commit a1a22fc8cf075cfed532359923bfec682641183e
author Sergio Benitez <sb@sergio.bz> Sat Sep 21 00:16:42 2019 -0700
committer Sergio Benitez <sb@sergio.bz> Sat Sep 21 00:16:42 2019 -0700
tree 2af7dddeef45222911ac769083d7427b79d022ec
parent cf62a7bac077a1755d254f5bfca6f097e56efe84

Add 'Literal::subspan()'

src/fallback.rs

diff --git a/src/fallback.rs b/src/fallback.rs
index 29c0621..2a710be 100644
--- a/src/fallback.rs
+++ b/src/fallback.rs
@@ -9,6 +9,7 @@
 use std::path::PathBuf;
 use std::str::FromStr;
 use std::vec;
+use std::ops::RangeBounds;
 
 use crate::strnom::{block_comment, skip_whitespace, whitespace, word_break, Cursor, PResult};
 use crate::{Delimiter, Punct, Spacing, TokenTree};
@@ -777,6 +778,10 @@
     pub fn set_span(&mut self, span: Span) {
         self.span = span;
     }
+
+    pub fn subspan<R: RangeBounds<usize>>(&self, _range: R) -> Option<Span> {
+        None
+    }
 }
 
 impl fmt::Display for Literal {

src/lib.rs

diff --git a/src/lib.rs b/src/lib.rs
index 30dd289..c3c7132 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -94,6 +94,7 @@
 use std::path::PathBuf;
 use std::rc::Rc;
 use std::str::FromStr;
+use std::ops::RangeBounds;
 
 #[macro_use]
 mod strnom;
@@ -1124,6 +1125,19 @@
     pub fn set_span(&mut self, span: Span) {
         self.inner.set_span(span.inner);
     }
+
+    /// Returns a `Span` that is a subset of `self.span()` containing only
+    /// the source bytes in range `range`. Returns `None` if the would-be
+    /// trimmed span is outside the bounds of `self`.
+    ///
+    /// Warning: the underlying [`proc_macro::Literal::subspan`] method is
+    /// nightly-only. When called from within a procedural macro not using a
+    /// nightly compiler, this method will always return `None`.
+    ///
+    /// [`proc_macro::Literal::subspan`]: https://doc.rust-lang.org/proc_macro/struct.Literal.html#method.subspan
+    pub fn subspan<R: RangeBounds<usize>>(&self, range: R) -> Option<Span> {
+        self.inner.subspan(range).map(Span::_new)
+    }
 }
 
 impl fmt::Debug for Literal {

src/wrapper.rs

diff --git a/src/wrapper.rs b/src/wrapper.rs
index 887e1e6..907f813 100644
--- a/src/wrapper.rs
+++ b/src/wrapper.rs
@@ -4,6 +4,7 @@
 #[cfg(super_unstable)]
 use std::path::PathBuf;
 use std::str::FromStr;
+use std::ops::RangeBounds;
 
 use crate::{fallback, Delimiter, Punct, Spacing, TokenTree};
 
@@ -860,6 +861,16 @@
         }
     }
 
+    pub fn subspan<R: RangeBounds<usize>>(&self, range: R) -> Option<Span> {
+        match self {
+            #[cfg(proc_macro_span)]
+            Literal::Compiler(lit) => lit.subspan(range).map(Span::Compiler),
+            #[cfg(not(proc_macro_span))]
+            Literal::Compiler(_lit) => None,
+            Literal::Fallback(lit) => lit.subspan(range).map(Span::Fallback),
+        }
+    }
+
     fn unwrap_nightly(self) -> proc_macro::Literal {
         match self {
             Literal::Compiler(s) => s,