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Extract util functions from redundant_pattern_match 
1 parent 650a0e5 commit 2f41ce4

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3 files changed

+191
-141
lines changed

3 files changed

+191
-141
lines changed

‎clippy_lints/src/matches/redundant_pattern_match.rs

Lines changed: 5 additions & 135 deletions
Original file line numberDiff line numberDiff line change
@@ -2,18 +2,14 @@ use super::REDUNDANT_PATTERN_MATCHING;
22
use clippy_utils::diagnostics::span_lint_and_then;
33
use clippy_utils::source::snippet;
44
use clippy_utils::sugg::Sugg;
5-
use clippy_utils::ty::{implements_trait, is_type_diagnostic_item, is_type_lang_item, match_type};
6-
use clippy_utils::{higher, match_def_path};
7-
use clippy_utils::{is_lang_ctor, is_trait_method, paths};
5+
use clippy_utils::ty::type_needs_ordered_drop;
6+
use clippy_utils::visitors::any_temporaries_need_ordered_drop;
7+
use clippy_utils::{higher, is_lang_ctor, is_trait_method, match_def_path, paths};
88
use if_chain::if_chain;
99
use rustc_ast::ast::LitKind;
10-
use rustc_data_structures::fx::FxHashSet;
1110
use rustc_errors::Applicability;
1211
use rustc_hir::LangItem::{OptionNone, PollPending};
13-
use rustc_hir::{
14-
intravisit::{walk_expr, Visitor},
15-
Arm, Block, Expr, ExprKind, LangItem, Node, Pat, PatKind, QPath, UnOp,
16-
};
12+
use rustc_hir::{Arm, Expr, ExprKind, Node, Pat, PatKind, QPath, UnOp};
1713
use rustc_lint::LateContext;
1814
use rustc_middle::ty::{self, subst::GenericArgKind, DefIdTree, Ty};
1915
use rustc_span::sym;
@@ -32,59 +28,6 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
3228
}
3329
}
3430

35-
/// Checks if the drop order for a type matters. Some std types implement drop solely to
36-
/// deallocate memory. For these types, and composites containing them, changing the drop order
37-
/// won't result in any observable side effects.
38-
fn type_needs_ordered_drop<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
39-
type_needs_ordered_drop_inner(cx, ty, &mut FxHashSet::default())
40-
}
41-
42-
fn type_needs_ordered_drop_inner<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, seen: &mut FxHashSet<Ty<'tcx>>) -> bool {
43-
if !seen.insert(ty) {
44-
return false;
45-
}
46-
if !ty.needs_drop(cx.tcx, cx.param_env) {
47-
false
48-
} else if !cx
49-
.tcx
50-
.lang_items()
51-
.drop_trait()
52-
.map_or(false, |id| implements_trait(cx, ty, id, &[]))
53-
{
54-
// This type doesn't implement drop, so no side effects here.
55-
// Check if any component type has any.
56-
match ty.kind() {
57-
ty::Tuple(fields) => fields.iter().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)),
58-
ty::Array(ty, _) => type_needs_ordered_drop_inner(cx, *ty, seen),
59-
ty::Adt(adt, subs) => adt
60-
.all_fields()
61-
.map(|f| f.ty(cx.tcx, subs))
62-
.any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)),
63-
_ => true,
64-
}
65-
}
66-
// Check for std types which implement drop, but only for memory allocation.
67-
else if is_type_diagnostic_item(cx, ty, sym::Vec)
68-
|| is_type_lang_item(cx, ty, LangItem::OwnedBox)
69-
|| is_type_diagnostic_item(cx, ty, sym::Rc)
70-
|| is_type_diagnostic_item(cx, ty, sym::Arc)
71-
|| is_type_diagnostic_item(cx, ty, sym::cstring_type)
72-
|| is_type_diagnostic_item(cx, ty, sym::BTreeMap)
73-
|| is_type_diagnostic_item(cx, ty, sym::LinkedList)
74-
|| match_type(cx, ty, &paths::WEAK_RC)
75-
|| match_type(cx, ty, &paths::WEAK_ARC)
76-
{
77-
// Check all of the generic arguments.
78-
if let ty::Adt(_, subs) = ty.kind() {
79-
subs.types().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen))
80-
} else {
81-
true
82-
}
83-
} else {
84-
true
85-
}
86-
}
87-
8831
// Extract the generic arguments out of a type
8932
fn try_get_generic_ty(ty: Ty<'_>, index: usize) -> Option<Ty<'_>> {
9033
if_chain! {
@@ -99,79 +42,6 @@ fn try_get_generic_ty(ty: Ty<'_>, index: usize) -> Option<Ty<'_>> {
9942
}
10043
}
10144

102-
// Checks if there are any temporaries created in the given expression for which drop order
103-
// matters.
104-
fn temporaries_need_ordered_drop<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
105-
struct V<'a, 'tcx> {
106-
cx: &'a LateContext<'tcx>,
107-
res: bool,
108-
}
109-
impl<'a, 'tcx> Visitor<'tcx> for V<'a, 'tcx> {
110-
fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
111-
match expr.kind {
112-
// Taking the reference of a value leaves a temporary
113-
// e.g. In `&String::new()` the string is a temporary value.
114-
// Remaining fields are temporary values
115-
// e.g. In `(String::new(), 0).1` the string is a temporary value.
116-
ExprKind::AddrOf(_, _, expr) | ExprKind::Field(expr, _) => {
117-
if !matches!(expr.kind, ExprKind::Path(_)) {
118-
if type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(expr)) {
119-
self.res = true;
120-
} else {
121-
self.visit_expr(expr);
122-
}
123-
}
124-
},
125-
// the base type is alway taken by reference.
126-
// e.g. In `(vec![0])[0]` the vector is a temporary value.
127-
ExprKind::Index(base, index) => {
128-
if !matches!(base.kind, ExprKind::Path(_)) {
129-
if type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(base)) {
130-
self.res = true;
131-
} else {
132-
self.visit_expr(base);
133-
}
134-
}
135-
self.visit_expr(index);
136-
},
137-
// Method calls can take self by reference.
138-
// e.g. In `String::new().len()` the string is a temporary value.
139-
ExprKind::MethodCall(_, [self_arg, args @ ..], _) => {
140-
if !matches!(self_arg.kind, ExprKind::Path(_)) {
141-
let self_by_ref = self
142-
.cx
143-
.typeck_results()
144-
.type_dependent_def_id(expr.hir_id)
145-
.map_or(false, |id| self.cx.tcx.fn_sig(id).skip_binder().inputs()[0].is_ref());
146-
if self_by_ref && type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(self_arg)) {
147-
self.res = true;
148-
} else {
149-
self.visit_expr(self_arg);
150-
}
151-
}
152-
args.iter().for_each(|arg| self.visit_expr(arg));
153-
},
154-
// Either explicitly drops values, or changes control flow.
155-
ExprKind::DropTemps(_)
156-
| ExprKind::Ret(_)
157-
| ExprKind::Break(..)
158-
| ExprKind::Yield(..)
159-
| ExprKind::Block(Block { expr: None, .. }, _)
160-
| ExprKind::Loop(..) => (),
161-
162-
// Only consider the final expression.
163-
ExprKind::Block(Block { expr: Some(expr), .. }, _) => self.visit_expr(expr),
164-
165-
_ => walk_expr(self, expr),
166-
}
167-
}
168-
}
169-
170-
let mut v = V { cx, res: false };
171-
v.visit_expr(expr);
172-
v.res
173-
}
174-
17545
fn find_sugg_for_if_let<'tcx>(
17646
cx: &LateContext<'tcx>,
17747
expr: &'tcx Expr<'_>,
@@ -243,7 +113,7 @@ fn find_sugg_for_if_let<'tcx>(
243113
// scrutinee would be, so they have to be considered as well.
244114
// e.g. in `if let Some(x) = foo.lock().unwrap().baz.as_ref() { .. }` the lock will be held
245115
// for the duration if body.
246-
let needs_drop = type_needs_ordered_drop(cx, check_ty) || temporaries_need_ordered_drop(cx, let_expr);
116+
let needs_drop = type_needs_ordered_drop(cx, check_ty) || any_temporaries_need_ordered_drop(cx, let_expr);
247117

248118
// check that `while_let_on_iterator` lint does not trigger
249119
if_chain! {

‎clippy_utils/src/ty.rs

Lines changed: 58 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -3,11 +3,11 @@
33
#![allow(clippy::module_name_repetitions)]
44

55
use rustc_ast::ast::Mutability;
6-
use rustc_data_structures::fx::FxHashMap;
6+
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
77
use rustc_hir as hir;
88
use rustc_hir::def::{CtorKind, DefKind, Res};
99
use rustc_hir::def_id::DefId;
10-
use rustc_hir::{Expr, TyKind, Unsafety};
10+
use rustc_hir::{Expr, LangItem, TyKind, Unsafety};
1111
use rustc_infer::infer::TyCtxtInferExt;
1212
use rustc_lint::LateContext;
1313
use rustc_middle::mir::interpret::{ConstValue, Scalar};
@@ -22,7 +22,7 @@ use rustc_trait_selection::infer::InferCtxtExt;
2222
use rustc_trait_selection::traits::query::normalize::AtExt;
2323
use std::iter;
2424

25-
use crate::{match_def_path, must_use_attr, path_res};
25+
use crate::{match_def_path, must_use_attr, path_res, paths};
2626

2727
// Checks if the given type implements copy.
2828
pub fn is_copy<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
@@ -590,3 +590,58 @@ pub fn is_c_void(cx: &LateContext<'_>, ty: Ty<'_>) -> bool {
590590
false
591591
}
592592
}
593+
594+
/// Checks if the drop order for a type matters. Some std types implement drop solely to
595+
/// deallocate memory. For these types, and composites containing them, changing the drop order
596+
/// won't result in any observable side effects.
597+
pub fn type_needs_ordered_drop<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
598+
type_needs_ordered_drop_inner(cx, ty, &mut FxHashSet::default())
599+
}
600+
601+
fn type_needs_ordered_drop_inner<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, seen: &mut FxHashSet<Ty<'tcx>>) -> bool {
602+
if !seen.insert(ty) {
603+
return false;
604+
}
605+
if !ty.needs_drop(cx.tcx, cx.param_env) {
606+
false
607+
} else if !cx
608+
.tcx
609+
.lang_items()
610+
.drop_trait()
611+
.map_or(false, |id| implements_trait(cx, ty, id, &[]))
612+
{
613+
// This type doesn't implement drop, so no side effects here.
614+
// Check if any component type has any.
615+
match ty.kind() {
616+
ty::Tuple(fields) => fields.iter().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)),
617+
ty::Array(ty, _) => type_needs_ordered_drop_inner(cx, *ty, seen),
618+
ty::Adt(adt, subs) => adt
619+
.all_fields()
620+
.map(|f| f.ty(cx.tcx, subs))
621+
.any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)),
622+
_ => true,
623+
}
624+
}
625+
// Check for std types which implement drop, but only for memory allocation.
626+
else if is_type_diagnostic_item(cx, ty, sym::Vec)
627+
|| is_type_lang_item(cx, ty, LangItem::OwnedBox)
628+
|| is_type_diagnostic_item(cx, ty, sym::Rc)
629+
|| is_type_diagnostic_item(cx, ty, sym::Arc)
630+
|| is_type_diagnostic_item(cx, ty, sym::cstring_type)
631+
|| is_type_diagnostic_item(cx, ty, sym::BTreeMap)
632+
|| is_type_diagnostic_item(cx, ty, sym::LinkedList)
633+
|| is_type_diagnostic_item(cx, ty, sym::HashSet)
634+
|| is_type_diagnostic_item(cx, ty, sym::HashMap)
635+
|| match_type(cx, ty, &paths::WEAK_RC)
636+
|| match_type(cx, ty, &paths::WEAK_ARC)
637+
{
638+
// Check all of the generic arguments.
639+
if let ty::Adt(_, subs) = ty.kind() {
640+
subs.types().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen))
641+
} else {
642+
true
643+
}
644+
} else {
645+
true
646+
}
647+
}

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