Move inherits_cfg function into clippy_utils

Author: GuillaumeGomez

clippy_lints/src/needless_pass_by_ref_mut.rs

@@ -1,7 +1,7 @@
 use super::needless_pass_by_value::requires_exact_signature;
 use clippy_utils::diagnostics::span_lint_hir_and_then;
 use clippy_utils::source::snippet;
-use clippy_utils::{get_parent_node, is_from_proc_macro, is_self};
+use clippy_utils::{get_parent_node, inherits_cfg, is_from_proc_macro, is_self};
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
 use rustc_errors::Applicability;
 use rustc_hir::intravisit::{walk_qpath, FnKind, Visitor};
@@ -12,11 +12,11 @@ use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::hir::map::associated_body;
 use rustc_middle::hir::nested_filter::OnlyBodies;
 use rustc_middle::mir::FakeReadCause;
-use rustc_middle::ty::{self, Ty, TyCtxt, UpvarId, UpvarPath};
+use rustc_middle::ty::{self, Ty, UpvarId, UpvarPath};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
-use rustc_span::def_id::{LocalDefId, CRATE_DEF_ID};
+use rustc_span::def_id::LocalDefId;
 use rustc_span::symbol::kw;
-use rustc_span::{sym, Span};
+use rustc_span::Span;
 use rustc_target::spec::abi::Abi;
 
 declare_clippy_lint! {
@@ -93,16 +93,6 @@ fn should_skip<'tcx>(
     is_from_proc_macro(cx, &input)
 }
 
-fn inherits_cfg(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
-    if def_id == CRATE_DEF_ID {
-        false
-    } else if tcx.has_attr(def_id, sym::cfg) {
-        true
-    } else {
-        inherits_cfg(tcx, tcx.parent_module_from_def_id(def_id))
-    }
-}
-
 impl<'tcx> LateLintPass<'tcx> for NeedlessPassByRefMut<'tcx> {
     fn check_fn(
         &mut self,

clippy_utils/src/lib.rs

@@ -2451,6 +2451,17 @@ pub fn is_in_cfg_test(tcx: TyCtxt<'_>, id: hir::HirId) -> bool {
         .any(is_cfg_test)
 }
 
+/// Checks if the item of any of its parents has `#[cfg(...)]` attribute applied.
+pub fn inherits_cfg(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
+    let hir = tcx.hir();
+
+    tcx.has_attr(def_id, sym::cfg)
+        || hir
+            .parent_iter(hir.local_def_id_to_hir_id(def_id))
+            .flat_map(|(parent_id, _)| hir.attrs(parent_id))
+            .any(|attr| attr.has_name(sym::cfg))
+}
+
 /// Checks whether item either has `test` attribute applied, or
 /// is a module with `test` in its name.
 ///