Struct Span

pub struct Span { /* private fields */ }

A region of source code, along with macro expansion information.

Implementations

impl Span

pub fn call_site() -> Self

The span of the invocation of the current procedural macro.

Identifiers created with this span will be resolved as if they were written directly at the macro call location (call-site hygiene) and other code at the macro call site will be able to refer to them as well.

pub fn mixed_site() -> Self

The span located at the invocation of the procedural macro, but with local variables, labels, and $crate resolved at the definition site of the macro. This is the same hygiene behavior as macro_rules.

pub fn def_site() -> Self

Available on procmacro2_semver_exempt only.

A span that resolves at the macro definition site.

This method is semver exempt and not exposed by default.

pub fn resolved_at(&self, other: Span) -> Span

Creates a new span with the same line/column information as self but that resolves symbols as though it were at other.

pub fn located_at(&self, other: Span) -> Span

Creates a new span with the same name resolution behavior as self but with the line/column information of other.

pub fn unwrap(self) -> Span

Convert proc_macro2::Span to proc_macro::Span.

This method is available when building with a nightly compiler, or when building with rustc 1.29+ without semver exempt features.

Panics

Panics if called from outside of a procedural macro. Unlike proc_macro2::Span, the proc_macro::Span type can only exist within the context of a procedural macro invocation.

pub fn source_file(&self) -> SourceFile

Available on procmacro2_semver_exempt only.

The original source file into which this span points.

This method is semver exempt and not exposed by default.

pub fn byte_range(&self) -> Range<usize>

Available on crate feature span-locations only.

Returns the span’s byte position range in the source file.

This method requires the "span-locations" feature to be enabled.

When executing in a procedural macro context, the returned range is only accurate if compiled with a nightly toolchain. The stable toolchain does not have this information available. When executing outside of a procedural macro, such as main.rs or build.rs, the byte range is always accurate regardless of toolchain.

pub fn start(&self) -> LineColumn

Available on crate feature span-locations only.

Get the starting line/column in the source file for this span.

This method requires the "span-locations" feature to be enabled.

When executing in a procedural macro context, the returned line/column are only meaningful if compiled with a nightly toolchain. The stable toolchain does not have this information available. When executing outside of a procedural macro, such as main.rs or build.rs, the line/column are always meaningful regardless of toolchain.

pub fn end(&self) -> LineColumn

Available on crate feature span-locations only.

Get the ending line/column in the source file for this span.

This method requires the "span-locations" feature to be enabled.

When executing in a procedural macro context, the returned line/column are only meaningful if compiled with a nightly toolchain. The stable toolchain does not have this information available. When executing outside of a procedural macro, such as main.rs or build.rs, the line/column are always meaningful regardless of toolchain.

pub fn join(&self, other: Span) -> Option<Span>

Create a new span encompassing self and other.

Returns None if self and other are from different files.

Warning: the underlying proc_macro::Span::join method is nightly-only. When called from within a procedural macro not using a nightly compiler, this method will always return None.

pub fn eq(&self, other: &Span) -> bool

Available on procmacro2_semver_exempt only.

Compares two spans to see if they’re equal.

This method is semver exempt and not exposed by default.

pub fn source_text(&self) -> Option<String>

Returns the source text behind a span. This preserves the original source code, including spaces and comments. It only returns a result if the span corresponds to real source code.

Note: The observable result of a macro should only rely on the tokens and not on this source text. The result of this function is a best effort to be used for diagnostics only.

Trait Implementations

impl Clone for Span

fn clone(&self) -> Span

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Span

Prints a span in a form convenient for debugging.

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

Formats the value using the given formatter.

impl From<Span> for Span

fn from(proc_span: Span) -> Self

Converts to this type from the input type.

impl Copy for Span