pub const fn assert_covers_model(arena: usize, source: &'static str)Expand description
Refuse, during CONST EVALUATION, an arena below this image’s model.
source names where arena came from — the knob for the default sizing,
the caller’s own constant otherwise — because a refusal that does not say
which number to move is the half-diagnostic issue 1036 was about.
Call it from a const _: () = ...; item; that is what makes it a build
error. Called at run time it is an ordinary panic with the same text.