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Don't show no_effect warning on unit structs implementing fn_once #7898

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Merged
merged 1 commit into from
Nov 17, 2021
Merged

Don't show no_effect warning on unit structs implementing fn_once #7898

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11 changes: 9 additions & 2 deletions clippy_lints/src/no_effect.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -133,9 +133,12 @@ fn has_no_effect(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
},
ExprKind::Call(callee, args) => {
if let ExprKind::Path(ref qpath) = callee.kind {
let res = cx.qpath_res(qpath, callee.hir_id);
if cx.typeck_results().type_dependent_def(expr.hir_id).is_some() {
// type-dependent function call like `impl FnOnce for X`
return false;
}
let def_matched = matches!(
res,
cx.qpath_res(qpath, callee.hir_id),
Res::Def(DefKind::Struct | DefKind::Variant | DefKind::Ctor(..), ..)
);
if def_matched || is_range_literal(expr) {
Expand Down Expand Up @@ -238,6 +241,10 @@ fn reduce_expression<'a>(cx: &LateContext<'_>, expr: &'a Expr<'a>) -> Option<Vec
},
ExprKind::Call(callee, args) => {
if let ExprKind::Path(ref qpath) = callee.kind {
if cx.typeck_results().type_dependent_def(expr.hir_id).is_some() {
// type-dependent function call like `impl FnOnce for X`
return None;
}
let res = cx.qpath_res(qpath, callee.hir_id);
match res {
Res::Def(DefKind::Struct | DefKind::Variant | DefKind::Ctor(..), ..)
Expand Down
35 changes: 34 additions & 1 deletion tests/ui/no_effect.rs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
#![feature(box_syntax)]
#![feature(box_syntax, fn_traits, unboxed_closures)]
#![warn(clippy::no_effect_underscore_binding)]
#![allow(dead_code)]
#![allow(path_statements)]
Expand Down Expand Up @@ -58,6 +58,36 @@ unsafe fn unsafe_fn() -> i32 {
0
}

struct GreetStruct1;

impl FnOnce<(&str,)> for GreetStruct1 {
type Output = ();

extern "rust-call" fn call_once(self, (who,): (&str,)) -> Self::Output {
println!("hello {}", who);
}
}

struct GreetStruct2();

impl FnOnce<(&str,)> for GreetStruct2 {
type Output = ();

extern "rust-call" fn call_once(self, (who,): (&str,)) -> Self::Output {
println!("hello {}", who);
}
}

struct GreetStruct3 {}

impl FnOnce<(&str,)> for GreetStruct3 {
type Output = ();

extern "rust-call" fn call_once(self, (who,): (&str,)) -> Self::Output {
println!("hello {}", who);
}
}

fn main() {
let s = get_struct();
let s2 = get_struct();
Expand Down Expand Up @@ -108,4 +138,7 @@ fn main() {
DropTuple(0);
DropEnum::Tuple(0);
DropEnum::Struct { field: 0 };
GreetStruct1("world");
GreetStruct2()("world");
GreetStruct3 {}("world");
}
60 changes: 30 additions & 30 deletions tests/ui/no_effect.stderr
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Original file line number Diff line number Diff line change
@@ -1,183 +1,183 @@
error: statement with no effect
--> $DIR/no_effect.rs:65:5
--> $DIR/no_effect.rs:95:5
|
LL | 0;
| ^^
|
= note: `-D clippy::no-effect` implied by `-D warnings`

error: statement with no effect
--> $DIR/no_effect.rs:66:5
--> $DIR/no_effect.rs:96:5
|
LL | s2;
| ^^^

error: statement with no effect
--> $DIR/no_effect.rs:67:5
--> $DIR/no_effect.rs:97:5
|
LL | Unit;
| ^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:68:5
--> $DIR/no_effect.rs:98:5
|
LL | Tuple(0);
| ^^^^^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:69:5
--> $DIR/no_effect.rs:99:5
|
LL | Struct { field: 0 };
| ^^^^^^^^^^^^^^^^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:70:5
--> $DIR/no_effect.rs:100:5
|
LL | Struct { ..s };
| ^^^^^^^^^^^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:71:5
--> $DIR/no_effect.rs:101:5
|
LL | Union { a: 0 };
| ^^^^^^^^^^^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:72:5
--> $DIR/no_effect.rs:102:5
|
LL | Enum::Tuple(0);
| ^^^^^^^^^^^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:73:5
--> $DIR/no_effect.rs:103:5
|
LL | Enum::Struct { field: 0 };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:74:5
--> $DIR/no_effect.rs:104:5
|
LL | 5 + 6;
| ^^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:75:5
--> $DIR/no_effect.rs:105:5
|
LL | *&42;
| ^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:76:5
--> $DIR/no_effect.rs:106:5
|
LL | &6;
| ^^^

error: statement with no effect
--> $DIR/no_effect.rs:77:5
--> $DIR/no_effect.rs:107:5
|
LL | (5, 6, 7);
| ^^^^^^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:78:5
--> $DIR/no_effect.rs:108:5
|
LL | box 42;
| ^^^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:79:5
--> $DIR/no_effect.rs:109:5
|
LL | ..;
| ^^^

error: statement with no effect
--> $DIR/no_effect.rs:80:5
--> $DIR/no_effect.rs:110:5
|
LL | 5..;
| ^^^^

error: statement with no effect
--> $DIR/no_effect.rs:81:5
--> $DIR/no_effect.rs:111:5
|
LL | ..5;
| ^^^^

error: statement with no effect
--> $DIR/no_effect.rs:82:5
--> $DIR/no_effect.rs:112:5
|
LL | 5..6;
| ^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:83:5
--> $DIR/no_effect.rs:113:5
|
LL | 5..=6;
| ^^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:84:5
--> $DIR/no_effect.rs:114:5
|
LL | [42, 55];
| ^^^^^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:85:5
--> $DIR/no_effect.rs:115:5
|
LL | [42, 55][1];
| ^^^^^^^^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:86:5
--> $DIR/no_effect.rs:116:5
|
LL | (42, 55).1;
| ^^^^^^^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:87:5
--> $DIR/no_effect.rs:117:5
|
LL | [42; 55];
| ^^^^^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:88:5
--> $DIR/no_effect.rs:118:5
|
LL | [42; 55][13];
| ^^^^^^^^^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:90:5
--> $DIR/no_effect.rs:120:5
|
LL | || x += 5;
| ^^^^^^^^^^

error: statement with no effect
--> $DIR/no_effect.rs:92:5
--> $DIR/no_effect.rs:122:5
|
LL | FooString { s: s };
| ^^^^^^^^^^^^^^^^^^^

error: binding to `_` prefixed variable with no side-effect
--> $DIR/no_effect.rs:93:5
--> $DIR/no_effect.rs:123:5
|
LL | let _unused = 1;
| ^^^^^^^^^^^^^^^^
|
= note: `-D clippy::no-effect-underscore-binding` implied by `-D warnings`

error: binding to `_` prefixed variable with no side-effect
--> $DIR/no_effect.rs:94:5
--> $DIR/no_effect.rs:124:5
|
LL | let _penguin = || println!("Some helpful closure");
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: binding to `_` prefixed variable with no side-effect
--> $DIR/no_effect.rs:95:5
--> $DIR/no_effect.rs:125:5
|
LL | let _duck = Struct { field: 0 };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: binding to `_` prefixed variable with no side-effect
--> $DIR/no_effect.rs:96:5
--> $DIR/no_effect.rs:126:5
|
LL | let _cat = [2, 4, 6, 8][2];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
Expand Down