Auto merge of #7067 - TaKO8Ki:fix-false-negative-on-needless-return, r=llogiq

Fix a false negative on `needless return`

closes #7042

changelog: fix a false negative on `needless return`

4 files changed, 268 insertions, 31 deletions

diff --git a/clippy_lints/src/returns.rs b/clippy_lints/src/returns.rs
index af772cf4a14..3a6151dce71 100644
--- a/clippy_lints/src/returns.rs
+++ b/clippy_lints/src/returns.rs
@@ -223,6 +223,7 @@ fn check_final_expr<'tcx>(
             },
             _ => (),
         },
+        ExprKind::DropTemps(expr) => check_final_expr(cx, expr, None, RetReplacement::Empty),
         _ => (),
     }
 }
diff --git a/tests/ui/needless_return.fixed b/tests/ui/needless_return.fixed
index 82d95cc041f..5c4fd466c04 100644
--- a/tests/ui/needless_return.fixed
+++ b/tests/ui/needless_return.fixed
@@ -1,4 +1,5 @@
 // run-rustfix
+// edition:2018
 
 #![allow(unused)]
 #![allow(
@@ -125,10 +126,85 @@ mod issue6501 {
     }
 }
 
-fn main() {
-    let _ = test_end_of_fn();
-    let _ = test_no_semicolon();
-    let _ = test_if_block();
-    let _ = test_match(true);
-    test_closure();
+async fn async_test_end_of_fn() -> bool {
+    if true {
+        // no error!
+        return true;
+    }
+    true
+}
+
+async fn async_test_no_semicolon() -> bool {
+    true
+}
+
+async fn async_test_if_block() -> bool {
+    if true {
+        true
+    } else {
+        false
+    }
+}
+
+async fn async_test_match(x: bool) -> bool {
+    match x {
+        true => false,
+        false => {
+            true
+        },
+    }
+}
+
+async fn async_test_closure() {
+    let _ = || {
+        true
+    };
+    let _ = || true;
+}
+
+async fn async_test_macro_call() -> i32 {
+    return the_answer!();
+}
+
+async fn async_test_void_fun() {
+    
+}
+
+async fn async_test_void_if_fun(b: bool) {
+    if b {
+        
+    } else {
+        
+    }
+}
+
+async fn async_test_void_match(x: u32) {
+    match x {
+        0 => (),
+        _ => {},
+    }
+}
+
+async fn async_read_line() -> String {
+    use std::io::BufRead;
+    let stdin = ::std::io::stdin();
+    return stdin.lock().lines().next().unwrap().unwrap();
 }
+
+async fn async_borrows_but_not_last(value: bool) -> String {
+    if value {
+        use std::io::BufRead;
+        let stdin = ::std::io::stdin();
+        let _a = stdin.lock().lines().next().unwrap().unwrap();
+        String::from("test")
+    } else {
+        String::new()
+    }
+}
+
+async fn async_test_return_in_macro() {
+    needed_return!(10);
+    needed_return!(0);
+}
+
+fn main() {}
diff --git a/tests/ui/needless_return.rs b/tests/ui/needless_return.rs
index 8a471f802e1..34811db7413 100644
--- a/tests/ui/needless_return.rs
+++ b/tests/ui/needless_return.rs
@@ -1,4 +1,5 @@
 // run-rustfix
+// edition:2018
 
 #![allow(unused)]
 #![allow(
@@ -125,10 +126,85 @@ mod issue6501 {
     }
 }
 
-fn main() {
-    let _ = test_end_of_fn();
-    let _ = test_no_semicolon();
-    let _ = test_if_block();
-    let _ = test_match(true);
-    test_closure();
+async fn async_test_end_of_fn() -> bool {
+    if true {
+        // no error!
+        return true;
+    }
+    return true;
+}
+
+async fn async_test_no_semicolon() -> bool {
+    return true;
+}
+
+async fn async_test_if_block() -> bool {
+    if true {
+        return true;
+    } else {
+        return false;
+    }
+}
+
+async fn async_test_match(x: bool) -> bool {
+    match x {
+        true => return false,
+        false => {
+            return true;
+        },
+    }
+}
+
+async fn async_test_closure() {
+    let _ = || {
+        return true;
+    };
+    let _ = || return true;
+}
+
+async fn async_test_macro_call() -> i32 {
+    return the_answer!();
+}
+
+async fn async_test_void_fun() {
+    return;
+}
+
+async fn async_test_void_if_fun(b: bool) {
+    if b {
+        return;
+    } else {
+        return;
+    }
+}
+
+async fn async_test_void_match(x: u32) {
+    match x {
+        0 => (),
+        _ => return,
+    }
+}
+
+async fn async_read_line() -> String {
+    use std::io::BufRead;
+    let stdin = ::std::io::stdin();
+    return stdin.lock().lines().next().unwrap().unwrap();
 }
+
+async fn async_borrows_but_not_last(value: bool) -> String {
+    if value {
+        use std::io::BufRead;
+        let stdin = ::std::io::stdin();
+        let _a = stdin.lock().lines().next().unwrap().unwrap();
+        return String::from("test");
+    } else {
+        return String::new();
+    }
+}
+
+async fn async_test_return_in_macro() {
+    needed_return!(10);
+    needed_return!(0);
+}
+
+fn main() {}
diff --git a/tests/ui/needless_return.stderr b/tests/ui/needless_return.stderr
index 075db22456f..74dda971fda 100644
--- a/tests/ui/needless_return.stderr
+++ b/tests/ui/needless_return.stderr
@@ -1,5 +1,5 @@
 error: unneeded `return` statement
-  --> $DIR/needless_return.rs:23:5
+  --> $DIR/needless_return.rs:24:5
    |
 LL |     return true;
    |     ^^^^^^^^^^^^ help: remove `return`: `true`
@@ -7,106 +7,190 @@ LL |     return true;
    = note: `-D clippy::needless-return` implied by `-D warnings`
 
 error: unneeded `return` statement
-  --> $DIR/needless_return.rs:27:5
+  --> $DIR/needless_return.rs:28:5
    |
 LL |     return true;
    |     ^^^^^^^^^^^^ help: remove `return`: `true`
 
 error: unneeded `return` statement
-  --> $DIR/needless_return.rs:32:9
+  --> $DIR/needless_return.rs:33:9
    |
 LL |         return true;
    |         ^^^^^^^^^^^^ help: remove `return`: `true`
 
 error: unneeded `return` statement
-  --> $DIR/needless_return.rs:34:9
+  --> $DIR/needless_return.rs:35:9
    |
 LL |         return false;
    |         ^^^^^^^^^^^^^ help: remove `return`: `false`
 
 error: unneeded `return` statement
-  --> $DIR/needless_return.rs:40:17
+  --> $DIR/needless_return.rs:41:17
    |
 LL |         true => return false,
    |                 ^^^^^^^^^^^^ help: remove `return`: `false`
 
 error: unneeded `return` statement
-  --> $DIR/needless_return.rs:42:13
+  --> $DIR/needless_return.rs:43:13
    |
 LL |             return true;
    |             ^^^^^^^^^^^^ help: remove `return`: `true`
 
 error: unneeded `return` statement
-  --> $DIR/needless_return.rs:49:9
+  --> $DIR/needless_return.rs:50:9
    |
 LL |         return true;
    |         ^^^^^^^^^^^^ help: remove `return`: `true`
 
 error: unneeded `return` statement
-  --> $DIR/needless_return.rs:51:16
+  --> $DIR/needless_return.rs:52:16
    |
 LL |     let _ = || return true;
    |                ^^^^^^^^^^^ help: remove `return`: `true`
 
 error: unneeded `return` statement
-  --> $DIR/needless_return.rs:59:5
+  --> $DIR/needless_return.rs:60:5
    |
 LL |     return;
    |     ^^^^^^^ help: remove `return`
 
 error: unneeded `return` statement
-  --> $DIR/needless_return.rs:64:9
+  --> $DIR/needless_return.rs:65:9
    |
 LL |         return;
    |         ^^^^^^^ help: remove `return`
 
 error: unneeded `return` statement
-  --> $DIR/needless_return.rs:66:9
+  --> $DIR/needless_return.rs:67:9
    |
 LL |         return;
    |         ^^^^^^^ help: remove `return`
 
 error: unneeded `return` statement
-  --> $DIR/needless_return.rs:73:14
+  --> $DIR/needless_return.rs:74:14
    |
 LL |         _ => return,
    |              ^^^^^^ help: replace `return` with an empty block: `{}`
 
 error: unneeded `return` statement
-  --> $DIR/needless_return.rs:88:9
+  --> $DIR/needless_return.rs:89:9
    |
 LL |         return String::from("test");
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove `return`: `String::from("test")`
 
 error: unneeded `return` statement
-  --> $DIR/needless_return.rs:90:9
+  --> $DIR/needless_return.rs:91:9
    |
 LL |         return String::new();
    |         ^^^^^^^^^^^^^^^^^^^^^ help: remove `return`: `String::new()`
 
 error: unneeded `return` statement
-  --> $DIR/needless_return.rs:111:32
+  --> $DIR/needless_return.rs:112:32
    |
 LL |         bar.unwrap_or_else(|_| return)
    |                                ^^^^^^ help: replace `return` with an empty block: `{}`
 
 error: unneeded `return` statement
-  --> $DIR/needless_return.rs:116:13
+  --> $DIR/needless_return.rs:117:13
    |
 LL |             return;
    |             ^^^^^^^ help: remove `return`
 
 error: unneeded `return` statement
-  --> $DIR/needless_return.rs:118:20
+  --> $DIR/needless_return.rs:119:20
    |
 LL |         let _ = || return;
    |                    ^^^^^^ help: replace `return` with an empty block: `{}`
 
 error: unneeded `return` statement
-  --> $DIR/needless_return.rs:124:32
+  --> $DIR/needless_return.rs:125:32
    |
 LL |         res.unwrap_or_else(|_| return Foo)
    |                                ^^^^^^^^^^ help: remove `return`: `Foo`
 
-error: aborting due to 18 previous errors
+error: unneeded `return` statement
+  --> $DIR/needless_return.rs:134:5
+   |
+LL |     return true;
+   |     ^^^^^^^^^^^^ help: remove `return`: `true`
+
+error: unneeded `return` statement
+  --> $DIR/needless_return.rs:138:5
+   |
+LL |     return true;
+   |     ^^^^^^^^^^^^ help: remove `return`: `true`
+
+error: unneeded `return` statement
+  --> $DIR/needless_return.rs:143:9
+   |
+LL |         return true;
+   |         ^^^^^^^^^^^^ help: remove `return`: `true`
+
+error: unneeded `return` statement
+  --> $DIR/needless_return.rs:145:9
+   |
+LL |         return false;
+   |         ^^^^^^^^^^^^^ help: remove `return`: `false`
+
+error: unneeded `return` statement
+  --> $DIR/needless_return.rs:151:17
+   |
+LL |         true => return false,
+   |                 ^^^^^^^^^^^^ help: remove `return`: `false`
+
+error: unneeded `return` statement
+  --> $DIR/needless_return.rs:153:13
+   |
+LL |             return true;
+   |             ^^^^^^^^^^^^ help: remove `return`: `true`
+
+error: unneeded `return` statement
+  --> $DIR/needless_return.rs:160:9
+   |
+LL |         return true;
+   |         ^^^^^^^^^^^^ help: remove `return`: `true`
+
+error: unneeded `return` statement
+  --> $DIR/needless_return.rs:162:16
+   |
+LL |     let _ = || return true;
+   |                ^^^^^^^^^^^ help: remove `return`: `true`
+
+error: unneeded `return` statement
+  --> $DIR/needless_return.rs:170:5
+   |
+LL |     return;
+   |     ^^^^^^^ help: remove `return`
+
+error: unneeded `return` statement
+  --> $DIR/needless_return.rs:175:9
+   |
+LL |         return;
+   |         ^^^^^^^ help: remove `return`
+
+error: unneeded `return` statement
+  --> $DIR/needless_return.rs:177:9
+   |
+LL |         return;
+   |         ^^^^^^^ help: remove `return`
+
+error: unneeded `return` statement
+  --> $DIR/needless_return.rs:184:14
+   |
+LL |         _ => return,
+   |              ^^^^^^ help: replace `return` with an empty block: `{}`
+
+error: unneeded `return` statement
+  --> $DIR/needless_return.rs:199:9
+   |
+LL |         return String::from("test");
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove `return`: `String::from("test")`
+
+error: unneeded `return` statement
+  --> $DIR/needless_return.rs:201:9
+   |
+LL |         return String::new();
+   |         ^^^^^^^^^^^^^^^^^^^^^ help: remove `return`: `String::new()`
+
+error: aborting due to 32 previous errors