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Do not replace .unwrap_or(vec![]) by .unwrap_or_default() #15699

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merged 2 commits into from
Sep 18, 2025
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Do not replace .unwrap_or(vec![]) by .unwrap_or_default() #15699

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68473ad
Check that `.unwrap_or(LITERAL)` doesn't trigger `unwrap_or_default`
samueltardieu Sep 18, 2025
ad21dff
Do not replace `.unwrap_or(vec![])` by `.unwrap_or_default()`
samueltardieu Sep 18, 2025
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7 changes: 7 additions & 0 deletions clippy_lints/src/methods/or_fun_call.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@ use std::ops::ControlFlow;

use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::eager_or_lazy::switch_to_lazy_eval;
use clippy_utils::higher::VecArgs;
use clippy_utils::source::snippet_with_context;
use clippy_utils::ty::{expr_type_is_certain, implements_trait, is_type_diagnostic_item};
use clippy_utils::visitors::for_each_expr;
Expand Down Expand Up @@ -97,6 +98,12 @@ pub(super) fn check<'tcx>(
return false;
}

// `.unwrap_or(vec![])` is as readable as `.unwrap_or_default()`. And if the expression is a
// non-empty `Vec`, then it will not be a default value anyway. Bail out in all cases.
if call_expr.and_then(|call_expr| VecArgs::hir(cx, call_expr)).is_some() {
return false;
}

// needs to target Default::default in particular or be *::new and have a Default impl
// available
if (is_new(fun) && output_type_implements_default(fun))
Expand Down
16 changes: 16 additions & 0 deletions tests/ui/or_fun_call.fixed
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Expand Up @@ -77,6 +77,22 @@ fn or_fun_call() {
with_default_type.unwrap_or_default();
//~^ unwrap_or_default

let with_default_literal = Some(1);
with_default_literal.unwrap_or(0);
// Do not lint because `.unwrap_or_default()` wouldn't be simpler

let with_default_literal = Some(1.0);
with_default_literal.unwrap_or(0.0);
// Do not lint because `.unwrap_or_default()` wouldn't be simpler

let with_default_literal = Some("foo");
with_default_literal.unwrap_or("");
// Do not lint because `.unwrap_or_default()` wouldn't be simpler

let with_default_vec_macro = Some(vec![1, 2, 3]);
with_default_vec_macro.unwrap_or(vec![]);
// Do not lint because `.unwrap_or_default()` wouldn't be simpler

let self_default = None::<FakeDefault>;
self_default.unwrap_or_else(<FakeDefault>::default);
//~^ or_fun_call
Expand Down
22 changes: 19 additions & 3 deletions tests/ui/or_fun_call.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -77,6 +77,22 @@ fn or_fun_call() {
with_default_type.unwrap_or(u64::default());
//~^ unwrap_or_default

let with_default_literal = Some(1);
with_default_literal.unwrap_or(0);
// Do not lint because `.unwrap_or_default()` wouldn't be simpler

let with_default_literal = Some(1.0);
with_default_literal.unwrap_or(0.0);
// Do not lint because `.unwrap_or_default()` wouldn't be simpler

let with_default_literal = Some("foo");
with_default_literal.unwrap_or("");
// Do not lint because `.unwrap_or_default()` wouldn't be simpler

let with_default_vec_macro = Some(vec![1, 2, 3]);
with_default_vec_macro.unwrap_or(vec![]);
// Do not lint because `.unwrap_or_default()` wouldn't be simpler

let self_default = None::<FakeDefault>;
self_default.unwrap_or(<FakeDefault>::default());
//~^ or_fun_call
Expand All @@ -86,7 +102,7 @@ fn or_fun_call() {
//~^ unwrap_or_default

let with_vec = Some(vec![1]);
with_vec.unwrap_or(vec![]);
with_vec.unwrap_or(Vec::new());
//~^ unwrap_or_default

let without_default = Some(Foo);
Expand All @@ -98,15 +114,15 @@ fn or_fun_call() {
//~^ unwrap_or_default

let mut map_vec = HashMap::<u64, Vec<i32>>::new();
map_vec.entry(42).or_insert(vec![]);
map_vec.entry(42).or_insert(Vec::new());
//~^ unwrap_or_default

let mut btree = BTreeMap::<u64, String>::new();
btree.entry(42).or_insert(String::new());
//~^ unwrap_or_default

let mut btree_vec = BTreeMap::<u64, Vec<i32>>::new();
btree_vec.entry(42).or_insert(vec![]);
btree_vec.entry(42).or_insert(Vec::new());
//~^ unwrap_or_default

let stringy = Some(String::new());
Expand Down
88 changes: 44 additions & 44 deletions tests/ui/or_fun_call.stderr
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Expand Up @@ -47,175 +47,175 @@ LL | with_default_type.unwrap_or(u64::default());
| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_default()`

error: function call inside of `unwrap_or`
--> tests/ui/or_fun_call.rs:81:18
--> tests/ui/or_fun_call.rs:97:18
|
LL | self_default.unwrap_or(<FakeDefault>::default());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_else(<FakeDefault>::default)`

error: use of `unwrap_or` to construct default value
--> tests/ui/or_fun_call.rs:85:18
--> tests/ui/or_fun_call.rs:101:18
|
LL | real_default.unwrap_or(<FakeDefault as Default>::default());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_default()`

error: use of `unwrap_or` to construct default value
--> tests/ui/or_fun_call.rs:89:14
--> tests/ui/or_fun_call.rs:105:14
|
LL | with_vec.unwrap_or(vec![]);
| ^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_default()`
LL | with_vec.unwrap_or(Vec::new());
| ^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_default()`

error: function call inside of `unwrap_or`
--> tests/ui/or_fun_call.rs:93:21
--> tests/ui/or_fun_call.rs:109:21
|
LL | without_default.unwrap_or(Foo::new());
| ^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_else(Foo::new)`

error: use of `or_insert` to construct default value
--> tests/ui/or_fun_call.rs:97:19
--> tests/ui/or_fun_call.rs:113:19
|
LL | map.entry(42).or_insert(String::new());
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `or_default()`

error: use of `or_insert` to construct default value
--> tests/ui/or_fun_call.rs:101:23
--> tests/ui/or_fun_call.rs:117:23
|
LL | map_vec.entry(42).or_insert(vec![]);
| ^^^^^^^^^^^^^^^^^ help: try: `or_default()`
LL | map_vec.entry(42).or_insert(Vec::new());
| ^^^^^^^^^^^^^^^^^^^^^ help: try: `or_default()`

error: use of `or_insert` to construct default value
--> tests/ui/or_fun_call.rs:105:21
--> tests/ui/or_fun_call.rs:121:21
|
LL | btree.entry(42).or_insert(String::new());
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `or_default()`

error: use of `or_insert` to construct default value
--> tests/ui/or_fun_call.rs:109:25
--> tests/ui/or_fun_call.rs:125:25
|
LL | btree_vec.entry(42).or_insert(vec![]);
| ^^^^^^^^^^^^^^^^^ help: try: `or_default()`
LL | btree_vec.entry(42).or_insert(Vec::new());
| ^^^^^^^^^^^^^^^^^^^^^ help: try: `or_default()`

error: use of `unwrap_or` to construct default value
--> tests/ui/or_fun_call.rs:113:21
--> tests/ui/or_fun_call.rs:129:21
|
LL | let _ = stringy.unwrap_or(String::new());
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_default()`

error: function call inside of `ok_or`
--> tests/ui/or_fun_call.rs:118:17
--> tests/ui/or_fun_call.rs:134:17
|
LL | let _ = opt.ok_or(format!("{} world.", hello));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `ok_or_else(|| format!("{} world.", hello))`

error: function call inside of `unwrap_or`
--> tests/ui/or_fun_call.rs:123:21
--> tests/ui/or_fun_call.rs:139:21
|
LL | let _ = Some(1).unwrap_or(map[&1]);
| ^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_else(|| map[&1])`

error: function call inside of `unwrap_or`
--> tests/ui/or_fun_call.rs:126:21
--> tests/ui/or_fun_call.rs:142:21
|
LL | let _ = Some(1).unwrap_or(map[&1]);
| ^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_else(|| map[&1])`

error: function call inside of `or`
--> tests/ui/or_fun_call.rs:151:35
--> tests/ui/or_fun_call.rs:167:35
|
LL | let _ = Some("a".to_string()).or(Some("b".to_string()));
| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `or_else(|| Some("b".to_string()))`

error: function call inside of `unwrap_or`
--> tests/ui/or_fun_call.rs:194:18
--> tests/ui/or_fun_call.rs:210:18
|
LL | None.unwrap_or(ptr_to_ref(s));
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_else(|| ptr_to_ref(s))`

error: function call inside of `unwrap_or`
--> tests/ui/or_fun_call.rs:202:14
--> tests/ui/or_fun_call.rs:218:14
|
LL | None.unwrap_or(unsafe { ptr_to_ref(s) });
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_else(|| unsafe { ptr_to_ref(s) })`

error: function call inside of `unwrap_or`
--> tests/ui/or_fun_call.rs:205:14
--> tests/ui/or_fun_call.rs:221:14
|
LL | None.unwrap_or( unsafe { ptr_to_ref(s) } );
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_else(|| unsafe { ptr_to_ref(s) })`

error: function call inside of `map_or`
--> tests/ui/or_fun_call.rs:281:25
--> tests/ui/or_fun_call.rs:297:25
|
LL | let _ = Some(4).map_or(g(), |v| v);
| ^^^^^^^^^^^^^^^^^^ help: try: `map_or_else(g, |v| v)`

error: function call inside of `map_or`
--> tests/ui/or_fun_call.rs:283:25
--> tests/ui/or_fun_call.rs:299:25
|
LL | let _ = Some(4).map_or(g(), f);
| ^^^^^^^^^^^^^^ help: try: `map_or_else(g, f)`

error: function call inside of `map_or`
--> tests/ui/or_fun_call.rs:286:25
--> tests/ui/or_fun_call.rs:302:25
|
LL | let _ = Some(4).map_or("asd".to_string().len() as i32, f);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map_or_else(|| "asd".to_string().len() as i32, f)`

error: use of `unwrap_or_else` to construct default value
--> tests/ui/or_fun_call.rs:317:18
--> tests/ui/or_fun_call.rs:333:18
|
LL | with_new.unwrap_or_else(Vec::new);
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_default()`

error: use of `unwrap_or_else` to construct default value
--> tests/ui/or_fun_call.rs:321:28
--> tests/ui/or_fun_call.rs:337:28
|
LL | with_default_trait.unwrap_or_else(Default::default);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_default()`

error: use of `unwrap_or_else` to construct default value
--> tests/ui/or_fun_call.rs:325:27
--> tests/ui/or_fun_call.rs:341:27
|
LL | with_default_type.unwrap_or_else(u64::default);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_default()`

error: use of `unwrap_or_else` to construct default value
--> tests/ui/or_fun_call.rs:329:22
--> tests/ui/or_fun_call.rs:345:22
|
LL | real_default.unwrap_or_else(<FakeDefault as Default>::default);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_default()`

error: use of `or_insert_with` to construct default value
--> tests/ui/or_fun_call.rs:333:23
--> tests/ui/or_fun_call.rs:349:23
|
LL | map.entry(42).or_insert_with(String::new);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `or_default()`

error: use of `or_insert_with` to construct default value
--> tests/ui/or_fun_call.rs:337:25
--> tests/ui/or_fun_call.rs:353:25
|
LL | btree.entry(42).or_insert_with(String::new);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `or_default()`

error: use of `unwrap_or_else` to construct default value
--> tests/ui/or_fun_call.rs:341:25
--> tests/ui/or_fun_call.rs:357:25
|
LL | let _ = stringy.unwrap_or_else(String::new);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_default()`

error: function call inside of `unwrap_or`
--> tests/ui/or_fun_call.rs:383:17
--> tests/ui/or_fun_call.rs:399:17
|
LL | let _ = opt.unwrap_or({ f() }); // suggest `.unwrap_or_else(f)`
| ^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_else(f)`

error: function call inside of `unwrap_or`
--> tests/ui/or_fun_call.rs:388:17
--> tests/ui/or_fun_call.rs:404:17
|
LL | let _ = opt.unwrap_or(f() + 1); // suggest `.unwrap_or_else(|| f() + 1)`
| ^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_else(|| f() + 1)`

error: function call inside of `unwrap_or`
--> tests/ui/or_fun_call.rs:393:17
--> tests/ui/or_fun_call.rs:409:17
|
LL | let _ = opt.unwrap_or({
| _________________^
Expand All @@ -235,55 +235,55 @@ LL ~ });
|

error: function call inside of `map_or`
--> tests/ui/or_fun_call.rs:399:17
--> tests/ui/or_fun_call.rs:415:17
|
LL | let _ = opt.map_or(f() + 1, |v| v); // suggest `.map_or_else(|| f() + 1, |v| v)`
| ^^^^^^^^^^^^^^^^^^^^^^ help: try: `map_or_else(|| f() + 1, |v| v)`

error: use of `unwrap_or` to construct default value
--> tests/ui/or_fun_call.rs:404:17
--> tests/ui/or_fun_call.rs:420:17
|
LL | let _ = opt.unwrap_or({ i32::default() });
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_default()`

error: function call inside of `unwrap_or`
--> tests/ui/or_fun_call.rs:411:21
--> tests/ui/or_fun_call.rs:427:21
|
LL | let _ = opt_foo.unwrap_or(Foo { val: String::default() });
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_else(|| Foo { val: String::default() })`

error: function call inside of `map_or`
--> tests/ui/or_fun_call.rs:426:19
--> tests/ui/or_fun_call.rs:442:19
|
LL | let _ = x.map_or(g(), |v| v);
| ^^^^^^^^^^^^^^^^^^ help: try: `map_or_else(|_| g(), |v| v)`

error: function call inside of `map_or`
--> tests/ui/or_fun_call.rs:428:19
--> tests/ui/or_fun_call.rs:444:19
|
LL | let _ = x.map_or(g(), f);
| ^^^^^^^^^^^^^^ help: try: `map_or_else(|_| g(), f)`

error: function call inside of `map_or`
--> tests/ui/or_fun_call.rs:431:19
--> tests/ui/or_fun_call.rs:447:19
|
LL | let _ = x.map_or("asd".to_string().len() as i32, f);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `map_or_else(|_| "asd".to_string().len() as i32, f)`

error: function call inside of `get_or_insert`
--> tests/ui/or_fun_call.rs:442:15
--> tests/ui/or_fun_call.rs:458:15
|
LL | let _ = x.get_or_insert(g());
| ^^^^^^^^^^^^^^^^^^ help: try: `get_or_insert_with(g)`

error: function call inside of `and`
--> tests/ui/or_fun_call.rs:452:15
--> tests/ui/or_fun_call.rs:468:15
|
LL | let _ = x.and(g());
| ^^^^^^^^ help: try: `and_then(|_| g())`

error: function call inside of `and`
--> tests/ui/or_fun_call.rs:462:15
--> tests/ui/or_fun_call.rs:478:15
|
LL | let _ = x.and(g());
| ^^^^^^^^ help: try: `and_then(|_| g())`
Expand Down
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