Using the example from the PEP:

a, *b, c = range(5)
print(b)

produces

{
	"owner": "_generated_diagnostic_collection_name_#0",
	"code": "use-before-def",
	"severity": 4,
	"message": "'b' used before definition",
	"source": "Python",
	"startLineNumber": 2,
	"startColumn": 7,
	"endLineNumber": 2,
	"endColumn": 8
}

Environment data

• VS Code version: 1.29.1
• Extension version (available under the Extensions sidebar): 2018.11.0
• OS and version: Windows 10 1803
• Python version (& distribution if applicable, e.g. Anaconda): CPython 3.7.0
• Python Language Server version: 0.1.65.0