fix(parser): report nesting and template errors consistently

lexer.js

@@ -1413,7 +1413,7 @@ function templateString () {
     if (ch === 92/*\*/)
       pos++;
   }
-  syntaxError();
+  throw new Error('Unterminated template.');
 }
 
 function blockComment () {

src/lexer.c

@@ -192,7 +192,7 @@ uint32_t parseCJS (uint16_t* _source, uint32_t _sourceLen, void (*_addExport)(co
         break;
       case '}':
         if (openTokenDepth == 0)
-          return syntaxError(2), false;
+          return syntaxError(2), error;
         if (openTokenDepth-- == templateDepth) {
           templateDepth = templateStack[--templateStackDepth];
           templateString();
@@ -259,8 +259,11 @@ uint32_t parseCJS (uint16_t* _source, uint32_t _sourceLen, void (*_addExport)(co
     lastTokenPos = pos;
   }
 
-  if (templateDepth != UINT16_MAX || openTokenDepth || error)
+  if (templateDepth != UINT16_MAX || openTokenDepth || error) {
+    if (!error)
+      syntaxError(1);
     return error;
+  }
 
   // success
   return 0;

test/_unit.js

@@ -64,6 +64,30 @@ suite('Lexer', () => {
     assert.deepStrictEqual(first, { exports: ['first'], reexports: [] });
   });
 
+  test('rejects unterminated and unexpected nesting', () => {
+    for (const source of ['(', '{', ')', '}', '({', '{(', 'exports.value = 1; }']) {
+      assert.throws(() => parse(source, 'nesting.js'), { name: 'Error' });
+      assert.deepStrictEqual(parse('exports.recovery = 1;'), {
+        exports: ['recovery'],
+        reexports: []
+      });
+    }
+    assert.deepStrictEqual(parse('({}); exports.value = 1;'), {
+      exports: ['value'],
+      reexports: []
+    });
+  });
+
+  test('rejects unterminated templates with a parser error', () => {
+    for (const source of ['`open', '`open ${value', 'const value = `open']) {
+      assert.throws(() => parse(source, 'template.js'), { name: 'Error' });
+      assert.deepStrictEqual(parse('exports.recovery = 1;'), {
+        exports: ['recovery'],
+        reexports: []
+      });
+    }
+  });
+
   test('automatic Wasm initialization', async () => {
     const lexer = await import('../dist/lexer.mjs?automatic-initialization');