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Fix option_if_let_else
* `break` and `continue` statments local to the would-be closure are allowed * don't lint in const contexts * don't lint when yield expressions are used * don't lint when the captures made by the would-be closure conflict with the other branch * don't lint when a field of a local is used when the type could be pontentially moved from * in some cases, don't lint when scrutinee expression conflicts with the captures of the would-be closure
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-12
lines changed

5 files changed

+186
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lines changed

‎clippy_lints/src/option_if_let_else.rs‎

Lines changed: 42 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -1,12 +1,16 @@
11
use clippy_utils::diagnostics::span_lint_and_sugg;
22
use clippy_utils::sugg::Sugg;
33
use clippy_utils::ty::is_type_diagnostic_item;
4-
use clippy_utils::usage::contains_return_break_continue_macro;
5-
use clippy_utils::{eager_or_lazy, in_macro, is_else_clause, is_lang_ctor};
4+
use clippy_utils::{
5+
can_move_expr_to_closure, eager_or_lazy, in_constant, in_macro, is_else_clause, is_lang_ctor, peel_hir_expr_while,
6+
CaptureKind,
7+
};
68
use if_chain::if_chain;
79
use rustc_errors::Applicability;
810
use rustc_hir::LangItem::OptionSome;
9-
use rustc_hir::{Arm, BindingAnnotation, Block, Expr, ExprKind, MatchSource, Mutability, PatKind, UnOp};
11+
use rustc_hir::{
12+
def::Res, Arm, BindingAnnotation, Block, Expr, ExprKind, MatchSource, Mutability, PatKind, Path, QPath, UnOp,
13+
};
1014
use rustc_lint::{LateContext, LateLintPass};
1115
use rustc_session::{declare_lint_pass, declare_tool_lint};
1216
use rustc_span::sym;
@@ -127,21 +131,30 @@ fn detect_option_if_let_else<'tcx>(
127131
) -> Option<OptionIfLetElseOccurence> {
128132
if_chain! {
129133
if !in_macro(expr.span); // Don't lint macros, because it behaves weirdly
130-
if let ExprKind::Match(cond_expr, arms, MatchSource::IfLetDesugar{contains_else_clause: true}) = &expr.kind;
134+
if !in_constant(cx, expr.hir_id);
135+
if let ExprKind::Match(cond_expr, [some_arm, none_arm], MatchSource::IfLetDesugar{contains_else_clause: true})
136+
= &expr.kind;
131137
if !is_else_clause(cx.tcx, expr);
132-
if arms.len() == 2;
133138
if !is_result_ok(cx, cond_expr); // Don't lint on Result::ok because a different lint does it already
134-
if let PatKind::TupleStruct(struct_qpath, [inner_pat], _) = &arms[0].pat.kind;
139+
if let PatKind::TupleStruct(struct_qpath, [inner_pat], _) = &some_arm.pat.kind;
135140
if is_lang_ctor(cx, struct_qpath, OptionSome);
136141
if let PatKind::Binding(bind_annotation, _, id, _) = &inner_pat.kind;
137-
if !contains_return_break_continue_macro(arms[0].body);
138-
if !contains_return_break_continue_macro(arms[1].body);
142+
if let Some(some_captures) = can_move_expr_to_closure(cx, some_arm.body);
143+
if let Some(none_captures) = can_move_expr_to_closure(cx, none_arm.body);
144+
if some_captures
145+
.iter()
146+
.filter_map(|(id, &c)| none_captures.get(id).map(|&c2| (c, c2)))
147+
.all(|(x, y)| x.is_imm_ref() && y.is_imm_ref());
139148

140149
then {
141150
let capture_mut = if bind_annotation == &BindingAnnotation::Mutable { "mut " } else { "" };
142-
let some_body = extract_body_from_arm(&arms[0])?;
143-
let none_body = extract_body_from_arm(&arms[1])?;
144-
let method_sugg = if eager_or_lazy::is_eagerness_candidate(cx, none_body) { "map_or" } else { "map_or_else" };
151+
let some_body = extract_body_from_arm(some_arm)?;
152+
let none_body = extract_body_from_arm(none_arm)?;
153+
let method_sugg = if eager_or_lazy::is_eagerness_candidate(cx, none_body) {
154+
"map_or"
155+
} else {
156+
"map_or_else"
157+
};
145158
let capture_name = id.name.to_ident_string();
146159
let (as_ref, as_mut) = match &cond_expr.kind {
147160
ExprKind::AddrOf(_, Mutability::Not, _) => (true, false),
@@ -153,6 +166,24 @@ fn detect_option_if_let_else<'tcx>(
153166
ExprKind::Unary(UnOp::Deref, expr) | ExprKind::AddrOf(_, _, expr) => expr,
154167
_ => cond_expr,
155168
};
169+
// Check if captures the closure will need conflict with borrows made in the scrutinee.
170+
// TODO: check all the references made in the scrutinee expression. This will require interacting
171+
// with the borrow checker. Currently only `<local>[.<field>]*` is checked for.
172+
if as_ref || as_mut {
173+
let e = peel_hir_expr_while(cond_expr, |e| match e.kind {
174+
ExprKind::Field(e, _) | ExprKind::AddrOf(_, _, e) => Some(e),
175+
_ => None,
176+
});
177+
if let ExprKind::Path(QPath::Resolved(None, Path { res: Res::Local(l), .. })) = e.kind {
178+
match some_captures.get(l)
179+
.or_else(|| (method_sugg == "map_or_else").then(|| ()).and_then(|_| none_captures.get(l)))
180+
{
181+
Some(CaptureKind::Value | CaptureKind::Ref(Mutability::Mut)) => return None,
182+
Some(CaptureKind::Ref(Mutability::Not)) if as_mut => return None,
183+
Some(CaptureKind::Ref(Mutability::Not)) | None => (),
184+
}
185+
}
186+
}
156187
Some(OptionIfLetElseOccurence {
157188
option: format_option_in_sugg(cx, cond_expr, as_ref, as_mut),
158189
method_sugg: method_sugg.to_string(),

‎clippy_utils/src/lib.rs‎

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -709,6 +709,11 @@ pub enum CaptureKind {
709709
Value,
710710
Ref(Mutability),
711711
}
712+
impl CaptureKind {
713+
pub fn is_imm_ref(self) -> bool {
714+
self == Self::Ref(Mutability::Not)
715+
}
716+
}
712717
impl std::ops::BitOr for CaptureKind {
713718
type Output = Self;
714719
fn bitor(self, rhs: Self) -> Self::Output {

‎tests/ui/option_if_let_else.fixed‎

Lines changed: 42 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -86,4 +86,46 @@ fn main() {
8686
test_map_or_else(None);
8787
let _ = negative_tests(None);
8888
let _ = impure_else(None);
89+
90+
let _ = Some(0).map_or(0, |x| loop {
91+
if x == 0 {
92+
break x;
93+
}
94+
});
95+
96+
// #7576
97+
const fn _f(x: Option<u32>) -> u32 {
98+
// Don't lint, `map_or` isn't const
99+
if let Some(x) = x { x } else { 10 }
100+
}
101+
102+
// #5822
103+
let s = String::new();
104+
// Don't lint, `Some` branch consumes `s`, but else branch uses `s`
105+
let _ = if let Some(x) = Some(0) {
106+
let s = s;
107+
s.len() + x
108+
} else {
109+
s.len()
110+
};
111+
112+
let s = String::new();
113+
// Lint, both branches immutably borrow `s`.
114+
let _ = Some(0).map_or_else(|| s.len(), |x| s.len() + x);
115+
116+
let s = String::new();
117+
// Lint, `Some` branch consumes `s`, but else branch doesn't use `s`.
118+
let _ = Some(0).map_or(1, |x| {
119+
let s = s;
120+
s.len() + x
121+
});
122+
123+
let s = Some(String::new());
124+
// Don't lint, `Some` branch borrows `s`, but else branch consumes `s`
125+
let _ = if let Some(x) = &s {
126+
x.len()
127+
} else {
128+
let _s = s;
129+
10
130+
};
89131
}

‎tests/ui/option_if_let_else.rs‎

Lines changed: 48 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -105,4 +105,52 @@ fn main() {
105105
test_map_or_else(None);
106106
let _ = negative_tests(None);
107107
let _ = impure_else(None);
108+
109+
let _ = if let Some(x) = Some(0) {
110+
loop {
111+
if x == 0 {
112+
break x;
113+
}
114+
}
115+
} else {
116+
0
117+
};
118+
119+
// #7576
120+
const fn _f(x: Option<u32>) -> u32 {
121+
// Don't lint, `map_or` isn't const
122+
if let Some(x) = x { x } else { 10 }
123+
}
124+
125+
// #5822
126+
let s = String::new();
127+
// Don't lint, `Some` branch consumes `s`, but else branch uses `s`
128+
let _ = if let Some(x) = Some(0) {
129+
let s = s;
130+
s.len() + x
131+
} else {
132+
s.len()
133+
};
134+
135+
let s = String::new();
136+
// Lint, both branches immutably borrow `s`.
137+
let _ = if let Some(x) = Some(0) { s.len() + x } else { s.len() };
138+
139+
let s = String::new();
140+
// Lint, `Some` branch consumes `s`, but else branch doesn't use `s`.
141+
let _ = if let Some(x) = Some(0) {
142+
let s = s;
143+
s.len() + x
144+
} else {
145+
1
146+
};
147+
148+
let s = Some(String::new());
149+
// Don't lint, `Some` branch borrows `s`, but else branch consumes `s`
150+
let _ = if let Some(x) = &s {
151+
x.len()
152+
} else {
153+
let _s = s;
154+
10
155+
};
108156
}

‎tests/ui/option_if_let_else.stderr‎

Lines changed: 49 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -148,5 +148,53 @@ error: use Option::map_or instead of an if let/else
148148
LL | let _ = if let Some(x) = optional { x + 2 } else { 5 };
149149
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `optional.map_or(5, |x| x + 2)`
150150

151-
error: aborting due to 11 previous errors
151+
error: use Option::map_or instead of an if let/else
152+
--> $DIR/option_if_let_else.rs:109:13
153+
|
154+
LL | let _ = if let Some(x) = Some(0) {
155+
| _____________^
156+
LL | | loop {
157+
LL | | if x == 0 {
158+
LL | | break x;
159+
... |
160+
LL | | 0
161+
LL | | };
162+
| |_____^
163+
|
164+
help: try
165+
|
166+
LL ~ let _ = Some(0).map_or(0, |x| loop {
167+
LL + if x == 0 {
168+
LL + break x;
169+
LL + }
170+
LL ~ });
171+
|
172+
173+
error: use Option::map_or_else instead of an if let/else
174+
--> $DIR/option_if_let_else.rs:137:13
175+
|
176+
LL | let _ = if let Some(x) = Some(0) { s.len() + x } else { s.len() };
177+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `Some(0).map_or_else(|| s.len(), |x| s.len() + x)`
178+
179+
error: use Option::map_or instead of an if let/else
180+
--> $DIR/option_if_let_else.rs:141:13
181+
|
182+
LL | let _ = if let Some(x) = Some(0) {
183+
| _____________^
184+
LL | | let s = s;
185+
LL | | s.len() + x
186+
LL | | } else {
187+
LL | | 1
188+
LL | | };
189+
| |_____^
190+
|
191+
help: try
192+
|
193+
LL ~ let _ = Some(0).map_or(1, |x| {
194+
LL + let s = s;
195+
LL + s.len() + x
196+
LL ~ });
197+
|
198+
199+
error: aborting due to 14 previous errors
152200

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