is_async_fn: use FnKind::asyncness (#15772)

changelog: none

Author: Alexendoo

clippy_lints/src/cognitive_complexity.rs

@@ -3,7 +3,7 @@ use clippy_utils::diagnostics::span_lint_and_help;
 use clippy_utils::source::{IntoSpan, SpanRangeExt};
 use clippy_utils::ty::is_type_diagnostic_item;
 use clippy_utils::visitors::for_each_expr_without_closures;
-use clippy_utils::{LimitStack, get_async_fn_body, is_async_fn, sym};
+use clippy_utils::{LimitStack, get_async_fn_body, sym};
 use core::ops::ControlFlow;
 use rustc_hir::intravisit::FnKind;
 use rustc_hir::{Attribute, Body, Expr, ExprKind, FnDecl};
@@ -147,7 +147,7 @@ impl<'tcx> LateLintPass<'tcx> for CognitiveComplexity {
         def_id: LocalDefId,
     ) {
         if !cx.tcx.has_attr(def_id, sym::test) {
-            let expr = if is_async_fn(kind) {
+            let expr = if kind.asyncness().is_async() {
                 match get_async_fn_body(cx.tcx, body) {
                     Some(b) => b,
                     None => {

clippy_lints/src/implicit_return.rs

@@ -1,7 +1,7 @@
 use clippy_utils::diagnostics::span_lint_hir_and_then;
 use clippy_utils::source::{snippet_with_applicability, snippet_with_context, walk_span_to_context};
 use clippy_utils::visitors::for_each_expr_without_closures;
-use clippy_utils::{desugar_await, get_async_closure_expr, get_async_fn_body, is_async_fn, is_from_proc_macro};
+use clippy_utils::{desugar_await, get_async_closure_expr, get_async_fn_body, is_from_proc_macro};
 use core::ops::ControlFlow;
 use rustc_errors::Applicability;
 use rustc_hir::intravisit::FnKind;
@@ -240,7 +240,7 @@ impl<'tcx> LateLintPass<'tcx> for ImplicitReturn {
             return;
         }
 
-        let expr = if is_async_fn(kind) {
+        let expr = if kind.asyncness().is_async() {
             match get_async_fn_body(cx.tcx, body) {
                 Some(e) => e,
                 None => return,

clippy_utils/src/lib.rs

@@ -98,7 +98,7 @@ use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{DefId, LocalDefId, LocalModDefId};
 use rustc_hir::definitions::{DefPath, DefPathData};
 use rustc_hir::hir_id::{HirIdMap, HirIdSet};
-use rustc_hir::intravisit::{FnKind, Visitor, walk_expr};
+use rustc_hir::intravisit::{Visitor, walk_expr};
 use rustc_hir::{
     self as hir, Arm, BindingMode, Block, BlockCheckMode, Body, ByRef, Closure, ConstArgKind, CoroutineDesugaring,
     CoroutineKind, CoroutineSource, Destination, Expr, ExprField, ExprKind, FnDecl, FnRetTy, GenericArg, GenericArgs,
@@ -1854,15 +1854,6 @@ pub fn if_sequence<'tcx>(mut expr: &'tcx Expr<'tcx>) -> (Vec<&'tcx Expr<'tcx>>,
     (conds, blocks)
 }
 
-/// Checks if the given function kind is an async function.
-pub fn is_async_fn(kind: FnKind<'_>) -> bool {
-    match kind {
-        FnKind::ItemFn(_, _, header) => header.asyncness.is_async(),
-        FnKind::Method(_, sig) => sig.header.asyncness.is_async(),
-        FnKind::Closure => false,
-    }
-}
-
 /// Peels away all the compiler generated code surrounding the body of an async closure.
 pub fn get_async_closure_expr<'tcx>(tcx: TyCtxt<'tcx>, expr: &Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
     if let ExprKind::Closure(&Closure {