clippy_lints/src/transmute/transmute_float_to_int.rs

   1 use super::TRANSMUTE_FLOAT_TO_INT;
   2 use crate::utils::{span_lint_and_then, sugg};
   3 use if_chain::if_chain;
   4 use rustc_ast as ast;
   5 use rustc_errors::Applicability;
   6 use rustc_hir::{Expr, ExprKind, UnOp};
   7 use rustc_lint::LateContext;
   8 use rustc_middle::ty::{self, Ty};
   9
  10 /// Checks for `transmute_float_to_int` lint.
  11 /// Returns `true` if it's triggered, otherwise returns `false`.
  12 pub(super) fn check<'tcx>(
  13     cx: &LateContext<'tcx>,
  14     e: &'tcx Expr<'_>,
  15     from_ty: Ty<'tcx>,
  16     to_ty: Ty<'tcx>,
  17     args: &'tcx [Expr<'_>],
  18     const_context: bool,
  19 ) -> bool {
  20     match (&from_ty.kind(), &to_ty.kind()) {
  21         (ty::Float(float_ty), ty::Int(_) | ty::Uint(_)) if !const_context => {
  22             span_lint_and_then(
  23                 cx,
  24                 TRANSMUTE_FLOAT_TO_INT,
  25                 e.span,
  26                 &format!("transmute from a `{}` to a `{}`", from_ty, to_ty),
  27                 |diag| {
  28                     let mut expr = &args[0];
  29                     let mut arg = sugg::Sugg::hir(cx, expr, "..");
  30
  31                     if let ExprKind::Unary(UnOp::Neg, inner_expr) = &expr.kind {
  32                         expr = &inner_expr;
  33                     }
  34
  35                     if_chain! {
  36                         // if the expression is a float literal and it is unsuffixed then
  37                         // add a suffix so the suggestion is valid and unambiguous
  38                         let op = format!("{}{}", arg, float_ty.name_str()).into();
  39                         if let ExprKind::Lit(lit) = &expr.kind;
  40                         if let ast::LitKind::Float(_, ast::LitFloatType::Unsuffixed) = lit.node;
  41                         then {
  42                             match arg {
  43                                 sugg::Sugg::MaybeParen(_) => arg = sugg::Sugg::MaybeParen(op),
  44                                 _ => arg = sugg::Sugg::NonParen(op)
  45                             }
  46                         }
  47                     }
  48
  49                     arg = sugg::Sugg::NonParen(format!("{}.to_bits()", arg.maybe_par()).into());
  50
  51                     // cast the result of `to_bits` if `to_ty` is signed
  52                     arg = if let ty::Int(int_ty) = to_ty.kind() {
  53                         arg.as_ty(int_ty.name_str().to_string())
  54                     } else {
  55                         arg
  56                     };
  57
  58                     diag.span_suggestion(e.span, "consider using", arg.to_string(), Applicability::Unspecified);
  59                 },
  60             );
  61             true
  62         },
  63         _ => false,
  64     }
  65 }