Lint ready

5 files changed, 163 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f1de51c936e..0e5d1688e4a 100644
--- a/CHANGELOG.md
+++ b/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
diff --git a/clippy_lints/src/declared_lints.rs b/clippy_lints/src/declared_lints.rs
index 6f468f01b2f..16c64830e70 100644
--- a/clippy_lints/src/declared_lints.rs
+++ b/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,
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index bc16a3b0c01..3604090b68c 100644
--- a/clippy_lints/src/lib.rs
+++ b/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`
 }
diff --git a/clippy_lints/src/non_zero_suggestions.rs b/clippy_lints/src/non_zero_suggestions.rs
new file mode 100644
index 00000000000..b9e7053db90
--- /dev/null
+++ b/clippy_lints/src/non_zero_suggestions.rs
@@ -0,0 +1,107 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::source::snippet;
+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
+    ///
+    /// ### Why is this bad?
+    ///
+    /// ### Example
+    /// ```no_run
+    /// // example code where clippy issues a warning
+    /// ```
+    /// Use instead:
+    /// ```no_run
+    /// // example code which does not raise clippy warning
+    /// ```
+    #[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::Call(func, [arg]) = expr.kind {
+            if let ExprKind::Path(qpath) = &func.kind {
+                if let Some(def_id) = cx.qpath_res(qpath, func.hir_id).opt_def_id() {
+                    let fn_name = cx.tcx.item_name(def_id);
+                    let target_ty = cx.typeck_results().expr_ty(expr);
+
+                    if let ExprKind::MethodCall(rcv_path, receiver, _, _) = &arg.kind {
+                        let receiver_ty = cx.typeck_results().expr_ty(receiver);
+                        if let ty::Adt(adt_def, _) = receiver_ty.kind() {
+                            if 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);
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+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,
+) {
+    let suggestion = format!("{}::{}({})", target_non_zero_type, fn_name, arg_snippet);
+    span_lint_and_sugg(
+        cx,
+        NON_ZERO_SUGGESTIONS,
+        expr.span,
+        format!(
+            "Consider using `{}::{}()` for more efficient and type-safe conversion",
+            target_non_zero_type, fn_name
+        ),
+        "Replace with",
+        suggestion,
+        Applicability::MachineApplicable,
+    );
+}
+
+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,
+    }
+}
diff --git a/tests/ui/non_zero_suggestions.rs b/tests/ui/non_zero_suggestions.rs
new file mode 100644
index 00000000000..1a5ee40dc3d
--- /dev/null
+++ b/tests/ui/non_zero_suggestions.rs
@@ -0,0 +1,52 @@
+#![warn(clippy::non_zero_suggestions)]
+
+use std::num::{
+    NonZeroI128, NonZeroI16, NonZeroI32, NonZeroI64, NonZeroI8, NonZeroIsize, NonZeroU128, NonZeroU16, NonZeroU32,
+    NonZeroU64, NonZeroU8, NonZeroUsize,
+};
+
+fn main() {
+    // Basic cases
+    let _ = u8::try_from(NonZeroU8::new(5).unwrap().get());
+
+    let _ = u16::from(NonZeroU16::new(10).unwrap().get());
+
+    // Different integer types
+    let _ = u32::from(NonZeroU32::new(15).unwrap().get());
+
+    let _ = u64::from(NonZeroU64::new(20).unwrap().get());
+
+    let _ = u128::from(NonZeroU128::new(25).unwrap().get());
+
+    let _ = usize::from(NonZeroUsize::new(30).unwrap().get());
+
+    // Signed integer types
+    let _ = i8::try_from(NonZeroI8::new(-5).unwrap().get());
+
+    let _ = i16::from(NonZeroI16::new(-10).unwrap().get());
+
+    let _ = i32::from(NonZeroI32::new(-15).unwrap().get());
+
+    // Edge cases
+
+    // Complex expression
+    let _ = u8::from(NonZeroU8::new(5).unwrap().get() + 1);
+
+    // Function call
+    fn get_non_zero() -> NonZeroU8 {
+        NonZeroU8::new(42).unwrap()
+    }
+    let _ = u8::from(get_non_zero().get());
+
+    // Method chaining
+    let _ = u16::from(NonZeroU16::new(100).unwrap().get().checked_add(1).unwrap());
+    // This should not trigger the lint
+
+    // Different conversion methods
+    let _ = u32::try_from(NonZeroU32::new(200).unwrap().get()).unwrap();
+
+    // Cases that should not trigger the lint
+    let _ = u8::from(5);
+    let _ = u16::from(10u8);
+    let _ = i32::try_from(40u32).unwrap();
+}