Merge #865

865: Parser decoupling r=matklad a=matklad

More work on making parser independent from text

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

1 files changed, 37 insertions, 156 deletions

diff --git a/crates/ra_syntax/src/parsing/event.rs b/crates/ra_syntax/src/parsing/event.rs
index f6f020eab..d6cbdffe0 100644
--- a/crates/ra_syntax/src/parsing/event.rs
+++ b/crates/ra_syntax/src/parsing/event.rs
@@ -10,13 +10,8 @@
 use std::mem;
 
 use crate::{
-    SmolStr,
     SyntaxKind::{self, *},
-    TextRange, TextUnit,
-    parsing::{
-        ParseError, TreeSink,
-        lexer::Token,
-    },
+    parsing::{ParseError, TreeSink},
 };
 
 /// `Parser` produces a flat list of `Event`s.
@@ -88,160 +83,46 @@ impl Event {
     }
 }
 
-pub(super) struct EventProcessor<'a, S: TreeSink> {
-    sink: S,
-    text_pos: TextUnit,
-    text: &'a str,
-    token_pos: usize,
-    tokens: &'a [Token],
-    events: &'a mut [Event],
-}
-
-impl<'a, S: TreeSink> EventProcessor<'a, S> {
-    pub(super) fn new(
-        sink: S,
-        text: &'a str,
-        tokens: &'a [Token],
-        events: &'a mut [Event],
-    ) -> EventProcessor<'a, S> {
-        EventProcessor { sink, text_pos: 0.into(), text, token_pos: 0, tokens, events }
-    }
-
-    /// Generate the syntax tree with the control of events.
-    pub(crate) fn process(mut self) -> S {
-        let mut forward_parents = Vec::new();
-
-        for i in 0..self.events.len() {
-            match mem::replace(&mut self.events[i], Event::tombstone()) {
-                Event::Start { kind: TOMBSTONE, .. } => (),
-
-                Event::Start { kind, forward_parent } => {
-                    // For events[A, B, C], B is A's forward_parent, C is B's forward_parent,
-                    // in the normal control flow, the parent-child relation: `A -> B -> C`,
-                    // while with the magic forward_parent, it writes: `C <- B <- A`.
-
-                    // append `A` into parents.
-                    forward_parents.push(kind);
-                    let mut idx = i;
-                    let mut fp = forward_parent;
-                    while let Some(fwd) = fp {
-                        idx += fwd as usize;
-                        // append `A`'s forward_parent `B`
-                        fp = match mem::replace(&mut self.events[idx], Event::tombstone()) {
-                            Event::Start { kind, forward_parent } => {
-                                forward_parents.push(kind);
-                                forward_parent
-                            }
-                            _ => unreachable!(),
-                        };
-                        // append `B`'s forward_parent `C` in the next stage.
-                    }
-
-                    for kind in forward_parents.drain(..).rev() {
-                        self.start(kind);
-                    }
-                }
-                Event::Finish => {
-                    let is_last = i == self.events.len() - 1;
-                    self.finish(is_last);
-                }
-                Event::Token { kind, n_raw_tokens } => {
-                    self.eat_trivias();
-                    let n_raw_tokens = n_raw_tokens as usize;
-                    let len = self.tokens[self.token_pos..self.token_pos + n_raw_tokens]
-                        .iter()
-                        .map(|it| it.len)
-                        .sum::<TextUnit>();
-                    self.leaf(kind, len, n_raw_tokens);
+/// Generate the syntax tree with the control of events.
+pub(super) fn process(sink: &mut impl TreeSink, mut events: Vec<Event>) {
+    let mut forward_parents = Vec::new();
+
+    for i in 0..events.len() {
+        match mem::replace(&mut events[i], Event::tombstone()) {
+            Event::Start { kind: TOMBSTONE, .. } => (),
+
+            Event::Start { kind, forward_parent } => {
+                // For events[A, B, C], B is A's forward_parent, C is B's forward_parent,
+                // in the normal control flow, the parent-child relation: `A -> B -> C`,
+                // while with the magic forward_parent, it writes: `C <- B <- A`.
+
+                // append `A` into parents.
+                forward_parents.push(kind);
+                let mut idx = i;
+                let mut fp = forward_parent;
+                while let Some(fwd) = fp {
+                    idx += fwd as usize;
+                    // append `A`'s forward_parent `B`
+                    fp = match mem::replace(&mut events[idx], Event::tombstone()) {
+                        Event::Start { kind, forward_parent } => {
+                            forward_parents.push(kind);
+                            forward_parent
+                        }
+                        _ => unreachable!(),
+                    };
+                    // append `B`'s forward_parent `C` in the next stage.
                 }
-                Event::Error { msg } => self.sink.error(msg),
-            }
-        }
-        self.sink
-    }
-
-    /// Add the node into syntax tree but discard the comments/whitespaces.
-    fn start(&mut self, kind: SyntaxKind) {
-        if kind == SOURCE_FILE {
-            self.sink.start_branch(kind);
-            return;
-        }
-        let n_trivias =
-            self.tokens[self.token_pos..].iter().take_while(|it| it.kind.is_trivia()).count();
-        let leading_trivias = &self.tokens[self.token_pos..self.token_pos + n_trivias];
-        let mut trivia_end =
-            self.text_pos + leading_trivias.iter().map(|it| it.len).sum::<TextUnit>();
 
-        let n_attached_trivias = {
-            let leading_trivias = leading_trivias.iter().rev().map(|it| {
-                let next_end = trivia_end - it.len;
-                let range = TextRange::from_to(next_end, trivia_end);
-                trivia_end = next_end;
-                (it.kind, &self.text[range])
-            });
-            n_attached_trivias(kind, leading_trivias)
-        };
-        self.eat_n_trivias(n_trivias - n_attached_trivias);
-        self.sink.start_branch(kind);
-        self.eat_n_trivias(n_attached_trivias);
-    }
-
-    fn finish(&mut self, is_last: bool) {
-        if is_last {
-            self.eat_trivias()
-        }
-        self.sink.finish_branch();
-    }
-
-    fn eat_trivias(&mut self) {
-        while let Some(&token) = self.tokens.get(self.token_pos) {
-            if !token.kind.is_trivia() {
-                break;
-            }
-            self.leaf(token.kind, token.len, 1);
-        }
-    }
-
-    fn eat_n_trivias(&mut self, n: usize) {
-        for _ in 0..n {
-            let token = self.tokens[self.token_pos];
-            assert!(token.kind.is_trivia());
-            self.leaf(token.kind, token.len, 1);
-        }
-    }
-
-    fn leaf(&mut self, kind: SyntaxKind, len: TextUnit, n_tokens: usize) {
-        let range = TextRange::offset_len(self.text_pos, len);
-        let text: SmolStr = self.text[range].into();
-        self.text_pos += len;
-        self.token_pos += n_tokens;
-        self.sink.leaf(kind, text);
-    }
-}
-
-fn n_attached_trivias<'a>(
-    kind: SyntaxKind,
-    trivias: impl Iterator<Item = (SyntaxKind, &'a str)>,
-) -> usize {
-    match kind {
-        CONST_DEF | TYPE_DEF | STRUCT_DEF | ENUM_DEF | ENUM_VARIANT | FN_DEF | TRAIT_DEF
-        | MODULE | NAMED_FIELD_DEF => {
-            let mut res = 0;
-            for (i, (kind, text)) in trivias.enumerate() {
-                match kind {
-                    WHITESPACE => {
-                        if text.contains("\n\n") {
-                            break;
-                        }
-                    }
-                    COMMENT => {
-                        res = i + 1;
-                    }
-                    _ => (),
+                for (j, kind) in forward_parents.drain(..).rev().enumerate() {
+                    let is_root_node = i == 0 && j == 0;
+                    sink.start_branch(kind, is_root_node);
                 }
             }
-            res
+            Event::Finish => sink.finish_branch(i == events.len() - 1),
+            Event::Token { kind, n_raw_tokens } => {
+                sink.leaf(kind, n_raw_tokens);
+            }
+            Event::Error { msg } => sink.error(msg),
         }
-        _ => 0,
     }
 }