Auto merge of rust-lang#129521 - matthiaskrgr:rollup-uigv77m, r=matth…

…iaskrgr

Rollup of 9 pull requests

Successful merges:

 - rust-lang#128596 (stabilize const_fn_floating_point_arithmetic)
 - rust-lang#129199 (make writes_through_immutable_pointer a hard error)
 - rust-lang#129246 (Retroactively feature gate `ConstArgKind::Path`)
 - rust-lang#129290 (Pin `cc` to 1.0.105)
 - rust-lang#129323 (Implement `ptr::fn_addr_eq`)
 - rust-lang#129500 (remove invalid `TyCompat` relation for effects)
 - rust-lang#129501 (panicking: improve hint for Miri's RUST_BACKTRACE behavior)
 - rust-lang#129505 (interpret: ImmTy: tighten sanity checks in offset logic)
 - rust-lang#129510 (Fix `elided_named_lifetimes` in code)

r? `@ghost`
`@rustbot` modify labels: rollup

core/src/lib.rs

@@ -193,6 +193,7 @@
 // Language features:
 // tidy-alphabetical-start
 #![cfg_attr(bootstrap, feature(asm_const))]
+#![cfg_attr(bootstrap, feature(const_fn_floating_point_arithmetic))]
 #![cfg_attr(bootstrap, feature(min_exhaustive_patterns))]
 #![feature(abi_unadjusted)]
 #![feature(adt_const_params)]
@@ -202,7 +203,6 @@
 #![feature(cfg_sanitize)]
 #![feature(cfg_target_has_atomic)]
 #![feature(cfg_target_has_atomic_equal_alignment)]
-#![feature(const_fn_floating_point_arithmetic)]
 #![feature(const_for)]
 #![feature(const_mut_refs)]
 #![feature(const_precise_live_drops)]

core/src/marker.rs

@@ -1097,7 +1097,6 @@ pub mod effects {
     pub trait TyCompat<T: ?Sized> {}
 
     impl<T: ?Sized> TyCompat<T> for T {}
-    impl<T: ?Sized> TyCompat<T> for Maybe {}
     impl<T: ?Sized> TyCompat<Maybe> for T {}
 
     #[lang = "EffectsIntersection"]

core/src/ptr/mod.rs

@@ -2130,6 +2130,33 @@ pub fn addr_eq<T: ?Sized, U: ?Sized>(p: *const T, q: *const U) -> bool {
     (p as *const ()) == (q as *const ())
 }
 
+/// Compares the *addresses* of the two function pointers for equality.
+///
+/// Function pointers comparisons can have surprising results since
+/// they are never guaranteed to be unique and could vary between different
+/// code generation units. Furthermore, different functions could have the
+/// same address after being merged together.
+///
+/// This is the same as `f == g` but using this function makes clear
+/// that you are aware of these potentially surprising semantics.
+///
+/// # Examples
+///
+/// ```
+/// #![feature(ptr_fn_addr_eq)]
+/// use std::ptr;
+///
+/// fn a() { println!("a"); }
+/// fn b() { println!("b"); }
+/// assert!(!ptr::fn_addr_eq(a as fn(), b as fn()));
+/// ```
+#[unstable(feature = "ptr_fn_addr_eq", issue = "129322")]
+#[inline(always)]
+#[must_use = "function pointer comparison produces a value"]
+pub fn fn_addr_eq<T: FnPtr, U: FnPtr>(f: T, g: U) -> bool {
+    f.addr() == g.addr()
+}
+
 /// Hash a raw pointer.
 ///
 /// This can be used to hash a `&T` reference (which coerces to `*const T` implicitly)

std/src/panicking.rs

@@ -275,7 +275,7 @@ fn default_hook(info: &PanicHookInfo<'_>) {
                     if cfg!(miri) {
                         let _ = writeln!(
                             err,
-                            "note: in Miri, you may have to set `-Zmiri-env-forward=RUST_BACKTRACE` \
+                            "note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` \
                                 for the environment variable to have an effect"
                         );
                     }