src/tools/clippy/clippy_lints/src/operators/float_equality_without_abs.rs

   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;
   9 use rustc_middle::ty;
  10 use rustc_span::source_map::Spanned;
  11
  12 use super::FLOAT_EQUALITY_WITHOUT_ABS;
  13
  14 pub(crate) fn check<'tcx>(
  15     cx: &LateContext<'tcx>,
  16     expr: &'tcx Expr<'_>,
  17     op: BinOpKind,
  18     lhs: &'tcx Expr<'_>,
  19     rhs: &'tcx Expr<'_>,
  20 ) {
  21     let (lhs, rhs) = match op {
  22         BinOpKind::Lt => (lhs, rhs),
  23         BinOpKind::Gt => (rhs, lhs),
  24         _ => return,
  25     };
  26
  27     if_chain! {
  28         // left hand side is a subtraction
  29         if let ExprKind::Binary(
  30             Spanned {
  31                 node: BinOpKind::Sub,
  32                 ..
  33             },
  34             val_l,
  35             val_r,
  36         ) = lhs.kind;
  37
  38         // right hand side matches either f32::EPSILON or f64::EPSILON
  39         if let ExprKind::Path(ref epsilon_path) = rhs.kind;
  40         if let Res::Def(DefKind::AssocConst, def_id) = cx.qpath_res(epsilon_path, rhs.hir_id);
  41         if match_def_path(cx, def_id, &paths::F32_EPSILON) || match_def_path(cx, def_id, &paths::F64_EPSILON);
  42
  43         // values of the subtractions on the left hand side are of the type float
  44         let t_val_l = cx.typeck_results().expr_ty(val_l);
  45         let t_val_r = cx.typeck_results().expr_ty(val_r);
  46         if let ty::Float(_) = t_val_l.kind();
  47         if let ty::Float(_) = t_val_r.kind();
  48
  49         then {
  50             let sug_l = sugg::Sugg::hir(cx, val_l, "..");
  51             let sug_r = sugg::Sugg::hir(cx, val_r, "..");
  52             // format the suggestion
  53             let suggestion = format!("{}.abs()", sugg::make_assoc(AssocOp::Subtract, &sug_l, &sug_r).maybe_par());
  54             // spans the lint
  55             span_lint_and_then(
  56                 cx,
  57                 FLOAT_EQUALITY_WITHOUT_ABS,
  58                 expr.span,
  59                 "float equality check without `.abs()`",
  60                 | diag | {
  61                     diag.span_suggestion(
  62                         lhs.span,
  63                         "add `.abs()`",
  64                         suggestion,
  65                         Applicability::MaybeIncorrect,
  66                     );
  67                 }
  68             );
  69         }
  70     }
  71 }