Added new non_zero_suggestions lint

CHANGELOG.md

@@ -5773,6 +5773,7 @@ Released 2018-09-13
 [`non_minimal_cfg`]: https://rust-lang.github.io/rust-clippy/master/index.html#non_minimal_cfg
 [`non_octal_unix_permissions`]: https://rust-lang.github.io/rust-clippy/master/index.html#non_octal_unix_permissions
 [`non_send_fields_in_send_ty`]: https://rust-lang.github.io/rust-clippy/master/index.html#non_send_fields_in_send_ty
+[`non_zero_suggestions`]: https://rust-lang.github.io/rust-clippy/master/index.html#non_zero_suggestions
 [`nonminimal_bool`]: https://rust-lang.github.io/rust-clippy/master/index.html#nonminimal_bool
 [`nonsensical_open_options`]: https://rust-lang.github.io/rust-clippy/master/index.html#nonsensical_open_options
 [`nonstandard_macro_braces`]: https://rust-lang.github.io/rust-clippy/master/index.html#nonstandard_macro_braces

clippy_lints/src/declared_lints.rs

@@ -557,6 +557,7 @@ pub static LINTS: &[&crate::LintInfo] = &[
     crate::non_expressive_names::SIMILAR_NAMES_INFO,
     crate::non_octal_unix_permissions::NON_OCTAL_UNIX_PERMISSIONS_INFO,
     crate::non_send_fields_in_send_ty::NON_SEND_FIELDS_IN_SEND_TY_INFO,
+    crate::non_zero_suggestions::NON_ZERO_SUGGESTIONS_INFO,
     crate::nonstandard_macro_braces::NONSTANDARD_MACRO_BRACES_INFO,
     crate::octal_escapes::OCTAL_ESCAPES_INFO,
     crate::only_used_in_recursion::ONLY_USED_IN_RECURSION_INFO,

clippy_lints/src/lib.rs

@@ -273,6 +273,7 @@ mod non_copy_const;
 mod non_expressive_names;
 mod non_octal_unix_permissions;
 mod non_send_fields_in_send_ty;
+mod non_zero_suggestions;
 mod nonstandard_macro_braces;
 mod octal_escapes;
 mod only_used_in_recursion;
@@ -940,5 +941,6 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
     store.register_late_pass(|_| Box::new(pointers_in_nomem_asm_block::PointersInNomemAsmBlock));
     store.register_late_pass(move |_| Box::new(manual_div_ceil::ManualDivCeil::new(conf)));
     store.register_late_pass(|_| Box::new(manual_is_power_of_two::ManualIsPowerOfTwo));
+    store.register_late_pass(|_| Box::new(non_zero_suggestions::NonZeroSuggestions));
     // add lints here, do not remove this comment, it's used in `new_lint`
 }

clippy_lints/src/non_zero_suggestions.rs

@@ -0,0 +1,143 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::source::snippet;
+use rustc_ast::ast::BinOpKind;
+use rustc_errors::Applicability;
+use rustc_hir::{Expr, ExprKind};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::ty::{self, Ty};
+use rustc_session::declare_lint_pass;
+use rustc_span::symbol::sym;
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for conversions from `NonZero` types to regular integer types,
+    /// and suggests using `NonZero` types for the target as well.
+    ///
+    /// ### Why is this bad?
+    /// Converting from `NonZero` types to regular integer types and then back to `NonZero`
+    /// types is less efficient and loses the type-safety guarantees provided by `NonZero` types.
+    /// Using `NonZero` types consistently can lead to more optimized code and prevent
+    /// certain classes of errors related to zero values.
+    ///
+    /// ### Example
+    /// ```no_run
+    /// use std::num::{NonZeroU32, NonZeroU64};
+    ///
+    /// fn example(x: u64, y: NonZeroU32) {
+    ///     // Bad: Converting NonZeroU32 to u64 unnecessarily
+    ///     let r1 = x / u64::from(y.get());
+    ///     let r2 = x % u64::from(y.get());
+    /// }
+    /// ```
+    /// Use instead:
+    /// ```no_run
+    /// use std::num::{NonZeroU32, NonZeroU64};
+    ///
+    /// fn example(x: u64, y: NonZeroU32) {
+    ///     // Good: Preserving the NonZero property
+    ///     let r1 = x / NonZeroU64::from(y);
+    ///     let r2 = x % NonZeroU64::from(y);
+    /// }
+    /// ```
+    #[clippy::version = "1.81.0"]
+    pub NON_ZERO_SUGGESTIONS,
+    restriction,
+    "suggests using `NonZero#` from `u#` or `i#` for more efficient and type-safe conversions"
+}
+
+declare_lint_pass!(NonZeroSuggestions => [NON_ZERO_SUGGESTIONS]);
+
+impl<'tcx> LateLintPass<'tcx> for NonZeroSuggestions {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
+        if let ExprKind::Binary(op, _, rhs) = expr.kind
+            && matches!(op.node, BinOpKind::Div | BinOpKind::Rem)
+        {
+            check_non_zero_conversion(cx, rhs, Applicability::MachineApplicable);
+        } else {
+            // Check if the parent expression is a binary operation
+            let parent_is_binary = cx.tcx.hir().parent_iter(expr.hir_id).any(|(_, node)| {
+                matches!(node, rustc_hir::Node::Expr(parent_expr) if matches!(parent_expr.kind, ExprKind::Binary(..)))
+            });
+
+            if !parent_is_binary {
+                check_non_zero_conversion(cx, expr, Applicability::MaybeIncorrect);
+            }
+        }
+    }
+}
+
+fn check_non_zero_conversion(cx: &LateContext<'_>, expr: &Expr<'_>, applicability: Applicability) {
+    // Check if the expression is a function call with one argument
+    if let ExprKind::Call(func, [arg]) = expr.kind
+        && let ExprKind::Path(qpath) = &func.kind
+        && let Some(def_id) = cx.qpath_res(qpath, func.hir_id).opt_def_id()
+        && let ExprKind::MethodCall(rcv_path, receiver, _, _) = &arg.kind
+        && rcv_path.ident.name.as_str() == "get"
+    {
+        let fn_name = cx.tcx.item_name(def_id);
+        let target_ty = cx.typeck_results().expr_ty(expr);
+        let receiver_ty = cx.typeck_results().expr_ty(receiver);
+
+        // Check if the receiver type is a NonZero type
+        if let ty::Adt(adt_def, _) = receiver_ty.kind()
+            && adt_def.is_struct()
+            && cx.tcx.get_diagnostic_name(adt_def.did()) == Some(sym::NonZero)
+        {
+            if let Some(target_non_zero_type) = get_target_non_zero_type(target_ty) {
+                let arg_snippet = get_arg_snippet(cx, arg, rcv_path);
+                suggest_non_zero_conversion(cx, expr, fn_name, target_non_zero_type, &arg_snippet, applicability);
+            }
+        }
+    }
+}
+
+fn get_arg_snippet(cx: &LateContext<'_>, arg: &Expr<'_>, rcv_path: &rustc_hir::PathSegment<'_>) -> String {
+    let arg_snippet = snippet(cx, arg.span, "..");
+    if let Some(index) = arg_snippet.rfind(&format!(".{}", rcv_path.ident.name)) {
+        arg_snippet[..index].trim().to_string()
+    } else {
+        arg_snippet.to_string()
+    }
+}
+
+fn suggest_non_zero_conversion(
+    cx: &LateContext<'_>,
+    expr: &Expr<'_>,
+    fn_name: rustc_span::Symbol,
+    target_non_zero_type: &str,
+    arg_snippet: &str,
+    applicability: Applicability,
+) {
+    let suggestion = format!("{target_non_zero_type}::{fn_name}({arg_snippet})");
+    span_lint_and_sugg(
+        cx,
+        NON_ZERO_SUGGESTIONS,
+        expr.span,
+        format!("consider using `{target_non_zero_type}::{fn_name}()` for more efficient and type-safe conversion"),
+        "replace with",
+        suggestion,
+        applicability,
+    );
+}
+
+fn get_target_non_zero_type(ty: Ty<'_>) -> Option<&'static str> {
+    match ty.kind() {
+        ty::Uint(uint_ty) => Some(match uint_ty {
+            ty::UintTy::U8 => "NonZeroU8",
+            ty::UintTy::U16 => "NonZeroU16",
+            ty::UintTy::U32 => "NonZeroU32",
+            ty::UintTy::U64 => "NonZeroU64",
+            ty::UintTy::U128 => "NonZeroU128",
+            ty::UintTy::Usize => "NonZeroUsize",
+        }),
+        ty::Int(int_ty) => Some(match int_ty {
+            ty::IntTy::I8 => "NonZeroI8",
+            ty::IntTy::I16 => "NonZeroI16",
+            ty::IntTy::I32 => "NonZeroI32",
+            ty::IntTy::I64 => "NonZeroI64",
+            ty::IntTy::I128 => "NonZeroI128",
+            ty::IntTy::Isize => "NonZeroIsize",
+        }),
+        _ => None,
+    }
+}

tests/ui/non_zero_suggestions.fixed

@@ -0,0 +1,65 @@
+#![warn(clippy::non_zero_suggestions)]
+use std::num::{NonZeroI16, NonZeroI8, NonZeroU16, NonZeroU32, NonZeroU64, NonZeroU8, NonZeroUsize};
+
+fn main() {
+    /// Positive test cases (lint should trigger)
+    // U32 -> U64
+    let x: u64 = 100;
+    let y = NonZeroU32::new(10).unwrap();
+    let r1 = x / NonZeroU64::from(y);
+    //~^ ERROR: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+
+    let r2 = x % NonZeroU64::from(y);
+    //~^ ERROR: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+
+    // U16 -> U32
+    let a: u32 = 50;
+    let b = NonZeroU16::new(5).unwrap();
+    let r3 = a / NonZeroU32::from(b);
+    //~^ ERROR: consider using `NonZeroU32::from()` for more efficient and type-safe conversion
+
+    let x = NonZeroU64::from(NonZeroU32::new(5).unwrap());
+    //~^ ERROR: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+
+    /// Negative test cases (lint should not trigger)
+    // Left hand side expressions should not be triggered
+    let c: u32 = 50;
+    let d = NonZeroU16::new(5).unwrap();
+    let r4 = u32::from(b.get()) / a;
+
+    // Should not trigger for any other operand other than `/` and `%`
+    let r5 = a + u32::from(b.get());
+    let r6 = a - u32::from(b.get());
+
+    // Same size types
+    let e: u32 = 200;
+    let f = NonZeroU32::new(20).unwrap();
+    let r7 = e / f.get();
+
+    // Smaller to larger, but not NonZero
+    let g: u64 = 1000;
+    let h: u32 = 50;
+    let r8 = g / u64::from(h);
+
+    // Using From correctly
+    let k: u64 = 300;
+    let l = NonZeroU32::new(15).unwrap();
+    let r9 = k / NonZeroU64::from(l);
+}
+
+// Additional function to test the lint in a different context
+fn divide_numbers(x: u64, y: NonZeroU32) -> u64 {
+    x / NonZeroU64::from(y)
+    //~^ ERROR: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+}
+
+struct Calculator {
+    value: u64,
+}
+
+impl Calculator {
+    fn divide(&self, divisor: NonZeroU32) -> u64 {
+        self.value / NonZeroU64::from(divisor)
+        //~^ ERROR: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+    }
+}

tests/ui/non_zero_suggestions.rs

@@ -0,0 +1,65 @@
+#![warn(clippy::non_zero_suggestions)]
+use std::num::{NonZeroI16, NonZeroI8, NonZeroU16, NonZeroU32, NonZeroU64, NonZeroU8, NonZeroUsize};
+
+fn main() {
+    /// Positive test cases (lint should trigger)
+    // U32 -> U64
+    let x: u64 = 100;
+    let y = NonZeroU32::new(10).unwrap();
+    let r1 = x / u64::from(y.get());
+    //~^ ERROR: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+
+    let r2 = x % u64::from(y.get());
+    //~^ ERROR: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+
+    // U16 -> U32
+    let a: u32 = 50;
+    let b = NonZeroU16::new(5).unwrap();
+    let r3 = a / u32::from(b.get());
+    //~^ ERROR: consider using `NonZeroU32::from()` for more efficient and type-safe conversion
+
+    let x = u64::from(NonZeroU32::new(5).unwrap().get());
+    //~^ ERROR: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+
+    /// Negative test cases (lint should not trigger)
+    // Left hand side expressions should not be triggered
+    let c: u32 = 50;
+    let d = NonZeroU16::new(5).unwrap();
+    let r4 = u32::from(b.get()) / a;
+
+    // Should not trigger for any other operand other than `/` and `%`
+    let r5 = a + u32::from(b.get());
+    let r6 = a - u32::from(b.get());
+
+    // Same size types
+    let e: u32 = 200;
+    let f = NonZeroU32::new(20).unwrap();
+    let r7 = e / f.get();
+
+    // Smaller to larger, but not NonZero
+    let g: u64 = 1000;
+    let h: u32 = 50;
+    let r8 = g / u64::from(h);
+
+    // Using From correctly
+    let k: u64 = 300;
+    let l = NonZeroU32::new(15).unwrap();
+    let r9 = k / NonZeroU64::from(l);
+}
+
+// Additional function to test the lint in a different context
+fn divide_numbers(x: u64, y: NonZeroU32) -> u64 {
+    x / u64::from(y.get())
+    //~^ ERROR: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+}
+
+struct Calculator {
+    value: u64,
+}
+
+impl Calculator {
+    fn divide(&self, divisor: NonZeroU32) -> u64 {
+        self.value / u64::from(divisor.get())
+        //~^ ERROR: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+    }
+}

tests/ui/non_zero_suggestions.stderr

@@ -0,0 +1,41 @@
+error: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+  --> tests/ui/non_zero_suggestions.rs:9:18
+   |
+LL |     let r1 = x / u64::from(y.get());
+   |                  ^^^^^^^^^^^^^^^^^^ help: replace with: `NonZeroU64::from(y)`
+   |
+   = note: `-D clippy::non-zero-suggestions` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::non_zero_suggestions)]`
+
+error: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+  --> tests/ui/non_zero_suggestions.rs:12:18
+   |
+LL |     let r2 = x % u64::from(y.get());
+   |                  ^^^^^^^^^^^^^^^^^^ help: replace with: `NonZeroU64::from(y)`
+
+error: consider using `NonZeroU32::from()` for more efficient and type-safe conversion
+  --> tests/ui/non_zero_suggestions.rs:18:18
+   |
+LL |     let r3 = a / u32::from(b.get());
+   |                  ^^^^^^^^^^^^^^^^^^ help: replace with: `NonZeroU32::from(b)`
+
+error: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+  --> tests/ui/non_zero_suggestions.rs:21:13
+   |
+LL |     let x = u64::from(NonZeroU32::new(5).unwrap().get());
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `NonZeroU64::from(NonZeroU32::new(5).unwrap())`
+
+error: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+  --> tests/ui/non_zero_suggestions.rs:52:9
+   |
+LL |     x / u64::from(y.get())
+   |         ^^^^^^^^^^^^^^^^^^ help: replace with: `NonZeroU64::from(y)`
+
+error: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+  --> tests/ui/non_zero_suggestions.rs:62:22
+   |
+LL |         self.value / u64::from(divisor.get())
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `NonZeroU64::from(divisor)`
+
+error: aborting due to 6 previous errors
+

tests/ui/non_zero_suggestions_unfixable.rs

@@ -0,0 +1,23 @@
+#![warn(clippy::non_zero_suggestions)]
+//@no-rustfix
+use std::num::{NonZeroI16, NonZeroI8, NonZeroU16, NonZeroU32, NonZeroU64, NonZeroU8, NonZeroUsize};
+
+fn main() {
+    let x: u64 = u64::from(NonZeroU32::new(5).unwrap().get());
+    //~^ ERROR: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+
+    let n = NonZeroU32::new(20).unwrap();
+    let y = u64::from(n.get());
+    //~^ ERROR: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+    some_fn_that_only_takes_u64(y);
+
+    let m = NonZeroU32::try_from(1).unwrap();
+    let _z: NonZeroU64 = m.into();
+}
+
+fn return_non_zero(x: u64, y: NonZeroU32) -> u64 {
+    u64::from(y.get())
+    //~^ ERROR: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+}
+
+fn some_fn_that_only_takes_u64(_: u64) {}

tests/ui/non_zero_suggestions_unfixable.stderr

@@ -0,0 +1,23 @@
+error: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+  --> tests/ui/non_zero_suggestions_unfixable.rs:6:18
+   |
+LL |     let x: u64 = u64::from(NonZeroU32::new(5).unwrap().get());
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `NonZeroU64::from(NonZeroU32::new(5).unwrap())`
+   |
+   = note: `-D clippy::non-zero-suggestions` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::non_zero_suggestions)]`
+
+error: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+  --> tests/ui/non_zero_suggestions_unfixable.rs:10:13
+   |
+LL |     let y = u64::from(n.get());
+   |             ^^^^^^^^^^^^^^^^^^ help: replace with: `NonZeroU64::from(n)`
+
+error: consider using `NonZeroU64::from()` for more efficient and type-safe conversion
+  --> tests/ui/non_zero_suggestions_unfixable.rs:19:5
+   |
+LL |     u64::from(y.get())
+   |     ^^^^^^^^^^^^^^^^^^ help: replace with: `NonZeroU64::from(y)`
+
+error: aborting due to 3 previous errors
+