fix error message for match

[JelleZijlstra]

Fixes #2648.

Haven't figured out how to test this yet.

[isidentical]

Humm, not sure if this is the perfect solution but how about this?

diff --git a/tests/data/pattern_matching_invalid.py b/tests/data/pattern_matching_invalid.py
new file mode 100644
index 0000000..22b5b94
--- /dev/null
+++ b/tests/data/pattern_matching_invalid.py
@@ -0,0 +1,18 @@
+# First match, no errors
+match something:
+    case bla():
+        pass
+
+# Problem on line 10
+match invalid_case:
+    case valid_case:
+        pass
+    case a := b:
+        pass
+    case valid_case:
+        pass
+
+# No problems either
+match something:
+    case bla():
+        pass
diff --git a/tests/test_format.py b/tests/test_format.py
index 8f8ffb3..f97d716 100644
--- a/tests/test_format.py
+++ b/tests/test_format.py
@@ -200,6 +200,15 @@ def test_python_310(filename: str) -> None:
     assert_format(source, expected, mode, minimum_version=(3, 10))
 
 
+def test_patma_invalid() -> None:
+    source, expected = read_data("pattern_matching_invalid")
+    mode = black.Mode(target_versions={black.TargetVersion.PY310})
+    with pytest.raises(black.parsing.InvalidInput) as exc_info:
+        assert_format(source, expected, mode, minimum_version=(3, 10))
+
+    exc_info.match("Cannot parse: 10:11")
+
+
 def test_docstring_no_string_normalization() -> None:
     """Like test_docstring but with string normalization off."""
     source, expected = read_data("docstring_no_string_normalization")

[JelleZijlstra]

Thanks, that's perfect!

[isidentical]

Cool solution!