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Rust: Clean up code / clarify responsibilities and fix the issue in rust/unused-value as well.

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This commit is contained in:
Geoffrey White
2024-11-05 15:03:11 +00:00
parent 278760c735
commit 93836a55e2
4 changed files with 26 additions and 17 deletions
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5
rust/ql/src/queries/unusedentities/UnusedVariable.ql
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@@ -12,5 +12,8 @@ import rust
import UnusedVariable
from Variable v
where isUnused(v)
where
isUnused(v) and
not isAllowableUnused(v) and
not v instanceof DiscardVariable
select v, "Variable '" + v + "' is not used."

26
rust/ql/src/queries/unusedentities/UnusedVariable.qll
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@@ -1,18 +1,28 @@
import rust
/** A deliberately unused variable. */
/**
* A deliberately unused variable, for example `_` or `_x`.
*/
class DiscardVariable extends Variable {
DiscardVariable() { this.getName().charAt(0) = "_" }
}
/** Holds if variable `v` is unused. */
/**
* Holds if variable `v` is unused.
*/
predicate isUnused(Variable v) {
// variable is accessed or initialized
not exists(v.getAnAccess()) and
not exists(v.getInitializer()) and
// variable is intentionally unused
not v instanceof DiscardVariable and
// variable is in a context where is may not have a use
not v.getPat().isInMacroExpansion() and
not exists(FnPtrType fp | fp.getParamList().getParam(_).getPat() = v.getPat())
not exists(v.getInitializer())
}
/**
* Holds if variable `v` is in a context where we may not find a use for it,
* but that's expected and should not be considered a problem.
*/
predicate isAllowableUnused(Variable v) {
// in a macro expansion
v.getPat().isInMacroExpansion() or
// function pointer parameters
exists(FnPtrType fp | fp.getParamList().getParam(_).getPat() = v.getPat())
}

4
rust/ql/test/query-tests/unusedentities/UnusedValue.expected
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@@ -15,10 +15,6 @@
| main.rs:373:9:373:9 | x | Variable $@ is assigned a value that is never used. | main.rs:373:9:373:9 | x | x |
| main.rs:381:17:381:17 | x | Variable $@ is assigned a value that is never used. | main.rs:381:17:381:17 | x | x |
| main.rs:482:9:482:9 | c | Variable $@ is assigned a value that is never used. | main.rs:482:9:482:9 | c | c |
| main.rs:494:16:494:16 | x | Variable $@ is assigned a value that is never used. | main.rs:494:16:494:16 | x | x |
| main.rs:495:16:495:16 | y | Variable $@ is assigned a value that is never used. | main.rs:495:16:495:16 | y | y |
| main.rs:496:12:496:12 | z | Variable $@ is assigned a value that is never used. | main.rs:496:12:496:12 | z | z |
| main.rs:499:18:499:18 | x | Variable $@ is assigned a value that is never used. | main.rs:499:18:499:18 | x | x |
| more.rs:44:9:44:14 | a_ptr4 | Variable $@ is assigned a value that is never used. | more.rs:44:9:44:14 | a_ptr4 | a_ptr4 |
| more.rs:59:9:59:13 | d_ptr | Variable $@ is assigned a value that is never used. | more.rs:59:9:59:13 | d_ptr | d_ptr |
| more.rs:65:9:65:17 | f_ptr | Variable $@ is assigned a value that is never used. | more.rs:65:13:65:17 | f_ptr | f_ptr |

8
rust/ql/test/query-tests/unusedentities/main.rs
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@@ -491,12 +491,12 @@ fn references() {
pub struct my_declaration {
field1: fn(i32) -> i32,
field2: fn(x: i32) -> i32, // $ SPURIOUS: Alert[rust/unused-value]
field3: fn(y: // $ SPURIOUS: Alert[rust/unused-value]
fn(z: i32) -> i32) -> i32, // $ SPURIOUS: Alert[rust/unused-value]
field2: fn(x: i32) -> i32,
field3: fn(y:
fn(z: i32) -> i32) -> i32,
}
type MyType = fn(x: i32) -> i32; // $ SPURIOUS: Alert[rust/unused-value]
type MyType = fn(x: i32) -> i32;
trait MyTrait {
fn my_func2(&self, x: i32) -> i32;