rollup merge of #19029: vberger/stability_function_body

Items defined in the body of a function has no visibility outside it, and thus have no reason to inherit its stability.

Closes #17488

src/test/compile-fail/lint-stability.rs

@@ -459,6 +459,20 @@ mod this_crate {
         foo.trait_stable();
     }
 
+    #[deprecated]
+    fn test_fn_body() {
+        fn fn_in_body() {}
+        fn_in_body();
+    }
+
+    impl MethodTester {
+        #[deprecated]
+        fn test_method_body(&self) {
+            fn fn_in_body() {}
+            fn_in_body();
+        }
+    }
+
     #[deprecated]
     pub trait DeprecatedTrait {}