Struct Subspan 

pub struct Subspan(/* private fields */);

Turns a byte range of the macro input’s source spelling into a span pointing exactly at those bytes.

This is how string-literal mode stops being imprecise. proc_macro::Literal::subspan does exactly this job, but it is unstable (proc_macro_span) and proc_macro2 does not re-export it, so this crate — which never touches proc_macro — takes it as a hook instead: cinrs-macros, compiled with its nightly feature, passes one in, and everything else passes None and keeps the (at line …) suffix.

The range is measured in bytes of the literal as written, r#" prefix, closing "# and escape sequences and all, which is what subspan wants; SourceMap does the translation from C-text offsets. Returning None — which the real subspan does whenever the literal has no source of its own, as under rust-analyzer — falls back to the whole-literal span.

Results are memoised, because a span is asked for once per generated token and the real implementation is a round trip into the compiler.

Implementations

impl Subspan

pub fn new(resolve: impl Fn(Range<usize>) -> Option<Span> + 'static) -> Self

Wraps a subspan implementation.

Trait Implementations

impl Clone for Subspan

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Subspan

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.