clippy_lints/src/transmute/transmute_int_to_char.rs

   1 use super::TRANSMUTE_INT_TO_CHAR;
   2 use clippy_utils::diagnostics::span_lint_and_then;
   3 use clippy_utils::sugg;
   4 use rustc_ast as ast;
   5 use rustc_errors::Applicability;
   6 use rustc_hir::Expr;
   7 use rustc_lint::LateContext;
   8 use rustc_middle::ty::{self, Ty};
   9
  10 /// Checks for `transmute_int_to_char` 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     arg: &'tcx Expr<'_>,
  18 ) -> bool {
  19     match (&from_ty.kind(), &to_ty.kind()) {
  20         (ty::Int(ty::IntTy::I32) | ty::Uint(ty::UintTy::U32), &ty::Char) => {
  21             span_lint_and_then(
  22                 cx,
  23                 TRANSMUTE_INT_TO_CHAR,
  24                 e.span,
  25                 &format!("transmute from a `{}` to a `char`", from_ty),
  26                 |diag| {
  27                     let arg = sugg::Sugg::hir(cx, arg, "..");
  28                     let arg = if let ty::Int(_) = from_ty.kind() {
  29                         arg.as_ty(ast::UintTy::U32.name_str())
  30                     } else {
  31                         arg
  32                     };
  33                     diag.span_suggestion(
  34                         e.span,
  35                         "consider using",
  36                         format!("std::char::from_u32({}).unwrap()", arg),
  37                         Applicability::Unspecified,
  38                     );
  39                 },
  40             );
  41             true
  42         },
  43         _ => false,
  44     }
  45 }