re-implement fix for rust-lang#11357

Author: KisaragiEffective

clippy_lints/src/redundant_closure_call.rs

@@ -4,8 +4,8 @@ use clippy_utils::get_parent_expr;
 use clippy_utils::sugg::Sugg;
 use rustc_errors::Applicability;
 use rustc_hir as hir;
-use rustc_hir::intravisit as hir_visit;
 use rustc_hir::intravisit::{Visitor as HirVisitor, Visitor};
+use rustc_hir::{intravisit as hir_visit, CoroutineKind, CoroutineSource};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::hir::nested_filter;
 use rustc_middle::lint::in_external_macro;
@@ -60,11 +60,14 @@ impl<'tcx> Visitor<'tcx> for ReturnVisitor {
     }
 }
 
-/// Checks if the body is owned by an async closure
-fn is_async_closure(body: &hir::Body<'_>) -> bool {
-    if let hir::ExprKind::Closure(closure) = body.value.kind
-        && let [resume_ty] = closure.fn_decl.inputs
-        && let hir::TyKind::Path(hir::QPath::LangItem(hir::LangItem::ResumeTy, ..)) = resume_ty.kind
+/// Checks if the body is owned by an async closure.
+/// Returns true for `async || whatever_expression`, but false for `|| async { whatever_expression
+/// }`.
+fn is_async_closure(cx: &LateContext<'_>, body: &hir::Body<'_>) -> bool {
+    if let hir::ExprKind::Closure(innermost_closure_generated_by_desugar) = body.value.kind
+        && let desugared_inner_closure_body = cx.tcx.hir().body(innermost_closure_generated_by_desugar.body)
+        // checks whether it is `async || whatever_expression`
+        && let Some(CoroutineKind::Async(CoroutineSource::Closure)) = desugared_inner_closure_body.coroutine_kind
     {
         true
     } else {
@@ -100,7 +103,7 @@ fn find_innermost_closure<'tcx>(
         data = Some((
             body.value,
             closure.fn_decl,
-            if is_async_closure(body) {
+            if is_async_closure(cx, body) {
                 ty::Asyncness::Yes
             } else {
                 ty::Asyncness::No

tests/ui/redundant_closure_call_fixable.fixed

@@ -3,6 +3,7 @@
 #![allow(clippy::redundant_async_block)]
 #![allow(clippy::type_complexity)]
 #![allow(unused)]
+#![allow(clippy::double_parens)]
 
 async fn something() -> u32 {
     21
@@ -84,3 +85,17 @@ fn issue9956() {
     bar()(42, 5);
     foo(42, 5);
 }
+
+async fn issue11357() {
+    (async {}).await;
+}
+
+mod issue11707 {
+    use core::future::Future;
+
+    fn spawn_on(fut: impl Future<Output = ()>) {}
+
+    fn demo() {
+        spawn_on((async move {}));
+    }
+}

tests/ui/redundant_closure_call_fixable.rs

@@ -3,6 +3,7 @@
 #![allow(clippy::redundant_async_block)]
 #![allow(clippy::type_complexity)]
 #![allow(unused)]
+#![allow(clippy::double_parens)]
 
 async fn something() -> u32 {
     21
@@ -84,3 +85,17 @@ fn issue9956() {
     bar()((|| || 42)()(), 5);
     foo((|| || 42)()(), 5);
 }
+
+async fn issue11357() {
+    (|| async {})().await;
+}
+
+mod issue11707 {
+    use core::future::Future;
+
+    fn spawn_on(fut: impl Future<Output = ()>) {}
+
+    fn demo() {
+        spawn_on(((|| async move {})()));
+    }
+}

tests/ui/redundant_closure_call_fixable.stderr

@@ -1,5 +1,5 @@
 error: try not to call a closure in the expression where it is declared
-  --> $DIR/redundant_closure_call_fixable.rs:16:13
+  --> $DIR/redundant_closure_call_fixable.rs:17:13
    |
 LL |     let a = (|| 42)();
    |             ^^^^^^^^^ help: try doing something like: `42`
@@ -8,7 +8,7 @@ LL |     let a = (|| 42)();
    = help: to override `-D warnings` add `#[allow(clippy::redundant_closure_call)]`
 
 error: try not to call a closure in the expression where it is declared
-  --> $DIR/redundant_closure_call_fixable.rs:17:13
+  --> $DIR/redundant_closure_call_fixable.rs:18:13
    |
 LL |       let b = (async || {
    |  _____________^
@@ -28,7 +28,7 @@ LL ~     };
    |
 
 error: try not to call a closure in the expression where it is declared
-  --> $DIR/redundant_closure_call_fixable.rs:22:13
+  --> $DIR/redundant_closure_call_fixable.rs:23:13
    |
 LL |       let c = (|| {
    |  _____________^
@@ -48,13 +48,13 @@ LL ~     };
    |
 
 error: try not to call a closure in the expression where it is declared
-  --> $DIR/redundant_closure_call_fixable.rs:27:13
+  --> $DIR/redundant_closure_call_fixable.rs:28:13
    |
 LL |     let d = (async || something().await)();
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try doing something like: `async { something().await }`
 
 error: try not to call a closure in the expression where it is declared
-  --> $DIR/redundant_closure_call_fixable.rs:36:13
+  --> $DIR/redundant_closure_call_fixable.rs:37:13
    |
 LL |             (|| m!())()
    |             ^^^^^^^^^^^ help: try doing something like: `m!()`
@@ -65,7 +65,7 @@ LL |     m2!();
    = note: this error originates in the macro `m2` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: try not to call a closure in the expression where it is declared
-  --> $DIR/redundant_closure_call_fixable.rs:31:13
+  --> $DIR/redundant_closure_call_fixable.rs:32:13
    |
 LL |             (|| 0)()
    |             ^^^^^^^^ help: try doing something like: `0`
@@ -76,52 +76,64 @@ LL |     m2!();
    = note: this error originates in the macro `m` which comes from the expansion of the macro `m2` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: try not to call a closure in the expression where it is declared
-  --> $DIR/redundant_closure_call_fixable.rs:44:16
+  --> $DIR/redundant_closure_call_fixable.rs:45:16
    |
 LL |     assert_eq!((|| || 43)()(), 42);
    |                ^^^^^^^^^^^^^^ help: try doing something like: `43`
 
 error: try not to call a closure in the expression where it is declared
-  --> $DIR/redundant_closure_call_fixable.rs:53:10
+  --> $DIR/redundant_closure_call_fixable.rs:54:10
    |
 LL |     dbg!((|| 42)());
    |          ^^^^^^^^^ help: try doing something like: `42`
 
 error: try not to call a closure in the expression where it is declared
-  --> $DIR/redundant_closure_call_fixable.rs:56:13
+  --> $DIR/redundant_closure_call_fixable.rs:57:13
    |
 LL |     let a = (|| || || 123)();
    |             ^^^^^^^^^^^^^^^^ help: try doing something like: `(|| || 123)`
 
 error: try not to call a closure in the expression where it is declared
-  --> $DIR/redundant_closure_call_fixable.rs:60:13
+  --> $DIR/redundant_closure_call_fixable.rs:61:13
    |
 LL |     let a = (|| || || || async || 1)()()()()();
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try doing something like: `async { 1 }`
 
 error: try not to call a closure in the expression where it is declared
-  --> $DIR/redundant_closure_call_fixable.rs:69:13
+  --> $DIR/redundant_closure_call_fixable.rs:70:13
    |
 LL |     let a = (|| echo!(|| echo!(|| 1)))()()();
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try doing something like: `1`
 
 error: try not to call a closure in the expression where it is declared
-  --> $DIR/redundant_closure_call_fixable.rs:71:13
+  --> $DIR/redundant_closure_call_fixable.rs:72:13
    |
 LL |     let a = (|| echo!((|| 123)))()();
    |             ^^^^^^^^^^^^^^^^^^^^^^^^ help: try doing something like: `123`
 
 error: try not to call a closure in the expression where it is declared
-  --> $DIR/redundant_closure_call_fixable.rs:84:11
+  --> $DIR/redundant_closure_call_fixable.rs:85:11
    |
 LL |     bar()((|| || 42)()(), 5);
    |           ^^^^^^^^^^^^^^ help: try doing something like: `42`
 
 error: try not to call a closure in the expression where it is declared
-  --> $DIR/redundant_closure_call_fixable.rs:85:9
+  --> $DIR/redundant_closure_call_fixable.rs:86:9
    |
 LL |     foo((|| || 42)()(), 5);
    |         ^^^^^^^^^^^^^^ help: try doing something like: `42`
 
-error: aborting due to 14 previous errors
+error: try not to call a closure in the expression where it is declared
+  --> $DIR/redundant_closure_call_fixable.rs:90:5
+   |
+LL |     (|| async {})().await;
+   |     ^^^^^^^^^^^^^^^ help: try doing something like: `(async {})`
+
+error: try not to call a closure in the expression where it is declared
+  --> $DIR/redundant_closure_call_fixable.rs:99:18
+   |
+LL |         spawn_on(((|| async move {})()));
+   |                  ^^^^^^^^^^^^^^^^^^^^^^ help: try doing something like: `(async move {})`
+
+error: aborting due to 16 previous errors