From b55e67711a678ab22234485f949c82c0d826a604 Mon Sep 17 00:00:00 2001
From: Berg Lucas <55436804+BergLucas@users.noreply.github.com>
Date: Tue, 26 Aug 2025 16:13:51 +0200
Subject: [PATCH 1/2] Fix the next_block of the new block in
 ControlFlowGraph.split_block

---
 src/bytecode/cfg.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/bytecode/cfg.py b/src/bytecode/cfg.py
index e511c045..c39124b5 100644
--- a/src/bytecode/cfg.py
+++ b/src/bytecode/cfg.py
@@ -710,6 +710,7 @@ def split_block(self, block: BasicBlock, index: int) -> BasicBlock:
         del block[index:]
 
         block2 = BasicBlock(instructions)
+        block2.next_block = block.next_block
         block.next_block = block2
 
         for block in self[block_index + 1 :]:

From 29d660fc77c80ca0f580b37ec736912549e1c749 Mon Sep 17 00:00:00 2001
From: Berg Lucas <55436804+BergLucas@users.noreply.github.com>
Date: Wed, 27 Aug 2025 00:08:14 +0200
Subject: [PATCH 2/2] Improve the split_block tests to verify the next blocks

---
 tests/test_cfg.py | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tests/test_cfg.py b/tests/test_cfg.py
index 5eb6afe6..077a2980 100644
--- a/tests/test_cfg.py
+++ b/tests/test_cfg.py
@@ -534,6 +534,8 @@ def test_split_block(self):
 
         label = code.split_block(code[0], 2)
         self.assertIs(label, code[1])
+        self.assertIs(code[0].next_block, label)
+        self.assertIs(label.next_block, None)
         self.assertBlocksEqual(
             code,
             [
@@ -546,6 +548,9 @@ def test_split_block(self):
 
         label2 = code.split_block(code[0], 1)
         self.assertIs(label2, code[1])
+        self.assertIs(code[0].next_block, label2)
+        self.assertIs(label2.next_block, label)
+        self.assertIs(label.next_block, None)
         self.assertBlocksEqual(
             code,
             [Instr("LOAD_SMALL_INT" if PY314 else "LOAD_CONST", 1, lineno=1)],
@@ -567,6 +572,8 @@ def test_split_block_end(self):
         # split at the end of the last block requires to add a new empty block
         label = code.split_block(code[0], 2)
         self.assertIs(label, code[1])
+        self.assertIs(code[0].next_block, label)
+        self.assertIs(label.next_block, None)
         self.assertBlocksEqual(
             code,
             [
@@ -581,6 +588,8 @@ def test_split_block_end(self):
         # add a new block
         label = code.split_block(code[0], 2)
         self.assertIs(label, code[1])
+        self.assertIs(code[0].next_block, label)
+        self.assertIs(label.next_block, None)
         self.assertBlocksEqual(
             code,
             [
@@ -596,6 +605,7 @@ def test_split_block_dont_split(self):
         # FIXME: is it really useful to support that?
         block = code.split_block(code[0], 0)
         self.assertIs(block, code[0])
+        self.assertIs(code[0].next_block, None)
         self.assertBlocksEqual(
             code,
             [