Auto merge of rust-lang#126793 - saethlin:mono-rawvec, r=scottmcm

Apply "polymorphization at home" to RawVec

The idea here is to move all the logic in RawVec into functions with explicit size and alignment parameters. This should eliminate all the fussing about how tweaking RawVec code produces large swings in compile times.

This uncovered rust-lang/rust-clippy#12979, so I've modified the relevant test in a way that tries to preserve the spirit of the test without tripping the ICE.

Author: bors

tests/ui/borrow_interior_mutable_const/others.rs

@@ -10,7 +10,7 @@ use std::sync::Once;
 
 const ATOMIC: AtomicUsize = AtomicUsize::new(5);
 const CELL: Cell<usize> = Cell::new(6);
-const ATOMIC_TUPLE: ([AtomicUsize; 1], Vec<AtomicUsize>, u8) = ([ATOMIC], Vec::new(), 7);
+const ATOMIC_TUPLE: ([AtomicUsize; 1], Option<Box<AtomicUsize>>, u8) = ([ATOMIC], None, 7);
 const INTEGER: u8 = 8;
 const STRING: String = String::new();
 const STR: &str = "012345";
@@ -74,7 +74,6 @@ fn main() {
     let _ = &(&&&&ATOMIC_TUPLE).0; //~ ERROR: interior mutability
     let _ = &ATOMIC_TUPLE.0[0]; //~ ERROR: interior mutability
     let _ = ATOMIC_TUPLE.0[0].load(Ordering::SeqCst); //~ ERROR: interior mutability
-    let _ = &*ATOMIC_TUPLE.1;
     let _ = &ATOMIC_TUPLE.2;
     let _ = (&&&&ATOMIC_TUPLE).0;
     let _ = (&&&&ATOMIC_TUPLE).2;

tests/ui/borrow_interior_mutable_const/others.stderr

@@ -92,23 +92,23 @@ LL |     let _ = ATOMIC_TUPLE.0[0].load(Ordering::SeqCst);
    = help: assign this const to a local or static variable, and use the variable here
 
 error: a `const` item with interior mutability should not be borrowed
-  --> tests/ui/borrow_interior_mutable_const/others.rs:82:13
+  --> tests/ui/borrow_interior_mutable_const/others.rs:81:13
    |
 LL |     let _ = ATOMIC_TUPLE.0[0];
    |             ^^^^^^^^^^^^
    |
    = help: assign this const to a local or static variable, and use the variable here
 
 error: a `const` item with interior mutability should not be borrowed
-  --> tests/ui/borrow_interior_mutable_const/others.rs:87:5
+  --> tests/ui/borrow_interior_mutable_const/others.rs:86:5
    |
 LL |     CELL.set(2);
    |     ^^^^
    |
    = help: assign this const to a local or static variable, and use the variable here
 
 error: a `const` item with interior mutability should not be borrowed
-  --> tests/ui/borrow_interior_mutable_const/others.rs:88:16
+  --> tests/ui/borrow_interior_mutable_const/others.rs:87:16
    |
 LL |     assert_eq!(CELL.get(), 6);
    |                ^^^^