1 files changed, 149 insertions, 0 deletions

diff --git a/crates/parser/src/lib.rs b/crates/parser/src/lib.rs
new file mode 100644
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+++ b/crates/parser/src/lib.rs
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+//! The Rust parser.
+//!
+//! The parser doesn't know about concrete representation of tokens and syntax
+//! trees. Abstract `TokenSource` and `TreeSink` traits are used instead. As a
+//! consequence, this crates does not contain a lexer.
+//!
+//! The `Parser` struct from the `parser` module is a cursor into the sequence
+//! of tokens. Parsing routines use `Parser` to inspect current state and
+//! advance the parsing.
+//!
+//! The actual parsing happens in the `grammar` module.
+//!
+//! Tests for this crate live in `syntax` crate.
+
+#[macro_use]
+mod token_set;
+#[macro_use]
+mod syntax_kind;
+mod event;
+mod parser;
+mod grammar;
+
+pub(crate) use token_set::TokenSet;
+
+pub use syntax_kind::SyntaxKind;
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct ParseError(pub Box<String>);
+
+/// `TokenSource` abstracts the source of the tokens parser operates on.
+///
+/// Hopefully this will allow us to treat text and token trees in the same way!
+pub trait TokenSource {
+    fn current(&self) -> Token;
+
+    /// Lookahead n token
+    fn lookahead_nth(&self, n: usize) -> Token;
+
+    /// bump cursor to next token
+    fn bump(&mut self);
+
+    /// Is the current token a specified keyword?
+    fn is_keyword(&self, kw: &str) -> bool;
+}
+
+/// `Token` abstracts the cursor of `TokenSource` operates on.
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub struct Token {
+    /// What is the current token?
+    pub kind: SyntaxKind,
+
+    /// Is the current token joined to the next one (`> >` vs `>>`).
+    pub is_jointed_to_next: bool,
+}
+
+/// `TreeSink` abstracts details of a particular syntax tree implementation.
+pub trait TreeSink {
+    /// Adds new token to the current branch.
+    fn token(&mut self, kind: SyntaxKind, n_tokens: u8);
+
+    /// Start new branch and make it current.
+    fn start_node(&mut self, kind: SyntaxKind);
+
+    /// Finish current branch and restore previous
+    /// branch as current.
+    fn finish_node(&mut self);
+
+    fn error(&mut self, error: ParseError);
+}
+
+fn parse_from_tokens<F>(token_source: &mut dyn TokenSource, tree_sink: &mut dyn TreeSink, f: F)
+where
+    F: FnOnce(&mut parser::Parser),
+{
+    let mut p = parser::Parser::new(token_source);
+    f(&mut p);
+    let events = p.finish();
+    event::process(tree_sink, events);
+}
+
+/// Parse given tokens into the given sink as a rust file.
+pub fn parse(token_source: &mut dyn TokenSource, tree_sink: &mut dyn TreeSink) {
+    parse_from_tokens(token_source, tree_sink, grammar::root);
+}
+
+#[derive(Debug, Clone, Copy, Eq, PartialEq, Hash)]
+pub enum FragmentKind {
+    Path,
+    Expr,
+    Statement,
+    Type,
+    Pattern,
+    Item,
+    Block,
+    Visibility,
+    MetaItem,
+
+    // These kinds are used when parsing the result of expansion
+    // FIXME: use separate fragment kinds for macro inputs and outputs?
+    Items,
+    Statements,
+}
+
+pub fn parse_fragment(
+    token_source: &mut dyn TokenSource,
+    tree_sink: &mut dyn TreeSink,
+    fragment_kind: FragmentKind,
+) {
+    let parser: fn(&'_ mut parser::Parser) = match fragment_kind {
+        FragmentKind::Path => grammar::fragments::path,
+        FragmentKind::Expr => grammar::fragments::expr,
+        FragmentKind::Type => grammar::fragments::type_,
+        FragmentKind::Pattern => grammar::fragments::pattern,
+        FragmentKind::Item => grammar::fragments::item,
+        FragmentKind::Block => grammar::fragments::block_expr,
+        FragmentKind::Visibility => grammar::fragments::opt_visibility,
+        FragmentKind::MetaItem => grammar::fragments::meta_item,
+        FragmentKind::Statement => grammar::fragments::stmt,
+        FragmentKind::Items => grammar::fragments::macro_items,
+        FragmentKind::Statements => grammar::fragments::macro_stmts,
+    };
+    parse_from_tokens(token_source, tree_sink, parser)
+}
+
+/// A parsing function for a specific braced-block.
+pub struct Reparser(fn(&mut parser::Parser));
+
+impl Reparser {
+    /// If the node is a braced block, return the corresponding `Reparser`.
+    pub fn for_node(
+        node: SyntaxKind,
+        first_child: Option<SyntaxKind>,
+        parent: Option<SyntaxKind>,
+    ) -> Option<Reparser> {
+        grammar::reparser(node, first_child, parent).map(Reparser)
+    }
+
+    /// Re-parse given tokens using this `Reparser`.
+    ///
+    /// Tokens must start with `{`, end with `}` and form a valid brace
+    /// sequence.
+    pub fn parse(self, token_source: &mut dyn TokenSource, tree_sink: &mut dyn TreeSink) {
+        let Reparser(r) = self;
+        let mut p = parser::Parser::new(token_source);
+        r(&mut p);
+        let events = p.finish();
+        event::process(tree_sink, events);
+    }
+}