letmuterr=self.err_handler().struct_span_err(bound.span(),"`~const` is not allowed here");
matchreason{
DisallowTildeConstContext::TraitObject=>err.note("trait objects cannot have `~const` trait bounds"),
DisallowTildeConstContext::ImplTrait=>err.note("`impl Trait`s cannot have `~const` trait bounds"),
DisallowTildeConstContext::Fn(FnKind::Closure(..))=>err.note("closures cannot have `~const` trait bounds"),
DisallowTildeConstContext::Fn(FnKind::Fn(_,ident,..))=>err.span_note(ident.span,"this function is not `const`, so it cannot have `~const` trait bounds"),