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Split out redundant_pattern_match

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This commit is contained in:
Jason Newcomb 2022-02-06 14:03:45 -05:00
parent 64548250e7
commit f2b6ed7cb2
2 changed files with 437 additions and 446 deletions
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447
clippy_lints/src/matches/mod.rs
View File

@ -32,6 +32,7 @@
mod match_like_matches;
mod match_same_arms;
mod redundant_pattern_match;
declare_clippy_lint! {
/// ### What it does
@ -1701,452 +1702,6 @@ fn cmp(&self, RangeBound(other_value, other_kind, _): &Self) -> Ordering {
None
}
mod redundant_pattern_match {
use super::REDUNDANT_PATTERN_MATCHING;
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::source::snippet;
use clippy_utils::sugg::Sugg;
use clippy_utils::ty::{implements_trait, is_type_diagnostic_item, is_type_lang_item, match_type};
use clippy_utils::{higher, match_def_path};
use clippy_utils::{is_lang_ctor, is_trait_method, paths};
use if_chain::if_chain;
use rustc_ast::ast::LitKind;
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::Applicability;
use rustc_hir::LangItem::{OptionNone, PollPending};
use rustc_hir::{
intravisit::{walk_expr, Visitor},
Arm, Block, Expr, ExprKind, LangItem, MatchSource, Node, Pat, PatKind, QPath, UnOp,
};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, subst::GenericArgKind, DefIdTree, Ty};
use rustc_span::sym;
pub fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if let Some(higher::IfLet {
if_else,
let_pat,
let_expr,
..
}) = higher::IfLet::hir(cx, expr)
{
find_sugg_for_if_let(cx, expr, let_pat, let_expr, "if", if_else.is_some());
}
if let ExprKind::Match(op, arms, MatchSource::Normal) = &expr.kind {
find_sugg_for_match(cx, expr, op, arms);
}
if let Some(higher::WhileLet { let_pat, let_expr, .. }) = higher::WhileLet::hir(expr) {
find_sugg_for_if_let(cx, expr, let_pat, let_expr, "while", false);
}
}
/// Checks if the drop order for a type matters. Some std types implement drop solely to
/// deallocate memory. For these types, and composites containing them, changing the drop order
/// won't result in any observable side effects.
fn type_needs_ordered_drop<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
type_needs_ordered_drop_inner(cx, ty, &mut FxHashSet::default())
}
fn type_needs_ordered_drop_inner<'tcx>(
cx: &LateContext<'tcx>,
ty: Ty<'tcx>,
seen: &mut FxHashSet<Ty<'tcx>>,
) -> bool {
if !seen.insert(ty) {
return false;
}
if !ty.needs_drop(cx.tcx, cx.param_env) {
false
} else if !cx
.tcx
.lang_items()
.drop_trait()
.map_or(false, |id| implements_trait(cx, ty, id, &[]))
{
// This type doesn't implement drop, so no side effects here.
// Check if any component type has any.
match ty.kind() {
ty::Tuple(_) => ty.tuple_fields().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)),
ty::Array(ty, _) => type_needs_ordered_drop_inner(cx, ty, seen),
ty::Adt(adt, subs) => adt
.all_fields()
.map(|f| f.ty(cx.tcx, subs))
.any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)),
_ => true,
}
}
// Check for std types which implement drop, but only for memory allocation.
else if is_type_diagnostic_item(cx, ty, sym::Vec)
|| is_type_lang_item(cx, ty, LangItem::OwnedBox)
|| is_type_diagnostic_item(cx, ty, sym::Rc)
|| is_type_diagnostic_item(cx, ty, sym::Arc)
|| is_type_diagnostic_item(cx, ty, sym::cstring_type)
|| is_type_diagnostic_item(cx, ty, sym::BTreeMap)
|| is_type_diagnostic_item(cx, ty, sym::LinkedList)
|| match_type(cx, ty, &paths::WEAK_RC)
|| match_type(cx, ty, &paths::WEAK_ARC)
{
// Check all of the generic arguments.
if let ty::Adt(_, subs) = ty.kind() {
subs.types().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen))
} else {
true
}
} else {
true
}
}
// Extract the generic arguments out of a type
fn try_get_generic_ty(ty: Ty<'_>, index: usize) -> Option<Ty<'_>> {
if_chain! {
if let ty::Adt(_, subs) = ty.kind();
if let Some(sub) = subs.get(index);
if let GenericArgKind::Type(sub_ty) = sub.unpack();
then {
Some(sub_ty)
} else {
None
}
}
}
// Checks if there are any temporaries created in the given expression for which drop order
// matters.
fn temporaries_need_ordered_drop<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
struct V<'a, 'tcx> {
cx: &'a LateContext<'tcx>,
res: bool,
}
impl<'a, 'tcx> Visitor<'tcx> for V<'a, 'tcx> {
fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
match expr.kind {
// Taking the reference of a value leaves a temporary
// e.g. In `&String::new()` the string is a temporary value.
// Remaining fields are temporary values
// e.g. In `(String::new(), 0).1` the string is a temporary value.
ExprKind::AddrOf(_, _, expr) | ExprKind::Field(expr, _) => {
if !matches!(expr.kind, ExprKind::Path(_)) {
if type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(expr)) {
self.res = true;
} else {
self.visit_expr(expr);
}
}
},
// the base type is alway taken by reference.
// e.g. In `(vec![0])[0]` the vector is a temporary value.
ExprKind::Index(base, index) => {
if !matches!(base.kind, ExprKind::Path(_)) {
if type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(base)) {
self.res = true;
} else {
self.visit_expr(base);
}
}
self.visit_expr(index);
},
// Method calls can take self by reference.
// e.g. In `String::new().len()` the string is a temporary value.
ExprKind::MethodCall(_, [self_arg, args @ ..], _) => {
if !matches!(self_arg.kind, ExprKind::Path(_)) {
let self_by_ref = self
.cx
.typeck_results()
.type_dependent_def_id(expr.hir_id)
.map_or(false, |id| self.cx.tcx.fn_sig(id).skip_binder().inputs()[0].is_ref());
if self_by_ref
&& type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(self_arg))
{
self.res = true;
} else {
self.visit_expr(self_arg);
}
}
args.iter().for_each(|arg| self.visit_expr(arg));
},
// Either explicitly drops values, or changes control flow.
ExprKind::DropTemps(_)
| ExprKind::Ret(_)
| ExprKind::Break(..)
| ExprKind::Yield(..)
| ExprKind::Block(Block { expr: None, .. }, _)
| ExprKind::Loop(..) => (),
// Only consider the final expression.
ExprKind::Block(Block { expr: Some(expr), .. }, _) => self.visit_expr(expr),
_ => walk_expr(self, expr),
}
}
}
let mut v = V { cx, res: false };
v.visit_expr(expr);
v.res
}
fn find_sugg_for_if_let<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx Expr<'_>,
let_pat: &Pat<'_>,
let_expr: &'tcx Expr<'_>,
keyword: &'static str,
has_else: bool,
) {
// also look inside refs
// if we have &None for example, peel it so we can detect "if let None = x"
let check_pat = match let_pat.kind {
PatKind::Ref(inner, _mutability) => inner,
_ => let_pat,
};
let op_ty = cx.typeck_results().expr_ty(let_expr);
// Determine which function should be used, and the type contained by the corresponding
// variant.
let (good_method, inner_ty) = match check_pat.kind {
PatKind::TupleStruct(ref qpath, [sub_pat], _) => {
if let PatKind::Wild = sub_pat.kind {
let res = cx.typeck_results().qpath_res(qpath, check_pat.hir_id);
let Some(id) = res.opt_def_id().and_then(|ctor_id| cx.tcx.parent(ctor_id)) else { return };
let lang_items = cx.tcx.lang_items();
if Some(id) == lang_items.result_ok_variant() {
("is_ok()", try_get_generic_ty(op_ty, 0).unwrap_or(op_ty))
} else if Some(id) == lang_items.result_err_variant() {
("is_err()", try_get_generic_ty(op_ty, 1).unwrap_or(op_ty))
} else if Some(id) == lang_items.option_some_variant() {
("is_some()", op_ty)
} else if Some(id) == lang_items.poll_ready_variant() {
("is_ready()", op_ty)
} else if match_def_path(cx, id, &paths::IPADDR_V4) {
("is_ipv4()", op_ty)
} else if match_def_path(cx, id, &paths::IPADDR_V6) {
("is_ipv6()", op_ty)
} else {
return;
}
} else {
return;
}
},
PatKind::Path(ref path) => {
let method = if is_lang_ctor(cx, path, OptionNone) {
"is_none()"
} else if is_lang_ctor(cx, path, PollPending) {
"is_pending()"
} else {
return;
};
// `None` and `Pending` don't have an inner type.
(method, cx.tcx.types.unit)
},
_ => return,
};
// If this is the last expression in a block or there is an else clause then the whole
// type needs to be considered, not just the inner type of the branch being matched on.
// Note the last expression in a block is dropped after all local bindings.
let check_ty = if has_else
|| (keyword == "if" && matches!(cx.tcx.hir().parent_iter(expr.hir_id).next(), Some((_, Node::Block(..)))))
{
op_ty
} else {
inner_ty
};
// All temporaries created in the scrutinee expression are dropped at the same time as the
// scrutinee would be, so they have to be considered as well.
// e.g. in `if let Some(x) = foo.lock().unwrap().baz.as_ref() { .. }` the lock will be held
// for the duration if body.
let needs_drop = type_needs_ordered_drop(cx, check_ty) || temporaries_need_ordered_drop(cx, let_expr);
// check that `while_let_on_iterator` lint does not trigger
if_chain! {
if keyword == "while";
if let ExprKind::MethodCall(method_path, _, _) = let_expr.kind;
if method_path.ident.name == sym::next;
if is_trait_method(cx, let_expr, sym::Iterator);
then {
return;
}
}
let result_expr = match &let_expr.kind {
ExprKind::AddrOf(_, _, borrowed) => borrowed,
ExprKind::Unary(UnOp::Deref, deref) => deref,
_ => let_expr,
};
span_lint_and_then(
cx,
REDUNDANT_PATTERN_MATCHING,
let_pat.span,
&format!("redundant pattern matching, consider using `{}`", good_method),
|diag| {
// if/while let ... = ... { ... }
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^
let expr_span = expr.span;
// if/while let ... = ... { ... }
// ^^^
let op_span = result_expr.span.source_callsite();
// if/while let ... = ... { ... }
// ^^^^^^^^^^^^^^^^^^^
let span = expr_span.until(op_span.shrink_to_hi());
let app = if needs_drop {
Applicability::MaybeIncorrect
} else {
Applicability::MachineApplicable
};
let sugg = Sugg::hir_with_macro_callsite(cx, result_expr, "_")
.maybe_par()
.to_string();
diag.span_suggestion(span, "try this", format!("{} {}.{}", keyword, sugg, good_method), app);
if needs_drop {
diag.note("this will change drop order of the result, as well as all temporaries");
diag.note("add `#[allow(clippy::redundant_pattern_matching)]` if this is important");
}
},
);
}
fn find_sugg_for_match<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, op: &Expr<'_>, arms: &[Arm<'_>]) {
if arms.len() == 2 {
let node_pair = (&arms[0].pat.kind, &arms[1].pat.kind);
let found_good_method = match node_pair {
(
PatKind::TupleStruct(ref path_left, patterns_left, _),
PatKind::TupleStruct(ref path_right, patterns_right, _),
) if patterns_left.len() == 1 && patterns_right.len() == 1 => {
if let (PatKind::Wild, PatKind::Wild) = (&patterns_left[0].kind, &patterns_right[0].kind) {
find_good_method_for_match(
cx,
arms,
path_left,
path_right,
&paths::RESULT_OK,
&paths::RESULT_ERR,
"is_ok()",
"is_err()",
)
.or_else(|| {
find_good_method_for_match(
cx,
arms,
path_left,
path_right,
&paths::IPADDR_V4,
&paths::IPADDR_V6,
"is_ipv4()",
"is_ipv6()",
)
})
} else {
None
}
},
(PatKind::TupleStruct(ref path_left, patterns, _), PatKind::Path(ref path_right))
| (PatKind::Path(ref path_left), PatKind::TupleStruct(ref path_right, patterns, _))
if patterns.len() == 1 =>
{
if let PatKind::Wild = patterns[0].kind {
find_good_method_for_match(
cx,
arms,
path_left,
path_right,
&paths::OPTION_SOME,
&paths::OPTION_NONE,
"is_some()",
"is_none()",
)
.or_else(|| {
find_good_method_for_match(
cx,
arms,
path_left,
path_right,
&paths::POLL_READY,
&paths::POLL_PENDING,
"is_ready()",
"is_pending()",
)
})
} else {
None
}
},
_ => None,
};
if let Some(good_method) = found_good_method {
let span = expr.span.to(op.span);
let result_expr = match &op.kind {
ExprKind::AddrOf(_, _, borrowed) => borrowed,
_ => op,
};
span_lint_and_then(
cx,
REDUNDANT_PATTERN_MATCHING,
expr.span,
&format!("redundant pattern matching, consider using `{}`", good_method),
|diag| {
diag.span_suggestion(
span,
"try this",
format!("{}.{}", snippet(cx, result_expr.span, "_"), good_method),
Applicability::MaybeIncorrect, // snippet
);
},
);
}
}
}
#[allow(clippy::too_many_arguments)]
fn find_good_method_for_match<'a>(
cx: &LateContext<'_>,
arms: &[Arm<'_>],
path_left: &QPath<'_>,
path_right: &QPath<'_>,
expected_left: &[&str],
expected_right: &[&str],
should_be_left: &'a str,
should_be_right: &'a str,
) -> Option<&'a str> {
let left_id = cx
.typeck_results()
.qpath_res(path_left, arms[0].pat.hir_id)
.opt_def_id()?;
let right_id = cx
.typeck_results()
.qpath_res(path_right, arms[1].pat.hir_id)
.opt_def_id()?;
let body_node_pair =
if match_def_path(cx, left_id, expected_left) && match_def_path(cx, right_id, expected_right) {
(&(*arms[0].body).kind, &(*arms[1].body).kind)
} else if match_def_path(cx, right_id, expected_left) && match_def_path(cx, right_id, expected_right) {
(&(*arms[1].body).kind, &(*arms[0].body).kind)
} else {
return None;
};
match body_node_pair {
(ExprKind::Lit(ref lit_left), ExprKind::Lit(ref lit_right)) => match (&lit_left.node, &lit_right.node) {
(LitKind::Bool(true), LitKind::Bool(false)) => Some(should_be_left),
(LitKind::Bool(false), LitKind::Bool(true)) => Some(should_be_right),
_ => None,
},
_ => None,
}
}
}
#[test]
fn test_overlapping() {
use rustc_span::source_map::DUMMY_SP;

436
clippy_lints/src/matches/redundant_pattern_match.rs Normal file
View File

@ -0,0 +1,436 @@
use super::REDUNDANT_PATTERN_MATCHING;
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::source::snippet;
use clippy_utils::sugg::Sugg;
use clippy_utils::ty::{implements_trait, is_type_diagnostic_item, is_type_lang_item, match_type};
use clippy_utils::{higher, match_def_path};
use clippy_utils::{is_lang_ctor, is_trait_method, paths};
use if_chain::if_chain;
use rustc_ast::ast::LitKind;
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::Applicability;
use rustc_hir::LangItem::{OptionNone, PollPending};
use rustc_hir::{
intravisit::{walk_expr, Visitor},
Arm, Block, Expr, ExprKind, LangItem, MatchSource, Node, Pat, PatKind, QPath, UnOp,
};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, subst::GenericArgKind, DefIdTree, Ty};
use rustc_span::sym;
pub fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if let Some(higher::IfLet {
if_else,
let_pat,
let_expr,
..
}) = higher::IfLet::hir(cx, expr)
{
find_sugg_for_if_let(cx, expr, let_pat, let_expr, "if", if_else.is_some());
}
if let ExprKind::Match(op, arms, MatchSource::Normal) = &expr.kind {
find_sugg_for_match(cx, expr, op, arms);
}
if let Some(higher::WhileLet { let_pat, let_expr, .. }) = higher::WhileLet::hir(expr) {
find_sugg_for_if_let(cx, expr, let_pat, let_expr, "while", false);
}
}
/// Checks if the drop order for a type matters. Some std types implement drop solely to
/// deallocate memory. For these types, and composites containing them, changing the drop order
/// won't result in any observable side effects.
fn type_needs_ordered_drop<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
type_needs_ordered_drop_inner(cx, ty, &mut FxHashSet::default())
}
fn type_needs_ordered_drop_inner<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, seen: &mut FxHashSet<Ty<'tcx>>) -> bool {
if !seen.insert(ty) {
return false;
}
if !ty.needs_drop(cx.tcx, cx.param_env) {
false
} else if !cx
.tcx
.lang_items()
.drop_trait()
.map_or(false, |id| implements_trait(cx, ty, id, &[]))
{
// This type doesn't implement drop, so no side effects here.
// Check if any component type has any.
match ty.kind() {
ty::Tuple(_) => ty.tuple_fields().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)),
ty::Array(ty, _) => type_needs_ordered_drop_inner(cx, ty, seen),
ty::Adt(adt, subs) => adt
.all_fields()
.map(|f| f.ty(cx.tcx, subs))
.any(|ty| type_needs_ordered_drop_inner(cx, ty, seen)),
_ => true,
}
}
// Check for std types which implement drop, but only for memory allocation.
else if is_type_diagnostic_item(cx, ty, sym::Vec)
|| is_type_lang_item(cx, ty, LangItem::OwnedBox)
|| is_type_diagnostic_item(cx, ty, sym::Rc)
|| is_type_diagnostic_item(cx, ty, sym::Arc)
|| is_type_diagnostic_item(cx, ty, sym::cstring_type)
|| is_type_diagnostic_item(cx, ty, sym::BTreeMap)
|| is_type_diagnostic_item(cx, ty, sym::LinkedList)
|| match_type(cx, ty, &paths::WEAK_RC)
|| match_type(cx, ty, &paths::WEAK_ARC)
{
// Check all of the generic arguments.
if let ty::Adt(_, subs) = ty.kind() {
subs.types().any(|ty| type_needs_ordered_drop_inner(cx, ty, seen))
} else {
true
}
} else {
true
}
}
// Extract the generic arguments out of a type
fn try_get_generic_ty(ty: Ty<'_>, index: usize) -> Option<Ty<'_>> {
if_chain! {
if let ty::Adt(_, subs) = ty.kind();
if let Some(sub) = subs.get(index);
if let GenericArgKind::Type(sub_ty) = sub.unpack();
then {
Some(sub_ty)
} else {
None
}
}
}
// Checks if there are any temporaries created in the given expression for which drop order
// matters.
fn temporaries_need_ordered_drop<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
struct V<'a, 'tcx> {
cx: &'a LateContext<'tcx>,
res: bool,
}
impl<'a, 'tcx> Visitor<'tcx> for V<'a, 'tcx> {
fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
match expr.kind {
// Taking the reference of a value leaves a temporary
// e.g. In `&String::new()` the string is a temporary value.
// Remaining fields are temporary values
// e.g. In `(String::new(), 0).1` the string is a temporary value.
ExprKind::AddrOf(_, _, expr) | ExprKind::Field(expr, _) => {
if !matches!(expr.kind, ExprKind::Path(_)) {
if type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(expr)) {
self.res = true;
} else {
self.visit_expr(expr);
}
}
},
// the base type is alway taken by reference.
// e.g. In `(vec![0])[0]` the vector is a temporary value.
ExprKind::Index(base, index) => {
if !matches!(base.kind, ExprKind::Path(_)) {
if type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(base)) {
self.res = true;
} else {
self.visit_expr(base);
}
}
self.visit_expr(index);
},
// Method calls can take self by reference.
// e.g. In `String::new().len()` the string is a temporary value.
ExprKind::MethodCall(_, [self_arg, args @ ..], _) => {
if !matches!(self_arg.kind, ExprKind::Path(_)) {
let self_by_ref = self
.cx
.typeck_results()
.type_dependent_def_id(expr.hir_id)
.map_or(false, |id| self.cx.tcx.fn_sig(id).skip_binder().inputs()[0].is_ref());
if self_by_ref && type_needs_ordered_drop(self.cx, self.cx.typeck_results().expr_ty(self_arg)) {
self.res = true;
} else {
self.visit_expr(self_arg);
}
}
args.iter().for_each(|arg| self.visit_expr(arg));
},
// Either explicitly drops values, or changes control flow.
ExprKind::DropTemps(_)
| ExprKind::Ret(_)
| ExprKind::Break(..)
| ExprKind::Yield(..)
| ExprKind::Block(Block { expr: None, .. }, _)
| ExprKind::Loop(..) => (),
// Only consider the final expression.
ExprKind::Block(Block { expr: Some(expr), .. }, _) => self.visit_expr(expr),
_ => walk_expr(self, expr),
}
}
}
let mut v = V { cx, res: false };
v.visit_expr(expr);
v.res
}
fn find_sugg_for_if_let<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx Expr<'_>,
let_pat: &Pat<'_>,
let_expr: &'tcx Expr<'_>,
keyword: &'static str,
has_else: bool,
) {
// also look inside refs
// if we have &None for example, peel it so we can detect "if let None = x"
let check_pat = match let_pat.kind {
PatKind::Ref(inner, _mutability) => inner,
_ => let_pat,
};
let op_ty = cx.typeck_results().expr_ty(let_expr);
// Determine which function should be used, and the type contained by the corresponding
// variant.
let (good_method, inner_ty) = match check_pat.kind {
PatKind::TupleStruct(ref qpath, [sub_pat], _) => {
if let PatKind::Wild = sub_pat.kind {
let res = cx.typeck_results().qpath_res(qpath, check_pat.hir_id);
let Some(id) = res.opt_def_id().and_then(|ctor_id| cx.tcx.parent(ctor_id)) else { return };
let lang_items = cx.tcx.lang_items();
if Some(id) == lang_items.result_ok_variant() {
("is_ok()", try_get_generic_ty(op_ty, 0).unwrap_or(op_ty))
} else if Some(id) == lang_items.result_err_variant() {
("is_err()", try_get_generic_ty(op_ty, 1).unwrap_or(op_ty))
} else if Some(id) == lang_items.option_some_variant() {
("is_some()", op_ty)
} else if Some(id) == lang_items.poll_ready_variant() {
("is_ready()", op_ty)
} else if match_def_path(cx, id, &paths::IPADDR_V4) {
("is_ipv4()", op_ty)
} else if match_def_path(cx, id, &paths::IPADDR_V6) {
("is_ipv6()", op_ty)
} else {
return;
}
} else {
return;
}
},
PatKind::Path(ref path) => {
let method = if is_lang_ctor(cx, path, OptionNone) {
"is_none()"
} else if is_lang_ctor(cx, path, PollPending) {
"is_pending()"
} else {
return;
};
// `None` and `Pending` don't have an inner type.
(method, cx.tcx.types.unit)
},
_ => return,
};
// If this is the last expression in a block or there is an else clause then the whole
// type needs to be considered, not just the inner type of the branch being matched on.
// Note the last expression in a block is dropped after all local bindings.
let check_ty = if has_else
|| (keyword == "if" && matches!(cx.tcx.hir().parent_iter(expr.hir_id).next(), Some((_, Node::Block(..)))))
{
op_ty
} else {
inner_ty
};
// All temporaries created in the scrutinee expression are dropped at the same time as the
// scrutinee would be, so they have to be considered as well.
// e.g. in `if let Some(x) = foo.lock().unwrap().baz.as_ref() { .. }` the lock will be held
// for the duration if body.
let needs_drop = type_needs_ordered_drop(cx, check_ty) || temporaries_need_ordered_drop(cx, let_expr);
// check that `while_let_on_iterator` lint does not trigger
if_chain! {
if keyword == "while";
if let ExprKind::MethodCall(method_path, _, _) = let_expr.kind;
if method_path.ident.name == sym::next;
if is_trait_method(cx, let_expr, sym::Iterator);
then {
return;
}
}
let result_expr = match &let_expr.kind {
ExprKind::AddrOf(_, _, borrowed) => borrowed,
ExprKind::Unary(UnOp::Deref, deref) => deref,
_ => let_expr,
};
span_lint_and_then(
cx,
REDUNDANT_PATTERN_MATCHING,
let_pat.span,
&format!("redundant pattern matching, consider using `{}`", good_method),
|diag| {
// if/while let ... = ... { ... }
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^
let expr_span = expr.span;
// if/while let ... = ... { ... }
// ^^^
let op_span = result_expr.span.source_callsite();
// if/while let ... = ... { ... }
// ^^^^^^^^^^^^^^^^^^^
let span = expr_span.until(op_span.shrink_to_hi());
let app = if needs_drop {
Applicability::MaybeIncorrect
} else {
Applicability::MachineApplicable
};
let sugg = Sugg::hir_with_macro_callsite(cx, result_expr, "_")
.maybe_par()
.to_string();
diag.span_suggestion(span, "try this", format!("{} {}.{}", keyword, sugg, good_method), app);
if needs_drop {
diag.note("this will change drop order of the result, as well as all temporaries");
diag.note("add `#[allow(clippy::redundant_pattern_matching)]` if this is important");
}
},
);
}
fn find_sugg_for_match<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, op: &Expr<'_>, arms: &[Arm<'_>]) {
if arms.len() == 2 {
let node_pair = (&arms[0].pat.kind, &arms[1].pat.kind);
let found_good_method = match node_pair {
(
PatKind::TupleStruct(ref path_left, patterns_left, _),
PatKind::TupleStruct(ref path_right, patterns_right, _),
) if patterns_left.len() == 1 && patterns_right.len() == 1 => {
if let (PatKind::Wild, PatKind::Wild) = (&patterns_left[0].kind, &patterns_right[0].kind) {
find_good_method_for_match(
cx,
arms,
path_left,
path_right,
&paths::RESULT_OK,
&paths::RESULT_ERR,
"is_ok()",
"is_err()",
)
.or_else(|| {
find_good_method_for_match(
cx,
arms,
path_left,
path_right,
&paths::IPADDR_V4,
&paths::IPADDR_V6,
"is_ipv4()",
"is_ipv6()",
)
})
} else {
None
}
},
(PatKind::TupleStruct(ref path_left, patterns, _), PatKind::Path(ref path_right))
| (PatKind::Path(ref path_left), PatKind::TupleStruct(ref path_right, patterns, _))
if patterns.len() == 1 =>
{
if let PatKind::Wild = patterns[0].kind {
find_good_method_for_match(
cx,
arms,
path_left,
path_right,
&paths::OPTION_SOME,
&paths::OPTION_NONE,
"is_some()",
"is_none()",
)
.or_else(|| {
find_good_method_for_match(
cx,
arms,
path_left,
path_right,
&paths::POLL_READY,
&paths::POLL_PENDING,
"is_ready()",
"is_pending()",
)
})
} else {
None
}
},
_ => None,
};
if let Some(good_method) = found_good_method {
let span = expr.span.to(op.span);
let result_expr = match &op.kind {
ExprKind::AddrOf(_, _, borrowed) => borrowed,
_ => op,
};
span_lint_and_then(
cx,
REDUNDANT_PATTERN_MATCHING,
expr.span,
&format!("redundant pattern matching, consider using `{}`", good_method),
|diag| {
diag.span_suggestion(
span,
"try this",
format!("{}.{}", snippet(cx, result_expr.span, "_"), good_method),
Applicability::MaybeIncorrect, // snippet
);
},
);
}
}
}
#[allow(clippy::too_many_arguments)]
fn find_good_method_for_match<'a>(
cx: &LateContext<'_>,
arms: &[Arm<'_>],
path_left: &QPath<'_>,
path_right: &QPath<'_>,
expected_left: &[&str],
expected_right: &[&str],
should_be_left: &'a str,
should_be_right: &'a str,
) -> Option<&'a str> {
let left_id = cx
.typeck_results()
.qpath_res(path_left, arms[0].pat.hir_id)
.opt_def_id()?;
let right_id = cx
.typeck_results()
.qpath_res(path_right, arms[1].pat.hir_id)
.opt_def_id()?;
let body_node_pair = if match_def_path(cx, left_id, expected_left) && match_def_path(cx, right_id, expected_right) {
(&(*arms[0].body).kind, &(*arms[1].body).kind)
} else if match_def_path(cx, right_id, expected_left) && match_def_path(cx, right_id, expected_right) {
(&(*arms[1].body).kind, &(*arms[0].body).kind)
} else {
return None;
};
match body_node_pair {
(ExprKind::Lit(ref lit_left), ExprKind::Lit(ref lit_right)) => match (&lit_left.node, &lit_right.node) {
(LitKind::Bool(true), LitKind::Bool(false)) => Some(should_be_left),
(LitKind::Bool(false), LitKind::Bool(true)) => Some(should_be_right),
_ => None,
},
_ => None,
}
}