diff options
Diffstat (limited to 'compiler/rustc_ast_pretty/src/pprust/state/delimited.rs')
-rw-r--r-- | compiler/rustc_ast_pretty/src/pprust/state/delimited.rs | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/compiler/rustc_ast_pretty/src/pprust/state/delimited.rs b/compiler/rustc_ast_pretty/src/pprust/state/delimited.rs new file mode 100644 index 000000000..fe0640baa --- /dev/null +++ b/compiler/rustc_ast_pretty/src/pprust/state/delimited.rs @@ -0,0 +1,41 @@ +use std::iter::Peekable; +use std::mem; +use std::ops::Deref; + +pub struct Delimited<I: Iterator> { + is_first: bool, + iter: Peekable<I>, +} + +pub trait IterDelimited: Iterator + Sized { + fn delimited(self) -> Delimited<Self> { + Delimited { is_first: true, iter: self.peekable() } + } +} + +impl<I: Iterator> IterDelimited for I {} + +pub struct IteratorItem<T> { + value: T, + pub is_first: bool, + pub is_last: bool, +} + +impl<I: Iterator> Iterator for Delimited<I> { + type Item = IteratorItem<I::Item>; + + fn next(&mut self) -> Option<Self::Item> { + let value = self.iter.next()?; + let is_first = mem::replace(&mut self.is_first, false); + let is_last = self.iter.peek().is_none(); + Some(IteratorItem { value, is_first, is_last }) + } +} + +impl<T> Deref for IteratorItem<T> { + type Target = T; + + fn deref(&self) -> &Self::Target { + &self.value + } +} |