properly handle #[cfg] (conditional compilation) on resources

tests/cpass/cfg.rs

@@ -0,0 +1,49 @@
+//! Compile-pass test that checks that `#[cfg]` attributes are respected
+
+#![deny(unsafe_code)]
+#![deny(warnings)]
+#![no_main]
+#![no_std]
+
+extern crate lm3s6965;
+extern crate panic_semihosting;
+extern crate rtfm;
+
+use rtfm::app;
+
+#[app(device = lm3s6965)]
+const APP: () = {
+    #[cfg(never)]
+    static mut FOO: u32 = 0;
+
+    #[init]
+    fn init() {
+        #[cfg(never)]
+        static mut BAR: u32 = 0;
+    }
+
+    #[idle]
+    fn idle() -> ! {
+        #[cfg(never)]
+        static mut BAR: u32 = 0;
+
+        loop {}
+    }
+
+    #[task(resources = [FOO])]
+    fn foo() {
+        #[cfg(never)]
+        static mut BAR: u32 = 0;
+    }
+
+    #[task(priority = 3, resources = [FOO])]
+    fn bar() {
+        #[cfg(never)]
+        static mut BAR: u32 = 0;
+    }
+
+    extern "C" {
+        fn UART0();
+        fn UART1();
+    }
+};