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Auto merge of #112261 - jieyouxu:c-like-ptr-arithmetics-diagnostics, r=WaffleLapkin

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Add help for trying to do C-like pointer arithmetics

This PR adds help messages for these cases:

```rust
fn main() {
    let ptr1: *const u32 = std::ptr::null();
    let ptr2: *const u32 = std::ptr::null();
    let a = ptr1 + 5;
    let b = ptr1 - 5;
    let c = ptr2 - ptr1;
    let d = ptr1[5];
}
```

### Current Output

```
error[E0369]: cannot add `{integer}` to `*const u32`
 --> tests/ui/typeck/issue-112252-ptr-arithmetics-help.rs:4:18
  |
4 |     let a = ptr1 + 5; //~ ERROR cannot add
  |             ---- ^ - {integer}
  |             |
  |             *const u32

error[E0369]: cannot subtract `{integer}` from `*const u32`
 --> tests/ui/typeck/issue-112252-ptr-arithmetics-help.rs:5:18
  |
5 |     let b = ptr1 - 5; //~ ERROR cannot subtract
  |             ---- ^ - {integer}
  |             |
  |             *const u32

error[E0369]: cannot subtract `*const u32` from `*const u32`
 --> tests/ui/typeck/issue-112252-ptr-arithmetics-help.rs:6:18
  |
6 |     let c = ptr2 - ptr1; //~ ERROR cannot subtract
  |             ---- ^ ---- *const u32
  |             |
  |             *const u32

error[E0608]: cannot index into a value of type `*const u32`
 --> tests/ui/typeck/issue-112252-ptr-arithmetics-help.rs:7:13
  |
7 |     let d = ptr1[5]; //~ ERROR cannot index
  |             ^^^^^^^

error: aborting due to 4 previous errors
```

### Output After This PR

```
error[E0369]: cannot add `{integer}` to `*const u32`
  --> $DIR/issue-112252-ptr-arithmetics-help.rs:6:20
   |
LL |     let _a = _ptr1 + 5;
   |              ------^--
   |              |       |
   |              |       {integer}
   |              *const u32
   |              help: consider using `wrapping_add` or `add` for pointer + {integer}: `_ptr1.wrapping_add(5)`

error[E0369]: cannot subtract `{integer}` from `*const u32`
  --> $DIR/issue-112252-ptr-arithmetics-help.rs:7:20
   |
LL |     let _b = _ptr1 - 5;
   |              ------^--
   |              |       |
   |              |       {integer}
   |              *const u32
   |              help: consider using `offset` for pointer - {integer}: `unsafe { _ptr1.offset(-5) }`

error[E0369]: cannot subtract `*const u32` from `*const u32`
  --> $DIR/issue-112252-ptr-arithmetics-help.rs:8:20
   |
LL |     let _c = _ptr2 - _ptr1;
   |              ------^------
   |              |       |
   |              |       *const u32
   |              *const u32
   |              help: consider using `offset_from` for pointer - pointer if the pointers point to the same allocation: `_ptr2.offset_from(_ptr1)`

error[E0608]: cannot index into a value of type `*const u32`
  --> $DIR/issue-112252-ptr-arithmetics-help.rs:9:14
   |
LL |     let _d = _ptr1[5];
   |              ^^^^^^^^
   |
help: consider using `wrapping_add` or `add` for indexing into raw pointer
   |
LL |     let _d = _ptr1.wrapping_add(5);
   |              ~~~~~~~~~~~~~~~~~~~~~

error: aborting due to 4 previous errors
```

Closes #112252.
This commit is contained in:
bors 2023-06-12 07:15:19 +00:00
commit fd0a3313f7
5 changed files with 135 additions and 0 deletions
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15
compiler/rustc_hir_typeck/src/expr.rs
View file

@ -2871,6 +2871,21 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
);
}
}
if base_t.is_unsafe_ptr() && idx_t.is_integral() {
err.multipart_suggestion(
"consider using `wrapping_add` or `add` for indexing into raw pointer",
vec![
(base.span.between(idx.span), ".wrapping_add(".to_owned()),
(
idx.span.shrink_to_hi().until(expr.span.shrink_to_hi()),
")".to_owned(),
),
],
Applicability::MaybeIncorrect,
);
}
let reported = err.emit();
self.tcx.ty_error(reported)
}

46
compiler/rustc_hir_typeck/src/op.rs
View file

@ -521,6 +521,52 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
}
}
}
// Suggest using `add`, `offset` or `offset_from` for pointer - {integer},
// pointer + {integer} or pointer - pointer.
if op.span.can_be_used_for_suggestions() {
match op.node {
hir::BinOpKind::Add if lhs_ty.is_unsafe_ptr() && rhs_ty.is_integral() => {
err.multipart_suggestion(
"consider using `wrapping_add` or `add` for pointer + {integer}",
vec![
(
lhs_expr.span.between(rhs_expr.span),
".wrapping_add(".to_owned(),
),
(rhs_expr.span.shrink_to_hi(), ")".to_owned()),
],
Applicability::MaybeIncorrect,
);
}
hir::BinOpKind::Sub => {
if lhs_ty.is_unsafe_ptr() && rhs_ty.is_integral() {
err.multipart_suggestion(
"consider using `wrapping_sub` or `sub` for pointer - {integer}",
vec![
(lhs_expr.span.between(rhs_expr.span), ".wrapping_sub(".to_owned()),
(rhs_expr.span.shrink_to_hi(), ")".to_owned()),
],
Applicability::MaybeIncorrect
);
}
if lhs_ty.is_unsafe_ptr() && rhs_ty.is_unsafe_ptr() {
err.multipart_suggestion(
"consider using `offset_from` for pointer - pointer if the pointers point to the same allocation",
vec![
(lhs_expr.span.shrink_to_lo(), "unsafe { ".to_owned()),
(lhs_expr.span.between(rhs_expr.span), ".offset_from(".to_owned()),
(rhs_expr.span.shrink_to_hi(), ") }".to_owned()),
],
Applicability::MaybeIncorrect
);
}
}
_ => {}
}
}
let reported = err.emit();
self.tcx.ty_error(reported)
}