From 8f69c5af08650c113fd68c2a75ba30b06b506e2f Mon Sep 17 00:00:00 2001
From: Earlopain <14981592+Earlopain@users.noreply.github.com>
Date: Thu, 15 Jan 2026 21:47:26 +0100
Subject: [PATCH] Fix locations for invalid syntax when using `expect1_opening`

Followup to https://github.com/ruby/prism/pull/3827

It sets the start to the opening but it should instead just
continue on as usual.
Fixes https://github.com/ruby/prism/issues/3851

Notice how the AST actually contains "123" in both the body and end keyword.
---
 src/prism.c               | 2 +-
 test/prism/errors_test.rb | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/prism.c b/src/prism.c
index b36a6da204..b158e505b2 100644
--- a/src/prism.c
+++ b/src/prism.c
@@ -12438,7 +12438,7 @@ expect1_opening(pm_parser_t *parser, pm_token_type_t type, pm_diagnostic_id_t di
 
     pm_parser_err(parser, opening->start, opening->end, diag_id);
 
-    parser->previous.start = opening->end;
+    parser->previous.start = parser->previous.end;
     parser->previous.type = PM_TOKEN_MISSING;
 }
 
diff --git a/test/prism/errors_test.rb b/test/prism/errors_test.rb
index 706b739557..aa264ae5b7 100644
--- a/test/prism/errors_test.rb
+++ b/test/prism/errors_test.rb
@@ -82,6 +82,11 @@ def test_regexp_encoding_option_mismatch_error
       assert_empty result.errors
     end
 
+    def test_incomplete_def_closing_loc
+      statement = Prism.parse_statement("def f; 123")
+      assert_empty(statement.end_keyword)
+    end
+
     private
 
     def assert_errors(filepath, version)