loop
 [`mistyped_literal_suffixes`]: https://rust-lang.github.io/rust-clippy/master/index.html#mistyped_literal_suffixes
 [`mixed_case_hex_literals`]: https://rust-lang.github.io/rust-clippy/master/index.html#mixed_case_hex_literals
 [`mod_module_files`]: https://rust-lang.github.io/rust-clippy/master/index.html#mod_module_files
@@ -3327,6 +3331,7 @@ Released 2018-09-13
 [`needless_for_each`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_for_each
 [`needless_late_init`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_late_init
 [`needless_lifetimes`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_lifetimes
+[`needless_match`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_match
 [`needless_option_as_deref`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_option_as_deref
 [`needless_pass_by_value`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_pass_by_value
 [`needless_question_mark`]: https://rust-lang.github.io/rust-clippy/master/index.html#needless_question_mark
@@ -3351,6 +3356,7 @@ Released 2018-09-13
 [`not_unsafe_ptr_arg_deref`]: https://rust-lang.github.io/rust-clippy/master/index.html#not_unsafe_ptr_arg_deref
 [`octal_escapes`]: https://rust-lang.github.io/rust-clippy/master/index.html#octal_escapes
 [`ok_expect`]: https://rust-lang.github.io/rust-clippy/master/index.html#ok_expect
+[`only_used_in_recursion`]: https://rust-lang.github.io/rust-clippy/master/index.html#only_used_in_recursion
 [`op_ref`]: https://rust-lang.github.io/rust-clippy/master/index.html#op_ref
 [`option_as_ref_deref`]: https://rust-lang.github.io/rust-clippy/master/index.html#option_as_ref_deref
 [`option_env_unwrap`]: https://rust-lang.github.io/rust-clippy/master/index.html#option_env_unwrap
@@ -3498,6 +3504,7 @@ Released 2018-09-13
 [`unit_return_expecting_ord`]: https://rust-lang.github.io/rust-clippy/master/index.html#unit_return_expecting_ord
 [`unnecessary_cast`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
 [`unnecessary_filter_map`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_filter_map
+[`unnecessary_find_map`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_find_map
 [`unnecessary_fold`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_fold
 [`unnecessary_lazy_evaluations`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_lazy_evaluations
 [`unnecessary_mut_passed`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_mut_passed

src/tools/clippy/Cargo.toml

@@ -50,7 +50,7 @@ syn = { version = "1.0", features = ["full"] }
 futures = "0.3"
 parking_lot = "0.11.2"
 tokio = { version = "1", features = ["io-util"] }
-num_cpus = "1.13"
+rustc-semver = "1.1"
 
 [build-dependencies]
 rustc_tools_util = { version = "0.2", path = "rustc_tools_util" }

src/tools/clippy/clippy_lints/src/attrs.rs

@@ -255,7 +255,38 @@ declare_clippy_lint! {
     "usage of `cfg(operating_system)` instead of `cfg(target_os = \"operating_system\")`"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for attributes that allow lints without a reason.
+    ///
+    /// (This requires the `lint_reasons` feature)
+    ///
+    /// ### Why is this bad?
+    /// Allowing a lint should always have a reason. This reason should be documented to
+    /// ensure that others understand the reasoning
+    ///
+    /// ### Example
+    /// Bad:
+    /// ```rust
+    /// #![feature(lint_reasons)]
+    ///
+    /// #![allow(clippy::some_lint)]
+    /// ```
+    ///
+    /// Good:
+    /// ```rust
+    /// #![feature(lint_reasons)]
+    ///
+    /// #![allow(clippy::some_lint, reason = "False positive rust-lang/rust-clippy#1002020")]
+    /// ```
+    #[clippy::version = "1.61.0"]
+    pub ALLOW_ATTRIBUTES_WITHOUT_REASON,
+    restriction,
+    "ensures that all `allow` and `expect` attributes have a reason"
+}
+
 declare_lint_pass!(Attributes => [
+    ALLOW_ATTRIBUTES_WITHOUT_REASON,
     INLINE_ALWAYS,
     DEPRECATED_SEMVER,
     USELESS_ATTRIBUTE,
@@ -269,6 +300,9 @@ impl<'tcx> LateLintPass<'tcx> for Attributes {
                 if is_lint_level(ident.name) {
                     check_clippy_lint_names(cx, ident.name, items);
                 }
+                if matches!(ident.name, sym::allow | sym::expect) {
+                    check_lint_reason(cx, ident.name, items, attr);
+                }
                 if items.is_empty() || !attr.has_name(sym::deprecated) {
                     return;
                 }
@@ -404,6 +438,30 @@ fn check_clippy_lint_names(cx: &LateContext<'_>, name: Symbol, items: &[NestedMe
     }
 }
 
+fn check_lint_reason(cx: &LateContext<'_>, name: Symbol, items: &[NestedMetaItem], attr: &'_ Attribute) {
+    // Check for the feature
+    if !cx.tcx.sess.features_untracked().lint_reasons {
+        return;
+    }
+
+    // Check if the reason is present
+    if let Some(item) = items.last().and_then(NestedMetaItem::meta_item)
+        && let MetaItemKind::NameValue(_) = &item.kind
+        && item.path == sym::reason
+    {
+        return;
+    }
+
+    span_lint_and_help(
+        cx,
+        ALLOW_ATTRIBUTES_WITHOUT_REASON,
+        attr.span,
+        &format!("`{}` attribute without specifying a reason", name.as_str()),
+        None,
+        "try adding a reason at the end with `, reason = \"..\"`",
+    );
+}
+
 fn is_relevant_item(cx: &LateContext<'_>, item: &Item<'_>) -> bool {
     if let ItemKind::Fn(_, _, eid) = item.kind {
         is_relevant_expr(cx, cx.tcx.typeck_body(eid), &cx.tcx.hir().body(eid).value)
@@ -659,5 +717,5 @@ fn check_mismatched_target_os(cx: &EarlyContext<'_>, attr: &Attribute) {
 }
 
 fn is_lint_level(symbol: Symbol) -> bool {
-    matches!(symbol, sym::allow | sym::warn | sym::deny | sym::forbid)
+    matches!(symbol, sym::allow | sym::expect | sym::warn | sym::deny | sym::forbid)
 }

src/tools/clippy/clippy_lints/src/casts/cast_slice_different_sizes.rs

@@ -0,0 +1,117 @@
+use clippy_utils::{diagnostics::span_lint_and_then, meets_msrv, msrvs, source::snippet_opt};
+use if_chain::if_chain;
+use rustc_ast::Mutability;
+use rustc_hir::{Expr, ExprKind, Node};
+use rustc_lint::LateContext;
+use rustc_middle::ty::{self, layout::LayoutOf, Ty, TypeAndMut};
+use rustc_semver::RustcVersion;
+
+use super::CAST_SLICE_DIFFERENT_SIZES;
+
+fn is_child_of_cast(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
+    let map = cx.tcx.hir();
+    if_chain! {
+        if let Some(parent_id) = map.find_parent_node(expr.hir_id);
+        if let Some(parent) = map.find(parent_id);
+        then {
+            let expr = match parent {
+                Node::Block(block) => {
+                    if let Some(parent_expr) = block.expr {
+                        parent_expr
+                    } else {
+                        return false;
+                    }
+                },
+                Node::Expr(expr) => expr,
+                _ => return false,
+            };
+
+            matches!(expr.kind, ExprKind::Cast(..))
+        } else {
+            false
+        }
+    }
+}
+
+pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, msrv: &Option<RustcVersion>) {
+    // suggestion is invalid if `ptr::slice_from_raw_parts` does not exist
+    if !meets_msrv(msrv.as_ref(), &msrvs::PTR_SLICE_RAW_PARTS) {
+        return;
+    }
+
+    // if this cast is the child of another cast expression then don't emit something for it, the full
+    // chain will be analyzed
+    if is_child_of_cast(cx, expr) {
+        return;
+    }
+
+    if let Some((from_slice_ty, to_slice_ty)) = expr_cast_chain_tys(cx, expr) {
+        if let (Ok(from_layout), Ok(to_layout)) = (cx.layout_of(from_slice_ty.ty), cx.layout_of(to_slice_ty.ty)) {
+            let from_size = from_layout.size.bytes();
+            let to_size = to_layout.size.bytes();
+            if from_size != to_size && from_size != 0 && to_size != 0 {
+                span_lint_and_then(
+                    cx,
+                    CAST_SLICE_DIFFERENT_SIZES,
+                    expr.span,
+                    &format!(
+                        "casting between raw pointers to `[{}]` (element size {}) and `[{}]` (element size {}) does not adjust the count",
+                        from_slice_ty, from_size, to_slice_ty, to_size,
+                    ),
+                    |diag| {
+                        let cast_expr = match expr.kind {
+                            ExprKind::Cast(cast_expr, ..) => cast_expr,
+                            _ => unreachable!("expr should be a cast as checked by expr_cast_chain_tys"),
+                        };
+                        let ptr_snippet = snippet_opt(cx, cast_expr.span).unwrap();
+
+                        let (mutbl_fn_str, mutbl_ptr_str) = match to_slice_ty.mutbl {
+                            Mutability::Mut => ("_mut", "mut"),
+                            Mutability::Not => ("", "const"),
+                        };
+                        let sugg = format!(
+                            "core::ptr::slice_from_raw_parts{mutbl_fn_str}({ptr_snippet} as *{mutbl_ptr_str} {to_slice_ty}, ..)"
+                        );
+
+                        diag.span_suggestion(
+                            expr.span,
+                            &format!("replace with `ptr::slice_from_raw_parts{mutbl_fn_str}`"),
+                            sugg,
+                            rustc_errors::Applicability::HasPlaceholders,
+                        );
+                    },
+                );
+            }
+        }
+    }
+}
+
+/// Returns the type T of the pointed to *const [T] or *mut [T] and the mutability of the slice if
+/// the type is one of those slices
+fn get_raw_slice_ty_mut(ty: Ty<'_>) -> Option<TypeAndMut<'_>> {
+    match ty.kind() {
+        ty::RawPtr(TypeAndMut { ty: slice_ty, mutbl }) => match slice_ty.kind() {
+            ty::Slice(ty) => Some(TypeAndMut { ty: *ty, mutbl: *mutbl }),
+            _ => None,
+        },
+        _ => None,
+    }
+}
+
+/// Returns the pair (original ptr T, final ptr U) if the expression is composed of casts
+/// Returns None if the expr is not a Cast
+fn expr_cast_chain_tys<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) -> Option<(TypeAndMut<'tcx>, TypeAndMut<'tcx>)> {
+    if let ExprKind::Cast(cast_expr, _cast_to_hir_ty) = expr.peel_blocks().kind {
+        let cast_to = cx.typeck_results().expr_ty(expr);
+        let to_slice_ty = get_raw_slice_ty_mut(cast_to)?;
+        if let Some((inner_from_ty, _inner_to_ty)) = expr_cast_chain_tys(cx, cast_expr) {
+            Some((inner_from_ty, to_slice_ty))
+        } else {
+            let cast_from = cx.typeck_results().expr_ty(cast_expr);
+            let from_slice_ty = get_raw_slice_ty_mut(cast_from)?;
+            Some((from_slice_ty, to_slice_ty))
+        }
+    } else {
+        None
+    }
+}

src/tools/clippy/clippy_lints/src/casts/mod.rs

@@ -5,6 +5,7 @@ mod cast_precision_loss;
 mod cast_ptr_alignment;
 mod cast_ref_to_mut;
 mod cast_sign_loss;
+mod cast_slice_different_sizes;
 mod char_lit_as_u8;
 mod fn_to_numeric_cast;
 mod fn_to_numeric_cast_any;
@@ -409,6 +410,50 @@ declare_clippy_lint! {
     "casts from an enum type to an integral type which will truncate the value"
 }
 
+declare_clippy_lint! {
+    /// Checks for `as` casts between raw pointers to slices with differently sized elements.
+    ///
+    /// ### Why is this bad?
+    /// The produced raw pointer to a slice does not update its length metadata. The produced
+    /// pointer will point to a different number of bytes than the original pointer because the
+    /// length metadata of a raw slice pointer is in elements rather than bytes.
+    /// Producing a slice reference from the raw pointer will either create a slice with
+    /// less data (which can be surprising) or create a slice with more data and cause Undefined Behavior.
+    ///
+    /// ### Example
+    /// // Missing data
+    /// ```rust
+    /// let a = [1_i32, 2, 3, 4];
+    /// let p = &a as *const [i32] as *const [u8];
+    /// unsafe {
+    ///     println!("{:?}", &*p);
+    /// }
+    /// ```
+    /// // Undefined Behavior (note: also potential alignment issues)
+    /// ```rust
+    /// let a = [1_u8, 2, 3, 4];
+    /// let p = &a as *const [u8] as *const [u32];
+    /// unsafe {
+    ///     println!("{:?}", &*p);
+    /// }
+    /// ```
+    /// Instead use `ptr::slice_from_raw_parts` to construct a slice from a data pointer and the correct length
+    /// ```rust
+    /// let a = [1_i32, 2, 3, 4];
+    /// let old_ptr = &a as *const [i32];
+    /// // The data pointer is cast to a pointer to the target `u8` not `[u8]`
+    /// // The length comes from the known length of 4 i32s times the 4 bytes per i32
+    /// let new_ptr = core::ptr::slice_from_raw_parts(old_ptr as *const u8, 16);
+    /// unsafe {
+    ///     println!("{:?}", &*new_ptr);
+    /// }
+    /// ```
+    #[clippy::version = "1.60.0"]
+    pub CAST_SLICE_DIFFERENT_SIZES,
+    correctness,
+    "casting using `as` between raw pointers to slices of types with different sizes"
+}
+
 pub struct Casts {
     msrv: Option<RustcVersion>,
 }
@@ -428,6 +473,7 @@ impl_lint_pass!(Casts => [
     CAST_LOSSLESS,
     CAST_REF_TO_MUT,
     CAST_PTR_ALIGNMENT,
+    CAST_SLICE_DIFFERENT_SIZES,
     UNNECESSARY_CAST,
     FN_TO_NUMERIC_CAST_ANY,
     FN_TO_NUMERIC_CAST,
@@ -478,6 +524,8 @@ impl<'tcx> LateLintPass<'tcx> for Casts {
         cast_ref_to_mut::check(cx, expr);
         cast_ptr_alignment::check(cx, expr);
         char_lit_as_u8::check(cx, expr);
+        ptr_as_ptr::check(cx, expr, &self.msrv);
+        cast_slice_different_sizes::check(cx, expr, &self.msrv);
     }
 
     extract_msrv_attr!(LateContext);