Rollup merge of #122964 - joboet:pointer_expose, r=Amanieu

Rename `expose_addr` to `expose_provenance`

`expose_addr` is a bad name, an address is just a number and cannot be exposed. The operation is actually about the provenance of the pointer.

This PR thus changes the name of the method to `expose_provenance` without changing its return type. There is sufficient precedence for returning a useful value from an operation that does something else without the name indicating such, e.g. [`Option::insert`](https://doc.rust-lang.org/nightly/std/option/enum.Option.html#method.insert) and [`MaybeUninit::write`](https://doc.rust-lang.org/nightly/std/mem/union.MaybeUninit.html#method.write).

Returning the address is merely convenient, not a fundamental part of the operation. This is implied by the fact that integers do not have provenance since
```rust
let addr = ptr.addr();
ptr.expose_provenance();
let new = ptr::with_exposed_provenance(addr);
```
must behave exactly like
```rust
let addr = ptr.expose_provenance();
let new = ptr::with_exposed_provenance(addr);
```
as the result of `ptr.expose_provenance()` and `ptr.addr()` is the same integer. Therefore, this PR removes the `#[must_use]` annotation on the function and updates the documentation to reflect the important part.

~~An alternative name would be `expose_provenance`. I'm not at all opposed to that, but it makes a stronger implication than we might want that the provenance of the pointer returned by `ptr::with_exposed_provenance`[^1] is the same as that what was exposed, which is not yet specified as such IIUC. IMHO `expose` does not make that connection.~~

A previous version of this PR suggested `expose` as name, libs-api [decided on](#122964 (comment)) `expose_provenance` to keep the symmetry with `with_exposed_provenance`.

CC `@RalfJung`
r? libs-api

[^1]: I'm using the new name for `from_exposed_addr` suggested by #122935 here.

Author: matthiaskrgr

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -2261,7 +2261,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         }
                     }
 
-                    CastKind::PointerExposeAddress => {
+                    CastKind::PointerExposeProvenance => {
                         let ty_from = op.ty(body, tcx);
                         let cast_ty_from = CastTy::from_ty(ty_from);
                         let cast_ty_to = CastTy::from_ty(*ty);
@@ -2271,7 +2271,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                                 span_mirbug!(
                                     self,
                                     rvalue,
-                                    "Invalid PointerExposeAddress cast {:?} -> {:?}",
+                                    "Invalid PointerExposeProvenance cast {:?} -> {:?}",
                                     ty_from,
                                     ty
                                 )

compiler/rustc_codegen_cranelift/src/base.rs

@@ -649,7 +649,7 @@ fn codegen_stmt<'tcx>(
                     | CastKind::IntToFloat
                     | CastKind::FnPtrToPtr
                     | CastKind::PtrToPtr
-                    | CastKind::PointerExposeAddress
+                    | CastKind::PointerExposeProvenance
                     | CastKind::PointerWithExposedProvenance,
                     ref operand,
                     to_ty,

compiler/rustc_codegen_cranelift/src/intrinsics/simd.rs

@@ -965,7 +965,7 @@ pub(super) fn codegen_simd_intrinsic_call<'tcx>(
             });
         }
 
-        sym::simd_expose_addr | sym::simd_with_exposed_provenance | sym::simd_cast_ptr => {
+        sym::simd_expose_provenance | sym::simd_with_exposed_provenance | sym::simd_cast_ptr => {
             intrinsic_args!(fx, args => (arg); intrinsic);
             ret.write_cvalue_transmute(fx, arg);
         }

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -2111,7 +2111,7 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
         return Ok(args[0].immediate());
     }
 
-    if name == sym::simd_expose_addr {
+    if name == sym::simd_expose_provenance {
         let (out_len, out_elem) = require_simd!(ret_ty, SimdReturn);
         require!(
             in_len == out_len,

compiler/rustc_codegen_ssa/src/mir/rvalue.rs

@@ -405,7 +405,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 let cast = bx.cx().layout_of(self.monomorphize(mir_cast_ty));
 
                 let val = match *kind {
-                    mir::CastKind::PointerExposeAddress => {
+                    mir::CastKind::PointerExposeProvenance => {
                         assert!(bx.cx().is_backend_immediate(cast));
                         let llptr = operand.immediate();
                         let llcast_ty = bx.cx().immediate_backend_type(cast);

compiler/rustc_const_eval/src/interpret/cast.rs

@@ -34,9 +34,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 self.unsize_into(src, cast_layout, dest)?;
             }
 
-            CastKind::PointerExposeAddress => {
+            CastKind::PointerExposeProvenance => {
                 let src = self.read_immediate(src)?;
-                let res = self.pointer_expose_address_cast(&src, cast_layout)?;
+                let res = self.pointer_expose_provenance_cast(&src, cast_layout)?;
                 self.write_immediate(*res, dest)?;
             }
 
@@ -225,7 +225,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         }
     }
 
-    pub fn pointer_expose_address_cast(
+    pub fn pointer_expose_provenance_cast(
         &mut self,
         src: &ImmTy<'tcx, M::Provenance>,
         cast_to: TyAndLayout<'tcx>,

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -544,7 +544,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                 // Unsizing is implemented for CTFE.
             }
 
-            Rvalue::Cast(CastKind::PointerExposeAddress, _, _) => {
+            Rvalue::Cast(CastKind::PointerExposeProvenance, _, _) => {
                 self.check_op(ops::RawPtrToIntCast);
             }
             Rvalue::Cast(CastKind::PointerWithExposedProvenance, _, _) => {

compiler/rustc_const_eval/src/transform/validate.rs

@@ -1077,7 +1077,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                     }
                     // FIXME: Add Checks for these
                     CastKind::PointerWithExposedProvenance
-                    | CastKind::PointerExposeAddress
+                    | CastKind::PointerExposeProvenance
                     | CastKind::PointerCoercion(_) => {}
                     CastKind::IntToInt | CastKind::IntToFloat => {
                         let input_valid = op_ty.is_integral() || op_ty.is_char() || op_ty.is_bool();

compiler/rustc_hir_analysis/src/check/intrinsic.rs

@@ -627,7 +627,7 @@ pub fn check_intrinsic_type(
             sym::simd_cast
             | sym::simd_as
             | sym::simd_cast_ptr
-            | sym::simd_expose_addr
+            | sym::simd_expose_provenance
             | sym::simd_with_exposed_provenance => (2, 0, vec![param(0)], param(1)),
             sym::simd_bitmask => (2, 0, vec![param(0)], param(1)),
             sym::simd_select | sym::simd_select_bitmask => {

compiler/rustc_hir_typeck/messages.ftl

@@ -91,7 +91,7 @@ hir_typeck_lossy_provenance_int2ptr =
 hir_typeck_lossy_provenance_ptr2int =
     under strict provenance it is considered bad style to cast pointer `{$expr_ty}` to integer `{$cast_ty}`
     .suggestion = use `.addr()` to obtain the address of a pointer
-    .help = if you can't comply with strict provenance and need to expose the pointer provenance you can use `.expose_addr()` instead
+    .help = if you can't comply with strict provenance and need to expose the pointer provenance you can use `.expose_provenance()` instead
 
 hir_typeck_method_call_on_unknown_raw_pointee =
     cannot call a method on a raw pointer with an unknown pointee type