Merge pull request #850 from Manishearth/note_31439

add a note of rust-lang/rust/#31439 to the wiki text

Author: mcarton

src/returns.rs

@@ -9,7 +9,7 @@ use utils::{span_lint, span_lint_and_then, snippet_opt, match_path_ast, in_exter
 ///
 /// **Why is this bad?** Removing the `return` and semicolon will make the code more rusty.
 ///
-/// **Known problems:** None
+/// **Known problems:** Following this lint's advice may currently run afoul of Rust issue [#31439](https://github.com/rust-lang/rust/issues/31439), so if you get lifetime errors, please roll back the change until that issue is fixed.
 ///
 /// **Example:** `fn foo(x: usize) { return x; }`
 declare_lint! {
@@ -21,7 +21,7 @@ declare_lint! {
 ///
 /// **Why is this bad?** It is just extraneous code. Remove it to make your code more rusty.
 ///
-/// **Known problems:** None
+/// **Known problems:** Following this lint's advice may currently run afoul of Rust issue [#31439](https://github.com/rust-lang/rust/issues/31439), so if you get lifetime errors, please roll back the change until that issue is fixed.
 ///
 /// **Example:** `{ let x = ..; x }`
 declare_lint! {