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Auto merge of rust-lang#112261 - jieyouxu:c-like-ptr-arithmetics-diagnostics, r=WaffleLapkin
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 rust-lang#112252.
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‎compiler/rustc_hir_typeck/src/expr.rs

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

‎compiler/rustc_hir_typeck/src/op.rs

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

‎tests/ui/typeck/issue-112252-ptr-arithmetics-help.fixed

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// run-rustfix
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fn main() {
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let _ptr1: *const u32 = std::ptr::null();
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let _ptr2: *const u32 = std::ptr::null();
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let _a = _ptr1.wrapping_add(5); //~ ERROR cannot add
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let _b = _ptr1.wrapping_sub(5); //~ ERROR cannot subtract
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let _c = unsafe { _ptr2.offset_from(_ptr1) }; //~ ERROR cannot subtract
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let _d = _ptr1.wrapping_add(5); //~ ERROR cannot index
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}

‎tests/ui/typeck/issue-112252-ptr-arithmetics-help.rs

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// run-rustfix
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fn main() {
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let _ptr1: *const u32 = std::ptr::null();
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let _ptr2: *const u32 = std::ptr::null();
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let _a = _ptr1 + 5; //~ ERROR cannot add
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let _b = _ptr1 - 5; //~ ERROR cannot subtract
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let _c = _ptr2 - _ptr1; //~ ERROR cannot subtract
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let _d = _ptr1[5]; //~ ERROR cannot index
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}

‎tests/ui/typeck/issue-112252-ptr-arithmetics-help.stderr

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error[E0369]: cannot add `{integer}` to `*const u32`
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--> $DIR/issue-112252-ptr-arithmetics-help.rs:6:20
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|
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LL | let _a = _ptr1 + 5;
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| ----- ^ - {integer}
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| |
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| *const u32
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|
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help: consider using `wrapping_add` or `add` for pointer + {integer}
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|
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LL | let _a = _ptr1.wrapping_add(5);
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| ~~~~~~~~~~~~~~ +
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error[E0369]: cannot subtract `{integer}` from `*const u32`
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--> $DIR/issue-112252-ptr-arithmetics-help.rs:7:20
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|
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LL | let _b = _ptr1 - 5;
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| ----- ^ - {integer}
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| |
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| *const u32
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|
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help: consider using `wrapping_sub` or `sub` for pointer - {integer}
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|
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LL | let _b = _ptr1.wrapping_sub(5);
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| ~~~~~~~~~~~~~~ +
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error[E0369]: cannot subtract `*const u32` from `*const u32`
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--> $DIR/issue-112252-ptr-arithmetics-help.rs:8:20
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|
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LL | let _c = _ptr2 - _ptr1;
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| ----- ^ ----- *const u32
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| |
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| *const u32
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|
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help: consider using `offset_from` for pointer - pointer if the pointers point to the same allocation
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|
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LL | let _c = unsafe { _ptr2.offset_from(_ptr1) };
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| ++++++++ ~~~~~~~~~~~~~ +++
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error[E0608]: cannot index into a value of type `*const u32`
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--> $DIR/issue-112252-ptr-arithmetics-help.rs:9:14
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|
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LL | let _d = _ptr1[5];
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| ^^^^^^^^
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|
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help: consider using `wrapping_add` or `add` for indexing into raw pointer
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|
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LL | let _d = _ptr1.wrapping_add(5);
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| ~~~~~~~~~~~~~~ ~
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error: aborting due to 4 previous errors
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Some errors have detailed explanations: E0369, E0608.
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For more information about an error, try `rustc --explain E0369`.

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