From b5021411a84822cb3f1e3aeffad9550dd15bdeb6 Mon Sep 17 00:00:00 2001
From: Aleksey Kladov <aleksey.kladov@gmail.com>
Date: Sun, 16 Sep 2018 12:54:24 +0300
Subject: rename all things

---
 crates/ra_syntax/src/parser_impl/event.rs | 154 ++++++++++++++++++++++++++++++
 1 file changed, 154 insertions(+)
 create mode 100644 crates/ra_syntax/src/parser_impl/event.rs

(limited to 'crates/ra_syntax/src/parser_impl/event.rs')

diff --git a/crates/ra_syntax/src/parser_impl/event.rs b/crates/ra_syntax/src/parser_impl/event.rs
new file mode 100644
index 000000000..9fd56b996
--- /dev/null
+++ b/crates/ra_syntax/src/parser_impl/event.rs
@@ -0,0 +1,154 @@
+//! This module provides a way to construct a `File`.
+//! It is intended to be completely decoupled from the
+//! 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
+//! tree builder: the parser produces a stream of events like
+//! `start node`, `finish node`, and `FileBuilder` converts
+//! this stream to a real tree.
+use std::mem;
+use {
+    lexer::Token,
+    parser_impl::Sink,
+    SyntaxKind::{self, TOMBSTONE},
+};
+
+
+/// `Parser` produces a flat list of `Event`s.
+/// They are converted to a tree-structure in
+/// a separate pass, via `TreeBuilder`.
+#[derive(Debug)]
+pub(crate) enum Event {
+    /// This event signifies the start of the node.
+    /// It should be either abandoned (in which case the
+    /// `kind` is `TOMBSTONE`, and the event is ignored),
+    /// or completed via a `Finish` event.
+    ///
+    /// All tokens between a `Start` and a `Finish` would
+    /// become the children of the respective node.
+    ///
+    /// For left-recursive syntactic constructs, the parser produces
+    /// a child node before it sees a parent. `forward_parent`
+    /// exists to allow to tweak parent-child relationships.
+    ///
+    /// Consider this path
+    ///
+    /// foo::bar
+    ///
+    /// The events for it would look like this:
+    ///
+    ///
+    /// START(PATH) IDENT('foo') FINISH START(PATH) COLONCOLON IDENT('bar') FINISH
+    ///       |                          /\
+    ///       |                          |
+    ///       +------forward-parent------+
+    ///
+    /// And the tree would look like this
+    ///
+    ///    +--PATH---------+
+    ///    |   |           |
+    ///    |   |           |
+    ///    |  '::'       'bar'
+    ///    |
+    ///   PATH
+    ///    |
+    ///   'foo'
+    ///
+    /// See also `CompletedMarker::precede`.
+    Start {
+        kind: SyntaxKind,
+        forward_parent: Option<u32>,
+    },
+
+    /// Complete the previous `Start` event
+    Finish,
+
+    /// Produce a single leaf-element.
+    /// `n_raw_tokens` is used to glue complex contextual tokens.
+    /// For example, lexer tokenizes `>>` as `>`, `>`, and
+    /// `n_raw_tokens = 2` is used to produced a single `>>`.
+    Token {
+        kind: SyntaxKind,
+        n_raw_tokens: u8,
+    },
+
+    Error {
+        msg: String,
+    },
+}
+
+
+pub(super) fn process<'a, S: Sink<'a>>(builder: &mut S, tokens: &[Token], mut events: Vec<Event>) {
+    fn tombstone() -> Event {
+        Event::Start { kind: TOMBSTONE, forward_parent: None }
+    }
+    let eat_ws = |idx: &mut usize, builder: &mut S| {
+        while let Some(token) = tokens.get(*idx) {
+            if !token.kind.is_trivia() {
+                break;
+            }
+            builder.leaf(token.kind, token.len);
+            *idx += 1
+        }
+    };
+
+    let events: &mut [Event] = &mut events;
+    let mut depth = 0;
+    let mut forward_parents = Vec::new();
+    let mut next_tok_idx = 0;
+    for i in 0..events.len() {
+        match mem::replace(&mut events[i], tombstone()) {
+            Event::Start {
+                kind: TOMBSTONE, ..
+            } => (),
+
+            Event::Start { kind, forward_parent } => {
+                forward_parents.push(kind);
+                let mut idx = i;
+                let mut fp = forward_parent;
+                while let Some(fwd) = fp {
+                    idx += fwd as usize;
+                    fp = match mem::replace(&mut events[idx], tombstone()) {
+                        Event::Start {
+                            kind,
+                            forward_parent,
+                        } => {
+                            forward_parents.push(kind);
+                            forward_parent
+                        },
+                        _ => unreachable!(),
+                    };
+                }
+                for kind in forward_parents.drain(..).rev() {
+                    if depth > 0 {
+                        eat_ws(&mut next_tok_idx, builder);
+                    }
+                    depth += 1;
+                    builder.start_internal(kind);
+                }
+            }
+            Event::Finish => {
+                depth -= 1;
+                if depth == 0 {
+                    eat_ws(&mut next_tok_idx, builder);
+                }
+
+                builder.finish_internal();
+            }
+            Event::Token {
+                kind,
+                mut n_raw_tokens,
+            } => {
+                eat_ws(&mut next_tok_idx, builder);
+                let mut len = 0.into();
+                for _ in 0..n_raw_tokens {
+                    len += tokens[next_tok_idx].len;
+                    next_tok_idx += 1;
+                }
+                builder.leaf(kind, len);
+            }
+            Event::Error { msg } => builder.error(msg),
+        }
+    }
+}
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