Merge #863

863: Token source r=matklad a=matklad

Some reshuffling of parser's API with the eye towards extracting parse **without** syntax tree into a separate crate, to be used with macro expansion

Co-authored-by: Aleksey Kladov <[email protected]>

10 files changed, 245 insertions, 358 deletions

diff --git a/crates/ra_syntax/src/parsing.rs b/crates/ra_syntax/src/parsing.rs
index 761accd7b..138d1394a 100644
--- a/crates/ra_syntax/src/parsing.rs
+++ b/crates/ra_syntax/src/parsing.rs
@@ -2,24 +2,77 @@
 mod token_set;
 mod builder;
 mod lexer;
-mod parser_impl;
-mod parser_api;
+mod event;
+mod input;
+mod parser;
 mod grammar;
 mod reparsing;
 
 use crate::{
-    SyntaxError,
-    parsing::builder::GreenBuilder,
+    SyntaxKind, SmolStr, SyntaxError,
+    parsing::{
+        builder::GreenBuilder,
+        input::ParserInput,
+        event::EventProcessor,
+        parser::Parser,
+    },
     syntax_node::GreenNode,
 };
 
 pub use self::lexer::{tokenize, Token};
 
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct ParseError(pub String);
+
 pub(crate) use self::reparsing::incremental_reparse;
 
 pub(crate) fn parse_text(text: &str) -> (GreenNode, Vec<SyntaxError>) {
     let tokens = tokenize(&text);
-    let (green, errors) =
-        parser_impl::parse_with(GreenBuilder::new(), text, &tokens, grammar::root);
-    (green, errors)
+    parse_with(GreenBuilder::default(), text, &tokens, grammar::root)
+}
+
+fn parse_with<S: TreeSink>(
+    tree_sink: S,
+    text: &str,
+    tokens: &[Token],
+    f: fn(&mut Parser),
+) -> S::Tree {
+    let mut events = {
+        let input = ParserInput::new(text, &tokens);
+        let mut p = Parser::new(&input);
+        f(&mut p);
+        p.finish()
+    };
+    EventProcessor::new(tree_sink, text, tokens, &mut events).process().finish()
+}
+
+/// `TreeSink` abstracts details of a particular syntax tree implementation.
+trait TreeSink {
+    type Tree;
+
+    /// Adds new leaf to the current branch.
+    fn leaf(&mut self, kind: SyntaxKind, text: SmolStr);
+
+    /// Start new branch and make it current.
+    fn start_branch(&mut self, kind: SyntaxKind);
+
+    /// Finish current branch and restore previous
+    /// branch as current.
+    fn finish_branch(&mut self);
+
+    fn error(&mut self, error: ParseError);
+
+    /// Complete tree building. Make sure that
+    /// `start_branch` and `finish_branch` calls
+    /// are paired!
+    fn finish(self) -> Self::Tree;
+}
+
+/// `TokenSource` abstracts the source of the tokens parser operates one.
+///
+/// Hopefully this will allow us to treat text and token trees in the same way!
+trait TokenSource {
+    fn token_kind(&self, pos: usize) -> SyntaxKind;
+    fn is_token_joint_to_next(&self, pos: usize) -> bool;
+    fn is_keyword(&self, pos: usize, kw: &str) -> bool;
 }
diff --git a/crates/ra_syntax/src/parsing/builder.rs b/crates/ra_syntax/src/parsing/builder.rs
index 9090c60c2..ee0e2cce7 100644
--- a/crates/ra_syntax/src/parsing/builder.rs
+++ b/crates/ra_syntax/src/parsing/builder.rs
@@ -1,26 +1,32 @@
 use crate::{
-    parsing::parser_impl::Sink,
+    SmolStr, SyntaxKind, SyntaxError, SyntaxErrorKind, TextUnit,
+    parsing::{TreeSink, ParseError},
     syntax_node::{GreenNode, RaTypes},
-    SmolStr, SyntaxKind, SyntaxError,
 };
 
 use rowan::GreenNodeBuilder;
 
 pub(crate) struct GreenBuilder {
+    text_pos: TextUnit,
     errors: Vec<SyntaxError>,
     inner: GreenNodeBuilder<RaTypes>,
 }
 
-impl GreenBuilder {
-    pub(crate) fn new() -> GreenBuilder {
-        GreenBuilder { errors: Vec::new(), inner: GreenNodeBuilder::new() }
+impl Default for GreenBuilder {
+    fn default() -> GreenBuilder {
+        GreenBuilder {
+            text_pos: TextUnit::default(),
+            errors: Vec::new(),
+            inner: GreenNodeBuilder::new(),
+        }
     }
 }
 
-impl Sink for GreenBuilder {
+impl TreeSink for GreenBuilder {
     type Tree = (GreenNode, Vec<SyntaxError>);
 
     fn leaf(&mut self, kind: SyntaxKind, text: SmolStr) {
+        self.text_pos += TextUnit::of_str(text.as_str());
         self.inner.leaf(kind, text);
     }
 
@@ -32,7 +38,8 @@ impl Sink for GreenBuilder {
         self.inner.finish_internal();
     }
 
-    fn error(&mut self, error: SyntaxError) {
+    fn error(&mut self, error: ParseError) {
+        let error = SyntaxError::new(SyntaxErrorKind::ParseError(error), self.text_pos);
         self.errors.push(error)
     }
 
diff --git a/crates/ra_syntax/src/parsing/parser_impl/event.rs b/crates/ra_syntax/src/parsing/event.rs
index 2ddbdd34d..f6f020eab 100644
--- a/crates/ra_syntax/src/parsing/parser_impl/event.rs
+++ b/crates/ra_syntax/src/parsing/event.rs
@@ -3,7 +3,7 @@
 //! parser, so as to allow to evolve the tree representation
 //! and the parser algorithm independently.
 //!
-//! The `Sink` trait is the bridge between the parser and the
+//! The `TreeSink` trait is the bridge between the parser and the
 //! tree builder: the parser produces a stream of events like
 //! `start node`, `finish node`, and `FileBuilder` converts
 //! this stream to a real tree.
@@ -13,14 +13,9 @@ use crate::{
     SmolStr,
     SyntaxKind::{self, *},
     TextRange, TextUnit,
-    syntax_error::{
-        ParseError,
-        SyntaxError,
-        SyntaxErrorKind,
-    },
     parsing::{
+        ParseError, TreeSink,
         lexer::Token,
-        parser_impl::Sink,
     },
 };
 
@@ -93,7 +88,7 @@ impl Event {
     }
 }
 
-pub(super) struct EventProcessor<'a, S: Sink> {
+pub(super) struct EventProcessor<'a, S: TreeSink> {
     sink: S,
     text_pos: TextUnit,
     text: &'a str,
@@ -102,7 +97,7 @@ pub(super) struct EventProcessor<'a, S: Sink> {
     events: &'a mut [Event],
 }
 
-impl<'a, S: Sink> EventProcessor<'a, S> {
+impl<'a, S: TreeSink> EventProcessor<'a, S> {
     pub(super) fn new(
         sink: S,
         text: &'a str,
@@ -113,7 +108,7 @@ impl<'a, S: Sink> EventProcessor<'a, S> {
     }
 
     /// Generate the syntax tree with the control of events.
-    pub(super) fn process(mut self) -> S {
+    pub(crate) fn process(mut self) -> S {
         let mut forward_parents = Vec::new();
 
         for i in 0..self.events.len() {
@@ -159,9 +154,7 @@ impl<'a, S: Sink> EventProcessor<'a, S> {
                         .sum::<TextUnit>();
                     self.leaf(kind, len, n_raw_tokens);
                 }
-                Event::Error { msg } => self
-                    .sink
-                    .error(SyntaxError::new(SyntaxErrorKind::ParseError(msg), self.text_pos)),
+                Event::Error { msg } => self.sink.error(msg),
             }
         }
         self.sink
diff --git a/crates/ra_syntax/src/parsing/grammar.rs b/crates/ra_syntax/src/parsing/grammar.rs
index bcdcd9f57..7ca9c223c 100644
--- a/crates/ra_syntax/src/parsing/grammar.rs
+++ b/crates/ra_syntax/src/parsing/grammar.rs
@@ -41,7 +41,7 @@ use crate::{
     SyntaxKind::{self, *},
     parsing::{
         token_set::TokenSet,
-        parser_api::{CompletedMarker, Marker, Parser}
+        parser::{CompletedMarker, Marker, Parser}
     },
 };
 
diff --git a/crates/ra_syntax/src/parsing/input.rs b/crates/ra_syntax/src/parsing/input.rs
new file mode 100644
index 000000000..96c03bb11
--- /dev/null
+++ b/crates/ra_syntax/src/parsing/input.rs
@@ -0,0 +1,68 @@
+use crate::{
+    SyntaxKind, SyntaxKind::EOF, TextRange, TextUnit,
+    parsing::{
+        TokenSource,
+        lexer::Token,
+    },
+};
+
+impl<'t> TokenSource for ParserInput<'t> {
+    fn token_kind(&self, pos: usize) -> SyntaxKind {
+        if !(pos < self.tokens.len()) {
+            return EOF;
+        }
+        self.tokens[pos].kind
+    }
+    fn is_token_joint_to_next(&self, pos: usize) -> bool {
+        if !(pos + 1 < self.tokens.len()) {
+            return true;
+        }
+        self.start_offsets[pos] + self.tokens[pos].len == self.start_offsets[pos + 1]
+    }
+    fn is_keyword(&self, pos: usize, kw: &str) -> bool {
+        if !(pos < self.tokens.len()) {
+            return false;
+        }
+        let range = TextRange::offset_len(self.start_offsets[pos], self.tokens[pos].len);
+
+        self.text[range] == *kw
+    }
+}
+
+pub(crate) struct ParserInput<'t> {
+    text: &'t str,
+    /// start position of each token(expect whitespace and comment)
+    /// ```non-rust
+    ///  struct Foo;
+    /// ^------^---
+    /// |      |  ^-
+    /// 0      7  10
+    /// ```
+    /// (token, start_offset): `[(struct, 0), (Foo, 7), (;, 10)]`
+    start_offsets: Vec<TextUnit>,
+    /// non-whitespace/comment tokens
+    /// ```non-rust
+    /// struct Foo {}
+    /// ^^^^^^ ^^^ ^^
+    /// ```
+    /// tokens: `[struct, Foo, {, }]`
+    tokens: Vec<Token>,
+}
+
+impl<'t> ParserInput<'t> {
+    /// Generate input from tokens(expect comment and whitespace).
+    pub fn new(text: &'t str, raw_tokens: &'t [Token]) -> ParserInput<'t> {
+        let mut tokens = Vec::new();
+        let mut start_offsets = Vec::new();
+        let mut len = 0.into();
+        for &token in raw_tokens.iter() {
+            if !token.kind.is_trivia() {
+                tokens.push(token);
+                start_offsets.push(len);
+            }
+            len += token.len;
+        }
+
+        ParserInput { text, start_offsets, tokens }
+    }
+}
diff --git a/crates/ra_syntax/src/parsing/parser_api.rs b/crates/ra_syntax/src/parsing/parser.rs
index 781c407de..923b0f2b2 100644
--- a/crates/ra_syntax/src/parsing/parser_api.rs
+++ b/crates/ra_syntax/src/parsing/parser.rs
@@ -1,10 +1,13 @@
+use std::cell::Cell;
+
 use drop_bomb::DropBomb;
 
 use crate::{
-    SyntaxKind::{self, ERROR},
+    SyntaxKind::{self, ERROR, EOF, TOMBSTONE},
     parsing::{
+        TokenSource, ParseError,
         token_set::TokenSet,
-        parser_impl::ParserImpl
+        event::Event,
     },
 };
 
@@ -17,9 +20,22 @@ use crate::{
 /// tree, but rather a flat stream of events of the form
 /// "start expression, consume number literal,
 /// finish expression". See `Event` docs for more.
-pub(crate) struct Parser<'t>(pub(super) ParserImpl<'t>);
+pub(crate) struct Parser<'t> {
+    token_source: &'t dyn TokenSource,
+    token_pos: usize,
+    events: Vec<Event>,
+    steps: Cell<u32>,
+}
 
 impl<'t> Parser<'t> {
+    pub(super) fn new(token_source: &'t dyn TokenSource) -> Parser<'t> {
+        Parser { token_source, token_pos: 0, events: Vec::new(), steps: Cell::new(0) }
+    }
+
+    pub(crate) fn finish(self) -> Vec<Event> {
+        self.events
+    }
+
     /// Returns the kind of the current token.
     /// If parser has already reached the end of input,
     /// the special `EOF` kind is returned.
@@ -32,7 +48,13 @@ impl<'t> Parser<'t> {
     ///
     /// Useful for parsing things like `>>`.
     pub(crate) fn current2(&self) -> Option<(SyntaxKind, SyntaxKind)> {
-        self.0.current2()
+        let c1 = self.token_source.token_kind(self.token_pos);
+        let c2 = self.token_source.token_kind(self.token_pos + 1);
+        if self.token_source.is_token_joint_to_next(self.token_pos) {
+            Some((c1, c2))
+        } else {
+            None
+        }
     }
 
     /// Returns the kinds of the current three tokens, if they are not separated
@@ -40,13 +62,25 @@ impl<'t> Parser<'t> {
     ///
     /// Useful for parsing things like `=>>`.
     pub(crate) fn current3(&self) -> Option<(SyntaxKind, SyntaxKind, SyntaxKind)> {
-        self.0.current3()
+        let c1 = self.token_source.token_kind(self.token_pos);
+        let c2 = self.token_source.token_kind(self.token_pos + 1);
+        let c3 = self.token_source.token_kind(self.token_pos + 2);
+        if self.token_source.is_token_joint_to_next(self.token_pos)
+            && self.token_source.is_token_joint_to_next(self.token_pos + 1)
+        {
+            Some((c1, c2, c3))
+        } else {
+            None
+        }
     }
 
     /// Lookahead operation: returns the kind of the next nth
     /// token.
-    pub(crate) fn nth(&self, n: u32) -> SyntaxKind {
-        self.0.nth(n)
+    pub(crate) fn nth(&self, n: usize) -> SyntaxKind {
+        let steps = self.steps.get();
+        assert!(steps <= 10_000_000, "the parser seems stuck");
+        self.steps.set(steps + 1);
+        self.token_source.token_kind(self.token_pos + n)
     }
 
     /// Checks if the current token is `kind`.
@@ -60,20 +94,26 @@ impl<'t> Parser<'t> {
     }
 
     /// Checks if the current token is contextual keyword with text `t`.
-    pub(crate) fn at_contextual_kw(&self, t: &str) -> bool {
-        self.0.at_kw(t)
+    pub(crate) fn at_contextual_kw(&self, kw: &str) -> bool {
+        self.token_source.is_keyword(self.token_pos, kw)
     }
 
     /// Starts a new node in the syntax tree. All nodes and tokens
     /// consumed between the `start` and the corresponding `Marker::complete`
     /// belong to the same node.
     pub(crate) fn start(&mut self) -> Marker {
-        Marker::new(self.0.start())
+        let pos = self.events.len() as u32;
+        self.push_event(Event::tombstone());
+        Marker::new(pos)
     }
 
     /// Advances the parser by one token unconditionally.
     pub(crate) fn bump(&mut self) {
-        self.0.bump();
+        let kind = self.nth(0);
+        if kind == EOF {
+            return;
+        }
+        self.do_bump(kind, 1);
     }
 
     /// Advances the parser by one token, remapping its kind.
@@ -83,14 +123,18 @@ impl<'t> Parser<'t> {
     /// `union` keyword, and keyword is what ends up in the
     /// final tree.
     pub(crate) fn bump_remap(&mut self, kind: SyntaxKind) {
-        self.0.bump_remap(kind);
+        if self.nth(0) == EOF {
+            // TODO: panic!?
+            return;
+        }
+        self.do_bump(kind, 1);
     }
 
     /// Advances the parser by `n` tokens, remapping its kind.
     /// This is useful to create compound tokens from parts. For
     /// example, an `<<` token is two consecutive remapped `<` tokens
     pub(crate) fn bump_compound(&mut self, kind: SyntaxKind, n: u8) {
-        self.0.bump_compound(kind, n);
+        self.do_bump(kind, n);
     }
 
     /// Emit error with the `message`
@@ -98,7 +142,8 @@ impl<'t> Parser<'t> {
     /// structured errors with spans and notes, like rustc
     /// does.
     pub(crate) fn error<T: Into<String>>(&mut self, message: T) {
-        self.0.error(message.into())
+        let msg = ParseError(message.into());
+        self.push_event(Event::Error { msg })
     }
 
     /// Consume the next token if `kind` matches.
@@ -136,6 +181,15 @@ impl<'t> Parser<'t> {
             m.complete(self, ERROR);
         };
     }
+
+    fn do_bump(&mut self, kind: SyntaxKind, n_raw_tokens: u8) {
+        self.token_pos += usize::from(n_raw_tokens);
+        self.push_event(Event::Token { kind, n_raw_tokens });
+    }
+
+    fn push_event(&mut self, event: Event) {
+        self.events.push(event)
+    }
 }
 
 /// See `Parser::start`.
@@ -154,7 +208,14 @@ impl Marker {
     /// operation like `.precede()` to deal with forward_parent.
     pub(crate) fn complete(mut self, p: &mut Parser, kind: SyntaxKind) -> CompletedMarker {
         self.bomb.defuse();
-        p.0.complete(self.pos, kind);
+        let idx = self.pos as usize;
+        match p.events[idx] {
+            Event::Start { kind: ref mut slot, .. } => {
+                *slot = kind;
+            }
+            _ => unreachable!(),
+        }
+        p.push_event(Event::Finish);
         CompletedMarker::new(self.pos, kind)
     }
 
@@ -162,7 +223,13 @@ impl Marker {
     /// are attached to its parent instead.
     pub(crate) fn abandon(mut self, p: &mut Parser) {
         self.bomb.defuse();
-        p.0.abandon(self.pos);
+        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!(),
+            }
+        }
     }
 }
 
@@ -186,7 +253,15 @@ impl CompletedMarker {
     /// then mark `NEWSTART` as `START`'s parent with saving its relative
     /// distance to `NEWSTART` into forward_parent(=2 in this case);
     pub(crate) fn precede(self, p: &mut Parser) -> Marker {
-        Marker::new(p.0.precede(self.0))
+        let new_pos = p.start();
+        let idx = self.0 as usize;
+        match p.events[idx] {
+            Event::Start { ref mut forward_parent, .. } => {
+                *forward_parent = Some(new_pos.pos - self.0);
+            }
+            _ => unreachable!(),
+        }
+        new_pos
     }
 
     pub(crate) fn kind(&self) -> SyntaxKind {
diff --git a/crates/ra_syntax/src/parsing/parser_impl.rs b/crates/ra_syntax/src/parsing/parser_impl.rs
deleted file mode 100644
index 8cce1ab01..000000000
--- a/crates/ra_syntax/src/parsing/parser_impl.rs
+++ /dev/null
@@ -1,200 +0,0 @@
-mod event;
-mod input;
-
-use std::cell::Cell;
-
-use crate::{
-    SmolStr,
-    syntax_error::{ParseError, SyntaxError},
-    parsing::{
-        lexer::Token,
-        parser_api::Parser,
-        parser_impl::{
-            event::{Event, EventProcessor},
-            input::{InputPosition, ParserInput},
-        },
-    },
-};
-
-use crate::SyntaxKind::{self, EOF, TOMBSTONE};
-
-pub(super) trait Sink {
-    type Tree;
-
-    /// Adds new leaf to the current branch.
-    fn leaf(&mut self, kind: SyntaxKind, text: SmolStr);
-
-    /// Start new branch and make it current.
-    fn start_branch(&mut self, kind: SyntaxKind);
-
-    /// Finish current branch and restore previous
-    /// branch as current.
-    fn finish_branch(&mut self);
-
-    fn error(&mut self, error: SyntaxError);
-
-    /// Complete tree building. Make sure that
-    /// `start_branch` and `finish_branch` calls
-    /// are paired!
-    fn finish(self) -> Self::Tree;
-}
-
-/// Parse a sequence of tokens into the representative node tree
-pub(super) fn parse_with<S: Sink>(
-    sink: S,
-    text: &str,
-    tokens: &[Token],
-    parser: fn(&mut Parser),
-) -> S::Tree {
-    let mut events = {
-        let input = input::ParserInput::new(text, tokens);
-        let parser_impl = ParserImpl::new(&input);
-        let mut parser_api = Parser(parser_impl);
-        parser(&mut parser_api);
-        parser_api.0.into_events()
-    };
-    EventProcessor::new(sink, text, tokens, &mut events).process().finish()
-}
-
-/// Implementation details of `Parser`, extracted
-/// to a separate struct in order not to pollute
-/// the public API of the `Parser`.
-pub(super) struct ParserImpl<'t> {
-    parser_input: &'t ParserInput<'t>,
-    pos: InputPosition,
-    events: Vec<Event>,
-    steps: Cell<u32>,
-}
-
-impl<'t> ParserImpl<'t> {
-    fn new(inp: &'t ParserInput<'t>) -> ParserImpl<'t> {
-        ParserImpl {
-            parser_input: inp,
-            pos: InputPosition::new(),
-            events: Vec::new(),
-            steps: Cell::new(0),
-        }
-    }
-
-    fn into_events(self) -> Vec<Event> {
-        assert_eq!(self.nth(0), EOF);
-        self.events
-    }
-
-    pub(super) fn current2(&self) -> Option<(SyntaxKind, SyntaxKind)> {
-        let c1 = self.parser_input.kind(self.pos);
-        let c2 = self.parser_input.kind(self.pos + 1);
-        if self.parser_input.token_start_at(self.pos + 1)
-            == self.parser_input.token_start_at(self.pos) + self.parser_input.token_len(self.pos)
-        {
-            Some((c1, c2))
-        } else {
-            None
-        }
-    }
-
-    pub(super) fn current3(&self) -> Option<(SyntaxKind, SyntaxKind, SyntaxKind)> {
-        let c1 = self.parser_input.kind(self.pos);
-        let c2 = self.parser_input.kind(self.pos + 1);
-        let c3 = self.parser_input.kind(self.pos + 2);
-        if self.parser_input.token_start_at(self.pos + 1)
-            == self.parser_input.token_start_at(self.pos) + self.parser_input.token_len(self.pos)
-            && self.parser_input.token_start_at(self.pos + 2)
-                == self.parser_input.token_start_at(self.pos + 1)
-                    + self.parser_input.token_len(self.pos + 1)
-        {
-            Some((c1, c2, c3))
-        } else {
-            None
-        }
-    }
-
-    /// Get the syntax kind of the nth token.
-    pub(super) fn nth(&self, n: u32) -> SyntaxKind {
-        let steps = self.steps.get();
-        assert!(steps <= 10_000_000, "the parser seems stuck");
-        self.steps.set(steps + 1);
-
-        self.parser_input.kind(self.pos + n)
-    }
-
-    pub(super) fn at_kw(&self, t: &str) -> bool {
-        self.parser_input.token_text(self.pos) == t
-    }
-
-    /// Start parsing right behind the last event.
-    pub(super) fn start(&mut self) -> u32 {
-        let pos = self.events.len() as u32;
-        self.push_event(Event::tombstone());
-        pos
-    }
-
-    /// Advances the parser by one token unconditionally.
-    pub(super) fn bump(&mut self) {
-        let kind = self.nth(0);
-        if kind == EOF {
-            return;
-        }
-        self.do_bump(kind, 1);
-    }
-
-    pub(super) fn bump_remap(&mut self, kind: SyntaxKind) {
-        if self.nth(0) == EOF {
-            // TODO: panic!?
-            return;
-        }
-        self.do_bump(kind, 1);
-    }
-
-    pub(super) fn bump_compound(&mut self, kind: SyntaxKind, n: u8) {
-        self.do_bump(kind, n);
-    }
-
-    fn do_bump(&mut self, kind: SyntaxKind, n_raw_tokens: u8) {
-        self.pos += u32::from(n_raw_tokens);
-        self.push_event(Event::Token { kind, n_raw_tokens });
-    }
-
-    /// Append one Error event to the back of events.
-    pub(super) fn error(&mut self, msg: String) {
-        self.push_event(Event::Error { msg: ParseError(msg) })
-    }
-
-    /// Complete an event with appending a `Finish` event.
-    pub(super) fn complete(&mut self, pos: u32, kind: SyntaxKind) {
-        match self.events[pos as usize] {
-            Event::Start { kind: ref mut slot, .. } => {
-                *slot = kind;
-            }
-            _ => unreachable!(),
-        }
-        self.push_event(Event::Finish);
-    }
-
-    /// Ignore the dummy `Start` event.
-    pub(super) fn abandon(&mut self, pos: u32) {
-        let idx = pos as usize;
-        if idx == self.events.len() - 1 {
-            match self.events.pop() {
-                Some(Event::Start { kind: TOMBSTONE, forward_parent: None }) => (),
-                _ => unreachable!(),
-            }
-        }
-    }
-
-    /// Save the relative distance of a completed event to its forward_parent.
-    pub(super) fn precede(&mut self, pos: u32) -> u32 {
-        let new_pos = self.start();
-        match self.events[pos as usize] {
-            Event::Start { ref mut forward_parent, .. } => {
-                *forward_parent = Some(new_pos - pos);
-            }
-            _ => unreachable!(),
-        }
-        new_pos
-    }
-
-    fn push_event(&mut self, event: Event) {
-        self.events.push(event)
-    }
-}
diff --git a/crates/ra_syntax/src/parsing/parser_impl/input.rs b/crates/ra_syntax/src/parsing/parser_impl/input.rs
deleted file mode 100644
index 275d94918..000000000
--- a/crates/ra_syntax/src/parsing/parser_impl/input.rs
+++ /dev/null
@@ -1,104 +0,0 @@
-use crate::{
-    SyntaxKind, SyntaxKind::EOF, TextRange, TextUnit,
-    parsing::lexer::Token,
-};
-
-use std::ops::{Add, AddAssign};
-
-pub(crate) struct ParserInput<'t> {
-    text: &'t str,
-    /// start position of each token(expect whitespace and comment)
-    /// ```non-rust
-    ///  struct Foo;
-    /// ^------^---
-    /// |      |  ^-
-    /// 0      7  10
-    /// ```
-    /// (token, start_offset): `[(struct, 0), (Foo, 7), (;, 10)]`
-    start_offsets: Vec<TextUnit>,
-    /// non-whitespace/comment tokens
-    /// ```non-rust
-    /// struct Foo {}
-    /// ^^^^^^ ^^^ ^^
-    /// ```
-    /// tokens: `[struct, Foo, {, }]`
-    tokens: Vec<Token>,
-}
-
-impl<'t> ParserInput<'t> {
-    /// Generate input from tokens(expect comment and whitespace).
-    pub fn new(text: &'t str, raw_tokens: &'t [Token]) -> ParserInput<'t> {
-        let mut tokens = Vec::new();
-        let mut start_offsets = Vec::new();
-        let mut len = 0.into();
-        for &token in raw_tokens.iter() {
-            if !token.kind.is_trivia() {
-                tokens.push(token);
-                start_offsets.push(len);
-            }
-            len += token.len;
-        }
-
-        ParserInput { text, start_offsets, tokens }
-    }
-
-    /// Get the syntax kind of token at given input position.
-    pub fn kind(&self, pos: InputPosition) -> SyntaxKind {
-        let idx = pos.0 as usize;
-        if !(idx < self.tokens.len()) {
-            return EOF;
-        }
-        self.tokens[idx].kind
-    }
-
-    /// Get the length of a token at given input position.
-    pub fn token_len(&self, pos: InputPosition) -> TextUnit {
-        let idx = pos.0 as usize;
-        if !(idx < self.tokens.len()) {
-            return 0.into();
-        }
-        self.tokens[idx].len
-    }
-
-    /// Get the start position of a taken at given input position.
-    pub fn token_start_at(&self, pos: InputPosition) -> TextUnit {
-        let idx = pos.0 as usize;
-        if !(idx < self.tokens.len()) {
-            return 0.into();
-        }
-        self.start_offsets[idx]
-    }
-
-    /// Get the raw text of a token at given input position.
-    pub fn token_text(&self, pos: InputPosition) -> &'t str {
-        let idx = pos.0 as usize;
-        if !(idx < self.tokens.len()) {
-            return "";
-        }
-        let range = TextRange::offset_len(self.start_offsets[idx], self.tokens[idx].len);
-        &self.text[range]
-    }
-}
-
-#[derive(Copy, Clone, Ord, PartialOrd, Eq, PartialEq)]
-pub(crate) struct InputPosition(u32);
-
-impl InputPosition {
-    pub fn new() -> Self {
-        InputPosition(0)
-    }
-}
-
-impl Add<u32> for InputPosition {
-    type Output = InputPosition;
-
-    fn add(self, rhs: u32) -> InputPosition {
-        InputPosition(self.0 + rhs)
-    }
-}
-
-impl AddAssign<u32> for InputPosition {
-    fn add_assign(&mut self, rhs: u32) {
-        self.0 += rhs
-    }
-}
diff --git a/crates/ra_syntax/src/parsing/reparsing.rs b/crates/ra_syntax/src/parsing/reparsing.rs
index edf3fa291..f2d218ab9 100644
--- a/crates/ra_syntax/src/parsing/reparsing.rs
+++ b/crates/ra_syntax/src/parsing/reparsing.rs
@@ -4,10 +4,9 @@ use crate::{
     syntax_node::{GreenNode, SyntaxNode},
     syntax_error::SyntaxError,
     parsing::{
-        grammar,
-        parser_impl,
+        grammar, parse_with,
         builder::GreenBuilder,
-        parser_api::Parser,
+        parser::Parser,
         lexer::{tokenize, Token},
     }
 };
@@ -62,8 +61,7 @@ fn reparse_block<'node>(
     if !is_balanced(&tokens) {
         return None;
     }
-    let (green, new_errors) =
-        parser_impl::parse_with(GreenBuilder::new(), &text, &tokens, reparser);
+    let (green, new_errors) = parse_with(GreenBuilder::default(), &text, &tokens, reparser);
     Some((node, green, new_errors))
 }
 
diff --git a/crates/ra_syntax/src/syntax_error.rs b/crates/ra_syntax/src/syntax_error.rs
index 4ff998090..1a00fcc27 100644
--- a/crates/ra_syntax/src/syntax_error.rs
+++ b/crates/ra_syntax/src/syntax_error.rs
@@ -1,6 +1,6 @@
 use std::fmt;
 
-use crate::{TextRange, TextUnit};
+use crate::{TextRange, TextUnit, parsing::ParseError};
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct SyntaxError {
@@ -95,9 +95,6 @@ pub enum SyntaxErrorKind {
     InvalidMatchInnerAttr,
 }
 
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct ParseError(pub String);
-
 impl fmt::Display for SyntaxErrorKind {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         use self::SyntaxErrorKind::*;