-use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg, span_lint_and_then, span_lint_hir_and_then};
+use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg, span_lint_hir_and_then};
use clippy_utils::source::{snippet, snippet_opt};
-use clippy_utils::ty::implements_trait;
use if_chain::if_chain;
use rustc_ast::ast::LitKind;
use rustc_errors::Applicability;
use rustc_hir::intravisit::FnKind;
use rustc_hir::{
self as hir, def, BinOpKind, BindingAnnotation, Body, Expr, ExprKind, FnDecl, HirId, Mutability, PatKind, Stmt,
- StmtKind, TyKind, UnOp,
+ StmtKind, TyKind,
};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::lint::in_external_macro;
-use rustc_middle::ty::{self, Ty};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::hygiene::DesugaringKind;
use rustc_span::source_map::{ExpnKind, Span};
-use rustc_span::symbol::sym;
-use clippy_utils::consts::{constant, Constant};
use clippy_utils::sugg::Sugg;
-use clippy_utils::{
- expr_path_res, get_item_name, get_parent_expr, in_constant, is_diag_trait_item, is_integer_const, iter_input_pats,
- last_path_segment, match_any_def_paths, paths, unsext, SpanlessEq,
-};
+use clippy_utils::{get_parent_expr, in_constant, iter_input_pats, last_path_segment, SpanlessEq};
declare_clippy_lint! {
/// ### What it does
/// dereferences, e.g., changing `*x` to `x` within the function.
///
/// ### Example
- /// ```rust,ignore
- /// // Bad
- /// fn foo(ref x: u8) -> bool {
- /// true
- /// }
- ///
- /// // Good
- /// fn foo(x: &u8) -> bool {
- /// true
- /// }
- /// ```
- #[clippy::version = "pre 1.29.0"]
- pub TOPLEVEL_REF_ARG,
- style,
- "an entire binding declared as `ref`, in a function argument or a `let` statement"
-}
-
-declare_clippy_lint! {
- /// ### What it does
- /// Checks for comparisons to NaN.
- ///
- /// ### Why is this bad?
- /// NaN does not compare meaningfully to anything – not
- /// even itself – so those comparisons are simply wrong.
- ///
- /// ### Example
- /// ```rust
- /// # let x = 1.0;
- ///
- /// // Bad
- /// if x == f32::NAN { }
- ///
- /// // Good
- /// if x.is_nan() { }
- /// ```
- #[clippy::version = "pre 1.29.0"]
- pub CMP_NAN,
- correctness,
- "comparisons to `NAN`, which will always return false, probably not intended"
-}
-
-declare_clippy_lint! {
- /// ### What it does
- /// Checks for (in-)equality comparisons on floating-point
- /// values (apart from zero), except in functions called `*eq*` (which probably
- /// implement equality for a type involving floats).
- ///
- /// ### Why is this bad?
- /// Floating point calculations are usually imprecise, so
- /// asking if two values are *exactly* equal is asking for trouble. For a good
- /// guide on what to do, see [the floating point
- /// guide](http://www.floating-point-gui.de/errors/comparison).
- ///
- /// ### Example
- /// ```rust
- /// let x = 1.2331f64;
- /// let y = 1.2332f64;
- ///
- /// // Bad
- /// if y == 1.23f64 { }
- /// if y != x {} // where both are floats
- ///
- /// // Good
- /// let error_margin = f64::EPSILON; // Use an epsilon for comparison
- /// // Or, if Rust <= 1.42, use `std::f64::EPSILON` constant instead.
- /// // let error_margin = std::f64::EPSILON;
- /// if (y - 1.23f64).abs() < error_margin { }
- /// if (y - x).abs() > error_margin { }
- /// ```
- #[clippy::version = "pre 1.29.0"]
- pub FLOAT_CMP,
- pedantic,
- "using `==` or `!=` on float values instead of comparing difference with an epsilon"
-}
-
-declare_clippy_lint! {
- /// ### What it does
- /// Checks for conversions to owned values just for the sake
- /// of a comparison.
- ///
- /// ### Why is this bad?
- /// The comparison can operate on a reference, so creating
- /// an owned value effectively throws it away directly afterwards, which is
- /// needlessly consuming code and heap space.
- ///
- /// ### Example
/// ```rust
- /// # let x = "foo";
- /// # let y = String::from("foo");
- /// if x.to_owned() == y {}
+ /// fn foo(ref _x: u8) {}
/// ```
- /// Could be written as
- /// ```rust
- /// # let x = "foo";
- /// # let y = String::from("foo");
- /// if x == y {}
- /// ```
- #[clippy::version = "pre 1.29.0"]
- pub CMP_OWNED,
- perf,
- "creating owned instances for comparing with others, e.g., `x == \"foo\".to_string()`"
-}
-
-declare_clippy_lint! {
- /// ### What it does
- /// Checks for getting the remainder of a division by one or minus
- /// one.
- ///
- /// ### Why is this bad?
- /// The result for a divisor of one can only ever be zero; for
- /// minus one it can cause panic/overflow (if the left operand is the minimal value of
- /// the respective integer type) or results in zero. No one will write such code
- /// deliberately, unless trying to win an Underhanded Rust Contest. Even for that
- /// contest, it's probably a bad idea. Use something more underhanded.
///
- /// ### Example
+ /// Use instead:
/// ```rust
- /// # let x = 1;
- /// let a = x % 1;
- /// let a = x % -1;
+ /// fn foo(_x: &u8) {}
/// ```
#[clippy::version = "pre 1.29.0"]
- pub MODULO_ONE,
- correctness,
- "taking a number modulo +/-1, which can either panic/overflow or always returns 0"
+ pub TOPLEVEL_REF_ARG,
+ style,
+ "an entire binding declared as `ref`, in a function argument or a `let` statement"
}
-
declare_clippy_lint! {
/// ### What it does
/// Checks for the use of bindings with a single leading
///
/// ### Example
/// ```rust
- /// // Bad
/// let a = 0 as *const u32;
+ /// ```
///
- /// // Good
+ /// Use instead:
+ /// ```rust
/// let a = std::ptr::null::<u32>();
/// ```
#[clippy::version = "pre 1.29.0"]
"using `0 as *{const, mut} T`"
}
-declare_clippy_lint! {
- /// ### What it does
- /// Checks for (in-)equality comparisons on floating-point
- /// value and constant, except in functions called `*eq*` (which probably
- /// implement equality for a type involving floats).
- ///
- /// ### Why is this bad?
- /// Floating point calculations are usually imprecise, so
- /// asking if two values are *exactly* equal is asking for trouble. For a good
- /// guide on what to do, see [the floating point
- /// guide](http://www.floating-point-gui.de/errors/comparison).
- ///
- /// ### Example
- /// ```rust
- /// let x: f64 = 1.0;
- /// const ONE: f64 = 1.00;
- ///
- /// // Bad
- /// if x == ONE { } // where both are floats
- ///
- /// // Good
- /// let error_margin = f64::EPSILON; // Use an epsilon for comparison
- /// // Or, if Rust <= 1.42, use `std::f64::EPSILON` constant instead.
- /// // let error_margin = std::f64::EPSILON;
- /// if (x - ONE).abs() < error_margin { }
- /// ```
- #[clippy::version = "pre 1.29.0"]
- pub FLOAT_CMP_CONST,
- restriction,
- "using `==` or `!=` on float constants instead of comparing difference with an epsilon"
-}
-
declare_lint_pass!(MiscLints => [
TOPLEVEL_REF_ARG,
- CMP_NAN,
- FLOAT_CMP,
- CMP_OWNED,
- MODULO_ONE,
USED_UNDERSCORE_BINDING,
SHORT_CIRCUIT_STATEMENT,
ZERO_PTR,
- FLOAT_CMP_CONST
]);
impl<'tcx> LateLintPass<'tcx> for MiscLints {
}
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
- match expr.kind {
- ExprKind::Cast(e, ty) => {
- check_cast(cx, expr.span, e, ty);
- return;
- },
- ExprKind::Binary(ref cmp, left, right) => {
- check_binary(cx, expr, cmp, left, right);
- return;
- },
- _ => {},
+ if let ExprKind::Cast(e, ty) = expr.kind {
+ check_cast(cx, expr.span, e, ty);
+ return;
}
if in_attributes_expansion(expr) || expr.span.is_desugaring(DesugaringKind::Await) {
// Don't lint things expanded by #[derive(...)], etc or `await` desugaring
}
}
-fn get_lint_and_message(
- is_comparing_constants: bool,
- is_comparing_arrays: bool,
-) -> (&'static rustc_lint::Lint, &'static str) {
- if is_comparing_constants {
- (
- FLOAT_CMP_CONST,
- if is_comparing_arrays {
- "strict comparison of `f32` or `f64` constant arrays"
- } else {
- "strict comparison of `f32` or `f64` constant"
- },
- )
- } else {
- (
- FLOAT_CMP,
- if is_comparing_arrays {
- "strict comparison of `f32` or `f64` arrays"
- } else {
- "strict comparison of `f32` or `f64`"
- },
- )
- }
-}
-
-fn check_nan(cx: &LateContext<'_>, expr: &Expr<'_>, cmp_expr: &Expr<'_>) {
- if_chain! {
- if !in_constant(cx, cmp_expr.hir_id);
- if let Some((value, _)) = constant(cx, cx.typeck_results(), expr);
- if match value {
- Constant::F32(num) => num.is_nan(),
- Constant::F64(num) => num.is_nan(),
- _ => false,
- };
- then {
- span_lint(
- cx,
- CMP_NAN,
- cmp_expr.span,
- "doomed comparison with `NAN`, use `{f32,f64}::is_nan()` instead",
- );
- }
- }
-}
-
-fn is_named_constant<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
- if let Some((_, res)) = constant(cx, cx.typeck_results(), expr) {
- res
- } else {
- false
- }
-}
-
-fn is_allowed<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
- match constant(cx, cx.typeck_results(), expr) {
- Some((Constant::F32(f), _)) => f == 0.0 || f.is_infinite(),
- Some((Constant::F64(f), _)) => f == 0.0 || f.is_infinite(),
- Some((Constant::Vec(vec), _)) => vec.iter().all(|f| match f {
- Constant::F32(f) => *f == 0.0 || (*f).is_infinite(),
- Constant::F64(f) => *f == 0.0 || (*f).is_infinite(),
- _ => false,
- }),
- _ => false,
- }
-}
-
-// Return true if `expr` is the result of `signum()` invoked on a float value.
-fn is_signum(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
- // The negation of a signum is still a signum
- if let ExprKind::Unary(UnOp::Neg, child_expr) = expr.kind {
- return is_signum(cx, child_expr);
- }
-
- if_chain! {
- if let ExprKind::MethodCall(method_name, _, [ref self_arg, ..], _) = expr.kind;
- if sym!(signum) == method_name.ident.name;
- // Check that the receiver of the signum() is a float (expressions[0] is the receiver of
- // the method call)
- then {
- return is_float(cx, self_arg);
- }
- }
- false
-}
-
-fn is_float(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
- let value = &cx.typeck_results().expr_ty(expr).peel_refs().kind();
-
- if let ty::Array(arr_ty, _) = value {
- return matches!(arr_ty.kind(), ty::Float(_));
- };
-
- matches!(value, ty::Float(_))
-}
-
-fn is_array(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
- matches!(&cx.typeck_results().expr_ty(expr).peel_refs().kind(), ty::Array(_, _))
-}
-
-#[allow(clippy::too_many_lines)]
-fn check_to_owned(cx: &LateContext<'_>, expr: &Expr<'_>, other: &Expr<'_>, left: bool) {
- #[derive(Default)]
- struct EqImpl {
- ty_eq_other: bool,
- other_eq_ty: bool,
- }
-
- impl EqImpl {
- fn is_implemented(&self) -> bool {
- self.ty_eq_other || self.other_eq_ty
- }
- }
-
- fn symmetric_partial_eq<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, other: Ty<'tcx>) -> Option<EqImpl> {
- cx.tcx.lang_items().eq_trait().map(|def_id| EqImpl {
- ty_eq_other: implements_trait(cx, ty, def_id, &[other.into()]),
- other_eq_ty: implements_trait(cx, other, def_id, &[ty.into()]),
- })
- }
-
- let (arg_ty, snip) = match expr.kind {
- ExprKind::MethodCall(.., args, _) if args.len() == 1 => {
- if_chain!(
- if let Some(expr_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
- if is_diag_trait_item(cx, expr_def_id, sym::ToString)
- || is_diag_trait_item(cx, expr_def_id, sym::ToOwned);
- then {
- (cx.typeck_results().expr_ty(&args[0]), snippet(cx, args[0].span, ".."))
- } else {
- return;
- }
- )
- },
- ExprKind::Call(path, [arg]) => {
- if expr_path_res(cx, path)
- .opt_def_id()
- .and_then(|id| match_any_def_paths(cx, id, &[&paths::FROM_STR_METHOD, &paths::FROM_FROM]))
- .is_some()
- {
- (cx.typeck_results().expr_ty(arg), snippet(cx, arg.span, ".."))
- } else {
- return;
- }
- },
- _ => return,
- };
-
- let other_ty = cx.typeck_results().expr_ty(other);
-
- let without_deref = symmetric_partial_eq(cx, arg_ty, other_ty).unwrap_or_default();
- let with_deref = arg_ty
- .builtin_deref(true)
- .and_then(|tam| symmetric_partial_eq(cx, tam.ty, other_ty))
- .unwrap_or_default();
-
- if !with_deref.is_implemented() && !without_deref.is_implemented() {
- return;
- }
-
- let other_gets_derefed = matches!(other.kind, ExprKind::Unary(UnOp::Deref, _));
-
- let lint_span = if other_gets_derefed {
- expr.span.to(other.span)
- } else {
- expr.span
- };
-
- span_lint_and_then(
- cx,
- CMP_OWNED,
- lint_span,
- "this creates an owned instance just for comparison",
- |diag| {
- // This also catches `PartialEq` implementations that call `to_owned`.
- if other_gets_derefed {
- diag.span_label(lint_span, "try implementing the comparison without allocating");
- return;
- }
-
- let expr_snip;
- let eq_impl;
- if with_deref.is_implemented() {
- expr_snip = format!("*{}", snip);
- eq_impl = with_deref;
- } else {
- expr_snip = snip.to_string();
- eq_impl = without_deref;
- };
-
- let span;
- let hint;
- if (eq_impl.ty_eq_other && left) || (eq_impl.other_eq_ty && !left) {
- span = expr.span;
- hint = expr_snip;
- } else {
- span = expr.span.to(other.span);
-
- let cmp_span = if other.span < expr.span {
- other.span.between(expr.span)
- } else {
- expr.span.between(other.span)
- };
- if eq_impl.ty_eq_other {
- hint = format!(
- "{}{}{}",
- expr_snip,
- snippet(cx, cmp_span, ".."),
- snippet(cx, other.span, "..")
- );
- } else {
- hint = format!(
- "{}{}{}",
- snippet(cx, other.span, ".."),
- snippet(cx, cmp_span, ".."),
- expr_snip
- );
- }
- }
-
- diag.span_suggestion(
- span,
- "try",
- hint,
- Applicability::MachineApplicable, // snippet
- );
- },
- );
-}
-
/// Heuristic to see if an expression is used. Should be compatible with
/// `unused_variables`'s idea
/// of what it means for an expression to be "used".
use rustc_span::hygiene::MacroKind;
if expr.span.from_expansion() {
let data = expr.span.ctxt().outer_expn_data();
- matches!(data.kind, ExpnKind::Macro(MacroKind::Attr, _))
+ matches!(data.kind, ExpnKind::Macro(MacroKind::Attr | MacroKind::Derive, _))
} else {
false
}
}
}
}
-
-fn check_binary<'a>(
- cx: &LateContext<'a>,
- expr: &Expr<'_>,
- cmp: &rustc_span::source_map::Spanned<rustc_hir::BinOpKind>,
- left: &'a Expr<'_>,
- right: &'a Expr<'_>,
-) {
- let op = cmp.node;
- if op.is_comparison() {
- check_nan(cx, left, expr);
- check_nan(cx, right, expr);
- check_to_owned(cx, left, right, true);
- check_to_owned(cx, right, left, false);
- }
- if (op == BinOpKind::Eq || op == BinOpKind::Ne) && (is_float(cx, left) || is_float(cx, right)) {
- if is_allowed(cx, left) || is_allowed(cx, right) {
- return;
- }
-
- // Allow comparing the results of signum()
- if is_signum(cx, left) && is_signum(cx, right) {
- return;
- }
-
- if let Some(name) = get_item_name(cx, expr) {
- let name = name.as_str();
- if name == "eq" || name == "ne" || name == "is_nan" || name.starts_with("eq_") || name.ends_with("_eq") {
- return;
- }
- }
- let is_comparing_arrays = is_array(cx, left) || is_array(cx, right);
- let (lint, msg) = get_lint_and_message(
- is_named_constant(cx, left) || is_named_constant(cx, right),
- is_comparing_arrays,
- );
- span_lint_and_then(cx, lint, expr.span, msg, |diag| {
- let lhs = Sugg::hir(cx, left, "..");
- let rhs = Sugg::hir(cx, right, "..");
-
- if !is_comparing_arrays {
- diag.span_suggestion(
- expr.span,
- "consider comparing them within some margin of error",
- format!(
- "({}).abs() {} error_margin",
- lhs - rhs,
- if op == BinOpKind::Eq { '<' } else { '>' }
- ),
- Applicability::HasPlaceholders, // snippet
- );
- }
- diag.note("`f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`");
- });
- } else if op == BinOpKind::Rem {
- if is_integer_const(cx, right, 1) {
- span_lint(cx, MODULO_ONE, expr.span, "any number modulo 1 will be 0");
- }
-
- if let ty::Int(ity) = cx.typeck_results().expr_ty(right).kind() {
- if is_integer_const(cx, right, unsext(cx.tcx, -1, *ity)) {
- span_lint(
- cx,
- MODULO_ONE,
- expr.span,
- "any number modulo -1 will panic/overflow or result in 0",
- );
- }
- };
- }
-}
projects / rust.git / blobdiff