new lint legacy_numeric_constants

CHANGELOG.md

@@ -5379,6 +5379,7 @@ Released 2018-09-13
 [`large_stack_arrays`]: https://rust-lang.github.io/rust-clippy/master/index.html#large_stack_arrays
 [`large_stack_frames`]: https://rust-lang.github.io/rust-clippy/master/index.html#large_stack_frames
 [`large_types_passed_by_value`]: https://rust-lang.github.io/rust-clippy/master/index.html#large_types_passed_by_value
+[`legacy_numeric_constants`]: https://rust-lang.github.io/rust-clippy/master/index.html#legacy_numeric_constants
 [`len_without_is_empty`]: https://rust-lang.github.io/rust-clippy/master/index.html#len_without_is_empty
 [`len_zero`]: https://rust-lang.github.io/rust-clippy/master/index.html#len_zero
 [`let_and_return`]: https://rust-lang.github.io/rust-clippy/master/index.html#let_and_return

book/src/lint_configuration.md

@@ -616,6 +616,7 @@ The minimum rust version that the project supports. Defaults to the `rust-versio
 * [`if_then_some_else_none`](https://rust-lang.github.io/rust-clippy/master/index.html#if_then_some_else_none)
 * [`index_refutable_slice`](https://rust-lang.github.io/rust-clippy/master/index.html#index_refutable_slice)
 * [`iter_kv_map`](https://rust-lang.github.io/rust-clippy/master/index.html#iter_kv_map)
+* [`legacy_numeric_constants`](https://rust-lang.github.io/rust-clippy/master/index.html#legacy_numeric_constants)
 * [`manual_bits`](https://rust-lang.github.io/rust-clippy/master/index.html#manual_bits)
 * [`manual_c_str_literals`](https://rust-lang.github.io/rust-clippy/master/index.html#manual_c_str_literals)
 * [`manual_clamp`](https://rust-lang.github.io/rust-clippy/master/index.html#manual_clamp)

clippy_config/src/conf.rs

@@ -262,7 +262,7 @@ define_Conf! {
     ///
     /// Suppress lints whenever the suggested change would cause breakage for other crates.
     (avoid_breaking_exported_api: bool = true),
-    /// Lint: MANUAL_SPLIT_ONCE, MANUAL_STR_REPEAT, CLONED_INSTEAD_OF_COPIED, REDUNDANT_FIELD_NAMES, OPTION_MAP_UNWRAP_OR, REDUNDANT_STATIC_LIFETIMES, FILTER_MAP_NEXT, CHECKED_CONVERSIONS, MANUAL_RANGE_CONTAINS, USE_SELF, MEM_REPLACE_WITH_DEFAULT, MANUAL_NON_EXHAUSTIVE, OPTION_AS_REF_DEREF, MAP_UNWRAP_OR, MATCH_LIKE_MATCHES_MACRO, MANUAL_STRIP, MISSING_CONST_FOR_FN, UNNESTED_OR_PATTERNS, FROM_OVER_INTO, PTR_AS_PTR, IF_THEN_SOME_ELSE_NONE, APPROX_CONSTANT, DEPRECATED_CFG_ATTR, INDEX_REFUTABLE_SLICE, MAP_CLONE, BORROW_AS_PTR, MANUAL_BITS, ERR_EXPECT, CAST_ABS_TO_UNSIGNED, UNINLINED_FORMAT_ARGS, MANUAL_CLAMP, MANUAL_LET_ELSE, UNCHECKED_DURATION_SUBTRACTION, COLLAPSIBLE_STR_REPLACE, SEEK_FROM_CURRENT, SEEK_REWIND, UNNECESSARY_LAZY_EVALUATIONS, TRANSMUTE_PTR_TO_REF, ALMOST_COMPLETE_RANGE, NEEDLESS_BORROW, DERIVABLE_IMPLS, MANUAL_IS_ASCII_CHECK, MANUAL_REM_EUCLID, MANUAL_RETAIN, TYPE_REPETITION_IN_BOUNDS, TUPLE_ARRAY_CONVERSIONS, MANUAL_TRY_FOLD, MANUAL_HASH_ONE, ITER_KV_MAP, MANUAL_C_STR_LITERALS, ASSIGNING_CLONES.
+    /// Lint: MANUAL_SPLIT_ONCE, MANUAL_STR_REPEAT, CLONED_INSTEAD_OF_COPIED, REDUNDANT_FIELD_NAMES, OPTION_MAP_UNWRAP_OR, REDUNDANT_STATIC_LIFETIMES, FILTER_MAP_NEXT, CHECKED_CONVERSIONS, MANUAL_RANGE_CONTAINS, USE_SELF, MEM_REPLACE_WITH_DEFAULT, MANUAL_NON_EXHAUSTIVE, OPTION_AS_REF_DEREF, MAP_UNWRAP_OR, MATCH_LIKE_MATCHES_MACRO, MANUAL_STRIP, MISSING_CONST_FOR_FN, UNNESTED_OR_PATTERNS, FROM_OVER_INTO, PTR_AS_PTR, IF_THEN_SOME_ELSE_NONE, APPROX_CONSTANT, DEPRECATED_CFG_ATTR, INDEX_REFUTABLE_SLICE, MAP_CLONE, BORROW_AS_PTR, MANUAL_BITS, ERR_EXPECT, CAST_ABS_TO_UNSIGNED, UNINLINED_FORMAT_ARGS, MANUAL_CLAMP, MANUAL_LET_ELSE, UNCHECKED_DURATION_SUBTRACTION, COLLAPSIBLE_STR_REPLACE, SEEK_FROM_CURRENT, SEEK_REWIND, UNNECESSARY_LAZY_EVALUATIONS, TRANSMUTE_PTR_TO_REF, ALMOST_COMPLETE_RANGE, NEEDLESS_BORROW, DERIVABLE_IMPLS, MANUAL_IS_ASCII_CHECK, MANUAL_REM_EUCLID, MANUAL_RETAIN, TYPE_REPETITION_IN_BOUNDS, TUPLE_ARRAY_CONVERSIONS, MANUAL_TRY_FOLD, MANUAL_HASH_ONE, ITER_KV_MAP, MANUAL_C_STR_LITERALS, ASSIGNING_CLONES, LEGACY_NUMERIC_CONSTANTS.
     ///
     /// The minimum rust version that the project supports. Defaults to the `rust-version` field in `Cargo.toml`
     #[default_text = ""]

clippy_config/src/msrvs.rs

@@ -36,7 +36,7 @@ msrv_aliases! {
     1,47,0 { TAU, IS_ASCII_DIGIT_CONST, ARRAY_IMPL_ANY_LEN }
     1,46,0 { CONST_IF_MATCH }
     1,45,0 { STR_STRIP_PREFIX }
-    1,43,0 { LOG2_10, LOG10_2 }
+    1,43,0 { LOG2_10, LOG10_2, NUMERIC_ASSOCIATED_CONSTANTS }
     1,42,0 { MATCHES_MACRO, SLICE_PATTERNS, PTR_SLICE_RAW_PARTS }
     1,41,0 { RE_REBALANCING_COHERENCE, RESULT_MAP_OR_ELSE }
     1,40,0 { MEM_TAKE, NON_EXHAUSTIVE, OPTION_AS_DEREF }

clippy_lints/src/casts/cast_possible_truncation.rs

@@ -41,7 +41,7 @@ fn apply_reductions(cx: &LateContext<'_>, nbits: u64, expr: &Expr<'_>, signed: b
                 })
             },
             BinOpKind::Rem | BinOpKind::BitAnd => get_constant_bits(cx, right)
-                .unwrap_or(u64::max_value())
+                .unwrap_or(u64::MAX)
                 .min(apply_reductions(cx, nbits, left, signed)),
             BinOpKind::Shr => apply_reductions(cx, nbits, left, signed)
                 .saturating_sub(constant_int(cx, right).map_or(0, |s| u64::try_from(s).unwrap_or_default())),
@@ -56,7 +56,7 @@ fn apply_reductions(cx: &LateContext<'_>, nbits: u64, expr: &Expr<'_>, signed: b
             } else {
                 None
             };
-            apply_reductions(cx, nbits, left, signed).min(max_bits.unwrap_or(u64::max_value()))
+            apply_reductions(cx, nbits, left, signed).min(max_bits.unwrap_or(u64::MAX))
         },
         ExprKind::MethodCall(method, _, [lo, hi], _) => {
             if method.ident.as_str() == "clamp" {

clippy_lints/src/declared_lints.rs

@@ -254,6 +254,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     crate::large_include_file::LARGE_INCLUDE_FILE_INFO,
     crate::large_stack_arrays::LARGE_STACK_ARRAYS_INFO,
     crate::large_stack_frames::LARGE_STACK_FRAMES_INFO,
+    crate::legacy_numeric_constants::LEGACY_NUMERIC_CONSTANTS_INFO,
     crate::len_zero::COMPARISON_TO_EMPTY_INFO,
     crate::len_zero::LEN_WITHOUT_IS_EMPTY_INFO,
     crate::len_zero::LEN_ZERO_INFO,

clippy_lints/src/legacy_numeric_constants.rs

@@ -0,0 +1,293 @@
+use clippy_config::msrvs::{Msrv, NUMERIC_ASSOCIATED_CONSTANTS};
+use clippy_utils::diagnostics::{span_lint_and_then, span_lint_hir_and_then};
+use clippy_utils::{get_parent_expr, is_from_proc_macro};
+use hir::def_id::DefId;
+use rustc_errors::{Applicability, SuggestionStyle};
+use rustc_hir as hir;
+use rustc_hir::{ExprKind, Item, ItemKind, QPath, UseKind};
+use rustc_lint::{LateContext, LateLintPass, LintContext};
+use rustc_middle::lint::in_external_macro;
+use rustc_session::impl_lint_pass;
+use rustc_span::symbol::kw;
+use rustc_span::{sym, Symbol};
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for usage of `<integer>::max_value()`, `std::<integer>::MAX`,
+    /// `std::<float>::EPSILON`, etc.
+    ///
+    /// ### Why is this bad?
+    /// All of these have been superceded by the associated constants on their respective types,
+    /// such as `i128::MAX`. These legacy items may be deprecated in a future version of rust.
+    ///
+    /// ### Example
+    /// ```rust
+    /// let eps = std::f32::EPSILON;
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// let eps = f32::EPSILON;
+    /// ```
+    #[clippy::version = "1.72.0"]
+    pub LEGACY_NUMERIC_CONSTANTS,
+    style,
+    "checks for usage of legacy std numeric constants and methods"
+}
+pub struct LegacyNumericConstants {
+    msrv: Msrv,
+}
+
+impl LegacyNumericConstants {
+    #[must_use]
+    pub fn new(msrv: Msrv) -> Self {
+        Self { msrv }
+    }
+}
+
+impl_lint_pass!(LegacyNumericConstants => [LEGACY_NUMERIC_CONSTANTS]);
+
+impl<'tcx> LateLintPass<'tcx> for LegacyNumericConstants {
+    fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'tcx>) {
+        let Self { msrv } = self;
+
+        if !msrv.meets(NUMERIC_ASSOCIATED_CONSTANTS) || in_external_macro(cx.sess(), item.span) {
+            return;
+        }
+
+        // Integer modules are "TBD" deprecated, and the contents are too,
+        // so lint on the `use` statement directly.
+        if let ItemKind::Use(path, kind @ (UseKind::Single | UseKind::Glob)) = item.kind
+            && let Some(def_id) = path.res[0].opt_def_id()
+        {
+            let module = if is_integer_module(cx, def_id) {
+                true
+            } else if is_numeric_const(cx, def_id) {
+                false
+            } else {
+                return;
+            };
+
+            span_lint_and_then(
+                cx,
+                LEGACY_NUMERIC_CONSTANTS,
+                path.span,
+                if module {
+                    "importing legacy numeric constants"
+                } else {
+                    "importing a legacy numeric constant"
+                },
+                |diag| {
+                    if item.ident.name == kw::Underscore {
+                        diag.help("remove this import");
+                        return;
+                    }
+
+                    let def_path = cx.get_def_path(def_id);
+
+                    if module && let [.., module_name] = &*def_path {
+                        if kind == UseKind::Glob {
+                            diag.help(format!("remove this import and use associated constants `{module_name}::<CONST>` from the primitive type instead"));
+                        } else {
+                            diag.help("remove this import").note(format!(
+                                "then `{module_name}::<CONST>` will resolve to the respective associated constant"
+                            ));
+                        }
+                    } else if let [.., module_name, name] = &*def_path {
+                        diag.help(
+                            format!("remove this import and use the associated constant `{module_name}::{name}` from the primitive type instead")
+                        );
+                    }
+                },
+            );
+        }
+    }
+
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx rustc_hir::Expr<'tcx>) {
+        let Self { msrv } = self;
+
+        if !msrv.meets(NUMERIC_ASSOCIATED_CONSTANTS) || in_external_macro(cx.sess(), expr.span) {
+            return;
+        }
+        let ExprKind::Path(qpath) = expr.kind else {
+            return;
+        };
+
+        // `std::<integer>::<CONST>` check
+        let (span, sugg, msg) = if let QPath::Resolved(None, path) = qpath
+            && let Some(def_id) = path.res.opt_def_id()
+            && is_numeric_const(cx, def_id)
+            && let def_path = cx.get_def_path(def_id)
+            && let [.., mod_name, name] = &*def_path
+            // Skip linting if this usage looks identical to the associated constant,
+            // since this would only require removing a `use` import (which is already linted).
+            && !is_numeric_const_path_canonical(path, [*mod_name, *name])
+        {
+            (
+                expr.span,
+                format!("{mod_name}::{name}"),
+                "usage of a legacy numeric constant",
+            )
+        // `<integer>::xxx_value` check
+        } else if let QPath::TypeRelative(_, last_segment) = qpath
+            && let Some(def_id) = cx.qpath_res(&qpath, expr.hir_id).opt_def_id()
+            && is_integer_method(cx, def_id)
+            && let Some(par_expr) = get_parent_expr(cx, expr)
+            && let ExprKind::Call(_, _) = par_expr.kind
+        {
+            let name = last_segment.ident.name.as_str();
+
+            (
+                last_segment.ident.span.with_hi(par_expr.span.hi()),
+                name[..=2].to_ascii_uppercase(),
+                "usage of a legacy numeric method",
+            )
+        } else {
+            return;
+        };
+
+        if is_from_proc_macro(cx, expr) {
+            return;
+        }
+
+        span_lint_hir_and_then(cx, LEGACY_NUMERIC_CONSTANTS, expr.hir_id, span, msg, |diag| {
+            diag.span_suggestion_with_style(
+                span,
+                "use the associated constant instead",
+                sugg,
+                Applicability::MaybeIncorrect,
+                SuggestionStyle::ShowAlways,
+            );
+        });
+    }
+
+    extract_msrv_attr!(LateContext);
+}
+
+fn is_integer_module(cx: &LateContext<'_>, did: DefId) -> bool {
+    matches!(
+        cx.tcx.get_diagnostic_name(did),
+        Some(
+            sym::isize_legacy_mod
+                | sym::i128_legacy_mod
+                | sym::i64_legacy_mod
+                | sym::i32_legacy_mod
+                | sym::i16_legacy_mod
+                | sym::i8_legacy_mod
+                | sym::usize_legacy_mod
+                | sym::u128_legacy_mod
+                | sym::u64_legacy_mod
+                | sym::u32_legacy_mod
+                | sym::u16_legacy_mod
+                | sym::u8_legacy_mod
+        )
+    )
+}
+
+fn is_numeric_const(cx: &LateContext<'_>, did: DefId) -> bool {
+    matches!(
+        cx.tcx.get_diagnostic_name(did),
+        Some(
+            sym::isize_legacy_const_max
+                | sym::isize_legacy_const_min
+                | sym::i128_legacy_const_max
+                | sym::i128_legacy_const_min
+                | sym::i16_legacy_const_max
+                | sym::i16_legacy_const_min
+                | sym::i32_legacy_const_max
+                | sym::i32_legacy_const_min
+                | sym::i64_legacy_const_max
+                | sym::i64_legacy_const_min
+                | sym::i8_legacy_const_max
+                | sym::i8_legacy_const_min
+                | sym::usize_legacy_const_max
+                | sym::usize_legacy_const_min
+                | sym::u128_legacy_const_max
+                | sym::u128_legacy_const_min
+                | sym::u16_legacy_const_max
+                | sym::u16_legacy_const_min
+                | sym::u32_legacy_const_max
+                | sym::u32_legacy_const_min
+                | sym::u64_legacy_const_max
+                | sym::u64_legacy_const_min
+                | sym::u8_legacy_const_max
+                | sym::u8_legacy_const_min
+                | sym::f32_legacy_const_digits
+                | sym::f32_legacy_const_epsilon
+                | sym::f32_legacy_const_infinity
+                | sym::f32_legacy_const_mantissa_dig
+                | sym::f32_legacy_const_max
+                | sym::f32_legacy_const_max_10_exp
+                | sym::f32_legacy_const_max_exp
+                | sym::f32_legacy_const_min
+                | sym::f32_legacy_const_min_10_exp
+                | sym::f32_legacy_const_min_exp
+                | sym::f32_legacy_const_min_positive
+                | sym::f32_legacy_const_nan
+                | sym::f32_legacy_const_neg_infinity
+                | sym::f32_legacy_const_radix
+                | sym::f64_legacy_const_digits
+                | sym::f64_legacy_const_epsilon
+                | sym::f64_legacy_const_infinity
+                | sym::f64_legacy_const_mantissa_dig
+                | sym::f64_legacy_const_max
+                | sym::f64_legacy_const_max_10_exp
+                | sym::f64_legacy_const_max_exp
+                | sym::f64_legacy_const_min
+                | sym::f64_legacy_const_min_10_exp
+                | sym::f64_legacy_const_min_exp
+                | sym::f64_legacy_const_min_positive
+                | sym::f64_legacy_const_nan
+                | sym::f64_legacy_const_neg_infinity
+                | sym::f64_legacy_const_radix
+        )
+    )
+}
+
+// Whether path expression looks like `i32::MAX`
+fn is_numeric_const_path_canonical(expr_path: &hir::Path<'_>, [mod_name, name]: [Symbol; 2]) -> bool {
+    let [
+        hir::PathSegment {
+            ident: one, args: None, ..
+        },
+        hir::PathSegment {
+            ident: two, args: None, ..
+        },
+    ] = expr_path.segments
+    else {
+        return false;
+    };
+
+    one.name == mod_name && two.name == name
+}
+
+fn is_integer_method(cx: &LateContext<'_>, did: DefId) -> bool {
+    matches!(
+        cx.tcx.get_diagnostic_name(did),
+        Some(
+            sym::isize_legacy_fn_max_value
+                | sym::isize_legacy_fn_min_value
+                | sym::i128_legacy_fn_max_value
+                | sym::i128_legacy_fn_min_value
+                | sym::i16_legacy_fn_max_value
+                | sym::i16_legacy_fn_min_value
+                | sym::i32_legacy_fn_max_value
+                | sym::i32_legacy_fn_min_value
+                | sym::i64_legacy_fn_max_value
+                | sym::i64_legacy_fn_min_value
+                | sym::i8_legacy_fn_max_value
+                | sym::i8_legacy_fn_min_value
+                | sym::usize_legacy_fn_max_value
+                | sym::usize_legacy_fn_min_value
+                | sym::u128_legacy_fn_max_value
+                | sym::u128_legacy_fn_min_value
+                | sym::u16_legacy_fn_max_value
+                | sym::u16_legacy_fn_min_value
+                | sym::u32_legacy_fn_max_value
+                | sym::u32_legacy_fn_min_value
+                | sym::u64_legacy_fn_max_value
+                | sym::u64_legacy_fn_min_value
+                | sym::u8_legacy_fn_max_value
+                | sym::u8_legacy_fn_min_value
+        )
+    )
+}

clippy_lints/src/lib.rs

@@ -186,6 +186,7 @@ mod large_futures;
 mod large_include_file;
 mod large_stack_arrays;
 mod large_stack_frames;
+mod legacy_numeric_constants;
 mod len_zero;
 mod let_if_seq;
 mod let_underscore;
@@ -1080,6 +1081,7 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
             allow_one_hash_in_raw_strings,
         })
     });
+    store.register_late_pass(move |_| Box::new(legacy_numeric_constants::LegacyNumericConstants::new(msrv())));
     store.register_late_pass(|_| Box::new(manual_range_patterns::ManualRangePatterns));
     store.register_early_pass(|| Box::new(visibility::Visibility));
     store.register_late_pass(move |_| Box::new(tuple_array_conversions::TupleArrayConversions { msrv: msrv() }));

clippy_utils/src/check_proc_macro.rs

@@ -24,7 +24,7 @@ use rustc_hir::{
 use rustc_lint::{LateContext, LintContext};
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
-use rustc_span::symbol::Ident;
+use rustc_span::symbol::{kw, Ident};
 use rustc_span::{Span, Symbol};
 use rustc_target::spec::abi::Abi;
 
@@ -99,9 +99,13 @@ fn qpath_search_pat(path: &QPath<'_>) -> (Pat, Pat) {
             let start = if ty.is_some() {
                 Pat::Str("<")
             } else {
-                path.segments
-                    .first()
-                    .map_or(Pat::Str(""), |seg| Pat::Sym(seg.ident.name))
+                path.segments.first().map_or(Pat::Str(""), |seg| {
+                    if seg.ident.name == kw::PathRoot {
+                        Pat::Str("::")
+                    } else {
+                        Pat::Sym(seg.ident.name)
+                    }
+                })
             };
             let end = path.segments.last().map_or(Pat::Str(""), |seg| {
                 if seg.args.is_some() {