Add new lint zero_repeat_side_effects

[Jacherr]

Fixes #6439

Adds a new suspicious lint zero_repeat_side_effects. This lint warns the user when initializing an array or Vec using the Repeat syntax, i.e., [x; y]. If x is an Expr::Call/MethodCall or contains an Expr::Call/MethodCall and y is zero, then there is a chance that the internal call can produce side effects, such as printing to console, which is not very obvious.

This lint warns against this and instead suggests to separate out the function call and the array/Vec initialization.

changelog: Add new lint zero_repeat_side_effects

[rustbot]

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[llogiq]

This looks good. As a possible extension, we have a quasi-purity test in must_use_candidate that could even allow us to suggest getting rid of the call altogether (although the user should check that, the test might fail to find some side effects).

[llogiq]

@bors r+

[bors]

📌 Commit 0c82fd0 has been approved by llogiq

It is now in the queue for this repository.

[bors]

⌛ Testing commit 0c82fd0 with merge d8a9068...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: llogiq
Pushing d8a9068 to master...