Warn about redundant casts #1705
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A cast is considered redundant if the target type of the cast is the same as the inferred type of the expression. A cast to a supertype like `cast(object, 1)` is not considered redundant because such a cast could be needed to work around deficiencies in type inference. Fixes python#958.
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carljm
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## Summary Following up from earlier discussion on Discord, this PR adds logic to flag casts as redundant when the inferred type of the expression is the same as the target type. It should follow the semantics from [mypy](python/mypy#1705). Example: ```python def f() -> int: return 10 # error: [redundant-cast] "Value is already of type `int`" cast(int, f()) ```
hauntsaninja
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while working on #18540 (which my original prototype based the code on `warn-redundant-casts`) I noticed the suggestion [here](#18540 (comment)) would probably make sense to apply to redundant-cast as well! I also made sure to include the example from the [original implementation](#1705 (comment)) just to make sure I wasn't regressing that as well since it seemed related.
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A cast is considered redundant if the target type of the cast is the
same as the inferred type of the expression. A cast to a supertype
like
cast(object, 1)is not considered redundant because such a castcould be needed to work around deficiencies in type inference.
Fixes #958.