From 3b166baa1705a2267e9b7dede17b19196f7392fa Mon Sep 17 00:00:00 2001
From: Alessandro Scandone <alescandone@gmail.com>
Date: Mon, 22 Jan 2024 14:04:28 +0100
Subject: [PATCH] added trailing comma for variants

---
 src/__snapshots__/parser.test.ts.snap | 22 ++++++++++++++++++++++
 src/parser.test.ts                    |  5 +++++
 src/parser.ts                         |  9 ++++++++-
 src/parser/grammar.ohm                |  2 +-
 4 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/src/__snapshots__/parser.test.ts.snap b/src/__snapshots__/parser.test.ts.snap
index 1a521b66..ea9673f0 100644
--- a/src/__snapshots__/parser.test.ts.snap
+++ b/src/__snapshots__/parser.test.ts.snap
@@ -1259,6 +1259,28 @@ exports[`parse let block with two let stmts 1`] = `
 }
 `;
 
+exports[`type declarations > trailing comma after variants 1`] = `
+{
+  "declarations": [],
+  "typeDeclarations": [
+    {
+      "name": "T",
+      "type": "adt",
+      "variants": [
+        {
+          "args": [],
+          "name": "A",
+        },
+        {
+          "args": [],
+          "name": "B",
+        },
+      ],
+    },
+  ],
+}
+`;
+
 exports[`type declarations > type with a variant with complex args 1`] = `
 {
   "declarations": [],
diff --git a/src/parser.test.ts b/src/parser.test.ts
index 9e162b93..232312b1 100644
--- a/src/parser.test.ts
+++ b/src/parser.test.ts
@@ -277,6 +277,11 @@ describe("type declarations", () => {
     const src = `type T { A, B }`;
     expect(unsafeParse(src)).toMatchSnapshot();
   });
+
+  test("trailing comma after variants", () => {
+    const src = `type T { A, B, }`;
+    expect(unsafeParse(src)).toMatchSnapshot();
+  });
 });
 
 function spanOf(src: string, substr: string = src): Span {
diff --git a/src/parser.ts b/src/parser.ts
index 4926d8b7..7730e06e 100644
--- a/src/parser.ts
+++ b/src/parser.ts
@@ -188,7 +188,14 @@ semantics.addOperation<TypeVariant>("typeVariant()", {
 });
 
 semantics.addOperation<Statement>("statement()", {
-  TypeDeclaration_typeDef(_type, typeName, _lbracket, variants, _rbracket) {
+  TypeDeclaration_typeDef(
+    _type,
+    typeName,
+    _lbracket,
+    variants,
+    _trailingComma,
+    _rbracket,
+  ) {
     const variants_ = variants
       .asIteration()
       .children.map<TypeVariant>((n) => n.typeVariant());
diff --git a/src/parser/grammar.ohm b/src/parser/grammar.ohm
index c0cc937d..7aaf6f2e 100644
--- a/src/parser/grammar.ohm
+++ b/src/parser/grammar.ohm
@@ -7,7 +7,7 @@ Program {
     = "let" ident (":" Type)? "=" Exp  -- letStmt
 
   TypeDeclaration
-    = "type" typeName "{" ListOf<TypeVariant, ","> "}" -- typeDef
+    = "type" typeName "{" ListOf<TypeVariant, ","> ","? "}" -- typeDef
 
   // --- Expressions