PEP 585 errors should always be enabled

[cdce8p]

Environment data

• Language Server version: 2021.2.0
• OS and version: darwin x64
• Python version: 3.8
• python.analysis.indexing: true
• python.analysis.typeCheckingMode: off / basic

Expected behaviour

PEP 585 errors should always be enabled, even if typeCheckingMode: off. Similar to how PEP 604 errors are handled.

Actual behaviour

typeCheckingMode: off
Only PEP 604 errors are shown.

typeCheckingMode: basic

Logs

--

Code Snippet / Additional information

var1: list[int]

var2: int | str

[erictraut]

Generally, we display parser errors unconditionally, but semantic errors that depend on type information are controlled by the reportGeneralTypeIssues diagnostic rule, which is off by default when typeCheckingMode is "off". We want to avoid showing any type-related errors that are potentially false positives when type checking is disabled.

In this particular case, I think an exception to this rule may be justified because the types in question are builtin types, and I can't think of any circumstance under which we'd generate a false positive error.

@jakebailey do you agree with that assessment?

[jakebailey]

I agree in general. Syntax errors are definite, but I am trying to think of some false positives. I suppose that this is no worse than getting an operand of | wrong, as it too requires type analysis, right? I'd think we are more likely to infer things as instance types and then hide the error than we are to infer variables to types themselves and then throw this error even in off mode...

[erictraut]

Thanks for the suggestion. This will be addressed in the next release.

[jakebailey]

This issue has been fixed in version 2021.2.1, which we've just released. You can find the changelog here: https://github.com/microsoft/pylance-release/blob/main/CHANGELOG.md#202121-10-february-2021