63ef74b6aa
Uplift `clippy::fn_null_check` lint
This PR aims at uplifting the `clippy::fn_null_check` lint into rustc.
## `incorrect_fn_null_checks`
(warn-by-default)
The `incorrect_fn_null_checks` lint checks for expression that checks if a function pointer is null.
### Example
```rust
let fn_ptr: fn() = /* somehow obtained nullable function pointer */
if (fn_ptr as *const ()).is_null() { /* ... */ }
```
### Explanation
Function pointers are assumed to be non-null, checking for their nullity is incorrect.
-----
Mostly followed the instructions for uplifting a clippy lint described here: https://github.com/rust-lang/rust/pull/99696#pullrequestreview-1134072751
`@rustbot` label: +I-lang-nominated
r? compiler
|
||
|---|---|---|
| .. | ||
| nonstandard_style | ||
| array_into_iter.rs | ||
| builtin.rs | ||
| cast_ref_to_mut.rs | ||
| context.rs | ||
| deref_into_dyn_supertrait.rs | ||
| drop_forget_useless.rs | ||
| early.rs | ||
| enum_intrinsics_non_enums.rs | ||
| errors.rs | ||
| expect.rs | ||
| fn_null_check.rs | ||
| for_loops_over_fallibles.rs | ||
| hidden_unicode_codepoints.rs | ||
| internal.rs | ||
| invalid_from_utf8.rs | ||
| late.rs | ||
| let_underscore.rs | ||
| levels.rs | ||
| lib.rs | ||
| lints.rs | ||
| map_unit_fn.rs | ||
| methods.rs | ||
| multiple_supertrait_upcastable.rs | ||
| non_ascii_idents.rs | ||
| non_fmt_panic.rs | ||
| nonstandard_style.rs | ||
| noop_method_call.rs | ||
| opaque_hidden_inferred_bound.rs | ||
| pass_by_value.rs | ||
| passes.rs | ||
| redundant_semicolon.rs | ||
| tests.rs | ||
| traits.rs | ||
| types.rs | ||
| unused.rs | ||