src/tools/clippy/clippy_lints/src/transmute/useless_transmute.rs

   1 use super::USELESS_TRANSMUTE;
   2 use clippy_utils::diagnostics::{span_lint, span_lint_and_then};
   3 use clippy_utils::sugg;
   4 use rustc_errors::Applicability;
   5 use rustc_hir::Expr;
   6 use rustc_lint::LateContext;
   7 use rustc_middle::ty::{self, Ty};
   8
   9 /// Checks for `useless_transmute` lint.
  10 /// Returns `true` if it's triggered, otherwise returns `false`.
  11 pub(super) fn check<'tcx>(
  12     cx: &LateContext<'tcx>,
  13     e: &'tcx Expr<'_>,
  14     from_ty: Ty<'tcx>,
  15     to_ty: Ty<'tcx>,
  16     args: &'tcx [Expr<'_>],
  17 ) -> bool {
  18     match (&from_ty.kind(), &to_ty.kind()) {
  19         _ if from_ty == to_ty => {
  20             span_lint(
  21                 cx,
  22                 USELESS_TRANSMUTE,
  23                 e.span,
  24                 &format!("transmute from a type (`{}`) to itself", from_ty),
  25             );
  26             true
  27         },
  28         (ty::Ref(_, rty, rty_mutbl), ty::RawPtr(ptr_ty)) => {
  29             span_lint_and_then(
  30                 cx,
  31                 USELESS_TRANSMUTE,
  32                 e.span,
  33                 "transmute from a reference to a pointer",
  34                 |diag| {
  35                     if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
  36                         let rty_and_mut = ty::TypeAndMut {
  37                             ty: rty,
  38                             mutbl: *rty_mutbl,
  39                         };
  40
  41                         let sugg = if *ptr_ty == rty_and_mut {
  42                             arg.as_ty(to_ty)
  43                         } else {
  44                             arg.as_ty(cx.tcx.mk_ptr(rty_and_mut)).as_ty(to_ty)
  45                         };
  46
  47                         diag.span_suggestion(e.span, "try", sugg.to_string(), Applicability::Unspecified);
  48                     }
  49                 },
  50             );
  51             true
  52         },
  53         (ty::Int(_) | ty::Uint(_), ty::RawPtr(_)) => {
  54             span_lint_and_then(
  55                 cx,
  56                 USELESS_TRANSMUTE,
  57                 e.span,
  58                 "transmute from an integer to a pointer",
  59                 |diag| {
  60                     if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
  61                         diag.span_suggestion(
  62                             e.span,
  63                             "try",
  64                             arg.as_ty(&to_ty.to_string()).to_string(),
  65                             Applicability::Unspecified,
  66                         );
  67                     }
  68                 },
  69             );
  70             true
  71         },
  72         _ => false,
  73     }
  74 }