Develop a partial syntax parser.

src/parser.experiments.ts

@@ -1,7 +1,7 @@
 import { CodePointString, sourceText } from 'source-region';
 import { parseDocument } from './parser';
 import { matchCodePointString } from './recognizers';
-import { Expr } from './syntax';
+import { Program, programOf } from './syntax';
 
 // === Experiments ===
 
@@ -10,7 +10,7 @@ function experiment00_emptyDocument(): void {
 }
 
 function experiment01_topLevelExpressions(): void {
-  logParse("top-level expressions", "foo 123 (bar baz_1 qux-2)");
+  logParse("top-level expressions", "foo 123 (bar baz_1 qux-2) [a, b, c]");
 }
 
 function experiment02_nestedLists(): void {
@@ -42,12 +42,24 @@ function experiment07_matchCodePointString(): void {
   console.log("cursor", cursor.current());
 }
 
+function experiment08_squareListSeparator(): void {
+  logParse("square list separator", "[a, b c, d]");
+}
+
+function experiment09_invalidNumberFragment(): void {
+  logParse("invalid number fragment", "123fasd");
+}
+
+function experiment10_repeatedLeadingComma(): void {
+  logParse("repeated leading comma", "[, , foo, bar]");
+}
+
 function logParse(name: string, input: string): void {
   const region = sourceText(input).fullRegion();
   const result = parseDocument(region);
   console.log(`==== parser:${name} ====`);
   console.log(input);
-  console.log(result.values.map(Expr.show));
+  console.log(result.syntax.tag, Program.show(programOf(result.syntax)));
   console.dir(result.errors, { depth: null });
 }
 
@@ -60,4 +72,7 @@ function logParse(name: string, input: string): void {
   experiment05_recoverInsideList,
   experiment06_unicodeSpans,
   experiment07_matchCodePointString,
+  experiment08_squareListSeparator,
+  experiment09_invalidNumberFragment,
+  experiment10_repeatedLeadingComma,
 ].forEach((experiment) => experiment());