From be03aa5ee79241a6d22a79625e37f2ce5559a345 Mon Sep 17 00:00:00 2001
From: Aleksey Kladov <aleksey.kladov@gmail.com>
Date: Thu, 31 Jan 2019 15:26:01 +0300
Subject: extract tt cursor

---
 crates/ra_macros/src/mbe_parser.rs | 102 +++----------------------------------
 1 file changed, 7 insertions(+), 95 deletions(-)

(limited to 'crates/ra_macros/src/mbe_parser.rs')

diff --git a/crates/ra_macros/src/mbe_parser.rs b/crates/ra_macros/src/mbe_parser.rs
index 93c2d40b4..024d3a040 100644
--- a/crates/ra_macros/src/mbe_parser.rs
+++ b/crates/ra_macros/src/mbe_parser.rs
@@ -1,99 +1,12 @@
 use crate::{tt, mbe};
+use crate::tt_cursor::TtCursor;
 
 /// This module parses a raw `tt::TokenStream` into macro-by-example token
 /// stream. This is a *mostly* identify function, expect for handling of
 /// `$var:tt_kind` and `$(repeat),*` constructs.
 
-struct RulesParser<'a> {
-    subtree: &'a tt::Subtree,
-    pos: usize,
-}
-
-impl<'a> RulesParser<'a> {
-    fn new(subtree: &'a tt::Subtree) -> RulesParser<'a> {
-        RulesParser { subtree, pos: 0 }
-    }
-
-    fn is_eof(&self) -> bool {
-        self.pos == self.subtree.token_trees.len()
-    }
-
-    fn current(&self) -> Option<&'a tt::TokenTree> {
-        self.subtree.token_trees.get(self.pos)
-    }
-
-    fn at_punct(&self) -> Option<&'a tt::Punct> {
-        match self.current() {
-            Some(tt::TokenTree::Leaf(tt::Leaf::Punct(it))) => Some(it),
-            _ => None,
-        }
-    }
-
-    fn at_char(&self, char: char) -> bool {
-        match self.at_punct() {
-            Some(tt::Punct { char: c }) if *c == char => true,
-            _ => false,
-        }
-    }
-
-    fn at_ident(&mut self) -> Option<&'a tt::Ident> {
-        match self.current() {
-            Some(tt::TokenTree::Leaf(tt::Leaf::Ident(i))) => Some(i),
-            _ => None,
-        }
-    }
-
-    fn bump(&mut self) {
-        self.pos += 1;
-    }
-
-    fn eat(&mut self) -> Option<&'a tt::TokenTree> {
-        match self.current() {
-            Some(it) => {
-                self.bump();
-                Some(it)
-            }
-            None => None,
-        }
-    }
-
-    fn eat_subtree(&mut self) -> Option<&'a tt::Subtree> {
-        match self.current()? {
-            tt::TokenTree::Subtree(sub) => {
-                self.bump();
-                Some(sub)
-            }
-            _ => return None,
-        }
-    }
-
-    fn eat_punct(&mut self) -> Option<&'a tt::Punct> {
-        if let Some(it) = self.at_punct() {
-            self.bump();
-            return Some(it);
-        }
-        None
-    }
-
-    fn eat_ident(&mut self) -> Option<&'a tt::Ident> {
-        if let Some(i) = self.at_ident() {
-            self.bump();
-            return Some(i);
-        }
-        None
-    }
-
-    fn expect_char(&mut self, char: char) -> Option<()> {
-        if self.at_char(char) {
-            self.bump();
-            return Some(());
-        }
-        None
-    }
-}
-
 pub fn parse(tt: &tt::Subtree) -> Option<mbe::MacroRules> {
-    let mut parser = RulesParser::new(tt);
+    let mut parser = TtCursor::new(tt);
     let mut rules = Vec::new();
     while !parser.is_eof() {
         rules.push(parse_rule(&mut parser)?)
@@ -101,7 +14,7 @@ pub fn parse(tt: &tt::Subtree) -> Option<mbe::MacroRules> {
     Some(mbe::MacroRules { rules })
 }
 
-fn parse_rule(p: &mut RulesParser) -> Option<mbe::Rule> {
+fn parse_rule(p: &mut TtCursor) -> Option<mbe::Rule> {
     let lhs = parse_subtree(p.eat_subtree()?)?;
     p.expect_char('=')?;
     p.expect_char('>')?;
@@ -111,7 +24,7 @@ fn parse_rule(p: &mut RulesParser) -> Option<mbe::Rule> {
 
 fn parse_subtree(tt: &tt::Subtree) -> Option<mbe::Subtree> {
     let mut token_trees = Vec::new();
-    let mut p = RulesParser::new(tt);
+    let mut p = TtCursor::new(tt);
     while let Some(tt) = p.eat() {
         let child: mbe::TokenTree = match tt {
             tt::TokenTree::Leaf(leaf) => match leaf {
@@ -142,7 +55,7 @@ fn parse_subtree(tt: &tt::Subtree) -> Option<mbe::Subtree> {
     })
 }
 
-fn parse_var(p: &mut RulesParser) -> Option<mbe::Var> {
+fn parse_var(p: &mut TtCursor) -> Option<mbe::Var> {
     let ident = p.eat_ident().unwrap();
     let text = ident.text.clone();
     let kind = if p.at_char(':') {
@@ -150,8 +63,7 @@ fn parse_var(p: &mut RulesParser) -> Option<mbe::Var> {
         if let Some(ident) = p.eat_ident() {
             Some(ident.text.clone())
         } else {
-            // ugly as hell :(
-            p.pos -= 1;
+            p.rev_bump();
             None
         }
     } else {
@@ -160,7 +72,7 @@ fn parse_var(p: &mut RulesParser) -> Option<mbe::Var> {
     Some(mbe::Var { text, kind })
 }
 
-fn parse_repeat(p: &mut RulesParser) -> Option<mbe::Repeat> {
+fn parse_repeat(p: &mut TtCursor) -> Option<mbe::Repeat> {
     let subtree = p.eat_subtree().unwrap();
     let subtree = parse_subtree(subtree)?;
     let sep = p.eat_punct()?;
-- 
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