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Better handle method/function calls
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@Serial-ATA
Serial-ATA committed Aug 5, 2022
1 parent 55e6fac commit d28e72b
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Showing 3 changed files with 49 additions and 37 deletions.
61 changes: 28 additions & 33 deletions clippy_lints/src/unused_peekable.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,9 +4,8 @@ use clippy_utils::{fn_def_id, path_to_local_id, paths, peel_ref_operators};
use rustc_ast::Mutability;
use rustc_hir::intravisit::{walk_expr, Visitor};
use rustc_hir::lang_items::LangItem;
use rustc_hir::{Block, Expr, ExprKind, HirId, Local, Node, PatKind, PathSegment, StmtKind};
use rustc_hir::{Block, Expr, ExprKind, HirId, Local, Node, PatKind, StmtKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty::Ty;
use rustc_session::{declare_tool_lint, impl_lint_pass};

declare_clippy_lint! {
Expand Down Expand Up @@ -117,6 +116,10 @@ impl<'a, 'tcx> PeekableVisitor<'a, 'tcx> {

impl<'tcx> Visitor<'_> for PeekableVisitor<'_, 'tcx> {
fn visit_expr(&mut self, ex: &'_ Expr<'_>) {
if self.found_peek_call {
return;
}

if path_to_local_id(ex, self.expected_hir_id) {
for (_, node) in self.cx.tcx.hir().parent_iter(ex.hir_id) {
match node {
Expand All @@ -138,50 +141,31 @@ impl<'tcx> Visitor<'_> for PeekableVisitor<'_, 'tcx> {
return;
}

for arg in args.iter().map(|arg| peel_ref_operators(self.cx, arg)) {
if let ExprKind::Path(_) = arg.kind
&& let Some(ty) = self
.cx
.typeck_results()
.expr_ty_opt(arg)
.map(Ty::peel_refs)
&& match_type(self.cx, ty, &paths::PEEKABLE)
{
self.found_peek_call = true;
return;
}
if args.iter().any(|arg| arg_is_mut_peekable(self.cx, arg)) {
self.found_peek_call = true;
return;
}
},
// Peekable::peek()
ExprKind::MethodCall(PathSegment { ident: method_name, .. }, [arg, ..], _) => {
// Catch anything taking a Peekable mutably
ExprKind::MethodCall(_, [arg, ..], _) => {
let arg = peel_ref_operators(self.cx, arg);
let method_name = method_name.name.as_str();

if (method_name == "peek"
|| method_name == "peek_mut"
|| method_name == "next_if"
|| method_name == "next_if_eq")
&& let ExprKind::Path(_) = arg.kind
&& let Some(ty) = self.cx.typeck_results().expr_ty_opt(arg).map(Ty::peel_refs)
&& match_type(self.cx, ty, &paths::PEEKABLE)
{

if arg_is_mut_peekable(self.cx, arg) {
self.found_peek_call = true;
return;
}
},
// Don't bother if moved into a struct
ExprKind::Struct(..) => {
ExprKind::AddrOf(_, Mutability::Mut, _) | ExprKind::Unary(..) | ExprKind::DropTemps(_) => {
},
ExprKind::AddrOf(_, Mutability::Not, _) => return,
_ => {
self.found_peek_call = true;
return;
},
_ => {},
}
},
Node::Local(Local { init: Some(init), .. }) => {
if let Some(ty) = self.cx.typeck_results().expr_ty_opt(init)
&& let (ty, _, Mutability::Mut) = peel_mid_ty_refs_is_mutable(ty)
&& match_type(self.cx, ty, &paths::PEEKABLE)
{
if arg_is_mut_peekable(self.cx, init) {
self.found_peek_call = true;
return;
}
Expand All @@ -206,3 +190,14 @@ impl<'tcx> Visitor<'_> for PeekableVisitor<'_, 'tcx> {
walk_expr(self, ex);
}
}

fn arg_is_mut_peekable(cx: &LateContext<'_>, arg: &Expr<'_>) -> bool {
if let Some(ty) = cx.typeck_results().expr_ty_opt(arg)
&& let (ty, _, Mutability::Mut) = peel_mid_ty_refs_is_mutable(ty)
&& match_type(cx, ty, &paths::PEEKABLE)
{
true
} else {
false
}
}
17 changes: 17 additions & 0 deletions tests/ui/unused_peekable.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,11 @@ fn invalid() {
let mut peekable_using_iterator_method = std::iter::empty::<u32>().peekable();
peekable_using_iterator_method.next();

// Passed by ref to another function
fn takes_ref(_peek: &Peekable<Empty<u32>>) {}
let passed_along_ref = std::iter::empty::<u32>().peekable();
takes_ref(&passed_along_ref);

let mut peekable_in_for_loop = std::iter::empty::<u32>().peekable();
for x in peekable_in_for_loop {}
}
Expand All @@ -43,6 +48,18 @@ fn valid() {
let passed_along = std::iter::empty::<u32>().peekable();
takes_peekable(passed_along);

// Passed to another method
struct PeekableConsumer;
impl PeekableConsumer {
fn consume(&self, _: Peekable<Empty<u32>>) {}
fn consume_mut_ref(&self, _: &mut Peekable<Empty<u32>>) {}
}

let peekable_consumer = PeekableConsumer;
let mut passed_along_to_method = std::iter::empty::<u32>().peekable();
peekable_consumer.consume_mut_ref(&mut passed_along_to_method);
peekable_consumer.consume(passed_along_to_method);

// `peek` called in another block
let mut peekable_in_block = std::iter::empty::<u32>().peekable();
{
Expand Down
8 changes: 4 additions & 4 deletions tests/ui/unused_peekable.stderr
View file
Original file line number Diff line number Diff line change
Expand Up @@ -32,15 +32,15 @@ LL | let peekable_from_fn = returns_peekable();
= help: consider removing the call to `peekable`

error: `peek` never called on `Peekable` iterator
--> $DIR/unused_peekable.rs:32:13
--> $DIR/unused_peekable.rs:37:9
|
LL | let mut peekable_using_iterator_method = std::iter::empty::<u32>().peekable();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
LL | let passed_along_ref = std::iter::empty::<u32>().peekable();
| ^^^^^^^^^^^^^^^^
|
= help: consider removing the call to `peekable`

error: `peek` never called on `Peekable` iterator
--> $DIR/unused_peekable.rs:35:13
--> $DIR/unused_peekable.rs:40:13
|
LL | let mut peekable_in_for_loop = std::iter::empty::<u32>().peekable();
| ^^^^^^^^^^^^^^^^^^^^
Expand Down

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