From 0b5d39f2a204e5ec6cd6205440e4cdc763162814 Mon Sep 17 00:00:00 2001
From: Aleksey Kladov <aleksey.kladov@gmail.com>
Date: Sat, 20 Jan 2018 23:25:34 +0300
Subject: Markers API

---
 src/parser/event_parser/parser.rs | 112 ++++++++++++++++++++++++++------------
 1 file changed, 76 insertions(+), 36 deletions(-)

(limited to 'src/parser/event_parser/parser.rs')

diff --git a/src/parser/event_parser/parser.rs b/src/parser/event_parser/parser.rs
index 6171b3579..2bc9dd34f 100644
--- a/src/parser/event_parser/parser.rs
+++ b/src/parser/event_parser/parser.rs
@@ -1,8 +1,71 @@
 use {Token, SyntaxKind, TextUnit};
-use super::{Event};
+use super::Event;
 use super::super::is_insignificant;
 use syntax_kinds::{L_CURLY, R_CURLY, ERROR};
-use tree::EOF;
+use tree::{EOF, TOMBSTONE};
+
+pub(crate) struct Marker {
+    pos: u32
+}
+
+impl Marker {
+    pub fn complete(self, p: &mut Parser, kind: SyntaxKind) -> CompleteMarker {
+        match self.event(p) {
+            &mut Event::Start { kind: ref mut slot, ..} => {
+                *slot = kind;
+            }
+            _ => unreachable!(),
+        }
+        p.event(Event::Finish);
+        let result = CompleteMarker { pos: self.pos };
+        ::std::mem::forget(self);
+        result
+    }
+
+    pub fn abandon(self, p: &mut Parser) {
+        let idx = self.pos as usize;
+        if idx == p.events.len() - 1 {
+            match p.events.pop() {
+                Some(Event::Start { kind: TOMBSTONE, forward_parent: None }) => (),
+                _ => unreachable!()
+            }
+        }
+        ::std::mem::forget(self);
+    }
+
+    fn event<'p>(&self, p: &'p mut Parser) -> &'p mut Event {
+        &mut p.events[self.idx()]
+    }
+
+    fn idx(&self) -> usize {
+        self.pos as usize
+    }
+}
+
+impl Drop for Marker {
+    fn drop(&mut self) {
+        if !::std::thread::panicking() {
+            panic!("Each marker should be eithe completed or abandoned");
+        }
+    }
+}
+
+pub(crate) struct CompleteMarker {
+    pos: u32
+}
+
+impl CompleteMarker {
+    pub(crate) fn precede(self, p: &mut Parser) -> Marker {
+        let m = p.start();
+        match p.events[self.pos as usize] {
+            Event::Start { ref mut forward_parent, ..} => {
+                *forward_parent = Some(m.pos - self.pos);
+            }
+            _ => unreachable!(),
+        }
+        m
+    }
+}
 
 
 pub(crate) struct Parser<'t> {
@@ -19,12 +82,9 @@ pub(crate) struct Parser<'t> {
     curly_limit: Option<i32>,
 }
 
-#[derive(Debug, Clone, Copy,PartialEq, Eq)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub(crate) struct Pos(u32);
 
-#[derive(Debug, Clone, Copy,PartialEq, Eq)]
-pub(crate) struct Mark(u32);
-
 impl<'t> Parser<'t> {
     pub(crate) fn new(text: &'t str, raw_tokens: &'t [Token]) -> Parser<'t> {
         let mut tokens = Vec::new();
@@ -50,31 +110,13 @@ impl<'t> Parser<'t> {
         }
     }
 
-    pub(crate) fn mark(&self) -> Mark {
-        Mark(self.events.len() as u32)
-    }
-
-    pub(crate) fn forward_parent(&mut self, child: Mark, parent: Mark) {
-        if child == parent || parent == self.mark() {
-            return
-        }
-        assert!(child.0 < parent.0);
-        let diff = parent.0 - child.0;
-        match self.events[child.0 as usize] {
-            Event::Start { ref mut forward_parent, .. } => {
-                *forward_parent = Some(diff);
-            }
-            _ => unreachable!()
-        }
-    }
-
     pub(crate) fn pos(&self) -> Pos {
         Pos(self.pos as u32)
     }
 
     pub(crate) fn into_events(self) -> Vec<Event> {
         assert!(self.curly_limit.is_none());
-        assert!(self.current() == EOF);
+        assert_eq!(self.current(), EOF);
         self.events
     }
 
@@ -85,18 +127,16 @@ impl<'t> Parser<'t> {
         let token = self.tokens[self.pos];
         if let Some(limit) = self.curly_limit {
             if limit == self.curly_level && token.kind == R_CURLY {
-                return EOF
+                return EOF;
             }
         }
         token.kind
     }
 
-    pub(crate) fn start(&mut self, kind: SyntaxKind) {
-        self.event(Event::Start { kind, forward_parent: None });
-    }
-
-    pub(crate) fn finish(&mut self) {
-        self.event(Event::Finish);
+    pub(crate) fn start(&mut self) -> Marker {
+        let m = Marker { pos: self.events.len() as u32 };
+        self.event(Event::Start { kind: TOMBSTONE, forward_parent: None });
+        m
     }
 
     pub(crate) fn error<'p>(&'p mut self) -> ErrorBuilder<'p, 't> {
@@ -124,20 +164,20 @@ impl<'t> Parser<'t> {
         let old_level = self.curly_level;
         let old_limit = self.curly_limit;
         if !self.expect(L_CURLY) {
-            return false
+            return false;
         }
         self.curly_limit = Some(self.curly_level);
         f(self);
         assert!(self.curly_level > old_level);
         self.curly_limit = old_limit;
         if !self.expect(R_CURLY) {
-            self.start(ERROR);
+            let err = self.start();
             while self.curly_level > old_level {
                 if self.bump() == EOF {
                     break;
                 }
             }
-            self.finish();
+            err.complete(self, ERROR);
         }
         true
     }
@@ -149,7 +189,7 @@ impl<'t> Parser<'t> {
 
 pub(crate) struct ErrorBuilder<'p, 't: 'p> {
     message: Option<String>,
-    parser: &'p mut Parser<'t>
+    parser: &'p mut Parser<'t>,
 }
 
 impl<'t, 'p> ErrorBuilder<'p, 't> {
-- 
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