244 lines
8.6 KiB
Rust
244 lines
8.6 KiB
Rust
use crate::rustc_lint::LintContext;
|
|
use clippy_utils::diagnostics::{span_lint, span_lint_and_then};
|
|
use clippy_utils::get_parent_expr;
|
|
use clippy_utils::sugg::Sugg;
|
|
use if_chain::if_chain;
|
|
use rustc_errors::Applicability;
|
|
use rustc_hir as hir;
|
|
use rustc_hir::intravisit as hir_visit;
|
|
use rustc_hir::intravisit::{Visitor as HirVisitor, Visitor};
|
|
use rustc_lint::{LateContext, LateLintPass};
|
|
use rustc_middle::hir::nested_filter;
|
|
use rustc_middle::lint::in_external_macro;
|
|
use rustc_middle::ty;
|
|
use rustc_session::{declare_lint_pass, declare_tool_lint};
|
|
|
|
declare_clippy_lint! {
|
|
/// ### What it does
|
|
/// Detects closures called in the same expression where they
|
|
/// are defined.
|
|
///
|
|
/// ### Why is this bad?
|
|
/// It is unnecessarily adding to the expression's
|
|
/// complexity.
|
|
///
|
|
/// ### Example
|
|
/// ```rust
|
|
/// let a = (|| 42)();
|
|
/// ```
|
|
///
|
|
/// Use instead:
|
|
/// ```rust
|
|
/// let a = 42;
|
|
/// ```
|
|
#[clippy::version = "pre 1.29.0"]
|
|
pub REDUNDANT_CLOSURE_CALL,
|
|
complexity,
|
|
"throwaway closures called in the expression they are defined"
|
|
}
|
|
|
|
declare_lint_pass!(RedundantClosureCall => [REDUNDANT_CLOSURE_CALL]);
|
|
|
|
// Used to find `return` statements or equivalents e.g., `?`
|
|
struct ReturnVisitor {
|
|
found_return: bool,
|
|
}
|
|
|
|
impl ReturnVisitor {
|
|
#[must_use]
|
|
fn new() -> Self {
|
|
Self { found_return: false }
|
|
}
|
|
}
|
|
|
|
impl<'tcx> Visitor<'tcx> for ReturnVisitor {
|
|
fn visit_expr(&mut self, ex: &'tcx hir::Expr<'tcx>) {
|
|
if let hir::ExprKind::Ret(_) | hir::ExprKind::Match(.., hir::MatchSource::TryDesugar(_)) = ex.kind {
|
|
self.found_return = true;
|
|
} else {
|
|
hir_visit::walk_expr(self, ex);
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Checks if the body is owned by an async closure
|
|
fn is_async_closure(body: &hir::Body<'_>) -> bool {
|
|
if let hir::ExprKind::Closure(closure) = body.value.kind
|
|
&& let [resume_ty] = closure.fn_decl.inputs
|
|
&& let hir::TyKind::Path(hir::QPath::LangItem(hir::LangItem::ResumeTy, ..)) = resume_ty.kind
|
|
{
|
|
true
|
|
} else {
|
|
false
|
|
}
|
|
}
|
|
|
|
/// Tries to find the innermost closure:
|
|
/// ```rust,ignore
|
|
/// (|| || || || 42)()()()()
|
|
/// ^^^^^^^^^^^^^^ given this nested closure expression
|
|
/// ^^^^^ we want to return this closure
|
|
/// ```
|
|
/// It also has a parameter for how many steps to go in at most, so as to
|
|
/// not take more closures than there are calls.
|
|
fn find_innermost_closure<'tcx>(
|
|
cx: &LateContext<'tcx>,
|
|
mut expr: &'tcx hir::Expr<'tcx>,
|
|
mut steps: usize,
|
|
) -> Option<(&'tcx hir::Expr<'tcx>, &'tcx hir::FnDecl<'tcx>, ty::Asyncness)> {
|
|
let mut data = None;
|
|
|
|
while let hir::ExprKind::Closure(closure) = expr.kind
|
|
&& let body = cx.tcx.hir().body(closure.body)
|
|
&& {
|
|
let mut visitor = ReturnVisitor::new();
|
|
visitor.visit_expr(body.value);
|
|
!visitor.found_return
|
|
}
|
|
&& steps > 0
|
|
{
|
|
expr = body.value;
|
|
data = Some((body.value, closure.fn_decl, if is_async_closure(body) {
|
|
ty::Asyncness::Yes
|
|
} else {
|
|
ty::Asyncness::No
|
|
}));
|
|
steps -= 1;
|
|
}
|
|
|
|
data
|
|
}
|
|
|
|
/// "Walks up" the chain of calls to find the outermost call expression, and returns the depth:
|
|
/// ```rust,ignore
|
|
/// (|| || || 3)()()()
|
|
/// ^^ this is the call expression we were given
|
|
/// ^^ this is what we want to return (and the depth is 3)
|
|
/// ```
|
|
fn get_parent_call_exprs<'tcx>(
|
|
cx: &LateContext<'tcx>,
|
|
mut expr: &'tcx hir::Expr<'tcx>,
|
|
) -> (&'tcx hir::Expr<'tcx>, usize) {
|
|
let mut depth = 1;
|
|
while let Some(parent) = get_parent_expr(cx, expr)
|
|
&& let hir::ExprKind::Call(recv, _) = parent.kind
|
|
&& expr.span == recv.span
|
|
{
|
|
expr = parent;
|
|
depth += 1;
|
|
}
|
|
(expr, depth)
|
|
}
|
|
|
|
impl<'tcx> LateLintPass<'tcx> for RedundantClosureCall {
|
|
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
|
|
if in_external_macro(cx.sess(), expr.span) {
|
|
return;
|
|
}
|
|
|
|
if let hir::ExprKind::Call(recv, _) = expr.kind
|
|
// don't lint if the receiver is a call, too.
|
|
// we do this in order to prevent linting multiple times; consider:
|
|
// `(|| || 1)()()`
|
|
// ^^ we only want to lint for this call (but we walk up the calls to consider both calls).
|
|
// without this check, we'd end up linting twice.
|
|
&& !matches!(recv.kind, hir::ExprKind::Call(..))
|
|
&& let (full_expr, call_depth) = get_parent_call_exprs(cx, expr)
|
|
&& let Some((body, fn_decl, coroutine_kind)) = find_innermost_closure(cx, recv, call_depth)
|
|
{
|
|
span_lint_and_then(
|
|
cx,
|
|
REDUNDANT_CLOSURE_CALL,
|
|
full_expr.span,
|
|
"try not to call a closure in the expression where it is declared",
|
|
|diag| {
|
|
if fn_decl.inputs.is_empty() {
|
|
let mut applicability = Applicability::MachineApplicable;
|
|
let mut hint = Sugg::hir_with_context(cx, body, full_expr.span.ctxt(), "..", &mut applicability);
|
|
|
|
if coroutine_kind.is_async()
|
|
&& let hir::ExprKind::Closure(closure) = body.kind
|
|
{
|
|
let async_closure_body = cx.tcx.hir().body(closure.body);
|
|
|
|
// `async x` is a syntax error, so it becomes `async { x }`
|
|
if !matches!(async_closure_body.value.kind, hir::ExprKind::Block(_, _)) {
|
|
hint = hint.blockify();
|
|
}
|
|
|
|
hint = hint.asyncify();
|
|
}
|
|
|
|
diag.span_suggestion(
|
|
full_expr.span,
|
|
"try doing something like",
|
|
hint.maybe_par(),
|
|
applicability
|
|
);
|
|
}
|
|
}
|
|
);
|
|
}
|
|
}
|
|
|
|
fn check_block(&mut self, cx: &LateContext<'tcx>, block: &'tcx hir::Block<'_>) {
|
|
fn count_closure_usage<'tcx>(
|
|
cx: &LateContext<'tcx>,
|
|
block: &'tcx hir::Block<'_>,
|
|
path: &'tcx hir::Path<'tcx>,
|
|
) -> usize {
|
|
struct ClosureUsageCount<'a, 'tcx> {
|
|
cx: &'a LateContext<'tcx>,
|
|
path: &'tcx hir::Path<'tcx>,
|
|
count: usize,
|
|
}
|
|
impl<'a, 'tcx> hir_visit::Visitor<'tcx> for ClosureUsageCount<'a, 'tcx> {
|
|
type NestedFilter = nested_filter::OnlyBodies;
|
|
|
|
fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
|
|
if_chain! {
|
|
if let hir::ExprKind::Call(closure, _) = expr.kind;
|
|
if let hir::ExprKind::Path(hir::QPath::Resolved(_, path)) = closure.kind;
|
|
if self.path.segments[0].ident == path.segments[0].ident;
|
|
if self.path.res == path.res;
|
|
then {
|
|
self.count += 1;
|
|
}
|
|
}
|
|
hir_visit::walk_expr(self, expr);
|
|
}
|
|
|
|
fn nested_visit_map(&mut self) -> Self::Map {
|
|
self.cx.tcx.hir()
|
|
}
|
|
}
|
|
let mut closure_usage_count = ClosureUsageCount { cx, path, count: 0 };
|
|
closure_usage_count.visit_block(block);
|
|
closure_usage_count.count
|
|
}
|
|
|
|
for w in block.stmts.windows(2) {
|
|
if_chain! {
|
|
if let hir::StmtKind::Local(local) = w[0].kind;
|
|
if let Option::Some(t) = local.init;
|
|
if let hir::ExprKind::Closure { .. } = t.kind;
|
|
if let hir::PatKind::Binding(_, _, ident, _) = local.pat.kind;
|
|
if let hir::StmtKind::Semi(second) = w[1].kind;
|
|
if let hir::ExprKind::Assign(_, call, _) = second.kind;
|
|
if let hir::ExprKind::Call(closure, _) = call.kind;
|
|
if let hir::ExprKind::Path(hir::QPath::Resolved(_, path)) = closure.kind;
|
|
if ident == path.segments[0].ident;
|
|
if count_closure_usage(cx, block, path) == 1;
|
|
then {
|
|
span_lint(
|
|
cx,
|
|
REDUNDANT_CLOSURE_CALL,
|
|
second.span,
|
|
"closure called just once immediately after it was declared",
|
|
);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|