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perf: check names before context in the used-underscore lints #17408

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perf: check names before context in the used-underscore lints #17408

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55 changes: 32 additions & 23 deletions clippy_lints/src/misc.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ use rustc_hir::def::Res;
use rustc_hir::{BinOpKind, Expr, ExprKind, QPath, Stmt, StmtKind};
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_session::declare_lint_pass;
use rustc_span::Symbol;

declare_clippy_lint! {
/// ### What it does
Expand Down Expand Up @@ -125,53 +126,61 @@ impl<'tcx> LateLintPass<'tcx> for LintPass {
}

fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if expr.span.in_external_macro(cx.sess().source_map())
|| expr.span.desugaring_kind().is_some()
|| in_automatically_derived(cx.tcx, expr.hir_id)
{
return;
}

used_underscore_binding(cx, expr);
used_underscore_items(cx, expr);
}
}

/// Contexts the underscore lints ignore. Expensive, so only checked once an
/// underscore-prefixed name has been found.
fn in_ignored_context(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
expr.span.in_external_macro(cx.sess().source_map())
|| expr.span.desugaring_kind().is_some()
|| in_automatically_derived(cx.tcx, expr.hir_id)
}

fn is_underscore_prefixed(name: Symbol) -> bool {
let name = name.as_str();
name.starts_with('_') && !name.starts_with("__")
}

fn used_underscore_items<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
let (def_id, ident) = match expr.kind {
let def_id = match expr.kind {
ExprKind::Call(func, ..) => {
if let ExprKind::Path(QPath::Resolved(.., path)) = func.kind
&& let Some(last_segment) = path.segments.last()
&& is_underscore_prefixed(last_segment.ident.name)
&& let Res::Def(_, def_id) = last_segment.res
{
(def_id, last_segment.ident)
def_id
} else {
return;
}
},
ExprKind::MethodCall(path, ..) => {
if let Some(def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id) {
(def_id, path.ident)
if is_underscore_prefixed(path.ident.name)
&& let Some(def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id)
{
def_id
} else {
return;
}
},
ExprKind::Struct(QPath::Resolved(_, path), ..) => {
if let Some(last_segment) = path.segments.last()
&& is_underscore_prefixed(last_segment.ident.name)
&& let Res::Def(_, def_id) = last_segment.res
{
(def_id, last_segment.ident)
def_id
} else {
return;
}
},
_ => return,
};

let name = ident.name.as_str();
let definition_span = cx.tcx.def_span(def_id);
if name.starts_with('_')
&& !name.starts_with("__")
if !in_ignored_context(cx, expr)
&& let definition_span = cx.tcx.def_span(def_id)
&& !definition_span.from_expansion()
&& def_id.is_local()
&& !cx.tcx.is_foreign_item(def_id)
Expand All @@ -189,34 +198,34 @@ fn used_underscore_items<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
}

fn used_underscore_binding<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
let (definition_hir_id, ident) = match expr.kind {
let definition_hir_id = match expr.kind {
ExprKind::Path(ref qpath) => {
if let QPath::Resolved(None, path) = qpath
&& let Res::Local(id) = path.res
&& is_underscore_prefixed(last_path_segment(qpath).ident.name)
&& is_used(cx, expr)
{
(id, last_path_segment(qpath).ident)
id
} else {
return;
}
},
ExprKind::Field(recv, ident) => {
if let Some(adt_def) = cx.typeck_results().expr_ty_adjusted(recv).ty_adt_def()
if is_underscore_prefixed(ident.name)
&& let Some(adt_def) = cx.typeck_results().expr_ty_adjusted(recv).ty_adt_def()
&& let Some(field) = adt_def.all_fields().find(|field| field.name == ident.name)
&& let Some(local_did) = field.did.as_local()
&& !cx.tcx.type_of(field.did).skip_binder().is_phantom_data()
{
(cx.tcx.local_def_id_to_hir_id(local_did), ident)
cx.tcx.local_def_id_to_hir_id(local_did)
} else {
return;
}
},
_ => return,
};

let name = ident.name.as_str();
if name.starts_with('_')
&& !name.starts_with("__")
if !in_ignored_context(cx, expr)
&& let definition_span = cx.tcx.hir_span(definition_hir_id)
&& !definition_span.from_expansion()
&& !fulfill_or_allowed(cx, USED_UNDERSCORE_BINDING, [expr.hir_id, definition_hir_id])
Expand Down