Parse lambdas, records, indexing

axc/foo.axs

@@ -0,0 +1 @@
+def a (x: String) = 2 + a::b["xyz"] + fn x y -> x + y + {a : b};

axc/src/parser.rs

@@ -3,7 +3,7 @@
 use std::{error::Error, fmt::Display};
 
 use chumsky::{
-    prelude::{choice, end, just, none_of, one_of, Simple},
+    prelude::{choice, end, just, none_of, one_of, todo, Simple},
     recursive::recursive,
     text::{ident, int, keyword, whitespace},
     Parser,
@@ -331,11 +331,22 @@ fn parse_class_def<'a>(
 }
 
 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| {
+    recursive(|full_expr| {
+        let lambda = parse_lambda_expr(m, full_expr.clone());
+        let record = parse_record_expr(m, full_expr.clone());
+
+        let base = choice((parse_literal(m), parse_var_ref_expr(m)));
+        let subscript = parse_subscript_expr(m, base);
+        let term = choice((lambda, record, subscript));
+
+        let unary = parse_unary(m, term);
+
+        let binary = (0..=10).rev().fold(unary.boxed(), |p, precedence| {
             parse_binary(m, precedence, p).boxed()
-        })
+        });
+
+        binary
+    })
 }
 
 fn parse_unary(
@@ -435,6 +446,79 @@ fn parse_binary<'a>(
     })
 }
 
+fn parse_record_expr(
+    _m: &ParserMeta,
+    base: impl Parser<char, Expr, Error = Simple<char>> + Clone,
+) -> impl Parser<char, Expr, Error = Simple<char>> + Clone {
+    ident()
+        .then_ignore(whitespace())
+        .then_ignore(just(':'))
+        .then_ignore(whitespace())
+        .then(base)
+        .separated_by(just(',').then(whitespace()))
+        .allow_trailing()
+        .delimited_by(just('{').then(whitespace()), just('}').then(whitespace()))
+        .map(Expr::Record)
+}
+
+fn parse_lambda_expr(
+    m: &ParserMeta,
+    base: impl Parser<char, Expr, Error = Simple<char>> + Clone,
+) -> impl Parser<char, Expr, Error = Simple<char>> + Clone {
+    keyword("fn")
+        .then(whitespace())
+        .ignore_then(parse_pattern(m).repeated())
+        .then_ignore(just("->").then(whitespace()))
+        .then(base)
+        .map(|(arguments, result)| Expr::Lambda {
+            arguments,
+            result: Box::new(result),
+        })
+}
+
+fn parse_subscript_expr(
+    _m: &ParserMeta,
+    base: impl Parser<char, Expr, Error = Simple<char>> + Clone,
+) -> impl Parser<char, Expr, Error = Simple<char>> + Clone {
+    enum SubscriptKind {
+        Dot,
+        Bracket,
+    }
+
+    base.clone()
+        .then(
+            choice((
+                just('.')
+                    .ignore_then(whitespace())
+                    .ignore_then(base.clone())
+                    .map(|e| (SubscriptKind::Dot, e)),
+                base.clone()
+                    .delimited_by(just('[').then(whitespace()), just(']').then(whitespace()))
+                    .map(|e| (SubscriptKind::Bracket, e)),
+            ))
+            .repeated(),
+        )
+        .map(|(l, subscripts): (Expr, Vec<(SubscriptKind, Expr)>)| {
+            subscripts.into_iter().fold(l, |l, (kind, r)| match kind {
+                SubscriptKind::Dot => Expr::DotSubscript {
+                    value: Box::new(l),
+                    subscript: Box::new(r),
+                },
+                SubscriptKind::Bracket => Expr::BracketSubscript {
+                    value: Box::new(l),
+                    subscript: Box::new(r),
+                },
+            })
+        })
+}
+
+fn parse_var_ref_expr(m: &ParserMeta) -> impl Parser<char, Expr, Error = Simple<char>> + Clone {
+    ident()
+        .then_ignore(whitespace())
+        .separated_by(just("::").then(whitespace()))
+        .map(Expr::VariableReference)
+}
+
 fn parse_literal(_m: &ParserMeta) -> impl Parser<char, Expr, Error = Simple<char>> + Clone {
     let string_char = none_of("\"\\").or(just('\\').ignore_then(choice((
         just('n').to('\n'),
@@ -540,7 +624,7 @@ fn parse_record_type(
         .map(Type::Record)
 }
 
-fn parse_pattern(m: &ParserMeta) -> impl Parser<char, Pattern, Error = Simple<char>> {
+fn parse_pattern(m: &ParserMeta) -> impl Parser<char, Pattern, Error = Simple<char>> + Clone {
     recursive(|rec| {
         choice((
             parse_ignore_pattern(m),

axc/src/syntax.rs

@@ -143,10 +143,7 @@ pub enum Expr {
     },
 
     /// Record initialization, e.g., `{ pointer: xyz, length: 12 }`.
-    Record {
-        /// The elements of the record.
-        elements: Vec<(String, Expr)>,
-    },
+    Record(Vec<(String, Expr)>),
 
     /// Anonymous functions, e.g., `fn x -> x + 1`.
     Lambda {
@@ -158,16 +155,13 @@ pub enum Expr {
         result: Box<Expr>,
     },
 
-    /// Variable references, possibly namespaced, e.g., `foo::bar::baz`.
-    VariableReference(Vec<String>),
-
     /// Dot subscripts, e.g., `foo.bar`.
     DotSubscript {
         /// The left side of the subscript.
         value: Box<Expr>,
 
-        /// The right side of the subscript; this is only allowed to be a single word.
-        subscript: String,
+        /// The right side of the subscript; semantically, this is only allowed to be a single word.
+        subscript: Box<Expr>,
     },
 
     /// Bracket subscripts, e.g., `foo[bar]`.
@@ -179,6 +173,9 @@ pub enum Expr {
         subscript: Box<Expr>,
     },
 
+    /// Variable references, possibly namespaced, e.g., `foo::bar::baz`.
+    VariableReference(Vec<String>),
+
     /// Literal tokens, e.g., strings and numbers.
     Literal(Literal),
 }