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Suggest ptr::null, ptr::null_mut over casting. #1047

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Stebalien opened this issue Jun 27, 2016 · 7 comments · Fixed by #1561
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Suggest ptr::null, ptr::null_mut over casting. #1047

Stebalien opened this issue Jun 27, 2016 · 7 comments · Fixed by #1561
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A-lint Area: New lints good-first-issue These issues are a good way to get started with Clippy L-style Lint: Belongs in the style lint group T-AST Type: Requires working with the AST

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@Stebalien
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Add a lint to suggest converting all instances of:

0 as *const T;
0 as *mut T;

To:

std::ptr::null();
std::ptr::null_mut();

See rust-lang/rust#34456
@oli-obk
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oli-obk commented Jun 27, 2016

These are also in core. We should probably figure out whether no_std is set and suggest core::ptr::* in that case.

@mcarton
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mcarton commented Jun 27, 2016

We should probably figure out whether no_std is set and suggest core::ptr::* in that case.

This could be done for a lot a paths in suggestions.

@mcarton mcarton added good-first-issue These issues are a good way to get started with Clippy A-lint Area: New lints T-AST Type: Requires working with the AST L-style Lint: Belongs in the style lint group labels Jun 27, 2016
@llogiq
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llogiq commented Jun 27, 2016

Sounds like we could use a utility function that walks the parent chain to look for #[no_std].

@mcarton
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mcarton commented Jun 27, 2016

You don't even need to walk the parent chain, the current crate is available as LateContext::krate which has attributes.

@llogiq
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llogiq commented Jun 28, 2016

True. I had forgotten that this attribute is crate-level only.

@alilleybrinker
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I'm happy to give this a shot.

@mcarton
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mcarton commented Oct 27, 2016

Great! Feel free to ask if you have any question.

llogiq added a commit that referenced this issue Feb 21, 2017
@llogiq
New zero_ptr lint.
2f7babb 
This fixes #1047. I did not bother to add a full suggestion,
because replacing with `std::ptr::null()` may still lead to
inference failures.
@llogiq llogiq mentioned this issue Feb 21, 2017
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A-lint Area: New lints good-first-issue These issues are a good way to get started with Clippy L-style Lint: Belongs in the style lint group T-AST Type: Requires working with the AST
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New zero_ptr lint. rust-lang/rust-clippy
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@Stebalien @oli-obk @alilleybrinker @mcarton @llogiq