initial parser signature

argus-core/src/expr/traits.rs

@@ -1,3 +1,5 @@
+use std::any::Any;
+
 use enum_dispatch::enum_dispatch;
 
 use super::{BoolExpr, ExprRef, NumExpr};
@@ -14,6 +16,9 @@ pub trait Expr {
     /// If the expression doesn't contain arguments (i.e., it is a leaf expression) then
     /// the vector is empty.
     fn args(&self) -> Vec<ExprRef<'_>>;
+
+    /// [`std::any::Any`] trampoline for expressions
+    fn as_any(&self) -> &dyn Any;
 }
 
 /// Marker trait for numeric expressions

argus-parser/src/lexer.rs

@@ -1,9 +1,10 @@
-use std::{env, fmt, fs};
+use std::fmt;
 
-use ariadne::{sources, Color, Label, Report, ReportKind};
 use chumsky::prelude::*;
 
 pub type Span = SimpleSpan<usize>;
+pub type Output<'a> = Vec<(Token<'a>, Span)>;
+pub type Error<'a> = extra::Err<Rich<'a, char, Span>>;
 
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub enum Token<'src> {
@@ -76,7 +77,7 @@ impl<'src> fmt::Display for Token<'src> {
     }
 }
 
-pub fn lexer<'src>() -> impl Parser<'src, &'src str, Vec<(Token<'src>, Span)>, extra::Err<Rich<'src, char, Span>>> {
+pub fn lexer<'src>() -> impl Parser<'src, &'src str, Output<'src>, Error<'src>> {
     // A parser for numbers
     let digits = text::digits(10).slice();
 
@@ -173,8 +174,6 @@ mod tests {
     #[test]
     fn simple_test() {
         use Token::*;
-        type Output<'a> = Vec<(Token<'a>, Span)>;
-        type MyErr<'a> = extra::Err<Rich<'a, char, Span>>;
         let cases = [
             ("true", vec![(Bool(true), Span::new(0, 4))]),
             ("false", vec![(Bool(false), Span::new(0, 5))]),

argus-parser/src/parser.rs

@@ -1 +1,18 @@
+use std::{env, fmt, fs};
 
+use ariadne::{sources, Color, Label, Report, ReportKind};
+use chumsky::{input::SpannedInput, prelude::*};
+
+use crate::lexer::{lexer, Span, Token};
+
+pub type Spanned<T> = (T, Span);
+
+// The type of the input that our parser operates on. The input is the `&[(Token, Span)]` token buffer generated by the
+// lexer, wrapped in a `SpannedInput` which 'splits' it apart into its constituent parts, tokens and spans, for chumsky
+// to understand.
+type ParserInput<'tokens, 'src> = SpannedInput<Token<'src>, Span, &'tokens [(Token<'src>, Span)]>;
+
+pub fn parser<'tokens, 'src: 'tokens>(
+) -> impl Parser<'tokens, ParserInput<'tokens, 'src>, Spanned<Expr<'src>>, extra::Err<Rich<'tokens, Token<'src>, Span>>>
+       + Clone {
+}