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Get basic expression parsing working

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This commit is contained in:
Alex Bethel 2022-08-06 18:54:47 -05:00
parent 3067af1304
commit cc32863afc
2 changed files with 176 additions and 35 deletions
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193
axc/src/parser.rs
View file

@ -3,12 +3,14 @@
use std::{error::Error, fmt::Display};
use chumsky::{
prelude::{choice, end, just, todo, Simple},
text::{ident, keyword},
prelude::{choice, end, just, one_of, todo, Simple},
text::{ident, keyword, whitespace},
Parser,
};
use crate::syntax::{ClassMember, Expr, Pattern, Statement, SyntaxTree, Type, TypeConstructor};
use crate::syntax::{
ClassMember, Expr, Literal, Pattern, Statement, SyntaxTree, Type, TypeConstructor,
};
/// Adapter to make `chumsky`'s parser errors usable as standard Rust errors.
#[derive(Debug)]
@ -50,6 +52,7 @@ struct OperatorDef {
}
/// The possible associativity directions of an operator.
#[derive(PartialEq, Eq, Clone, Copy)]
enum Associativity {
Left,
Right,
@ -210,14 +213,24 @@ impl Default for ParserMeta {
}
/// Parser for AlexScript code.
pub fn parser(m: &ParserMeta) -> impl Parser<char, SyntaxTree, Error = Simple<char>> {
parse_statement(m)
pub fn parser<'a>(m: &'a ParserMeta) -> impl Parser<char, SyntaxTree, Error = Simple<char>> + 'a {
// parse_statement(m)
// .repeated()
// .map(SyntaxTree)
// .then_ignore(end())
parse_expression(m)
.then_ignore(just(";").then(whitespace()))
.repeated()
.map(SyntaxTree)
.then_ignore(end())
.map(|exprs| {
println!("{:#?}", exprs);
todo!()
})
}
fn parse_statement(m: &ParserMeta) -> impl Parser<char, Statement, Error = Simple<char>> {
fn parse_statement<'a>(
m: &'a ParserMeta,
) -> impl Parser<char, Statement, Error = Simple<char>> + 'a {
choice((
parse_type_def(m),
parse_instance_def(m),
@ -229,9 +242,9 @@ fn parse_statement(m: &ParserMeta) -> impl Parser<char, Statement, Error = Simpl
fn parse_type_def(m: &ParserMeta) -> impl Parser<char, Statement, Error = Simple<char>> {
keyword("data")
.ignore_then(parse_type(m))
.then_ignore(just('='))
.then_ignore(just('=').then(whitespace()))
.then(parse_constructor(m).repeated())
.then_ignore(just(';'))
.then_ignore(just(';').then(whitespace()))
.map(|(typ, constructors)| Statement::TypeDefinition { typ, constructors })
}
@ -241,14 +254,16 @@ fn parse_constructor(m: &ParserMeta) -> impl Parser<char, TypeConstructor, Error
.map(|(name, args)| TypeConstructor { name, args })
}
fn parse_instance_def(m: &ParserMeta) -> impl Parser<char, Statement, Error = Simple<char>> {
fn parse_instance_def<'a>(
m: &'a ParserMeta,
) -> impl Parser<char, Statement, Error = Simple<char>> + 'a {
keyword("instance")
.ignore_then(ident())
.then(parse_type(m))
.then(
parse_class_member(m)
.repeated()
.delimited_by(just('{'), just('}')),
.delimited_by(just('{').then(whitespace()), just('}').then(whitespace())),
)
.map(|((classname, typ), decls)| Statement::InstanceDefinition {
class_name: classname,
@ -257,20 +272,31 @@ fn parse_instance_def(m: &ParserMeta) -> impl Parser<char, Statement, Error = Si
})
}
fn parse_class_decl_stmt(m: &ParserMeta) -> impl Parser<char, Statement, Error = Simple<char>> {
fn parse_class_decl_stmt<'a>(
m: &'a ParserMeta,
) -> impl Parser<char, Statement, Error = Simple<char>> + 'a {
parse_class_member(m).map(Statement::ClassMember)
}
fn parse_class_member(m: &ParserMeta) -> impl Parser<char, ClassMember, Error = Simple<char>> {
fn parse_class_member<'a>(
m: &'a ParserMeta,
) -> impl Parser<char, ClassMember, Error = Simple<char>> + 'a {
choice((parse_func_decl(m), parse_type_alias(m)))
}
fn parse_func_decl(m: &ParserMeta) -> impl Parser<char, ClassMember, Error = Simple<char>> {
fn parse_func_decl<'a>(
m: &'a ParserMeta,
) -> impl Parser<char, ClassMember, Error = Simple<char>> + 'a {
keyword("def")
.ignore_then(ident())
.then(parse_pattern(m).repeated())
.then(just('=').ignore_then(parse_expression(m)).or_not())
.then_ignore(just(';'))
.then(
just('=')
.then(whitespace())
.ignore_then(parse_expression(m))
.or_not(),
)
.then_ignore(just(';').then(whitespace()))
.map(|((name, arguments), definition)| ClassMember::Function {
name,
arguments,
@ -281,31 +307,146 @@ fn parse_func_decl(m: &ParserMeta) -> impl Parser<char, ClassMember, Error = Sim
fn parse_type_alias(m: &ParserMeta) -> impl Parser<char, ClassMember, Error = Simple<char>> {
keyword("type")
.ignore_then(parse_type(m))
.then(just('=').ignore_then(parse_type(m)).or_not())
.then_ignore(just(';'))
.then(
just('=')
.then(whitespace())
.ignore_then(parse_type(m))
.or_not(),
)
.then_ignore(just(';').then(whitespace()))
.map(|(left, right)| ClassMember::TypeAlias { left, right })
}
fn parse_class_def(m: &ParserMeta) -> impl Parser<char, Statement, Error = Simple<char>> {
fn parse_class_def<'a>(
m: &'a ParserMeta,
) -> impl Parser<char, Statement, Error = Simple<char>> + 'a {
keyword("class")
.ignore_then(ident())
.then(ident())
.then(
parse_class_member(m)
.repeated()
.delimited_by(just('{'), just('}')),
.delimited_by(just('{').then(whitespace()), just('}').then(whitespace())),
)
.map(|((name, var), decls)| Statement::ClassDefinition { name, var, decls })
}
fn parse_expression(m: &ParserMeta) -> impl Parser<char, Expr, Error = Simple<char>> {
fn parse_expression<'a>(m: &'a ParserMeta) -> impl Parser<char, Expr, Error = Simple<char>> + 'a {
(0..=10)
.rev()
.fold(parse_unary(m, parse_literal(m)).boxed(), |p, precedence| {
parse_binary(m, precedence, p).boxed()
})
}
fn parse_unary(
_m: &ParserMeta,
base: impl Parser<char, Expr, Error = Simple<char>> + Clone,
) -> impl Parser<char, Expr, Error = Simple<char>> + Clone {
choice((just("-").to("-"), just("+").to("+")))
.then_ignore(whitespace())
.repeated()
.then(base.clone())
.map(|(ops, exp)| {
ops.into_iter().fold(exp, |exp, op| Expr::UnaryOp {
kind: op.to_string(),
val: Box::new(exp),
})
})
}
fn parse_binary<'a>(
m: &'a ParserMeta,
prec: u32,
base: impl Parser<char, Expr, Error = Simple<char>> + Clone + 'a,
) -> impl Parser<char, Expr, Error = Simple<char>> + 'a + Clone {
let op_defs = m.operators.iter().filter(|def| def.precedence == prec);
let op_parsers = op_defs.map(|def| {
just(def.name.to_string())
.then(whitespace())
.ignore_then(base.clone())
.map(|e| (&def.name, &def.assoc, e))
});
let zero = one_of([]).map(|_| unreachable!()).boxed();
let any_op = op_parsers.fold(zero, |l, r| l.or(r).boxed());
let ops = any_op.repeated();
base.then(ops).map(|(first, others)| {
let mut assocs = others.iter().map(|(_, assoc, _)| assoc);
let first_assoc = assocs.next();
if !first_assoc.map_or(true, |first| assocs.all(|a| a == first)) {
// TODO: Crash the parser properly here, with error recovery etc.
panic!("Precedence parsing error: conflicting associativities");
}
let all_assoc = first_assoc.map(|o| **o).flatten();
if all_assoc == None && others.len() >= 2 {
panic!("Precedence parsing error: non-associative operation applied associatively");
}
match all_assoc {
None | Some(Associativity::Left) => {
others
.into_iter()
.fold(first, |left, (op_name, _assoc, right)| Expr::BinaryOp {
kind: op_name.to_owned(),
left: Box::new(left),
right: Box::new(right),
})
}
Some(Associativity::Right) => {
// Right now we have:
// a ^ b X c ^ d
// | \-/ \-/ \-/
// | \---+---/
// . |
// first .
// others
// To parse right-associatively, we need:
// a ^ b X c ^ d
// \-/ \-/ \-/ |
// \---+---/ |
// | |
// . last
// others_l
let others_l = std::iter::once(&first)
.chain(others.iter().map(|(_name, _assoc, expr)| expr))
.zip(others.iter().map(|(name, _assoc, _expr)| name))
.collect::<Vec<_>>();
let last = others
.iter()
.last()
.map(|(_name, _assoc, expr)| expr)
.unwrap_or(&first);
// And then we can fold as with left-associative operators.
others_l
.into_iter()
.rev()
.fold(last.to_owned(), |r, (l, op)| Expr::BinaryOp {
kind: op.to_string(),
left: Box::new(l.to_owned()),
right: Box::new(r),
})
}
}
})
}
fn parse_literal(_m: &ParserMeta) -> impl Parser<char, Expr, Error = Simple<char>> + Clone {
// TODO: add all the literals.
chumsky::text::int(10)
.then_ignore(whitespace())
.map(|s: String| Expr::Literal(Literal::Integer(s.parse().unwrap())))
}
fn parse_type(_m: &ParserMeta) -> impl Parser<char, Type, Error = Simple<char>> {
todo()
}
fn parse_type(m: &ParserMeta) -> impl Parser<char, Type, Error = Simple<char>> {
todo()
}
fn parse_pattern(m: &ParserMeta) -> impl Parser<char, Pattern, Error = Simple<char>> {
fn parse_pattern(_m: &ParserMeta) -> impl Parser<char, Pattern, Error = Simple<char>> {
todo()
}

18
axc/src/syntax.rs
View file

@ -5,11 +5,11 @@ use num_bigint::BigUint;
/// A concrete syntax tree. This represents the full content of an AlexScript program, including all
/// whitespace, comments, and tokens: the source code of the original program can be recovered
/// completely using the syntax tree.
#[derive(Clone)]
#[derive(Clone, Debug)]
pub struct SyntaxTree(pub Vec<Statement>);
/// Top-level statements, making up the overall program.
#[derive(Clone)]
#[derive(Clone, Debug)]
pub enum Statement {
/// Declaration of an abstract data type.
TypeDefinition {
@ -53,7 +53,7 @@ pub enum Statement {
/// Top-level statements that are also allowed to occur within a type class definition, and which
/// therefore have an optional rather than strictly-required right-hand side, e.g., `type X;` rather
/// than `type X = Y;`.
#[derive(Clone)]
#[derive(Clone, Debug)]
pub enum ClassMember {
/// Declaration of a function or constant.
Function {
@ -78,7 +78,7 @@ pub enum ClassMember {
}
/// A possible constructor for an abstract data type.
#[derive(Clone)]
#[derive(Clone, Debug)]
pub struct TypeConstructor {
/// The name of the constructor.
pub name: String,
@ -88,7 +88,7 @@ pub struct TypeConstructor {
}
/// Expressions.
#[derive(Clone)]
#[derive(Clone, Debug)]
pub enum Expr {
/// Unary operators, e.g., `-5`.
UnaryOp {
@ -184,7 +184,7 @@ pub enum Expr {
}
/// Type names.
#[derive(Clone)]
#[derive(Clone, Debug)]
pub enum Type {
/// `Foo`
Named(String),
@ -208,7 +208,7 @@ pub enum Type {
/// Patterns for use in function arguments, lambda arguments, `let` statements, and `match`
/// statements.
#[derive(Clone)]
#[derive(Clone, Debug)]
pub enum Pattern {
/// `(a, b)`
Tuple(Vec<Pattern>),
@ -239,7 +239,7 @@ pub enum Pattern {
}
/// Record syntax blocks, e.g., "{a: b, c: d, ...}".
#[derive(Clone)]
#[derive(Clone, Debug)]
pub struct Record {
/// The named members of the record, in order of occurrence.
pub members: Vec<(String, Expr)>,
@ -249,7 +249,7 @@ pub struct Record {
}
/// Literal values included in source code.
#[derive(Clone)]
#[derive(Clone, Debug)]
pub enum Literal {
/// `"hello"`
String(String),