rust-clippy/clippy_lints/src/transmute/transmute_ref_to_ref.rs
Nicholas Nethercote 5fa961b951 Overhaul TyS and Ty.
Specifically, change `Ty` from this:
```
pub type Ty<'tcx> = &'tcx TyS<'tcx>;
```
to this
```
pub struct Ty<'tcx>(Interned<'tcx, TyS<'tcx>>);
```
There are two benefits to this.
- It's now a first class type, so we can define methods on it. This
  means we can move a lot of methods away from `TyS`, leaving `TyS` as a
  barely-used type, which is appropriate given that it's not meant to
  be used directly.
- The uniqueness requirement is now explicit, via the `Interned` type.
  E.g. the pointer-based `Eq` and `Hash` comes from `Interned`, rather
  than via `TyS`, which wasn't obvious at all.

Much of this commit is boring churn. The interesting changes are in
these files:
- compiler/rustc_middle/src/arena.rs
- compiler/rustc_middle/src/mir/visit.rs
- compiler/rustc_middle/src/ty/context.rs
- compiler/rustc_middle/src/ty/mod.rs

Specifically:
- Most mentions of `TyS` are removed. It's very much a dumb struct now;
  `Ty` has all the smarts.
- `TyS` now has `crate` visibility instead of `pub`.
- `TyS::make_for_test` is removed in favour of the static `BOOL_TY`,
  which just works better with the new structure.
- The `Eq`/`Ord`/`Hash` impls are removed from `TyS`. `Interned`s impls
  of `Eq`/`Hash` now suffice. `Ord` is now partly on `Interned`
  (pointer-based, for the `Equal` case) and partly on `TyS`
  (contents-based, for the other cases).
- There are many tedious sigil adjustments, i.e. adding or removing `*`
  or `&`. They seem to be unavoidable.
2022-02-15 16:03:24 +11:00

87 lines
3.3 KiB
Rust

use super::{TRANSMUTE_BYTES_TO_STR, TRANSMUTE_PTR_TO_PTR};
use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then};
use clippy_utils::source::snippet;
use clippy_utils::sugg;
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::{Expr, Mutability};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
/// Checks for `transmute_bytes_to_str` and `transmute_ptr_to_ptr` lints.
/// Returns `true` if either one triggered, otherwise returns `false`.
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
from_ty: Ty<'tcx>,
to_ty: Ty<'tcx>,
arg: &'tcx Expr<'_>,
const_context: bool,
) -> bool {
let mut triggered = false;
if let (ty::Ref(_, ty_from, from_mutbl), ty::Ref(_, ty_to, to_mutbl)) = (&from_ty.kind(), &to_ty.kind()) {
if_chain! {
if let (&ty::Slice(slice_ty), &ty::Str) = (&ty_from.kind(), &ty_to.kind());
if let ty::Uint(ty::UintTy::U8) = slice_ty.kind();
if from_mutbl == to_mutbl;
then {
let postfix = if *from_mutbl == Mutability::Mut {
"_mut"
} else {
""
};
span_lint_and_sugg(
cx,
TRANSMUTE_BYTES_TO_STR,
e.span,
&format!("transmute from a `{}` to a `{}`", from_ty, to_ty),
"consider using",
format!(
"std::str::from_utf8{}({}).unwrap()",
postfix,
snippet(cx, arg.span, ".."),
),
Applicability::Unspecified,
);
triggered = true;
} else {
if (cx.tcx.erase_regions(from_ty) != cx.tcx.erase_regions(to_ty))
&& !const_context {
span_lint_and_then(
cx,
TRANSMUTE_PTR_TO_PTR,
e.span,
"transmute from a reference to a reference",
|diag| if let Some(arg) = sugg::Sugg::hir_opt(cx, arg) {
let ty_from_and_mut = ty::TypeAndMut {
ty: *ty_from,
mutbl: *from_mutbl
};
let ty_to_and_mut = ty::TypeAndMut { ty: *ty_to, mutbl: *to_mutbl };
let sugg_paren = arg
.as_ty(cx.tcx.mk_ptr(ty_from_and_mut))
.as_ty(cx.tcx.mk_ptr(ty_to_and_mut));
let sugg = if *to_mutbl == Mutability::Mut {
sugg_paren.mut_addr_deref()
} else {
sugg_paren.addr_deref()
};
diag.span_suggestion(
e.span,
"try",
sugg.to_string(),
Applicability::Unspecified,
);
},
);
triggered = true;
}
}
}
}
triggered
}