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Fix noop_method_call detection #116201

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Sep 29, 2023
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6 changes: 6 additions & 0 deletions compiler/rustc_lint/src/noop_method_call.rs
Original file line number Diff line number Diff line change
Expand Up @@ -98,6 +98,12 @@ impl<'tcx> LateLintPass<'tcx> for NoopMethodCall {
let Ok(Some(i)) = ty::Instance::resolve(cx.tcx, cx.param_env, did, args) else { return };
// (Re)check that it implements the noop diagnostic.
let Some(name) = cx.tcx.get_diagnostic_name(i.def_id()) else { return };
if !matches!(
name,
sym::noop_method_borrow | sym::noop_method_clone | sym::noop_method_deref
) {
return;
}

let receiver_ty = cx.typeck_results().expr_ty(receiver);
let expr_ty = cx.typeck_results().expr_ty_adjusted(expr);
Expand Down
13 changes: 13 additions & 0 deletions tests/ui/lint/noop-method-call.fixed
Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
// check-pass
// run-rustfix

#![feature(rustc_attrs)]
#![allow(unused)]

use std::borrow::Borrow;
Expand Down Expand Up @@ -49,3 +50,15 @@ fn non_generic(non_clone_type: &PlainType<u32>) {
non_clone_type;
//~^ WARN call to `.clone()` on a reference in this situation does nothing
}

struct DiagnosticClone;
impl Clone for DiagnosticClone {
#[rustc_diagnostic_item = "other_clone"]
fn clone(&self) -> Self {
DiagnosticClone
}
}

fn with_other_diagnostic_item(x: DiagnosticClone) {
x.clone();
}
13 changes: 13 additions & 0 deletions tests/ui/lint/noop-method-call.rs
Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
// check-pass
// run-rustfix

#![feature(rustc_attrs)]
#![allow(unused)]

use std::borrow::Borrow;
Expand Down Expand Up @@ -49,3 +50,15 @@ fn non_generic(non_clone_type: &PlainType<u32>) {
non_clone_type.clone();
//~^ WARN call to `.clone()` on a reference in this situation does nothing
}

struct DiagnosticClone;
impl Clone for DiagnosticClone {
#[rustc_diagnostic_item = "other_clone"]
fn clone(&self) -> Self {
DiagnosticClone
}
}

fn with_other_diagnostic_item(x: DiagnosticClone) {
x.clone();
}
14 changes: 7 additions & 7 deletions tests/ui/lint/noop-method-call.stderr
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
warning: call to `.clone()` on a reference in this situation does nothing
--> $DIR/noop-method-call.rs:15:25
--> $DIR/noop-method-call.rs:16:25
|
LL | let _ = &mut encoded.clone();
| ^^^^^^^^ help: remove this redundant call
Expand All @@ -8,47 +8,47 @@ LL | let _ = &mut encoded.clone();
= note: `#[warn(noop_method_call)]` on by default

warning: call to `.clone()` on a reference in this situation does nothing
--> $DIR/noop-method-call.rs:17:21
--> $DIR/noop-method-call.rs:18:21
|
LL | let _ = &encoded.clone();
| ^^^^^^^^ help: remove this redundant call
|
= note: the type `[u8]` does not implement `Clone`, so calling `clone` on `&[u8]` copies the reference, which does not do anything and can be removed

warning: call to `.clone()` on a reference in this situation does nothing
--> $DIR/noop-method-call.rs:23:71
--> $DIR/noop-method-call.rs:24:71
|
LL | let non_clone_type_ref_clone: &PlainType<u32> = non_clone_type_ref.clone();
| ^^^^^^^^ help: remove this redundant call
|
= note: the type `PlainType<u32>` does not implement `Clone`, so calling `clone` on `&PlainType<u32>` copies the reference, which does not do anything and can be removed

warning: call to `.deref()` on a reference in this situation does nothing
--> $DIR/noop-method-call.rs:31:63
--> $DIR/noop-method-call.rs:32:63
|
LL | let non_deref_type_deref: &PlainType<u32> = non_deref_type.deref();
| ^^^^^^^^ help: remove this redundant call
|
= note: the type `PlainType<u32>` does not implement `Deref`, so calling `deref` on `&PlainType<u32>` copies the reference, which does not do anything and can be removed

warning: call to `.borrow()` on a reference in this situation does nothing
--> $DIR/noop-method-call.rs:35:66
--> $DIR/noop-method-call.rs:36:66
|
LL | let non_borrow_type_borrow: &PlainType<u32> = non_borrow_type.borrow();
| ^^^^^^^^^ help: remove this redundant call
|
= note: the type `PlainType<u32>` does not implement `Borrow`, so calling `borrow` on `&PlainType<u32>` copies the reference, which does not do anything and can be removed

warning: call to `.clone()` on a reference in this situation does nothing
--> $DIR/noop-method-call.rs:44:19
--> $DIR/noop-method-call.rs:45:19
|
LL | non_clone_type.clone();
| ^^^^^^^^ help: remove this redundant call
|
= note: the type `PlainType<T>` does not implement `Clone`, so calling `clone` on `&PlainType<T>` copies the reference, which does not do anything and can be removed

warning: call to `.clone()` on a reference in this situation does nothing
--> $DIR/noop-method-call.rs:49:19
--> $DIR/noop-method-call.rs:50:19
|
LL | non_clone_type.clone();
| ^^^^^^^^ help: remove this redundant call
Expand Down
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