rustc_safe_intrinsic: Add UI test

src/test/ui/intrinsics/safe-intrinsic-mismatch.rs

@@ -0,0 +1,11 @@
+#![feature(intrinsics)]
+#![feature(rustc_attrs)]
+
+extern "rust-intrinsic" {
+    fn size_of<T>() -> usize; //~ ERROR intrinsic safety mismatch
+
+    #[rustc_safe_intrinsic]
+    fn assume(b: bool); //~ ERROR intrinsic safety mismatch
+}
+
+fn main() {}

src/test/ui/intrinsics/safe-intrinsic-mismatch.stderr

@@ -0,0 +1,14 @@
+error: intrinsic safety mismatch between list of intrinsics within the compiler and core library intrinsics for intrinsic `size_of`
+  --> $DIR/safe-intrinsic-mismatch.rs:5:5
+   |
+LL |     fn size_of<T>() -> usize;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: intrinsic safety mismatch between list of intrinsics within the compiler and core library intrinsics for intrinsic `assume`
+  --> $DIR/safe-intrinsic-mismatch.rs:8:5
+   |
+LL |     fn assume(b: bool);
+   |     ^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+