more precise wording

Author: RalfJung

promotion.md

@@ -99,9 +99,9 @@ declaration. We can thus be less conservative. This is called *explicit*
 promotion.
 
 Currently, the following are considered explicit promotion contexts:
-* `#[rustc_args_required_const]` arguments and inline assembly `const` operands
+* `#[rustc_args_required_const]` arguments and inline assembly `const` operands everywhere
 * lifetime extension in the bodies of `const` and `static` items and array lengths
-* the bodies of `const fn` -- but this is not justified by the above discussion; since `const fn` can be runtime-evaluated, the concerns about introducing hard errors where there would be none apply for `const fn` in exactly the same way as for `fn`, but this was overlooked when implementing the checks
+* lifetime extension in the bodies of `const fn` -- but this is not justified by the above discussion; since `const fn` can be runtime-evaluated, the concerns about introducing hard errors where there would be none apply for `const fn` in exactly the same way as for `fn`, but this was overlooked when implementing the checks
 
 Everything else is an implicit promotion context, in particular non-`Copy` array initializers.