Add a few more UI tests.

Author: cr1901

macros/tests/ui/interrupt_bad_cs_import.rs

@@ -0,0 +1,20 @@
+#![no_main]
+
+use msp430::interrupt::CriticalSection as CritSec;
+use msp430_rt_macros::{entry, interrupt};
+
+// If we use "msp430::interrupt::CriticalSection", we get unused import warning for CritSec,
+// which is correct but misleading b/c of interrupt sig requirements.
+fn arg(_cs: msp430::interrupt::CriticalSection) {
+    /* initialize hardware */
+}
+
+#[entry]
+fn main() -> ! {
+    unimplemented!()
+}
+
+#[interrupt]
+fn TIM2(_cs: CritSec) {
+    unimplemented!()
+}

macros/tests/ui/interrupt_bad_cs_import.stderr

@@ -0,0 +1,13 @@
+error: `#[interrupt]` handlers must have signature `[unsafe] fn([<name>: CriticalSection]) [-> !]`
+  --> tests/ui/interrupt_bad_cs_import.rs:18:1
+   |
+18 | fn TIM2(_cs: CritSec) {
+   | ^^^^^^^^^^^^^^^^^^^^^
+
+warning: unused import: `msp430::interrupt::CriticalSection as CritSec`
+ --> tests/ui/interrupt_bad_cs_import.rs:3:5
+  |
+3 | use msp430::interrupt::CriticalSection as CritSec;
+  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  |
+  = note: `#[warn(unused_imports)]` on by default

macros/tests/ui/interrupt_wrong_import.rs

@@ -0,0 +1,14 @@
+#![no_main]
+
+// Incorrect w/ bad error message- use of undeclared crate or module `interrupt`.
+use msp430_rt_macros::{entry, interrupt};
+
+#[entry]
+fn main() -> ! {
+    unimplemented!()
+}
+
+#[interrupt]
+fn TIM2() {
+    unimplemented!()
+}