Rollup merge of #130350 - RalfJung:strict-provenance, r=dtolnay

stabilize Strict Provenance and Exposed Provenance APIs

Given that [RFC 3559](https://rust-lang.github.io/rfcs/3559-rust-has-provenance.html) has been accepted, t-lang has approved the concept of provenance to exist in the language. So I think it's time that we stabilize the strict provenance and exposed provenance APIs, and discuss provenance explicitly in the docs:
```rust
// core::ptr
pub const fn without_provenance<T>(addr: usize) -> *const T;
pub const fn dangling<T>() -> *const T;
pub const fn without_provenance_mut<T>(addr: usize) -> *mut T;
pub const fn dangling_mut<T>() -> *mut T;
pub fn with_exposed_provenance<T>(addr: usize) -> *const T;
pub fn with_exposed_provenance_mut<T>(addr: usize) -> *mut T;

impl<T: ?Sized> *const T {
    pub fn addr(self) -> usize;
    pub fn expose_provenance(self) -> usize;
    pub fn with_addr(self, addr: usize) -> Self;
    pub fn map_addr(self, f: impl FnOnce(usize) -> usize) -> Self;
}

impl<T: ?Sized> *mut T {
    pub fn addr(self) -> usize;
    pub fn expose_provenance(self) -> usize;
    pub fn with_addr(self, addr: usize) -> Self;
    pub fn map_addr(self, f: impl FnOnce(usize) -> usize) -> Self;
}

impl<T: ?Sized> NonNull<T> {
    pub fn addr(self) -> NonZero<usize>;
    pub fn with_addr(self, addr: NonZero<usize>) -> Self;
    pub fn map_addr(self, f: impl FnOnce(NonZero<usize>) -> NonZero<usize>) -> Self;
}
```

I also did a pass over the docs to adjust them, because this is no longer an "experiment". The `ptr` docs now discuss the concept of provenance in general, and then they go into the two families of APIs for dealing with provenance: Strict Provenance and Exposed Provenance. I removed the discussion of how pointers also have an associated "address space" -- that is not actually tracked in the pointer value, it is tracked in the type, so IMO it just distracts from the core point of provenance. I also adjusted the docs for `with_exposed_provenance` to make it clear that we cannot guarantee much about this function, it's all best-effort.

There are two unstable lints associated with the strict_provenance feature gate; I moved them to a new [strict_provenance_lints](#130351) feature since I didn't want this PR to have an even bigger FCP. ;)

`@rust-lang/opsem` Would be great to get some feedback on the docs here. :)
Nominating for `@rust-lang/libs-api.`

Part of #95228.

[FCP comment](#130350 (comment))

Author: matthiaskrgr

compiler/rustc_arena/src/lib.rs

@@ -23,7 +23,6 @@
 #![feature(maybe_uninit_slice)]
 #![feature(rustc_attrs)]
 #![feature(rustdoc_internals)]
-#![feature(strict_provenance)]
 #![warn(unreachable_pub)]
 // tidy-alphabetical-end
 

compiler/rustc_codegen_ssa/src/lib.rs

@@ -11,7 +11,6 @@
 #![feature(let_chains)]
 #![feature(negative_impls)]
 #![feature(rustdoc_internals)]
-#![feature(strict_provenance)]
 #![feature(trait_alias)]
 #![feature(try_blocks)]
 #![warn(unreachable_pub)]

compiler/rustc_codegen_ssa/src/mir/rvalue.rs

@@ -361,12 +361,16 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             (Int(..) | Float(_), Int(..) | Float(_)) => bx.bitcast(imm, to_backend_ty),
             (Pointer(..), Pointer(..)) => bx.pointercast(imm, to_backend_ty),
             (Int(..), Pointer(..)) => bx.ptradd(bx.const_null(bx.type_ptr()), imm),
-            (Pointer(..), Int(..)) => bx.ptrtoint(imm, to_backend_ty),
+            (Pointer(..), Int(..)) => {
+                // FIXME: this exposes the provenance, which shouldn't be necessary.
+                bx.ptrtoint(imm, to_backend_ty)
+            }
             (Float(_), Pointer(..)) => {
                 let int_imm = bx.bitcast(imm, bx.cx().type_isize());
                 bx.ptradd(bx.const_null(bx.type_ptr()), int_imm)
             }
             (Pointer(..), Float(_)) => {
+                // FIXME: this exposes the provenance, which shouldn't be necessary.
                 let int_imm = bx.ptrtoint(imm, bx.cx().type_isize());
                 bx.bitcast(int_imm, to_backend_ty)
             }

compiler/rustc_const_eval/src/lib.rs

@@ -10,7 +10,6 @@
 #![feature(never_type)]
 #![feature(rustdoc_internals)]
 #![feature(slice_ptr_get)]
-#![feature(strict_provenance)]
 #![feature(trait_alias)]
 #![feature(try_blocks)]
 #![feature(unqualified_local_imports)]

compiler/rustc_data_structures/src/lib.rs

@@ -33,7 +33,6 @@
 #![feature(ptr_alignment_type)]
 #![feature(rustc_attrs)]
 #![feature(rustdoc_internals)]
-#![feature(strict_provenance)]
 #![feature(test)]
 #![feature(thread_id_value)]
 #![feature(type_alias_impl_trait)]

compiler/rustc_feature/src/unstable.rs

@@ -595,7 +595,7 @@ declare_features! (
     /// Allows attributes on expressions and non-item statements.
     (unstable, stmt_expr_attributes, "1.6.0", Some(15701)),
     /// Allows lints part of the strict provenance effort.
-    (unstable, strict_provenance, "1.61.0", Some(95228)),
+    (unstable, strict_provenance_lints, "1.61.0", Some(130351)),
     /// Allows string patterns to dereference values to match them.
     (unstable, string_deref_patterns, "1.67.0", Some(87121)),
     /// Allows the use of `#[target_feature]` on safe functions.

compiler/rustc_lint_defs/src/builtin.rs

@@ -2667,7 +2667,6 @@ declare_lint! {
     /// ### Example
     ///
     /// ```rust
-    /// #![feature(strict_provenance)]
     /// #![warn(fuzzy_provenance_casts)]
     ///
     /// fn main() {
@@ -2701,7 +2700,7 @@ declare_lint! {
     pub FUZZY_PROVENANCE_CASTS,
     Allow,
     "a fuzzy integer to pointer cast is used",
-    @feature_gate = strict_provenance;
+    @feature_gate = strict_provenance_lints;
 }
 
 declare_lint! {
@@ -2711,7 +2710,6 @@ declare_lint! {
     /// ### Example
     ///
     /// ```rust
-    /// #![feature(strict_provenance)]
     /// #![warn(lossy_provenance_casts)]
     ///
     /// fn main() {
@@ -2747,7 +2745,7 @@ declare_lint! {
     pub LOSSY_PROVENANCE_CASTS,
     Allow,
     "a lossy pointer to integer cast is used",
-    @feature_gate = strict_provenance;
+    @feature_gate = strict_provenance_lints;
 }
 
 declare_lint! {

compiler/rustc_middle/src/lib.rs

@@ -56,7 +56,6 @@
 #![feature(ptr_alignment_type)]
 #![feature(rustc_attrs)]
 #![feature(rustdoc_internals)]
-#![feature(strict_provenance)]
 #![feature(trait_upcasting)]
 #![feature(trusted_len)]
 #![feature(try_blocks)]

compiler/rustc_span/src/symbol.rs

@@ -1913,7 +1913,7 @@ symbols! {
         str_trim,
         str_trim_end,
         str_trim_start,
-        strict_provenance,
+        strict_provenance_lints,
         string_as_mut_str,
         string_as_str,
         string_deref_patterns,

library/alloc/benches/lib.rs

@@ -4,7 +4,8 @@
 #![feature(iter_next_chunk)]
 #![feature(repr_simd)]
 #![feature(slice_partition_dedup)]
-#![feature(strict_provenance)]
+#![cfg_attr(bootstrap, feature(strict_provenance))]
+#![cfg_attr(not(bootstrap), feature(strict_provenance_lints))]
 #![feature(test)]
 #![deny(fuzzy_provenance_casts)]