Not reporting any error when function returns bool type while expecting str type

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使用 mypy 0.782、Python 3.7.7 以及列出的 --strict-equality 和 --ignore-missing-imports 选项复现报告中的函数，然后将诊断信息与预期的返回类型错误进行比较。跟踪返回表达式和未知类型的类型检查路径；当行为得到修正，或通过回归测试得到清晰记录时，即视为完成。

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描述

feature

Hi

I noticed a situation where I wasn't getting a type error from mypy when I would have expected to get one.

Below is the code I have. I purposefully set the return type to str because I wanted to see a mypy error, and specifically I expected the error to be that I had set the wrong return type (e.g. as the code is doing a comparison, which will thus return a bool type, I expected mypy to say the return type should be of type bool):

def is_dev() -> str:
    return settings.get("environment") == "dev"

In that code snippet you'll see settings.get(...), which is a function that returns a string, and we compare that string against another string.

Note: as settings.get is custom code, mypy knows nothing about what type is being returned.

My hypothesis is that because my specific example uses code that mypy can't identify the type for (i.e. settings.get()), mypy just goes ahead and ignores any other possible type check errors (such as me specifying the return type as str).

If that's expected of mypy then fine, but it just confused me.

I'm using mypy version 0.782 and Python version 3.7.7.

I'm running mypy in two places:

  1. vim integration (e.g. mypy --ignore-missing-imports --strict-equality)
  2. tox (e.g. mypy --ignore-missing-imports --package foo)

Note: I've tried also changing to --no-strict-equality and it makes no difference.

Thank you for any guidance you can give me.

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