Document Peek trait
diff --git a/src/lookahead.rs b/src/lookahead.rs
index 47ac71c..8c36b92 100644
--- a/src/lookahead.rs
+++ b/src/lookahead.rs
@@ -63,7 +63,12 @@
/// Types that can be parsed by looking at just one token.
///
+/// Use [`ParseStream::peek`] to peek one of these types in a parse stream
+/// without consuming it from the stream.
+///
/// This trait is sealed and cannot be implemented for types outside of Syn.
+///
+/// [`ParseStream::peek`]: struct.ParseBuffer.html#method.peek
pub trait Peek: private::Sealed {
// Not public API.
#[doc(hidden)]