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Don't report function calls as unnecessary operation if used in array index #7453

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Aug 25, 2021
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Don't report function calls as unnecessary operation if used in array index #7453

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69 changes: 52 additions & 17 deletions clippy_lints/src/no_effect.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -94,28 +94,63 @@ impl<'tcx> LateLintPass<'tcx> for NoEffect {
if has_no_effect(cx, expr) {
span_lint_hir(cx, NO_EFFECT, expr.hir_id, stmt.span, "statement with no effect");
} else if let Some(reduced) = reduce_expression(cx, expr) {
let mut snippet = String::new();
for e in reduced {
for e in &reduced {
if e.span.from_expansion() {
return;
}
if let Some(snip) = snippet_opt(cx, e.span) {
snippet.push_str(&snip);
snippet.push(';');
} else {
return;
}
if let ExprKind::Index(..) = &expr.kind {
let snippet;
if_chain! {
if let Some(arr) = snippet_opt(cx, reduced[0].span);
if let Some(func) = snippet_opt(cx, reduced[1].span);
then {
snippet = format!("assert!({}.len() > {});", &arr, &func);
} else {
return;
}
}
span_lint_hir_and_then(
cx,
UNNECESSARY_OPERATION,
expr.hir_id,
stmt.span,
"unnecessary operation",
|diag| {
diag.span_suggestion(
stmt.span,
"statement can be written as",
snippet,
Applicability::MaybeIncorrect,
);
},
);
} else {
let mut snippet = String::new();
for e in reduced {
if let Some(snip) = snippet_opt(cx, e.span) {
snippet.push_str(&snip);
snippet.push(';');
} else {
return;
}
}
span_lint_hir_and_then(
cx,
UNNECESSARY_OPERATION,
expr.hir_id,
stmt.span,
"unnecessary operation",
|diag| {
diag.span_suggestion(
stmt.span,
"statement can be reduced to",
snippet,
Applicability::MachineApplicable,
);
},
);
}
span_lint_hir_and_then(
cx,
UNNECESSARY_OPERATION,
expr.hir_id,
stmt.span,
"statement can be reduced",
|diag| {
diag.span_suggestion(stmt.span, "replace it with", snippet, Applicability::MachineApplicable);
},
);
}
}
}
Expand Down
4 changes: 2 additions & 2 deletions tests/ui/unnecessary_operation.fixed
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Original file line number Diff line number Diff line change
Expand Up @@ -62,10 +62,10 @@ fn main() {
get_number();
5;get_number();
42;get_number();
[42, 55];get_usize();
assert!([42, 55].len() > get_usize());
42;get_number();
get_number();
[42; 55];get_usize();
assert!([42; 55].len() > get_usize());
get_number();
String::from("blah");

Expand Down
80 changes: 40 additions & 40 deletions tests/ui/unnecessary_operation.stderr
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Original file line number Diff line number Diff line change
@@ -1,128 +1,128 @@
error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:51:5
|
LL | Tuple(get_number());
| ^^^^^^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
| ^^^^^^^^^^^^^^^^^^^^ help: statement can be reduced to: `get_number();`
|
= note: `-D clippy::unnecessary-operation` implied by `-D warnings`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:52:5
|
LL | Struct { field: get_number() };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: statement can be reduced to: `get_number();`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:53:5
|
LL | Struct { ..get_struct() };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `get_struct();`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: statement can be reduced to: `get_struct();`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:54:5
|
LL | Enum::Tuple(get_number());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: statement can be reduced to: `get_number();`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:55:5
|
LL | Enum::Struct { field: get_number() };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: statement can be reduced to: `get_number();`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:56:5
|
LL | 5 + get_number();
| ^^^^^^^^^^^^^^^^^ help: replace it with: `5;get_number();`
| ^^^^^^^^^^^^^^^^^ help: statement can be reduced to: `5;get_number();`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:57:5
|
LL | *&get_number();
| ^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
| ^^^^^^^^^^^^^^^ help: statement can be reduced to: `get_number();`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:58:5
|
LL | &get_number();
| ^^^^^^^^^^^^^^ help: replace it with: `get_number();`
| ^^^^^^^^^^^^^^ help: statement can be reduced to: `get_number();`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:59:5
|
LL | (5, 6, get_number());
| ^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `5;6;get_number();`
| ^^^^^^^^^^^^^^^^^^^^^ help: statement can be reduced to: `5;6;get_number();`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:60:5
|
LL | box get_number();
| ^^^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
| ^^^^^^^^^^^^^^^^^ help: statement can be reduced to: `get_number();`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:61:5
|
LL | get_number()..;
| ^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
| ^^^^^^^^^^^^^^^ help: statement can be reduced to: `get_number();`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:62:5
|
LL | ..get_number();
| ^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
| ^^^^^^^^^^^^^^^ help: statement can be reduced to: `get_number();`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:63:5
|
LL | 5..get_number();
| ^^^^^^^^^^^^^^^^ help: replace it with: `5;get_number();`
| ^^^^^^^^^^^^^^^^ help: statement can be reduced to: `5;get_number();`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:64:5
|
LL | [42, get_number()];
| ^^^^^^^^^^^^^^^^^^^ help: replace it with: `42;get_number();`
| ^^^^^^^^^^^^^^^^^^^ help: statement can be reduced to: `42;get_number();`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:65:5
|
LL | [42, 55][get_usize()];
| ^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `[42, 55];get_usize();`
| ^^^^^^^^^^^^^^^^^^^^^^ help: statement can be written as: `assert!([42, 55].len() > get_usize());`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:66:5
|
LL | (42, get_number()).1;
| ^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `42;get_number();`
| ^^^^^^^^^^^^^^^^^^^^^ help: statement can be reduced to: `42;get_number();`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:67:5
|
LL | [get_number(); 55];
| ^^^^^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
| ^^^^^^^^^^^^^^^^^^^ help: statement can be reduced to: `get_number();`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:68:5
|
LL | [42; 55][get_usize()];
| ^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `[42; 55];get_usize();`
| ^^^^^^^^^^^^^^^^^^^^^^ help: statement can be written as: `assert!([42; 55].len() > get_usize());`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:69:5
|
LL | / {
LL | | get_number()
LL | | };
| |______^ help: replace it with: `get_number();`
| |______^ help: statement can be reduced to: `get_number();`

error: statement can be reduced
error: unnecessary operation
--> $DIR/unnecessary_operation.rs:72:5
|
LL | / FooString {
LL | | s: String::from("blah"),
LL | | };
| |______^ help: replace it with: `String::from("blah");`
| |______^ help: statement can be reduced to: `String::from("blah");`

error: aborting due to 20 previous errors