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Fix option_if_let_else

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* `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
This commit is contained in:
Jason Newcomb 2021-08-16 15:42:52 -04:00
parent 983e5b877e
commit 8b3ca9a315
No known key found for this signature in database
GPG Key ID: DA59E8643A37ED06
5 changed files with 186 additions and 12 deletions
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53
clippy_lints/src/option_if_let_else.rs
View File

@ -1,12 +1,16 @@
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::sugg::Sugg;
use clippy_utils::ty::is_type_diagnostic_item;
use clippy_utils::usage::contains_return_break_continue_macro;
use clippy_utils::{eager_or_lazy, in_macro, is_else_clause, is_lang_ctor};
use clippy_utils::{
can_move_expr_to_closure, eager_or_lazy, in_constant, in_macro, is_else_clause, is_lang_ctor, peel_hir_expr_while,
CaptureKind,
};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::LangItem::OptionSome;
use rustc_hir::{Arm, BindingAnnotation, Block, Expr, ExprKind, MatchSource, Mutability, PatKind, UnOp};
use rustc_hir::{
def::Res, Arm, BindingAnnotation, Block, Expr, ExprKind, MatchSource, Mutability, PatKind, Path, QPath, UnOp,
};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::sym;
@ -127,21 +131,30 @@ fn detect_option_if_let_else<'tcx>(
) -> Option<OptionIfLetElseOccurence> {
if_chain! {
if !in_macro(expr.span); // Don't lint macros, because it behaves weirdly
if let ExprKind::Match(cond_expr, arms, MatchSource::IfLetDesugar{contains_else_clause: true}) = &expr.kind;
if !in_constant(cx, expr.hir_id);
if let ExprKind::Match(cond_expr, [some_arm, none_arm], MatchSource::IfLetDesugar{contains_else_clause: true})
= &expr.kind;
if !is_else_clause(cx.tcx, expr);
if arms.len() == 2;
if !is_result_ok(cx, cond_expr); // Don't lint on Result::ok because a different lint does it already
if let PatKind::TupleStruct(struct_qpath, [inner_pat], _) = &arms[0].pat.kind;
if let PatKind::TupleStruct(struct_qpath, [inner_pat], _) = &some_arm.pat.kind;
if is_lang_ctor(cx, struct_qpath, OptionSome);
if let PatKind::Binding(bind_annotation, _, id, _) = &inner_pat.kind;
if !contains_return_break_continue_macro(arms[0].body);
if !contains_return_break_continue_macro(arms[1].body);
if let Some(some_captures) = can_move_expr_to_closure(cx, some_arm.body);
if let Some(none_captures) = can_move_expr_to_closure(cx, none_arm.body);
if some_captures
.iter()
.filter_map(|(id, &c)| none_captures.get(id).map(|&c2| (c, c2)))
.all(|(x, y)| x.is_imm_ref() && y.is_imm_ref());
then {
let capture_mut = if bind_annotation == &BindingAnnotation::Mutable { "mut " } else { "" };
let some_body = extract_body_from_arm(&arms[0])?;
let none_body = extract_body_from_arm(&arms[1])?;
let method_sugg = if eager_or_lazy::is_eagerness_candidate(cx, none_body) { "map_or" } else { "map_or_else" };
let some_body = extract_body_from_arm(some_arm)?;
let none_body = extract_body_from_arm(none_arm)?;
let method_sugg = if eager_or_lazy::is_eagerness_candidate(cx, none_body) {
"map_or"
} else {
"map_or_else"
};
let capture_name = id.name.to_ident_string();
let (as_ref, as_mut) = match &cond_expr.kind {
ExprKind::AddrOf(_, Mutability::Not, _) => (true, false),
@ -153,6 +166,24 @@ fn detect_option_if_let_else<'tcx>(
ExprKind::Unary(UnOp::Deref, expr) | ExprKind::AddrOf(_, _, expr) => expr,
_ => cond_expr,
};
// Check if captures the closure will need conflict with borrows made in the scrutinee.
// TODO: check all the references made in the scrutinee expression. This will require interacting
// with the borrow checker. Currently only `<local>[.<field>]*` is checked for.
if as_ref || as_mut {
let e = peel_hir_expr_while(cond_expr, |e| match e.kind {
ExprKind::Field(e, _) | ExprKind::AddrOf(_, _, e) => Some(e),
_ => None,
});
if let ExprKind::Path(QPath::Resolved(None, Path { res: Res::Local(l), .. })) = e.kind {
match some_captures.get(l)
.or_else(|| (method_sugg == "map_or_else").then(|| ()).and_then(|_| none_captures.get(l)))
{
Some(CaptureKind::Value | CaptureKind::Ref(Mutability::Mut)) => return None,
Some(CaptureKind::Ref(Mutability::Not)) if as_mut => return None,
Some(CaptureKind::Ref(Mutability::Not)) | None => (),
}
}
}
Some(OptionIfLetElseOccurence {
option: format_option_in_sugg(cx, cond_expr, as_ref, as_mut),
method_sugg: method_sugg.to_string(),

5
clippy_utils/src/lib.rs
View File

@ -709,6 +709,11 @@ pub enum CaptureKind {
Value,
Ref(Mutability),
}
impl CaptureKind {
pub fn is_imm_ref(self) -> bool {
self == Self::Ref(Mutability::Not)
}
}
impl std::ops::BitOr for CaptureKind {
type Output = Self;
fn bitor(self, rhs: Self) -> Self::Output {

42
tests/ui/option_if_let_else.fixed
View File

@ -86,4 +86,46 @@ fn main() {
test_map_or_else(None);
let _ = negative_tests(None);
let _ = impure_else(None);
let _ = Some(0).map_or(0, |x| loop {
if x == 0 {
break x;
}
});
// #7576
const fn _f(x: Option<u32>) -> u32 {
// Don't lint, `map_or` isn't const
if let Some(x) = x { x } else { 10 }
}
// #5822
let s = String::new();
// Don't lint, `Some` branch consumes `s`, but else branch uses `s`
let _ = if let Some(x) = Some(0) {
let s = s;
s.len() + x
} else {
s.len()
};
let s = String::new();
// Lint, both branches immutably borrow `s`.
let _ = Some(0).map_or_else(|| s.len(), |x| s.len() + x);
let s = String::new();
// Lint, `Some` branch consumes `s`, but else branch doesn't use `s`.
let _ = Some(0).map_or(1, |x| {
let s = s;
s.len() + x
});
let s = Some(String::new());
// Don't lint, `Some` branch borrows `s`, but else branch consumes `s`
let _ = if let Some(x) = &s {
x.len()
} else {
let _s = s;
10
};
}

48
tests/ui/option_if_let_else.rs
View File

@ -105,4 +105,52 @@ fn main() {
test_map_or_else(None);
let _ = negative_tests(None);
let _ = impure_else(None);
let _ = if let Some(x) = Some(0) {
loop {
if x == 0 {
break x;
}
}
} else {
0
};
// #7576
const fn _f(x: Option<u32>) -> u32 {
// Don't lint, `map_or` isn't const
if let Some(x) = x { x } else { 10 }
}
// #5822
let s = String::new();
// Don't lint, `Some` branch consumes `s`, but else branch uses `s`
let _ = if let Some(x) = Some(0) {
let s = s;
s.len() + x
} else {
s.len()
};
let s = String::new();
// Lint, both branches immutably borrow `s`.
let _ = if let Some(x) = Some(0) { s.len() + x } else { s.len() };
let s = String::new();
// Lint, `Some` branch consumes `s`, but else branch doesn't use `s`.
let _ = if let Some(x) = Some(0) {
let s = s;
s.len() + x
} else {
1
};
let s = Some(String::new());
// Don't lint, `Some` branch borrows `s`, but else branch consumes `s`
let _ = if let Some(x) = &s {
x.len()
} else {
let _s = s;
10
};
}

50
tests/ui/option_if_let_else.stderr
View File

@ -148,5 +148,53 @@ error: use Option::map_or instead of an if let/else
LL | let _ = if let Some(x) = optional { x + 2 } else { 5 };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `optional.map_or(5, |x| x + 2)`
error: aborting due to 11 previous errors
error: use Option::map_or instead of an if let/else
--> $DIR/option_if_let_else.rs:109:13
|
LL | let _ = if let Some(x) = Some(0) {
| _____________^
LL | | loop {
LL | | if x == 0 {
LL | | break x;
... |
LL | | 0
LL | | };
| |_____^
|
help: try
|
LL ~ let _ = Some(0).map_or(0, |x| loop {
LL + if x == 0 {
LL + break x;
LL + }
LL ~ });
|
error: use Option::map_or_else instead of an if let/else
--> $DIR/option_if_let_else.rs:137:13
|
LL | let _ = if let Some(x) = Some(0) { s.len() + x } else { s.len() };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `Some(0).map_or_else(|| s.len(), |x| s.len() + x)`
error: use Option::map_or instead of an if let/else
--> $DIR/option_if_let_else.rs:141:13
|
LL | let _ = if let Some(x) = Some(0) {
| _____________^
LL | | let s = s;
LL | | s.len() + x
LL | | } else {
LL | | 1
LL | | };
| |_____^
|
help: try
|
LL ~ let _ = Some(0).map_or(1, |x| {
LL + let s = s;
LL + s.len() + x
LL ~ });
|
error: aborting due to 14 previous errors