Added new ui tests to show what errors MIR can now find at compile time

Author: felix91gr

src/test/ui/mir/mir_detects_invalid_ops.rs

@@ -0,0 +1,24 @@
+// build-fail
+
+fn main() {
+    divide_by_zero();
+    mod_by_zero();
+    oob_error_for_slices();
+}
+
+fn divide_by_zero() {
+    let y = 0;
+    let _z = 1 / y; //~ ERROR this operation will panic at runtime [unconditional_panic]
+}
+
+fn mod_by_zero() {
+    let y = 0;
+    let _z = 1 % y; //~ ERROR this operation will panic at runtime [unconditional_panic]
+}
+
+fn oob_error_for_slices() {
+    let a: *const [_] = &[1, 2, 3];
+    unsafe {
+        let _b = (*a)[3]; //~ ERROR this operation will panic at runtime [unconditional_panic]
+    }
+}

src/test/ui/mir/mir_detects_invalid_ops.stderr

@@ -0,0 +1,22 @@
+error: this operation will panic at runtime
+  --> $DIR/mir_detects_invalid_ops.rs:11:14
+   |
+LL |     let _z = 1 / y;
+   |              ^^^^^ attempt to divide by zero
+   |
+   = note: `#[deny(unconditional_panic)]` on by default
+
+error: this operation will panic at runtime
+  --> $DIR/mir_detects_invalid_ops.rs:16:14
+   |
+LL |     let _z = 1 % y;
+   |              ^^^^^ attempt to calculate the remainder with a divisor of zero
+
+error: this operation will panic at runtime
+  --> $DIR/mir_detects_invalid_ops.rs:22:18
+   |
+LL |         let _b = (*a)[3];
+   |                  ^^^^^^^ index out of bounds: the len is 3 but the index is 3
+
+error: aborting due to 3 previous errors
+