changelog: Add as_slice_instead_of_reference_full_range lint

Author: nils-degroot

CHANGELOG.md

@@ -5620,6 +5620,7 @@ Released 2018-09-13
 [`as_conversions`]: https://rust-lang.github.io/rust-clippy/master/index.html#as_conversions
 [`as_pointer_underscore`]: https://rust-lang.github.io/rust-clippy/master/index.html#as_pointer_underscore
 [`as_ptr_cast_mut`]: https://rust-lang.github.io/rust-clippy/master/index.html#as_ptr_cast_mut
+[`as_slice_instead_of_reference_full_range`]: https://rust-lang.github.io/rust-clippy/master/index.html#as_slice_instead_of_reference_full_range
 [`as_underscore`]: https://rust-lang.github.io/rust-clippy/master/index.html#as_underscore
 [`assertions_on_constants`]: https://rust-lang.github.io/rust-clippy/master/index.html#assertions_on_constants
 [`assertions_on_result_states`]: https://rust-lang.github.io/rust-clippy/master/index.html#assertions_on_result_states

clippy_lints/src/as_slice_instead_of_reference_full_range.rs

@@ -0,0 +1,69 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::source::snippet_with_applicability;
+use rustc_errors::Applicability;
+use rustc_hir::*;
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::declare_lint_pass;
+
+declare_clippy_lint! {
+    /// ### What it does
+    ///
+    /// Detects if a full range slice reference is used instead of using the `.as_slice()` method.
+    ///
+    /// ### Why is this bad?
+    ///
+    /// Using the `some_value.as_slice()` method is more explicit then using `&some_value[..]`
+    ///
+    /// ### Example
+    /// ```no_run
+    /// let array = [u8; 4];
+    /// let slice = &array[..];
+    /// ```
+    /// Use instead:
+    /// ```no_run
+    /// let array = [u8; 4];
+    /// let slice = array.as_slice;
+    /// ```
+    #[clippy::version = "1.88.0"]
+    pub AS_SLICE_INSTEAD_OF_REFERENCE_FULL_RANGE,
+    nursery,
+    "Use as slice instead of borrow full range."
+}
+declare_lint_pass!(AsSliceInsteadOfReferenceFullRange => [AS_SLICE_INSTEAD_OF_REFERENCE_FULL_RANGE]);
+
+impl LateLintPass<'_> for AsSliceInsteadOfReferenceFullRange {
+    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
+        if let ExprKind::AddrOf(_, mutability, borrow) = expr.kind
+            && let ExprKind::Index(name, indexing, _) = borrow.kind
+            && let ExprKind::Struct(qpath, _, _) = indexing.kind
+            && let QPath::LangItem(LangItem::RangeFull, _) = qpath
+        {
+            let snippet = snippet_with_applicability(cx, name.span, "..", &mut Applicability::Unspecified);
+
+            match mutability {
+                Mutability::Not => {
+                    span_lint_and_sugg(
+                        cx,
+                        AS_SLICE_INSTEAD_OF_REFERENCE_FULL_RANGE,
+                        expr.span,
+                        format!("Use `.as_slice()` instead of full range slice"),
+                        "try",
+                        format!("{snippet}.as_slice()"),
+                        Applicability::Unspecified,
+                    );
+                },
+                Mutability::Mut => {
+                    span_lint_and_sugg(
+                        cx,
+                        AS_SLICE_INSTEAD_OF_REFERENCE_FULL_RANGE,
+                        expr.span,
+                        format!("Use `.as_mut_slice()` instead of full range slice"),
+                        "try",
+                        format!("{snippet}.as_mut_slice()"),
+                        Applicability::Unspecified,
+                    );
+                },
+            }
+        }
+    }
+}

clippy_lints/src/declared_lints.rs

@@ -9,6 +9,7 @@ pub static LINTS: &[&crate::LintInfo] = &[
     crate::arbitrary_source_item_ordering::ARBITRARY_SOURCE_ITEM_ORDERING_INFO,
     crate::arc_with_non_send_sync::ARC_WITH_NON_SEND_SYNC_INFO,
     crate::as_conversions::AS_CONVERSIONS_INFO,
+    crate::as_slice_instead_of_reference_full_range::AS_SLICE_INSTEAD_OF_REFERENCE_FULL_RANGE_INFO,
     crate::asm_syntax::INLINE_ASM_X86_ATT_SYNTAX_INFO,
     crate::asm_syntax::INLINE_ASM_X86_INTEL_SYNTAX_INFO,
     crate::assertions_on_constants::ASSERTIONS_ON_CONSTANTS_INFO,

clippy_lints/src/lib.rs

@@ -76,6 +76,7 @@ mod approx_const;
 mod arbitrary_source_item_ordering;
 mod arc_with_non_send_sync;
 mod as_conversions;
+mod as_slice_instead_of_reference_full_range;
 mod asm_syntax;
 mod assertions_on_constants;
 mod assertions_on_result_states;
@@ -944,5 +945,7 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
     store.register_late_pass(|_| Box::new(single_option_map::SingleOptionMap));
     store.register_late_pass(move |_| Box::new(redundant_test_prefix::RedundantTestPrefix));
     store.register_late_pass(|_| Box::new(cloned_ref_to_slice_refs::ClonedRefToSliceRefs::new(conf)));
+    store
+        .register_late_pass(|_| Box::new(as_slice_instead_of_reference_full_range::AsSliceInsteadOfReferenceFullRange));
     // add lints here, do not remove this comment, it's used in `new_lint`
 }

tests/ui/array_as_slice_instead_of_unbounded_slice.stderr

@@ -0,0 +1,12 @@
+error: Oh noooo
+  --> tests/ui/array_as_slice_instead_of_unbounded_slice.rs:5:25
+   |
+LL |     let slice: &[u8] = &array[..];
+   |                         ^^^^^^^^^
+   |
+   = help: .as_slice()
+   = note: `-D clippy::array-as-slice-instead-of-unbounded-slice` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::array_as_slice_instead_of_unbounded_slice)]`
+
+error: aborting due to 1 previous error
+

tests/ui/as_slice_instead_of_reference_full_range.fixed

@@ -0,0 +1,20 @@
+#![warn(clippy::as_slice_instead_of_reference_full_range)]
+
+mod nested_1 {
+    pub(crate) mod nested_2 {
+        pub(crate) const SOME_VALUE: [u8; 4] = [1, 2, 3, 4];
+    }
+}
+
+fn main() {
+    let array: [u8; 4] = [0; 4];
+    let slice: &[u8] = array.as_slice();
+    //~^ as_slice_instead_of_reference_full_range
+
+    let mut array: [u8; 4] = [0; 4];
+    let mut slice: &[u8] = array.as_mut_slice();
+    //~^ as_slice_instead_of_reference_full_range
+
+    let slice: &[u8] = nested_1::nested_2::SOME_VALUE.as_slice();
+    //~^ as_slice_instead_of_reference_full_range
+}

tests/ui/as_slice_instead_of_reference_full_range.rs

@@ -0,0 +1,20 @@
+#![warn(clippy::as_slice_instead_of_reference_full_range)]
+
+mod nested_1 {
+    pub(crate) mod nested_2 {
+        pub(crate) const SOME_VALUE: [u8; 4] = [1, 2, 3, 4];
+    }
+}
+
+fn main() {
+    let array: [u8; 4] = [0; 4];
+    let slice: &[u8] = &array[..];
+    //~^ as_slice_instead_of_reference_full_range
+
+    let mut array: [u8; 4] = [0; 4];
+    let mut slice: &[u8] = &mut array[..];
+    //~^ as_slice_instead_of_reference_full_range
+
+    let slice: &[u8] = &nested_1::nested_2::SOME_VALUE[..];
+    //~^ as_slice_instead_of_reference_full_range
+}

tests/ui/as_slice_instead_of_reference_full_range.stderr

@@ -0,0 +1,23 @@
+error: Use `.as_slice()` instead of full range slice
+  --> tests/ui/as_slice_instead_of_reference_full_range.rs:11:24
+   |
+LL |     let slice: &[u8] = &array[..];
+   |                        ^^^^^^^^^^ help: try: `array.as_slice()`
+   |
+   = note: `-D clippy::as-slice-instead-of-reference-full-range` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::as_slice_instead_of_reference_full_range)]`
+
+error: Use `.as_mut_slice()` instead of full range slice
+  --> tests/ui/as_slice_instead_of_reference_full_range.rs:15:28
+   |
+LL |     let mut slice: &[u8] = &mut array[..];
+   |                            ^^^^^^^^^^^^^^ help: try: `array.as_mut_slice()`
+
+error: Use `.as_slice()` instead of full range slice
+  --> tests/ui/as_slice_instead_of_reference_full_range.rs:18:24
+   |
+LL |     let slice: &[u8] = &nested_1::nested_2::SOME_VALUE[..];
+   |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `nested_1::nested_2::SOME_VALUE.as_slice()`
+
+error: aborting due to 3 previous errors
+