add thunk syntax

src/parser.rs

@@ -145,6 +145,14 @@ where
             .delimited_by(just(Token::OpenParen), just(Token::CloseParen))
             .labelled("block");
 
+        let thunk = expr
+            .clone()
+            .separated_by(semicolon.clone())
+            .allow_trailing()
+            .collect()
+            .delimited_by(just(Token::OpenBracket), just(Token::CloseBracket))
+            .labelled("thunk");
+
         let map = expr
             .clone()
             .separated_by(semicolon.clone())
@@ -208,6 +216,11 @@ where
             ident.map(Ast::Var).labelled("variable"),
             map,
             block.map(Ast::Block),
+            thunk.map(|body| Ast::Fn {
+                inputs: vec![],
+                outputs: vec![],
+                body,
+            }),
         ))
         .boxed();
 

src/tests/parser.rs

@@ -197,3 +197,21 @@ counter_b.dec {};
 ",
     );
 }
+
+#[test]
+fn thunks() {
+    test(
+        "
+if [wow = cool]() [
+  then branch stuff; cool;
+] [
+  else branch stuff; cool;
+]
+",
+        "
+((((if (fn ([] []) (wow = cool))) ()) \
+    (fn ([] []) ((then branch) stuff) cool)) \
+    (fn ([] []) ((else branch) stuff) cool))
+        ",
+    );
+}