Auto merge of #6681 - 1c3t3a:1c3t3a-issue-6467, r=xFrednet,flip1995,phansch

Adds a new lint that checks if there is a semicolon on the last block statement if it returns nothing

changelog: Added a new lint: `SEMICOLON_IF_NOTHING_RETURNED`
fixes #6467
Adds the `SEMICOLON_IF_NOTHING_RETURNED` lint and therefore closes #6467.

tests/ui/semicolon_if_nothing_returned.rs

@@ -0,0 +1,55 @@
+#![warn(clippy::semicolon_if_nothing_returned)]
+#![feature(label_break_value)]
+
+fn get_unit() {}
+
+// the functions below trigger the lint
+fn main() {
+    println!("Hello")
+}
+
+fn hello() {
+    get_unit()
+}
+
+fn basic101(x: i32) {
+    let y: i32;
+    y = x + 1
+}
+
+// this is fine
+fn print_sum(a: i32, b: i32) {
+    println!("{}", a + b);
+    assert_eq!(true, false);
+}
+
+fn foo(x: i32) {
+    let y: i32;
+    if x < 1 {
+        y = 4;
+    } else {
+        y = 5;
+    }
+}
+
+fn bar(x: i32) {
+    let y: i32;
+    match x {
+        1 => y = 4,
+        _ => y = 32,
+    }
+}
+
+fn foobar(x: i32) {
+    let y: i32;
+    'label: {
+        y = x + 1;
+    }
+}
+
+fn loop_test(x: i32) {
+    let y: i32;
+    for &ext in &["stdout", "stderr", "fixed"] {
+        println!("{}", ext);
+    }
+}

tests/ui/semicolon_if_nothing_returned.stderr

@@ -0,0 +1,22 @@
+error: consider adding a `;` to the last statement for consistent formatting
+  --> $DIR/semicolon_if_nothing_returned.rs:8:5
+   |
+LL |     println!("Hello")
+   |     ^^^^^^^^^^^^^^^^^ help: add a `;` here: `println!("Hello");`
+   |
+   = note: `-D clippy::semicolon-if-nothing-returned` implied by `-D warnings`
+
+error: consider adding a `;` to the last statement for consistent formatting
+  --> $DIR/semicolon_if_nothing_returned.rs:12:5
+   |
+LL |     get_unit()
+   |     ^^^^^^^^^^ help: add a `;` here: `get_unit();`
+
+error: consider adding a `;` to the last statement for consistent formatting
+  --> $DIR/semicolon_if_nothing_returned.rs:17:5
+   |
+LL |     y = x + 1
+   |     ^^^^^^^^^ help: add a `;` here: `y = x + 1;`
+
+error: aborting due to 3 previous errors
+