[proc macros] confusing statement

[evgeniy-terekhin]

link: https://doc.rust-lang.org/reference/procedural-macros.html#the-proc_macro-crate

When token span's are mentioned there is this phrase.

All tokens have an associated Span. A Span is an opaque value that cannot be modified but can be manufactured. Spans represent an extent of source code within a program and are primarily used for error reporting. You can modify the Span of any token.

To me it seems like a contradiction. I would have submit a fix straight away but I am not sure how to express it correctly.

[bjorn3]

You can change what span a token has, but you can't change for example the start or end character of a span, or change it's file. This means that if you want to change the span of a token, you either have to get it from another token, or you have to use Span::call_site() or Span::def_site() to get the span of the macro invocation cq the macro definition.

[evgeniy-terekhin]

@bjorn3 thanks for the clarification. Maybe somthing like whar you wrote should be added to the reference to make the phrasing less confusing.

[Havvy]

It might be better to say that spans are immutable while the span a token has is not.