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fix(map_entry): don't autofix when {e.insert(_); None } would be required #15810

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fix(map_entry): don't autofix when {e.insert(_); None } would be required #15810

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816cc54
clean-up, add some comments
ada4a Sep 24, 2025
283d07e
fix(map_entry): don't autofix when `{e.insert(_); None }` would be re…
ada4a Sep 24, 2025
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85 changes: 49 additions & 36 deletions clippy_lints/src/entry.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -87,8 +87,8 @@ impl<'tcx> LateLintPass<'tcx> for HashMapPass {

let lint_msg = format!("usage of `contains_key` followed by `insert` on a `{}`", map_ty.name());
let mut app = Applicability::MachineApplicable;
let map_str = snippet_with_context(cx, contains_expr.map.span, contains_expr.call_ctxt, "..", &mut app).0;
let key_str = snippet_with_context(cx, contains_expr.key.span, contains_expr.call_ctxt, "..", &mut app).0;
let map_str = snippet_with_context(cx, contains_expr.map.span, contains_expr.call_ctxt, "(_)", &mut app).0;
let key_str = snippet_with_context(cx, contains_expr.key.span, contains_expr.call_ctxt, "_", &mut app).0;

let sugg = if let Some(else_expr) = else_expr {
let Some(else_search) = find_insert_calls(cx, &contains_expr, else_expr) else {
Expand Down Expand Up @@ -142,8 +142,11 @@ impl<'tcx> LateLintPass<'tcx> for HashMapPass {
let indent_str = snippet_indent(cx, expr.span);
let indent_str = indent_str.as_deref().unwrap_or("");
Some(format!(
"match {map_str}.entry({key_str}) {{\n{indent_str} {entry}::{then_entry} => {}\n\
{indent_str} {entry}::{else_entry} => {}\n{indent_str}}}",
"\
match {map_str}.entry({key_str}) {{
{indent_str} {entry}::{then_entry} => {}
{indent_str} {entry}::{else_entry} => {}
{indent_str}}}",
reindent_multiline(&then_str, true, Some(4 + indent_str.len())),
reindent_multiline(&else_str, true, Some(4 + indent_str.len())),
entry = map_ty.entry_path(),
Expand All @@ -167,7 +170,7 @@ impl<'tcx> LateLintPass<'tcx> for HashMapPass {
map_ty.entry_path(),
))
} else if let Some(insertion) = then_search.as_single_insertion() {
let value_str = snippet_with_context(cx, insertion.value.span, then_expr.span.ctxt(), "..", &mut app).0;
let value_str = snippet_with_context(cx, insertion.value.span, then_expr.span.ctxt(), "_", &mut app).0;
if contains_expr.negated {
if insertion.value.can_have_side_effects() {
Some(format!("{map_str}.entry({key_str}).or_insert_with(|| {value_str});"))
Expand Down Expand Up @@ -312,15 +315,12 @@ struct InsertExpr<'tcx> {
///
/// If the given expression is not an `insert` call into a `BTreeMap` or a `HashMap`, return `None`.
fn try_parse_insert<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<InsertExpr<'tcx>> {
if let ExprKind::MethodCall(_, map, [key, value], _) = expr.kind {
let id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
if let Some(insert) = cx.tcx.get_diagnostic_name(id)
&& matches!(insert, sym::btreemap_insert | sym::hashmap_insert)
{
Some(InsertExpr { map, key, value })
} else {
None
}
if let ExprKind::MethodCall(_, map, [key, value], _) = expr.kind
&& let Some(id) = cx.typeck_results().type_dependent_def_id(expr.hir_id)
&& let Some(insert) = cx.tcx.get_diagnostic_name(id)
&& matches!(insert, sym::btreemap_insert | sym::hashmap_insert)
{
Some(InsertExpr { map, key, value })
} else {
None
}
Expand Down Expand Up @@ -524,15 +524,15 @@ impl<'tcx> Visitor<'tcx> for InsertSearcher<'_, 'tcx> {
ExprKind::If(cond_expr, then_expr, Some(else_expr)) => {
self.is_single_insert = false;
self.visit_non_tail_expr(cond_expr);
// Each branch may contain it's own insert expression.
// Each branch may contain its own insert expression.
let mut is_map_used = self.visit_cond_arm(then_expr);
is_map_used |= self.visit_cond_arm(else_expr);
self.is_map_used = is_map_used;
},
ExprKind::Match(scrutinee_expr, arms, _) => {
self.is_single_insert = false;
self.visit_non_tail_expr(scrutinee_expr);
// Each branch may contain it's own insert expression.
// Each branch may contain its own insert expression.
let mut is_map_used = self.is_map_used;
for arm in arms {
self.visit_pat(arm.pat);
Expand Down Expand Up @@ -609,6 +609,25 @@ impl<'tcx> InsertSearchResults<'tcx> {
self.is_single_insert.then(|| self.edits[0].as_insertion().unwrap())
}

/// Create a snippet with all the `insert`s on the map replaced with `insert`s on the entry.
///
/// `write_wrapped` will be called whenever the `insert` is an expression that is used, or has
/// its type unified with another branch -- for example, in cases like:
/// ```ignore
/// let _ = if !m.contains(&k) {
/// m.insert(k, v)
/// } else {
/// None
/// };
///
/// let _ = if m.contains(&k) {
/// if true { m.insert(k, v) } else { m.insert(k, v2) }
/// } else {
/// m.insert(k, v3)
/// }
/// ```
/// The idea is that it will wrap the `insert` call so that it still type-checks with the code
/// surrounding it.
fn snippet(
&self,
cx: &LateContext<'_>,
Expand All @@ -619,6 +638,7 @@ impl<'tcx> InsertSearchResults<'tcx> {
let ctxt = span.ctxt();
let mut res = String::new();
for insertion in self.edits.iter().filter_map(|e| e.as_insertion()) {
// Take everything until the call verbatim
res.push_str(&snippet_with_applicability(
cx,
span.until(insertion.call.span),
Expand All @@ -628,11 +648,8 @@ impl<'tcx> InsertSearchResults<'tcx> {
if is_expr_used_or_unified(cx.tcx, insertion.call) {
write_wrapped(&mut res, insertion, ctxt, app);
} else {
let _: fmt::Result = write!(
res,
"e.insert({})",
snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0
);
let value_str = snippet_with_context(cx, insertion.value.span, ctxt, "_", app).0;
let _: fmt::Result = write!(res, "e.insert({value_str})");
}
span = span.trim_start(insertion.call.span).unwrap_or(DUMMY_SP);
}
Expand All @@ -644,11 +661,8 @@ impl<'tcx> InsertSearchResults<'tcx> {
(
self.snippet(cx, span, app, |res, insertion, ctxt, app| {
// Insertion into a map would return `Some(&mut value)`, but the entry returns `&mut value`
let _: fmt::Result = write!(
res,
"Some(e.insert({}))",
snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0
);
let value_str = snippet_with_context(cx, insertion.value.span, ctxt, "_", app).0;
let _: fmt::Result = write!(res, "Some(e.insert({value_str}))");
}),
"Occupied(mut e)",
)
Expand All @@ -658,20 +672,18 @@ impl<'tcx> InsertSearchResults<'tcx> {
(
self.snippet(cx, span, app, |res, insertion, ctxt, app| {
// Insertion into a map would return `None`, but the entry returns a mutable reference.
let value_str = snippet_with_context(cx, insertion.value.span, ctxt, "_", app).0;
let _: fmt::Result = if is_expr_final_block_expr(cx.tcx, insertion.call) {
write!(
res,
"e.insert({});\n{}None",
snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0,
snippet_indent(cx, insertion.call.span).as_deref().unwrap_or(""),
"e.insert({value_str});\n{indent}None",
indent = snippet_indent(cx, insertion.call.span).as_deref().unwrap_or(""),
)
} else {
write!(
res,
"{{ e.insert({}); None }}",
snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0,
)
write!(res, "{{ e.insert({value_str}); None }}")
};
// This might leave `None`'s type ambiguous, so reduce applicability
*app = Applicability::MaybeIncorrect;
}),
"Vacant(e)",
)
Expand All @@ -683,14 +695,15 @@ impl<'tcx> InsertSearchResults<'tcx> {
for edit in &self.edits {
match *edit {
Edit::Insertion(insertion) => {
// Cut out the value from `map.insert(key, value)`
// Take everything until the call verbatim
res.push_str(&snippet_with_applicability(
cx,
span.until(insertion.call.span),
"..",
app,
));
res.push_str(&snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0);
let value_str = snippet_with_context(cx, insertion.value.span, ctxt, "_", app).0;
res.push_str(&value_str);
span = span.trim_start(insertion.call.span).unwrap_or(DUMMY_SP);
},
Edit::RemoveSemi(semi_span) => {
Expand Down
2 changes: 1 addition & 1 deletion tests/ui/entry.fixed
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
//@needs-asm-support

#![allow(unused, clippy::needless_pass_by_value, clippy::collapsible_if)]
#![allow(clippy::needless_pass_by_value, clippy::collapsible_if)]
#![warn(clippy::map_entry)]

use std::arch::asm;
Expand Down
2 changes: 1 addition & 1 deletion tests/ui/entry.rs
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
//@needs-asm-support

#![allow(unused, clippy::needless_pass_by_value, clippy::collapsible_if)]
#![allow(clippy::needless_pass_by_value, clippy::collapsible_if)]
#![warn(clippy::map_entry)]

use std::arch::asm;
Expand Down
1 change: 0 additions & 1 deletion tests/ui/entry_btree.fixed
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Original file line number Diff line number Diff line change
@@ -1,5 +1,4 @@
#![warn(clippy::map_entry)]
#![allow(dead_code)]

use std::collections::BTreeMap;

Expand Down
1 change: 0 additions & 1 deletion tests/ui/entry_btree.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,4 @@
#![warn(clippy::map_entry)]
#![allow(dead_code)]

use std::collections::BTreeMap;

Expand Down
2 changes: 1 addition & 1 deletion tests/ui/entry_btree.stderr
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
error: usage of `contains_key` followed by `insert` on a `BTreeMap`
--> tests/ui/entry_btree.rs:10:5
--> tests/ui/entry_btree.rs:9:5
|
LL | / if !m.contains_key(&k) {
LL | |
Expand Down
76 changes: 42 additions & 34 deletions tests/ui/entry_unfixable.rs
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
//@no-rustfix
#![allow(clippy::needless_pass_by_value, clippy::collapsible_if)]
#![warn(clippy::map_entry)]

Expand All @@ -14,40 +15,6 @@ macro_rules! insert {
};
}

mod issue13306 {
use std::collections::HashMap;

struct Env {
enclosing: Option<Box<Env>>,
values: HashMap<String, usize>,
}

impl Env {
fn assign(&mut self, name: String, value: usize) -> bool {
if !self.values.contains_key(&name) {
//~^ map_entry
self.values.insert(name, value);
true
} else if let Some(enclosing) = &mut self.enclosing {
enclosing.assign(name, value)
} else {
false
}
}
}
}

fn issue9925(mut hm: HashMap<String, bool>) {
let key = "hello".to_string();
if hm.contains_key(&key) {
//~^ map_entry
let bval = hm.get_mut(&key).unwrap();
*bval = false;
} else {
hm.insert(key, true);
}
}

mod issue9470 {
use std::collections::HashMap;
use std::sync::Mutex;
Expand Down Expand Up @@ -90,4 +57,45 @@ mod issue9470 {
}
}

fn issue9925(mut hm: HashMap<String, bool>) {
let key = "hello".to_string();
if hm.contains_key(&key) {
//~^ map_entry
let bval = hm.get_mut(&key).unwrap();
*bval = false;
} else {
hm.insert(key, true);
}
}

mod issue13306 {
use std::collections::HashMap;

struct Env {
enclosing: Option<Box<Env>>,
values: HashMap<String, usize>,
}

impl Env {
fn assign(&mut self, name: String, value: usize) -> bool {
if !self.values.contains_key(&name) {
//~^ map_entry
self.values.insert(name, value);
true
} else if let Some(enclosing) = &mut self.enclosing {
enclosing.assign(name, value)
} else {
false
}
}
}
}

fn issue15307<K: Eq + Hash, V>(mut m: HashMap<K, V>, k: K, v: V) {
if !m.contains_key(&k) {
//~^ map_entry
assert!(m.insert(k, v).is_none());
}
}

fn main() {}
45 changes: 31 additions & 14 deletions tests/ui/entry_unfixable.stderr
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Original file line number Diff line number Diff line change
@@ -1,12 +1,12 @@
error: usage of `contains_key` followed by `insert` on a `HashMap`
--> tests/ui/entry_unfixable.rs:27:13
--> tests/ui/entry_unfixable.rs:47:13
|
LL | / if !self.values.contains_key(&name) {
LL | / if self.globals.contains_key(&name) {
LL | |
LL | | self.values.insert(name, value);
LL | | true
... |
LL | | false
LL | | self.globals.insert(name, value);
LL | | } else {
LL | | let interner = INTERNER.lock().unwrap();
LL | | return Err(interner.resolve(name).unwrap().to_owned());
LL | | }
| |_____________^
|
Expand All @@ -15,7 +15,7 @@ LL | | }
= help: to override `-D warnings` add `#[allow(clippy::map_entry)]`

error: usage of `contains_key` followed by `insert` on a `HashMap`
--> tests/ui/entry_unfixable.rs:42:5
--> tests/ui/entry_unfixable.rs:62:5
|
LL | / if hm.contains_key(&key) {
LL | |
Expand All @@ -29,18 +29,35 @@ LL | | }
= help: consider using the `Entry` API: https://doc.rust-lang.org/std/collections/struct.HashMap.html#entry-api

error: usage of `contains_key` followed by `insert` on a `HashMap`
--> tests/ui/entry_unfixable.rs:80:13
--> tests/ui/entry_unfixable.rs:81:13
|
LL | / if self.globals.contains_key(&name) {
LL | / if !self.values.contains_key(&name) {
LL | |
LL | | self.globals.insert(name, value);
LL | | } else {
LL | | let interner = INTERNER.lock().unwrap();
LL | | return Err(interner.resolve(name).unwrap().to_owned());
LL | | self.values.insert(name, value);
LL | | true
... |
LL | | false
LL | | }
| |_____________^
|
= help: consider using the `Entry` API: https://doc.rust-lang.org/std/collections/struct.HashMap.html#entry-api

error: aborting due to 3 previous errors
error: usage of `contains_key` followed by `insert` on a `HashMap`
--> tests/ui/entry_unfixable.rs:95:5
|
LL | / if !m.contains_key(&k) {
LL | |
LL | | assert!(m.insert(k, v).is_none());
LL | | }
| |_____^
|
help: try
|
LL ~ if let std::collections::hash_map::Entry::Vacant(e) = m.entry(k) {
LL +
LL + assert!({ e.insert(v); None }.is_none());
LL + }
|

error: aborting due to 4 previous errors

2 changes: 1 addition & 1 deletion tests/ui/entry_with_else.fixed
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
#![allow(unused, clippy::needless_pass_by_value, clippy::collapsible_if)]
#![allow(clippy::needless_pass_by_value, clippy::collapsible_if)]
#![warn(clippy::map_entry)]

use std::collections::{BTreeMap, HashMap};
Expand Down
2 changes: 1 addition & 1 deletion tests/ui/entry_with_else.rs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
#![allow(unused, clippy::needless_pass_by_value, clippy::collapsible_if)]
#![allow(clippy::needless_pass_by_value, clippy::collapsible_if)]
#![warn(clippy::map_entry)]

use std::collections::{BTreeMap, HashMap};
Expand Down