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Increase accuracy of lint trigger

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This commit is contained in:
Esteban Küber 2021-01-12 18:37:32 -08:00 • committed by Ryan Levick
parent 49f32e0c8e
commit e48670c34a
3 changed files with 43 additions and 28 deletions
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58
compiler/rustc_lint/src/noop_method_call.rs
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@ -62,33 +62,45 @@ impl<'tcx> LateLintPass<'tcx> for NoopMethodCall {
// Resolve the trait method instance
if let Ok(Some(i)) = ty::Instance::resolve(cx.tcx, param_env, did, substs) {
// Check that it implements the noop diagnostic
if [
sym::noop_method_borrow,
sym::noop_method_clone,
sym::noop_method_deref,
for (s, peel_ref) in [
(sym::noop_method_borrow, true),
(sym::noop_method_clone, false),
(sym::noop_method_deref, true),
]
.iter()
.any(|s| cx.tcx.is_diagnostic_item(*s, i.def_id()))
{
let method = &call.ident.name;
let receiver = &elements[0];
let receiver_ty = cx.typeck_results().expr_ty(receiver);
let expr_span = expr.span;
let note = format!(
"the type `{:?}` which `{}` is being called on is the same as the type returned from `{}`, \
so the method call does not do anything and can be removed.",
receiver_ty, method, method
);
let span = expr_span.with_lo(receiver.span.hi());
cx.struct_span_lint(NOOP_METHOD_CALL, span, |lint| {
if cx.tcx.is_diagnostic_item(*s, i.def_id()) {
let method = &call.ident.name;
let message = format!("call to `.{}()` on a reference in this situation does nothing", &method);
lint.build(&message)
.span_label(span, "unnecessary method call")
.note(&note)
.emit()
});
let receiver = &elements[0];
let receiver_ty = cx.typeck_results().expr_ty(receiver);
let receiver_ty = match receiver_ty.kind() {
// Remove one borrow from the receiver as all the trait methods
// we care about here have a `&self` receiver.
ty::Ref(_, ty, _) if *peel_ref => ty,
_ => receiver_ty,
};
let expr_ty = cx.typeck_results().expr_ty_adjusted(expr);
if receiver_ty != expr_ty {
return;
}
let expr_span = expr.span;
let note = format!(
"the type `{:?}` which `{}` is being called on is the same as \
the type returned from `{}`, so the method call does not do \
anything and can be removed",
receiver_ty, method, method,
);
let span = expr_span.with_lo(receiver.span.hi());
cx.struct_span_lint(NOOP_METHOD_CALL, span, |lint| {
let method = &call.ident.name;
let message = format!("call to `.{}()` on a reference in this situation does nothing", &method);
lint.build(&message)
.span_label(span, "unnecessary method call")
.note(&note)
.emit()
});
}
}
}
}