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Auto merge of #9491 - kraktus:drop_copy, r=Jarcho

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[`drop_copy`]: Do not lint idiomatic in match arm

close https://github.com/rust-lang/rust-clippy/issues/9482

changelog: [`drop_copy`]: Do not lint idiomatic in match arm
This commit is contained in:
bors 2022-09-27 19:18:29 +00:00
commit 672fb8e42e
3 changed files with 81 additions and 5 deletions
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28
clippy_lints/src/drop_forget_ref.rs
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@ -1,7 +1,8 @@
use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_note};
use clippy_utils::get_parent_node;
use clippy_utils::is_must_use_func_call;
use clippy_utils::ty::{is_copy, is_must_use_ty, is_type_lang_item};
use rustc_hir::{Expr, ExprKind, LangItem};
use rustc_hir::{Arm, Expr, ExprKind, LangItem, Node};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::sym;
@ -202,11 +203,13 @@ impl<'tcx> LateLintPass<'tcx> for DropForgetRef {
&& let Some(fn_name) = cx.tcx.get_diagnostic_name(def_id)
{
let arg_ty = cx.typeck_results().expr_ty(arg);
let is_copy = is_copy(cx, arg_ty);
let drop_is_single_call_in_arm = is_single_call_in_arm(cx, arg, expr);
let (lint, msg) = match fn_name {
sym::mem_drop if arg_ty.is_ref() => (DROP_REF, DROP_REF_SUMMARY),
sym::mem_forget if arg_ty.is_ref() => (FORGET_REF, FORGET_REF_SUMMARY),
sym::mem_drop if is_copy(cx, arg_ty) => (DROP_COPY, DROP_COPY_SUMMARY),
sym::mem_forget if is_copy(cx, arg_ty) => (FORGET_COPY, FORGET_COPY_SUMMARY),
sym::mem_drop if is_copy && !drop_is_single_call_in_arm => (DROP_COPY, DROP_COPY_SUMMARY),
sym::mem_forget if is_copy => (FORGET_COPY, FORGET_COPY_SUMMARY),
sym::mem_drop if is_type_lang_item(cx, arg_ty, LangItem::ManuallyDrop) => {
span_lint_and_help(
cx,
@ -221,7 +224,9 @@ impl<'tcx> LateLintPass<'tcx> for DropForgetRef {
sym::mem_drop
if !(arg_ty.needs_drop(cx.tcx, cx.param_env)
|| is_must_use_func_call(cx, arg)
|| is_must_use_ty(cx, arg_ty)) =>
|| is_must_use_ty(cx, arg_ty)
|| drop_is_single_call_in_arm
) =>
{
(DROP_NON_DROP, DROP_NON_DROP_SUMMARY)
},
@ -241,3 +246,18 @@ impl<'tcx> LateLintPass<'tcx> for DropForgetRef {
}
}
}
// dropping returned value of a function like in the following snippet is considered idiomatic, see
// #9482 for examples match <var> {
// <pat> => drop(fn_with_side_effect_and_returning_some_value()),
// ..
// }
fn is_single_call_in_arm<'tcx>(cx: &LateContext<'tcx>, arg: &'tcx Expr<'_>, drop_expr: &'tcx Expr<'_>) -> bool {
if matches!(arg.kind, ExprKind::Call(..) | ExprKind::MethodCall(..)) {
let parent_node = get_parent_node(cx.tcx, drop_expr.hir_id);
if let Some(Node::Arm(Arm { body, .. })) = &parent_node {
return body.hir_id == drop_expr.hir_id;
}
}
false
}