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Add new lint unneeded_struct_pattern (#13465)
Closes #13400. changelog: [`unneeded_struct_pattern`]: Add new lint
2 parents a895beb + 52abb8f commit 34d109f

9 files changed

+660
-2
lines changed

‎CHANGELOG.md

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@@ -6179,6 +6179,7 @@ Released 2018-09-13
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[`unnecessary_unwrap`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_unwrap
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[`unnecessary_wraps`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_wraps
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[`unneeded_field_pattern`]: https://rust-lang.github.io/rust-clippy/master/index.html#unneeded_field_pattern
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[`unneeded_struct_pattern`]: https://rust-lang.github.io/rust-clippy/master/index.html#unneeded_struct_pattern
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[`unneeded_wildcard_pattern`]: https://rust-lang.github.io/rust-clippy/master/index.html#unneeded_wildcard_pattern
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[`unnested_or_patterns`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnested_or_patterns
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[`unreachable`]: https://rust-lang.github.io/rust-clippy/master/index.html#unreachable

‎clippy_lints/src/arbitrary_source_item_ordering.rs

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@@ -445,8 +445,8 @@ fn convert_assoc_item_kind(value: AssocItemKind) -> SourceItemOrderingTraitAssoc
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#[allow(clippy::enum_glob_use)] // Very local glob use for legibility.
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use SourceItemOrderingTraitAssocItemKind::*;
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match value {
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AssocItemKind::Const { .. } => Const,
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AssocItemKind::Type { .. } => Type,
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AssocItemKind::Const => Const,
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AssocItemKind::Type => Type,
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AssocItemKind::Fn { .. } => Fn,
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}
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}

‎clippy_lints/src/declared_lints.rs

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@@ -757,6 +757,7 @@ pub static LINTS: &[&crate::LintInfo] = &[
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crate::unnecessary_self_imports::UNNECESSARY_SELF_IMPORTS_INFO,
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crate::unnecessary_struct_initialization::UNNECESSARY_STRUCT_INITIALIZATION_INFO,
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crate::unnecessary_wraps::UNNECESSARY_WRAPS_INFO,
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crate::unneeded_struct_pattern::UNNEEDED_STRUCT_PATTERN_INFO,
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crate::unnested_or_patterns::UNNESTED_OR_PATTERNS_INFO,
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crate::unsafe_removed_from_name::UNSAFE_REMOVED_FROM_NAME_INFO,
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crate::unused_async::UNUSED_ASYNC_INFO,

‎clippy_lints/src/lib.rs

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@@ -374,6 +374,7 @@ mod unnecessary_owned_empty_strings;
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mod unnecessary_self_imports;
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mod unnecessary_struct_initialization;
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mod unnecessary_wraps;
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mod unneeded_struct_pattern;
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mod unnested_or_patterns;
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mod unsafe_removed_from_name;
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mod unused_async;
@@ -970,5 +971,6 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
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store.register_late_pass(|_| Box::new(manual_ignore_case_cmp::ManualIgnoreCaseCmp));
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store.register_late_pass(|_| Box::new(unnecessary_literal_bound::UnnecessaryLiteralBound));
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store.register_late_pass(move |_| Box::new(arbitrary_source_item_ordering::ArbitrarySourceItemOrdering::new(conf)));
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store.register_late_pass(|_| Box::new(unneeded_struct_pattern::UnneededStructPattern));
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// add lints here, do not remove this comment, it's used in `new_lint`
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}

‎clippy_lints/src/unneeded_struct_pattern.rs

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@@ -0,0 +1,76 @@
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use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::is_from_proc_macro;
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use rustc_errors::Applicability;
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use rustc_hir::def::{DefKind, Res};
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use rustc_hir::{Pat, PatKind, QPath};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::declare_lint_pass;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for struct patterns that match against unit variant.
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///
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/// ### Why is this bad?
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/// Struct pattern `{ }` or `{ .. }` is not needed for unit variant.
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///
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/// ### Example
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/// ```no_run
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/// match Some(42) {
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/// Some(v) => v,
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/// None { .. } => 0,
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/// };
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/// // Or
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/// match Some(42) {
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/// Some(v) => v,
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/// None { } => 0,
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/// };
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/// ```
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/// Use instead:
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/// ```no_run
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/// match Some(42) {
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/// Some(v) => v,
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/// None => 0,
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/// };
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/// ```
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#[clippy::version = "1.83.0"]
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pub UNNEEDED_STRUCT_PATTERN,
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style,
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"using struct pattern to match against unit variant"
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}
40+
41+
declare_lint_pass!(UnneededStructPattern => [UNNEEDED_STRUCT_PATTERN]);
42+
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impl LateLintPass<'_> for UnneededStructPattern {
44+
fn check_pat(&mut self, cx: &LateContext<'_>, pat: &Pat<'_>) {
45+
if !pat.span.from_expansion()
46+
&& let PatKind::Struct(path, [], _) = &pat.kind
47+
&& let QPath::Resolved(_, path) = path
48+
&& let Res::Def(DefKind::Variant, did) = path.res
49+
{
50+
let enum_did = cx.tcx.parent(did);
51+
let variant = cx.tcx.adt_def(enum_did).variant_with_id(did);
52+
53+
let has_only_fields_brackets = variant.ctor.is_some() && variant.fields.is_empty();
54+
let non_exhaustive_activated = !variant.def_id.is_local() && variant.is_field_list_non_exhaustive();
55+
if !has_only_fields_brackets || non_exhaustive_activated {
56+
return;
57+
}
58+
59+
if is_from_proc_macro(cx, *path) {
60+
return;
61+
}
62+
63+
if let Some(brackets_span) = pat.span.trim_start(path.span) {
64+
span_lint_and_sugg(
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cx,
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UNNEEDED_STRUCT_PATTERN,
67+
brackets_span,
68+
"struct pattern is not needed for a unit variant",
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"remove the struct pattern",
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String::new(),
71+
Applicability::MachineApplicable,
72+
);
73+
}
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}
75+
}
76+
}

‎tests/ui/auxiliary/non-exhaustive-enum.rs

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@@ -6,3 +6,24 @@ pub enum ErrorKind {
66
#[doc(hidden)]
77
Uncategorized,
88
}
9+
10+
#[non_exhaustive]
11+
pub enum ExtNonExhaustiveEnum {
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Unit,
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Tuple(i32),
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Struct { field: i32 },
15+
}
16+
17+
pub enum ExtNonExhaustiveVariant {
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ExhaustiveUnit,
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#[non_exhaustive]
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Unit,
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#[non_exhaustive]
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Tuple(i32),
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#[non_exhaustive]
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StructNoField {},
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#[non_exhaustive]
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Struct {
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field: i32,
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},
29+
}

‎tests/ui/unneeded_struct_pattern.fixed

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@@ -0,0 +1,177 @@
1+
//@aux-build:non-exhaustive-enum.rs
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#![allow(
3+
clippy::manual_unwrap_or_default,
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clippy::manual_unwrap_or,
5+
clippy::redundant_pattern_matching
6+
)]
7+
#![warn(clippy::unneeded_struct_pattern)]
8+
9+
extern crate non_exhaustive_enum;
10+
use non_exhaustive_enum::*;
11+
12+
fn noop() {}
13+
14+
fn main() {
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match Some(114514) {
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Some(v) => v,
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None => 0,
18+
};
19+
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match Some(1919810) {
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Some(v) => v,
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None => 0,
23+
};
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match Some(123456) {
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Some(v) => v,
27+
None => 0,
28+
};
29+
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match Some(Some(123456)) {
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Some(Some(v)) => v,
32+
Some(None) => 0,
33+
None => 0,
34+
};
35+
36+
if let None = Some(0) {}
37+
if let None = Some(0) {}
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if let Some(None) = Some(Some(0)) {}
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let None = Some(0) else { panic!() };
40+
let None = Some(0) else { panic!() };
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let Some(None) = Some(Some(0)) else { panic!() };
42+
43+
enum Custom {
44+
HasFields {
45+
field: i32,
46+
},
47+
HasBracketsNoFields {},
48+
NoBrackets,
49+
#[non_exhaustive]
50+
NoBracketsNonExhaustive,
51+
Init,
52+
};
53+
54+
match Custom::Init {
55+
Custom::HasFields { field: value } => value,
56+
Custom::HasBracketsNoFields {} => 0,
57+
Custom::NoBrackets => 0, //~ ERROR: struct pattern is not needed for a unit variant
58+
Custom::NoBracketsNonExhaustive => 0, //~ ERROR: struct pattern is not needed for a unit variant
59+
_ => 0,
60+
};
61+
62+
match Custom::Init {
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Custom::HasFields { field: value } => value,
64+
Custom::HasBracketsNoFields { .. } => 0,
65+
Custom::NoBrackets => 0, //~ ERROR: struct pattern is not needed for a unit variant
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Custom::NoBracketsNonExhaustive => 0, //~ ERROR: struct pattern is not needed for a unit variant
67+
_ => 0,
68+
};
69+
70+
match Custom::Init {
71+
Custom::NoBrackets if true => 0, //~ ERROR: struct pattern is not needed for a unit variant
72+
_ => 0,
73+
};
74+
75+
match Custom::Init {
76+
Custom::NoBrackets | Custom::NoBracketsNonExhaustive => 0, //~ ERROR: struct pattern is not needed for a unit variant
77+
_ => 0,
78+
};
79+
80+
if let Custom::HasFields { field: value } = Custom::Init {
81+
noop();
82+
}
83+
if let Custom::HasBracketsNoFields {} = Custom::Init {
84+
noop();
85+
}
86+
if let Custom::HasBracketsNoFields { .. } = Custom::Init {
87+
noop();
88+
}
89+
if let Custom::NoBrackets = Custom::Init {
90+
//~^ ERROR: struct pattern is not needed for a unit variant
91+
noop();
92+
}
93+
if let Custom::NoBrackets = Custom::Init {
94+
//~^ ERROR: struct pattern is not needed for a unit variant
95+
noop();
96+
}
97+
if let Custom::NoBrackets | Custom::NoBracketsNonExhaustive = Custom::Init {
98+
//~^ ERROR: struct pattern is not needed for a unit variant
99+
noop();
100+
}
101+
if let Custom::NoBracketsNonExhaustive = Custom::Init {
102+
//~^ ERROR: struct pattern is not needed for a unit variant
103+
noop();
104+
}
105+
if let Custom::NoBracketsNonExhaustive = Custom::Init {
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//~^ ERROR: struct pattern is not needed for a unit variant
107+
noop();
108+
}
109+
110+
let Custom::HasFields { field: value } = Custom::Init else {
111+
panic!()
112+
};
113+
114+
let Custom::HasBracketsNoFields {} = Custom::Init else {
115+
panic!()
116+
};
117+
118+
let Custom::HasBracketsNoFields { .. } = Custom::Init else {
119+
panic!()
120+
};
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let Custom::NoBrackets = Custom::Init else { panic!() }; //~ ERROR: struct pattern is not needed for a unit variant
122+
123+
let Custom::NoBrackets = Custom::Init else {
124+
//~^ ERROR: struct pattern is not needed for a unit variant
125+
panic!()
126+
};
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let Custom::NoBracketsNonExhaustive = Custom::Init else {
128+
//~^ ERROR: struct pattern is not needed for a unit variant
129+
panic!()
130+
};
131+
let Custom::NoBracketsNonExhaustive = Custom::Init else {
132+
//~^ ERROR: struct pattern is not needed for a unit variant
133+
panic!()
134+
};
135+
136+
enum Refutable {
137+
Variant,
138+
}
139+
140+
fn pat_in_fn_param_1(Refutable::Variant: Refutable) {} //~ ERROR: struct pattern is not needed for a unit variant
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fn pat_in_fn_param_2(Refutable::Variant: Refutable) {} //~ ERROR: struct pattern is not needed for a unit variant
142+
143+
for Refutable::Variant in [] {} //~ ERROR: struct pattern is not needed for a unit variant
144+
for Refutable::Variant in [] {} //~ ERROR: struct pattern is not needed for a unit variant
145+
}
146+
147+
fn external_crate() {
148+
use ExtNonExhaustiveVariant::*;
149+
150+
match ExhaustiveUnit {
151+
// Expected
152+
ExhaustiveUnit => 0,
153+
_ => 0,
154+
};
155+
156+
match ExhaustiveUnit {
157+
// Exhaustive variant
158+
ExhaustiveUnit => 0, //~ ERROR: struct pattern is not needed for a unit variant
159+
_ => 0,
160+
};
161+
162+
match ExhaustiveUnit {
163+
// Exhaustive variant
164+
ExhaustiveUnit => 0, //~ ERROR: struct pattern is not needed for a unit variant
165+
_ => 0,
166+
};
167+
168+
match ExhaustiveUnit {
169+
ExhaustiveUnit => 0,
170+
// vvvvv Non-exhaustive variants, should all be ignored
171+
Unit { .. } => 0,
172+
Tuple { 0: field, .. } => field,
173+
StructNoField { .. } => 0,
174+
Struct { field, .. } => field,
175+
_ => 0,
176+
};
177+
}

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