Auto merge of #140079 - ChrisDenton:rollup-2h5cg94, r=ChrisDenton

Rollup of 5 pull requests

Successful merges:

 - #137953 (simd intrinsics with mask: accept unsigned integer masks, and fix some of the errors)
 - #139990 (transmutability: remove NFA intermediate representation)
 - #140044 (rustc-dev-guide subtree update)
 - #140051 (Switch exploit mitigations to mdbook footnotes)
 - #140054 (docs: fix typo change from inconstants to invariants)

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

Author: bors

src/helpers.rs

@@ -1382,6 +1382,11 @@ pub(crate) fn bool_to_simd_element(b: bool, size: Size) -> Scalar {
 }
 
 pub(crate) fn simd_element_to_bool(elem: ImmTy<'_>) -> InterpResult<'_, bool> {
+    assert!(
+        matches!(elem.layout.ty.kind(), ty::Int(_) | ty::Uint(_)),
+        "SIMD mask element type must be an integer, but this is `{}`",
+        elem.layout.ty
+    );
     let val = elem.to_scalar().to_int(elem.layout.size)?;
     interp_ok(match val {
         0 => false,