1 use clippy_utils::diagnostics::span_lint_and_then;
2 use clippy_utils::{match_def_path, paths, sugg};
3 use if_chain::if_chain;
4 use rustc_ast::util::parser::AssocOp;
5 use rustc_errors::Applicability;
6 use rustc_hir::def::{DefKind, Res};
7 use rustc_hir::{BinOpKind, Expr, ExprKind};
8 use rustc_lint::{LateContext, LateLintPass};
10 use rustc_session::{declare_lint_pass, declare_tool_lint};
11 use rustc_span::source_map::Spanned;
13 declare_clippy_lint! {
14 /// **What it does:** Checks for statements of the form `(a - b) < f32::EPSILON` or
15 /// `(a - b) < f64::EPSILON`. Notes the missing `.abs()`.
17 /// **Why is this bad?** The code without `.abs()` is more likely to have a bug.
19 /// **Known problems:** If the user can ensure that b is larger than a, the `.abs()` is
20 /// technically unneccessary. However, it will make the code more robust and doesn't have any
21 /// large performance implications. If the abs call was deliberately left out for performance
22 /// reasons, it is probably better to state this explicitly in the code, which then can be done
28 /// pub fn is_roughly_equal(a: f32, b: f32) -> bool {
29 /// (a - b) < f32::EPSILON
34 /// pub fn is_roughly_equal(a: f32, b: f32) -> bool {
35 /// (a - b).abs() < f32::EPSILON
38 pub FLOAT_EQUALITY_WITHOUT_ABS,
40 "float equality check without `.abs()`"
43 declare_lint_pass!(FloatEqualityWithoutAbs => [FLOAT_EQUALITY_WITHOUT_ABS]);
45 impl<'tcx> LateLintPass<'tcx> for FloatEqualityWithoutAbs {
46 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
50 // check if expr is a binary expression with a lt or gt operator
51 if let ExprKind::Binary(op, ref left, ref right) = expr.kind {
69 // left hand side is a substraction
70 if let ExprKind::Binary(
79 // right hand side matches either f32::EPSILON or f64::EPSILON
80 if let ExprKind::Path(ref epsilon_path) = rhs.kind;
81 if let Res::Def(DefKind::AssocConst, def_id) = cx.qpath_res(epsilon_path, rhs.hir_id);
82 if match_def_path(cx, def_id, &paths::F32_EPSILON) || match_def_path(cx, def_id, &paths::F64_EPSILON);
84 // values of the substractions on the left hand side are of the type float
85 let t_val_l = cx.typeck_results().expr_ty(val_l);
86 let t_val_r = cx.typeck_results().expr_ty(val_r);
87 if let ty::Float(_) = t_val_l.kind();
88 if let ty::Float(_) = t_val_r.kind();
91 let sug_l = sugg::Sugg::hir(cx, &val_l, "..");
92 let sug_r = sugg::Sugg::hir(cx, &val_r, "..");
93 // format the suggestion
94 let suggestion = format!("{}.abs()", sugg::make_assoc(AssocOp::Subtract, &sug_l, &sug_r).maybe_par());
98 FLOAT_EQUALITY_WITHOUT_ABS,
100 "float equality check without `.abs()`",
102 diag.span_suggestion(
106 Applicability::MaybeIncorrect,