comacro 0.0.1

Declarative Rust static analysis with macro-like syntax
Documentation 
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use std::io::Write;
use std::fmt::Display;

use crate::trace::*;
use crate::visitor::Visitor;

pub(crate) trait Emitter {
    fn meta(&mut self, x: u32);
    fn item(&mut self, s: impl Display);
    fn text_item(&mut self, s: impl Display);
    fn opener(&mut self, s: impl Display);
    fn closer(&mut self);
    fn maybe_break(&mut self) {}
    fn finish(self) -> Vec<u8>;
}

pub(crate) struct ReprEmitter {
    buf: std::io::Cursor<Vec<u8>>,
    sibling: bool,
}

impl ReprEmitter {
    pub fn new() -> Self {
        let buf = std::io::Cursor::new(Vec::new());
        let sibling = false;
        ReprEmitter { buf, sibling }
    }

    fn maybe_comma(&mut self) {
        if self.sibling { self.comma(); }
    }

    fn comma(&mut self) {
        write!(self.buf, " ").unwrap();
    }
}

impl Emitter for ReprEmitter {
    fn meta(&mut self, x: u32) {
        self.maybe_comma();
        write!(self.buf, "${}", x);
        self.sibling = true;
    }

    fn item(&mut self, s: impl Display) {
        self.maybe_comma();
        write!(self.buf, "{}", s);
        self.sibling = true;
    }

    fn text_item(&mut self, s: impl Display) {
        self.maybe_comma();
        write!(self.buf, "{}", s);
        self.sibling = true;
    }

    fn opener(&mut self, s: impl Display) {
        self.maybe_comma();
        write!(self.buf, "{}{{", s);
        self.sibling = true;
    }

    fn closer(&mut self) {
        self.maybe_comma();
        write!(self.buf, "}}");
        self.sibling = true;
    }

    fn maybe_break(&mut self) {
        if self.buf.position() != 0 {
            write!(self.buf, "\n");
            self.sibling = false;
        }
    }

    fn finish(self) -> Vec<u8> {
        self.buf.into_inner()
    }
}

pub(crate) struct JsonEmitter {
    buf: std::io::Cursor<Vec<u8>>,
    sibling: bool,
    scalar_context: bool,
}

impl JsonEmitter {
    pub fn new() -> Self {
        let mut buf = std::io::Cursor::new(Vec::new());
        write!(buf, "[");
        let sibling = false;
        JsonEmitter { buf, sibling, scalar_context: false }
    }

    pub fn new_scalar() -> Self {
        let buf = std::io::Cursor::new(Vec::new());
        let sibling = false;
        JsonEmitter { buf, sibling, scalar_context: true }
    }

    fn maybe_comma(&mut self) {
        if self.sibling { self.comma(); }
    }

    fn comma(&mut self) {
        write!(self.buf, ",").unwrap();
    }
}

impl Emitter for JsonEmitter {
    fn finish(mut self) -> Vec<u8> {
        if !self.scalar_context {
            write!(self.buf, "]");
        }
        self.buf.into_inner()
    }

    fn meta(&mut self, x: u32) {
        self.maybe_comma();
        write!(self.buf, "\"${}\"", x);
        self.sibling = true;
    }

    fn item(&mut self, s: impl Display) {
        self.maybe_comma();
        write!(self.buf, "{}", s);
        self.sibling = true;
    }

    fn text_item(&mut self, s: impl Display) {
        self.maybe_comma();
        write!(self.buf, "\"{}\"", s);
        self.sibling = true;
    }

    fn opener(&mut self, s: impl Display) {
        self.maybe_comma();
        write!(self.buf, "[\"{}\"", s);
        self.sibling = true;
    }

    fn closer(&mut self) {
        write!(self.buf, "]");
        self.sibling = true;
    }
}

/// An AST visitor that compares compiled MatchCode for a pattern with the AST for that pattern's
/// <nodes> or <ids> tree to emit a representation of the pattern.
pub(crate) struct ReprGenerator<E> {
    emitter: E,
    trace: ReTracer,
}

impl<E: Emitter> ReprGenerator<E> {
    pub fn new(old: Trace, emitter: E) -> Self {
        let trace = ReTracer::new(old);
        ReprGenerator { emitter, trace }
    }

    pub fn finish(self) -> Vec<u8> {
        self.emitter.finish()
    }
}

impl<E: Emitter> Visitor<'_> for ReprGenerator<E> {
    fn open_expr(&mut self, x: &syn::Expr) -> Result<(), ()> {
        if let Err(()) = self.trace.open_subtree() {
            let x = u32::from(self.trace.consume_meta());
            self.emitter.meta(x);
            return Err(());
        }
        self.emitter.opener(crate::names::expr_discrim(x));
        Ok(())
    }
    fn open_ident(&mut self, x: &syn::Ident) -> Result<(), ()> {
        if let Err(()) = self.trace.open_subtree() {
            let x = u32::from(self.trace.consume_meta());
            self.emitter.meta(x);
            return Err(());
        }
        self.emitter.text_item(x);
        Ok(())
    }
    fn open_stmt(&mut self, x: &syn::Stmt) {
        self.open_subtree();
        self.emitter.maybe_break();
        self.emitter.opener(crate::names::stmt_discrim(x));
    }
    fn open_pat(&mut self, x: &syn::Pat) {
        self.open_subtree();
        self.emitter.opener(crate::names::pat_discrim(x));
    }
    fn open_lit_int(&mut self, x: &syn::LitInt) {
        self.open_datum();
        self.emitter.item(x.value());
    }

    fn close_expr(&mut self, _: &syn::Expr) {
        self.close_subtree();
        self.emitter.closer();
    }
    fn close_stmt(&mut self, _: &syn::Stmt) {
        self.close_subtree();
        self.emitter.closer();
    }
    fn close_pat(&mut self, _: &syn::Pat) {
        self.close_subtree();
        self.emitter.closer();
    }

    fn open_subtree(&mut self) { self.trace.open_subtree().unwrap(); }
    fn close_subtree(&mut self) { self.trace.close_subtree().unwrap(); }
    fn open_datum(&mut self) { self.trace.open_datum(); }
    fn close_datum(&mut self) { self.trace.close_datum(); }
    fn push_byte(&mut self, x: u8) { self.trace.push_byte(x); }
    fn extend_bytes(&mut self, x: &[u8]) { self.trace.extend_bytes(x); }
}

/// Serialize a normal AST (no metavars)
pub(crate) struct PlainAstRepr<E> {
    emitter: E,
}

impl<E: Emitter> PlainAstRepr<E> {
    pub fn new(emitter: E) -> Self {
        PlainAstRepr { emitter }
    }

    pub fn finish(self) -> Vec<u8> {
        self.emitter.finish()
    }
}


impl<E: Emitter> Visitor<'_> for PlainAstRepr<E> {
    fn open_expr(&mut self, x: &syn::Expr) -> Result<(), ()> {
        self.emitter.opener(crate::names::expr_discrim(x));
        Ok(())
    }
    fn open_ident(&mut self, x: &syn::Ident) -> Result<(), ()> {
        self.emitter.text_item(x);
        Ok(())
    }
    fn open_stmt(&mut self, x: &syn::Stmt) {
        self.emitter.maybe_break();
        self.emitter.opener(crate::names::stmt_discrim(x));
    }
    fn open_pat(&mut self, x: &syn::Pat) {
        self.emitter.opener(crate::names::pat_discrim(x));
    }
    fn open_lit_int(&mut self, x: &syn::LitInt) {
        self.emitter.item(x.value());
    }

    fn close_expr(&mut self, _: &syn::Expr) {
        self.emitter.closer();
    }
    fn close_stmt(&mut self, _: &syn::Stmt) {
        self.emitter.closer();
    }
    fn close_pat(&mut self, _: &syn::Pat) {
        self.emitter.closer();
    }

    fn open_subtree(&mut self) {}
    fn close_subtree(&mut self) {}
    fn open_datum(&mut self) {}
    fn close_datum(&mut self) {}
    fn push_byte(&mut self, x: u8) {}
    fn extend_bytes(&mut self, x: &[u8]) {}
}