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Auto merge of #111717 - Urgau:uplift_fn_null_check, r=oli-obk

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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
This commit is contained in:
bors 2023-07-11 09:34:48 +00:00
commit a8939e5eae
9 changed files with 64 additions and 223 deletions
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1
clippy_lints/src/declared_lints.rs
View file

@ -171,7 +171,6 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
crate::float_literal::LOSSY_FLOAT_LITERAL_INFO,
crate::floating_point_arithmetic::IMPRECISE_FLOPS_INFO,
crate::floating_point_arithmetic::SUBOPTIMAL_FLOPS_INFO,
crate::fn_null_check::FN_NULL_CHECK_INFO,
crate::format::USELESS_FORMAT_INFO,
crate::format_args::FORMAT_IN_FORMAT_ARGS_INFO,
crate::format_args::TO_STRING_IN_FORMAT_ARGS_INFO,

102
clippy_lints/src/fn_null_check.rs
View file

@ -1,102 +0,0 @@
use clippy_utils::consts::{constant, Constant};
use clippy_utils::diagnostics::span_lint_and_help;
use clippy_utils::{is_integer_literal, is_path_diagnostic_item};
use rustc_hir::{BinOpKind, Expr, ExprKind, TyKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::sym;
declare_clippy_lint! {
/// ### What it does
/// Checks for comparing a function pointer to null.
///
/// ### Why is this bad?
/// Function pointers are assumed to not be null.
///
/// ### Example
/// ```rust,ignore
/// let fn_ptr: fn() = /* somehow obtained nullable function pointer */
///
/// if (fn_ptr as *const ()).is_null() { ... }
/// ```
/// Use instead:
/// ```rust,ignore
/// let fn_ptr: Option<fn()> = /* somehow obtained nullable function pointer */
///
/// if fn_ptr.is_none() { ... }
/// ```
#[clippy::version = "1.68.0"]
pub FN_NULL_CHECK,
correctness,
"`fn()` type assumed to be nullable"
}
declare_lint_pass!(FnNullCheck => [FN_NULL_CHECK]);
fn lint_expr(cx: &LateContext<'_>, expr: &Expr<'_>) {
span_lint_and_help(
cx,
FN_NULL_CHECK,
expr.span,
"function pointer assumed to be nullable, even though it isn't",
None,
"try wrapping your function pointer type in `Option<T>` instead, and using `is_none` to check for null pointer value",
);
}
fn is_fn_ptr_cast(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
if let ExprKind::Cast(cast_expr, cast_ty) = expr.kind
&& let TyKind::Ptr(_) = cast_ty.kind
{
cx.typeck_results().expr_ty_adjusted(cast_expr).is_fn()
} else {
false
}
}
impl<'tcx> LateLintPass<'tcx> for FnNullCheck {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
match expr.kind {
// Catching:
// (fn_ptr as *<const/mut> <ty>).is_null()
ExprKind::MethodCall(method_name, receiver, _, _)
if method_name.ident.as_str() == "is_null" && is_fn_ptr_cast(cx, receiver) =>
{
lint_expr(cx, expr);
},
ExprKind::Binary(op, left, right) if matches!(op.node, BinOpKind::Eq) => {
let to_check: &Expr<'_>;
if is_fn_ptr_cast(cx, left) {
to_check = right;
} else if is_fn_ptr_cast(cx, right) {
to_check = left;
} else {
return;
}
match to_check.kind {
// Catching:
// (fn_ptr as *<const/mut> <ty>) == (0 as <ty>)
ExprKind::Cast(cast_expr, _) if is_integer_literal(cast_expr, 0) => {
lint_expr(cx, expr);
},
// Catching:
// (fn_ptr as *<const/mut> <ty>) == std::ptr::null()
ExprKind::Call(func, []) if is_path_diagnostic_item(cx, func, sym::ptr_null) => {
lint_expr(cx, expr);
},
// Catching:
// (fn_ptr as *<const/mut> <ty>) == <const that evaluates to null_ptr>
_ if matches!(constant(cx, cx.typeck_results(), to_check), Some(Constant::RawPtr(0))) => {
lint_expr(cx, expr);
},
_ => {},
}
},
_ => {},
}
}
}

2
clippy_lints/src/lib.rs
View file

@ -131,7 +131,6 @@ mod extra_unused_type_parameters;
mod fallible_impl_from;
mod float_literal;
mod floating_point_arithmetic;
mod fn_null_check;
mod format;
mod format_args;
mod format_impl;
@ -1003,7 +1002,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
semicolon_outside_block_ignore_multiline,
))
});
store.register_late_pass(|_| Box::new(fn_null_check::FnNullCheck));
store.register_late_pass(|_| Box::new(permissions_set_readonly_false::PermissionsSetReadonlyFalse));
store.register_late_pass(|_| Box::new(size_of_ref::SizeOfRef));
store.register_late_pass(|_| Box::new(multiple_unsafe_ops_per_block::MultipleUnsafeOpsPerBlock));

1
clippy_lints/src/renamed_lints.rs
View file

@ -42,6 +42,7 @@ pub static RENAMED_LINTS: &[(&str, &str)] = &[
("clippy::for_loops_over_fallibles", "for_loops_over_fallibles"),
("clippy::forget_copy", "forgetting_copy_types"),
("clippy::forget_ref", "forgetting_references"),
("clippy::fn_null_check", "incorrect_fn_null_checks"),
("clippy::into_iter_on_array", "array_into_iter"),
("clippy::invalid_atomic_ordering", "invalid_atomic_ordering"),
("clippy::invalid_ref", "invalid_value"),