342 lines
12 KiB
Rust
342 lines
12 KiB
Rust
use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg, span_lint_hir_and_then};
|
|
use clippy_utils::source::{snippet, snippet_opt};
|
|
use if_chain::if_chain;
|
|
use rustc_ast::ast::LitKind;
|
|
use rustc_errors::Applicability;
|
|
use rustc_hir::intravisit::FnKind;
|
|
use rustc_hir::{
|
|
self as hir, def, BinOpKind, BindingAnnotation, Body, ByRef, Expr, ExprKind, FnDecl, HirId, Mutability, PatKind,
|
|
Stmt, StmtKind, TyKind,
|
|
};
|
|
use rustc_lint::{LateContext, LateLintPass};
|
|
use rustc_middle::lint::in_external_macro;
|
|
use rustc_session::{declare_lint_pass, declare_tool_lint};
|
|
use rustc_span::hygiene::DesugaringKind;
|
|
use rustc_span::source_map::{ExpnKind, Span};
|
|
|
|
use clippy_utils::sugg::Sugg;
|
|
use clippy_utils::{get_parent_expr, in_constant, iter_input_pats, last_path_segment, SpanlessEq};
|
|
|
|
declare_clippy_lint! {
|
|
/// ### What it does
|
|
/// Checks for function arguments and let bindings denoted as
|
|
/// `ref`.
|
|
///
|
|
/// ### Why is this bad?
|
|
/// The `ref` declaration makes the function take an owned
|
|
/// value, but turns the argument into a reference (which means that the value
|
|
/// is destroyed when exiting the function). This adds not much value: either
|
|
/// take a reference type, or take an owned value and create references in the
|
|
/// body.
|
|
///
|
|
/// For let bindings, `let x = &foo;` is preferred over `let ref x = foo`. The
|
|
/// type of `x` is more obvious with the former.
|
|
///
|
|
/// ### Known problems
|
|
/// If the argument is dereferenced within the function,
|
|
/// removing the `ref` will lead to errors. This can be fixed by removing the
|
|
/// dereferences, e.g., changing `*x` to `x` within the function.
|
|
///
|
|
/// ### Example
|
|
/// ```rust
|
|
/// fn foo(ref _x: u8) {}
|
|
/// ```
|
|
///
|
|
/// Use instead:
|
|
/// ```rust
|
|
/// fn foo(_x: &u8) {}
|
|
/// ```
|
|
#[clippy::version = "pre 1.29.0"]
|
|
pub TOPLEVEL_REF_ARG,
|
|
style,
|
|
"an entire binding declared as `ref`, in a function argument or a `let` statement"
|
|
}
|
|
declare_clippy_lint! {
|
|
/// ### What it does
|
|
/// Checks for the use of bindings with a single leading
|
|
/// underscore.
|
|
///
|
|
/// ### Why is this bad?
|
|
/// A single leading underscore is usually used to indicate
|
|
/// that a binding will not be used. Using such a binding breaks this
|
|
/// expectation.
|
|
///
|
|
/// ### Known problems
|
|
/// The lint does not work properly with desugaring and
|
|
/// macro, it has been allowed in the mean time.
|
|
///
|
|
/// ### Example
|
|
/// ```rust
|
|
/// let _x = 0;
|
|
/// let y = _x + 1; // Here we are using `_x`, even though it has a leading
|
|
/// // underscore. We should rename `_x` to `x`
|
|
/// ```
|
|
#[clippy::version = "pre 1.29.0"]
|
|
pub USED_UNDERSCORE_BINDING,
|
|
pedantic,
|
|
"using a binding which is prefixed with an underscore"
|
|
}
|
|
|
|
declare_clippy_lint! {
|
|
/// ### What it does
|
|
/// Checks for the use of short circuit boolean conditions as
|
|
/// a
|
|
/// statement.
|
|
///
|
|
/// ### Why is this bad?
|
|
/// Using a short circuit boolean condition as a statement
|
|
/// may hide the fact that the second part is executed or not depending on the
|
|
/// outcome of the first part.
|
|
///
|
|
/// ### Example
|
|
/// ```rust,ignore
|
|
/// f() && g(); // We should write `if f() { g(); }`.
|
|
/// ```
|
|
#[clippy::version = "pre 1.29.0"]
|
|
pub SHORT_CIRCUIT_STATEMENT,
|
|
complexity,
|
|
"using a short circuit boolean condition as a statement"
|
|
}
|
|
|
|
declare_clippy_lint! {
|
|
/// ### What it does
|
|
/// Catch casts from `0` to some pointer type
|
|
///
|
|
/// ### Why is this bad?
|
|
/// This generally means `null` and is better expressed as
|
|
/// {`std`, `core`}`::ptr::`{`null`, `null_mut`}.
|
|
///
|
|
/// ### Example
|
|
/// ```rust
|
|
/// let a = 0 as *const u32;
|
|
/// ```
|
|
///
|
|
/// Use instead:
|
|
/// ```rust
|
|
/// let a = std::ptr::null::<u32>();
|
|
/// ```
|
|
#[clippy::version = "pre 1.29.0"]
|
|
pub ZERO_PTR,
|
|
style,
|
|
"using `0 as *{const, mut} T`"
|
|
}
|
|
|
|
declare_lint_pass!(MiscLints => [
|
|
TOPLEVEL_REF_ARG,
|
|
USED_UNDERSCORE_BINDING,
|
|
SHORT_CIRCUIT_STATEMENT,
|
|
ZERO_PTR,
|
|
]);
|
|
|
|
impl<'tcx> LateLintPass<'tcx> for MiscLints {
|
|
fn check_fn(
|
|
&mut self,
|
|
cx: &LateContext<'tcx>,
|
|
k: FnKind<'tcx>,
|
|
decl: &'tcx FnDecl<'_>,
|
|
body: &'tcx Body<'_>,
|
|
span: Span,
|
|
_: HirId,
|
|
) {
|
|
if let FnKind::Closure = k {
|
|
// Does not apply to closures
|
|
return;
|
|
}
|
|
if in_external_macro(cx.tcx.sess, span) {
|
|
return;
|
|
}
|
|
for arg in iter_input_pats(decl, body) {
|
|
if let PatKind::Binding(BindingAnnotation(ByRef::Yes, _), ..) = arg.pat.kind {
|
|
span_lint(
|
|
cx,
|
|
TOPLEVEL_REF_ARG,
|
|
arg.pat.span,
|
|
"`ref` directly on a function argument is ignored. \
|
|
Consider using a reference type instead",
|
|
);
|
|
}
|
|
}
|
|
}
|
|
|
|
fn check_stmt(&mut self, cx: &LateContext<'tcx>, stmt: &'tcx Stmt<'_>) {
|
|
if_chain! {
|
|
if !in_external_macro(cx.tcx.sess, stmt.span);
|
|
if let StmtKind::Local(local) = stmt.kind;
|
|
if let PatKind::Binding(BindingAnnotation(ByRef::Yes, mutabl), .., name, None) = local.pat.kind;
|
|
if let Some(init) = local.init;
|
|
then {
|
|
// use the macro callsite when the init span (but not the whole local span)
|
|
// comes from an expansion like `vec![1, 2, 3]` in `let ref _ = vec![1, 2, 3];`
|
|
let sugg_init = if init.span.from_expansion() && !local.span.from_expansion() {
|
|
Sugg::hir_with_macro_callsite(cx, init, "..")
|
|
} else {
|
|
Sugg::hir(cx, init, "..")
|
|
};
|
|
let (mutopt, initref) = if mutabl == Mutability::Mut {
|
|
("mut ", sugg_init.mut_addr())
|
|
} else {
|
|
("", sugg_init.addr())
|
|
};
|
|
let tyopt = if let Some(ty) = local.ty {
|
|
format!(": &{mutopt}{ty}", mutopt=mutopt, ty=snippet(cx, ty.span, ".."))
|
|
} else {
|
|
String::new()
|
|
};
|
|
span_lint_hir_and_then(
|
|
cx,
|
|
TOPLEVEL_REF_ARG,
|
|
init.hir_id,
|
|
local.pat.span,
|
|
"`ref` on an entire `let` pattern is discouraged, take a reference with `&` instead",
|
|
|diag| {
|
|
diag.span_suggestion(
|
|
stmt.span,
|
|
"try",
|
|
format!(
|
|
"let {name}{tyopt} = {initref};",
|
|
name=snippet(cx, name.span, ".."),
|
|
tyopt=tyopt,
|
|
initref=initref,
|
|
),
|
|
Applicability::MachineApplicable,
|
|
);
|
|
}
|
|
);
|
|
}
|
|
};
|
|
if_chain! {
|
|
if let StmtKind::Semi(expr) = stmt.kind;
|
|
if let ExprKind::Binary(ref binop, a, b) = expr.kind;
|
|
if binop.node == BinOpKind::And || binop.node == BinOpKind::Or;
|
|
if let Some(sugg) = Sugg::hir_opt(cx, a);
|
|
then {
|
|
span_lint_hir_and_then(
|
|
cx,
|
|
SHORT_CIRCUIT_STATEMENT,
|
|
expr.hir_id,
|
|
stmt.span,
|
|
"boolean short circuit operator in statement may be clearer using an explicit test",
|
|
|diag| {
|
|
let sugg = if binop.node == BinOpKind::Or { !sugg } else { sugg };
|
|
diag.span_suggestion(
|
|
stmt.span,
|
|
"replace it with",
|
|
format!(
|
|
"if {} {{ {}; }}",
|
|
sugg,
|
|
&snippet(cx, b.span, ".."),
|
|
),
|
|
Applicability::MachineApplicable, // snippet
|
|
);
|
|
});
|
|
}
|
|
};
|
|
}
|
|
|
|
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
|
|
if let ExprKind::Cast(e, ty) = expr.kind {
|
|
check_cast(cx, expr.span, e, ty);
|
|
return;
|
|
}
|
|
if in_attributes_expansion(expr) || expr.span.is_desugaring(DesugaringKind::Await) {
|
|
// Don't lint things expanded by #[derive(...)], etc or `await` desugaring
|
|
return;
|
|
}
|
|
let sym;
|
|
let binding = match expr.kind {
|
|
ExprKind::Path(ref qpath) if !matches!(qpath, hir::QPath::LangItem(..)) => {
|
|
let binding = last_path_segment(qpath).ident.as_str();
|
|
if binding.starts_with('_') &&
|
|
!binding.starts_with("__") &&
|
|
binding != "_result" && // FIXME: #944
|
|
is_used(cx, expr) &&
|
|
// don't lint if the declaration is in a macro
|
|
non_macro_local(cx, cx.qpath_res(qpath, expr.hir_id))
|
|
{
|
|
Some(binding)
|
|
} else {
|
|
None
|
|
}
|
|
},
|
|
ExprKind::Field(_, ident) => {
|
|
sym = ident.name;
|
|
let name = sym.as_str();
|
|
if name.starts_with('_') && !name.starts_with("__") {
|
|
Some(name)
|
|
} else {
|
|
None
|
|
}
|
|
},
|
|
_ => None,
|
|
};
|
|
if let Some(binding) = binding {
|
|
span_lint(
|
|
cx,
|
|
USED_UNDERSCORE_BINDING,
|
|
expr.span,
|
|
&format!(
|
|
"used binding `{}` which is prefixed with an underscore. A leading \
|
|
underscore signals that a binding will not be used",
|
|
binding
|
|
),
|
|
);
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Heuristic to see if an expression is used. Should be compatible with
|
|
/// `unused_variables`'s idea
|
|
/// of what it means for an expression to be "used".
|
|
fn is_used(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
|
|
get_parent_expr(cx, expr).map_or(true, |parent| match parent.kind {
|
|
ExprKind::Assign(_, rhs, _) | ExprKind::AssignOp(_, _, rhs) => SpanlessEq::new(cx).eq_expr(rhs, expr),
|
|
_ => is_used(cx, parent),
|
|
})
|
|
}
|
|
|
|
/// Tests whether an expression is in a macro expansion (e.g., something
|
|
/// generated by `#[derive(...)]` or the like).
|
|
fn in_attributes_expansion(expr: &Expr<'_>) -> bool {
|
|
use rustc_span::hygiene::MacroKind;
|
|
if expr.span.from_expansion() {
|
|
let data = expr.span.ctxt().outer_expn_data();
|
|
matches!(data.kind, ExpnKind::Macro(MacroKind::Attr | MacroKind::Derive, _))
|
|
} else {
|
|
false
|
|
}
|
|
}
|
|
|
|
/// Tests whether `res` is a variable defined outside a macro.
|
|
fn non_macro_local(cx: &LateContext<'_>, res: def::Res) -> bool {
|
|
if let def::Res::Local(id) = res {
|
|
!cx.tcx.hir().span(id).from_expansion()
|
|
} else {
|
|
false
|
|
}
|
|
}
|
|
|
|
fn check_cast(cx: &LateContext<'_>, span: Span, e: &Expr<'_>, ty: &hir::Ty<'_>) {
|
|
if_chain! {
|
|
if let TyKind::Ptr(ref mut_ty) = ty.kind;
|
|
if let ExprKind::Lit(ref lit) = e.kind;
|
|
if let LitKind::Int(0, _) = lit.node;
|
|
if !in_constant(cx, e.hir_id);
|
|
then {
|
|
let (msg, sugg_fn) = match mut_ty.mutbl {
|
|
Mutability::Mut => ("`0 as *mut _` detected", "std::ptr::null_mut"),
|
|
Mutability::Not => ("`0 as *const _` detected", "std::ptr::null"),
|
|
};
|
|
|
|
let (sugg, appl) = if let TyKind::Infer = mut_ty.ty.kind {
|
|
(format!("{}()", sugg_fn), Applicability::MachineApplicable)
|
|
} else if let Some(mut_ty_snip) = snippet_opt(cx, mut_ty.ty.span) {
|
|
(format!("{}::<{}>()", sugg_fn, mut_ty_snip), Applicability::MachineApplicable)
|
|
} else {
|
|
// `MaybeIncorrect` as type inference may not work with the suggested code
|
|
(format!("{}()", sugg_fn), Applicability::MaybeIncorrect)
|
|
};
|
|
span_lint_and_sugg(cx, ZERO_PTR, span, msg, "try", sugg, appl);
|
|
}
|
|
}
|
|
}
|