From 2dd20183adb63635d4c3d828d064f1c8b8946e99 Mon Sep 17 00:00:00 2001
From: Earlopain <14981592+Earlopain@users.noreply.github.com>
Date: Thu, 9 Apr 2026 13:11:13 +0200
Subject: [PATCH] Reject `return` and similar with block pass argument

Same handling as for `yield`. Fixes [Bug #21988]
---
 src/prism.c                                   |  9 +++++
 test/prism/errors/block_pass_return_value.txt | 33 +++++++++++++++++++
 2 files changed, 42 insertions(+)
 create mode 100644 test/prism/errors/block_pass_return_value.txt

diff --git a/src/prism.c b/src/prism.c
index 72c49da6f2..3ae6ca3d7b 100644
--- a/src/prism.c
+++ b/src/prism.c
@@ -19685,6 +19685,15 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, u
                         PM_PARSER_ERR_TOKEN_FORMAT(parser, &next, PM_ERR_EXPECT_EOL_AFTER_STATEMENT, pm_token_str(next.type));
                     }
                 }
+
+                // It's possible that we've parsed a block argument through our
+                // call to parse_arguments. If we found one, we should mark it
+                // as invalid and destroy it, as we don't have a place for it.
+                if (arguments.block != NULL) {
+                    pm_parser_err_node(parser, arguments.block, PM_ERR_UNEXPECTED_BLOCK_ARGUMENT);
+                    pm_node_unreference(parser, arguments.block);
+                    arguments.block = NULL;
+                }
             }
 
             switch (keyword.type) {
diff --git a/test/prism/errors/block_pass_return_value.txt b/test/prism/errors/block_pass_return_value.txt
new file mode 100644
index 0000000000..c9d12281d9
--- /dev/null
+++ b/test/prism/errors/block_pass_return_value.txt
@@ -0,0 +1,33 @@
+return &b
+       ^ unexpected '&', expecting end-of-input
+       ^ unexpected '&', ignoring it
+
+return(&b)
+       ^ unexpected '&', ignoring it
+       ^ unexpected '&', expecting end-of-input
+       ^ unexpected '&', ignoring it
+       ^ expected a matching `)`
+       ^ unexpected '&', expecting end-of-input
+       ^ unexpected '&', ignoring it
+         ^ unexpected ')', expecting end-of-input
+         ^ unexpected ')', ignoring it
+
+return a, &b
+          ^~ block argument should not be given
+
+return(a, &b)
+       ^~ unexpected write target
+          ^ unexpected '&', expecting end-of-input
+          ^ unexpected '&', ignoring it
+         ^ expected a matching `)`
+          ^ unexpected '&', expecting end-of-input
+          ^ unexpected '&', ignoring it
+            ^ unexpected ')', expecting end-of-input
+            ^ unexpected ')', ignoring it
+
+tap { break a, &b }
+               ^~ block argument should not be given
+
+tap { next a, &b }
+              ^~ block argument should not be given
+