From cb4cdbc652362c544682d6c75953eeba98c22f34 Mon Sep 17 00:00:00 2001
From: Jukka Lehtosalo <jukka.lehtosalo@iki.fi>
Date: Tue, 14 Dec 2021 14:49:02 +0000
Subject: [PATCH] Don't crash on unsupported Python 3.10 match statement

Generate a syntax error instead.
---
 mypy/fastparse.py                   | 4 ++++
 mypy/test/testcheck.py              | 2 ++
 test-data/unit/check-python310.test | 7 +++++++
 3 files changed, 13 insertions(+)
 create mode 100644 test-data/unit/check-python310.test

diff --git a/mypy/fastparse.py b/mypy/fastparse.py
index a0d0ec8e34b0..bd348e6a0237 100644
--- a/mypy/fastparse.py
+++ b/mypy/fastparse.py
@@ -1286,6 +1286,10 @@ def visit_Index(self, n: Index) -> Node:
         # cast for mypyc's benefit on Python 3.9
         return self.visit(cast(Any, n).value)
 
+    def visit_Match(self, n: Any) -> None:
+        self.fail("Match statement is not supported",
+                  line=n.lineno, column=n.col_offset, blocker=True)
+
 
 class TypeConverter:
     def __init__(self,
diff --git a/mypy/test/testcheck.py b/mypy/test/testcheck.py
index 642721c1b073..355a400168f6 100644
--- a/mypy/test/testcheck.py
+++ b/mypy/test/testcheck.py
@@ -104,6 +104,8 @@
     typecheck_files.append('check-python38.test')
 if sys.version_info >= (3, 9):
     typecheck_files.append('check-python39.test')
+if sys.version_info >= (3, 10):
+    typecheck_files.append('check-python310.test')
 
 # Special tests for platforms with case-insensitive filesystems.
 if sys.platform in ('darwin', 'win32'):
diff --git a/test-data/unit/check-python310.test b/test-data/unit/check-python310.test
new file mode 100644
index 000000000000..3bcac61855b4
--- /dev/null
+++ b/test-data/unit/check-python310.test
@@ -0,0 +1,7 @@
+[case testMatchStatementNotSupported]
+# flags: --python-version 3.10
+match str():  # E: Match statement is not supported
+    case 'x':
+        1 + ''
+    case _:
+        1 + b''