Fix suggestion for async in redundant_closure_call

Fix redundant_closure_call for single-expression async closures

Add Sugg::asyncify

Use Sugg for redundant_closure_call implementation

tests/ui/redundant_closure_call_fixable.fixed

@@ -1,8 +1,28 @@
 // run-rustfix
 
+#![feature(async_closure)]
 #![warn(clippy::redundant_closure_call)]
 #![allow(unused)]
 
+async fn something() -> u32 {
+    21
+}
+
+async fn something_else() -> u32 {
+    2
+}
+
 fn main() {
     let a = 42;
+    let b = async {
+        let x = something().await;
+        let y = something_else().await;
+        x * y
+    };
+    let c = {
+        let x = 21;
+        let y = 2;
+        x * y
+    };
+    let d = async { something().await };
 }

tests/ui/redundant_closure_call_fixable.rs

@@ -1,8 +1,28 @@
 // run-rustfix
 
+#![feature(async_closure)]
 #![warn(clippy::redundant_closure_call)]
 #![allow(unused)]
 
+async fn something() -> u32 {
+    21
+}
+
+async fn something_else() -> u32 {
+    2
+}
+
 fn main() {
     let a = (|| 42)();
+    let b = (async || {
+        let x = something().await;
+        let y = something_else().await;
+        x * y
+    })();
+    let c = (|| {
+        let x = 21;
+        let y = 2;
+        x * y
+    })();
+    let d = (async || something().await)();
 }

tests/ui/redundant_closure_call_fixable.stderr

@@ -1,10 +1,56 @@
 error: try not to call a closure in the expression where it is declared
-  --> $DIR/redundant_closure_call_fixable.rs:7:13
+  --> $DIR/redundant_closure_call_fixable.rs:16:13
    |
 LL |     let a = (|| 42)();
    |             ^^^^^^^^^ help: try doing something like: `42`
    |
    = note: `-D clippy::redundant-closure-call` implied by `-D warnings`
 
-error: aborting due to previous error
+error: try not to call a closure in the expression where it is declared
+  --> $DIR/redundant_closure_call_fixable.rs:17:13
+   |
+LL |       let b = (async || {
+   |  _____________^
+LL | |         let x = something().await;
+LL | |         let y = something_else().await;
+LL | |         x * y
+LL | |     })();
+   | |________^
+   |
+help: try doing something like
+   |
+LL ~     let b = async {
+LL +         let x = something().await;
+LL +         let y = something_else().await;
+LL +         x * y
+LL ~     };
+   |
+
+error: try not to call a closure in the expression where it is declared
+  --> $DIR/redundant_closure_call_fixable.rs:22:13
+   |
+LL |       let c = (|| {
+   |  _____________^
+LL | |         let x = 21;
+LL | |         let y = 2;
+LL | |         x * y
+LL | |     })();
+   | |________^
+   |
+help: try doing something like
+   |
+LL ~     let c = {
+LL +         let x = 21;
+LL +         let y = 2;
+LL +         x * y
+LL ~     };
+   |
+
+error: try not to call a closure in the expression where it is declared
+  --> $DIR/redundant_closure_call_fixable.rs:27:13
+   |
+LL |     let d = (async || something().await)();
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try doing something like: `async { something().await }`
+
+error: aborting due to 4 previous errors