Fix unused_unit false positive

Fixes #4076

clippy_lints/src/returns.rs

@@ -277,7 +277,7 @@ impl EarlyLintPass for Return {
  if_chain! {
  if let Some(ref stmt) = block.stmts.last();
  if let ast::StmtKind::Expr(ref expr) = stmt.node;
- if is_unit_expr(expr) && !expr.span.from_expansion();
+ if is_unit_expr(expr) && !stmt.span.from_expansion();
  then {
  let sp = expr.span;
  span_lint_and_then(cx, UNUSED_UNIT, sp, "unneeded unit expression", |db| {

tests/ui/unused_unit.rs

@@ -43,3 +43,16 @@ fn main() {
  }
  return();
 }
+
+// https://github.com/rust-lang/rust-clippy/issues/4076
+fn foo() {
+ macro_rules! foo {
+ (recv($r:expr) -> $res:pat => $body:expr) => {
+ $body
+ }
+ }
+
+ foo! {
+ recv(rx) -> _x => ()
+ }
+}