1 files changed, 28 insertions, 14 deletions

diff --git a/crates/libsyntax2/src/lexer/ptr.rs b/crates/libsyntax2/src/lexer/ptr.rs
index d1391fd5f..aa59e33cc 100644
--- a/crates/libsyntax2/src/lexer/ptr.rs
+++ b/crates/libsyntax2/src/lexer/ptr.rs
@@ -2,12 +2,14 @@ use TextUnit;
 
 use std::str::Chars;
 
+/// A simple view into the characters of a string.
 pub(crate) struct Ptr<'s> {
     text: &'s str,
     len: TextUnit,
 }
 
 impl<'s> Ptr<'s> {
+    /// Creates a new `Ptr` from a string.
     pub fn new(text: &'s str) -> Ptr<'s> {
         Ptr {
             text,
@@ -15,45 +17,55 @@ impl<'s> Ptr<'s> {
         }
     }
 
+    /// Gets the length of the remaining string.
     pub fn into_len(self) -> TextUnit {
         self.len
     }
 
-    pub fn next(&self) -> Option<char> {
+    /// Gets the current character, if one exists.
+    pub fn current(&self) -> Option<char> {
         self.chars().next()
     }
 
-    pub fn nnext(&self) -> Option<char> {
-        let mut chars = self.chars();
-        chars.next()?;
-        chars.next()
+    /// Gets the nth character from the current.
+    /// For example, 0 will return the current token, 1 will return the next, etc.
+    pub fn nth(&self, n: u32) -> Option<char> {
+        let mut chars = self.chars().peekable();
+        chars.by_ref().skip(n as usize).next()
     }
 
-    pub fn next_is(&self, c: char) -> bool {
-        self.next() == Some(c)
+    /// Checks whether the current character is `c`.
+    pub fn at(&self, c: char) -> bool {
+        self.current() == Some(c)
     }
 
-    pub fn nnext_is(&self, c: char) -> bool {
-        self.nnext() == Some(c)
+    /// Checks whether the next characters match `s`.
+    pub fn at_str(&self, s: &str) -> bool {
+        let chars = self.chars();
+        chars.as_str().starts_with(s)
     }
 
-    pub fn next_is_p<P: Fn(char) -> bool>(&self, p: P) -> bool {
-        self.next().map(p) == Some(true)
+    /// Checks whether the current character satisfies the predicate `p`.
+    pub fn at_p<P: Fn(char) -> bool>(&self, p: P) -> bool {
+        self.current().map(p) == Some(true)
     }
 
-    pub fn nnext_is_p<P: Fn(char) -> bool>(&self, p: P) -> bool {
-        self.nnext().map(p) == Some(true)
+    /// Checks whether the nth character satisfies the predicate `p`.
+    pub fn nth_is_p<P: Fn(char) -> bool>(&self, n: u32, p: P) -> bool {
+        self.nth(n).map(p) == Some(true)
     }
 
+    /// Moves to the next character.
     pub fn bump(&mut self) -> Option<char> {
         let ch = self.chars().next()?;
         self.len += TextUnit::of_char(ch);
         Some(ch)
     }
 
+    /// Moves to the next character as long as `pred` is satisfied.
     pub fn bump_while<F: Fn(char) -> bool>(&mut self, pred: F) {
         loop {
-            match self.next() {
+            match self.current() {
                 Some(c) if pred(c) => {
                     self.bump();
                 }
@@ -62,11 +74,13 @@ impl<'s> Ptr<'s> {
         }
     }
 
+    /// Returns the text up to the current point.
     pub fn current_token_text(&self) -> &str {
         let len: u32 = self.len.into();
         &self.text[..len as usize]
     }
 
+    /// Returns an iterator over the remaining characters.
     fn chars(&self) -> Chars {
         let len: u32 = self.len.into();
         self.text[len as usize..].chars()