test: add pointer/alignment test cases from PRs #812, #877, #1004

Consolidate test coverage from superseded PRs into this branch:
- interior-mut3.rs (from #812)
- ptr_offset.rs (from #877)
- alignment-check.rs, local-raw.rs, ptr-through-wrapper.rs,
  raw-ptr-cast.rs, ref-ptr-cast-elem.rs, ref-ptr-cast-elem-offset.rs
  (from #1004)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Stevengre

kmir/src/tests/integration/data/prove-rs/alignment-check.rs

@@ -0,0 +1,14 @@
+// Test for issue #638: alignment check in raw pointer dereference.
+// The compiler inserts an alignment check that transmutes a pointer to usize.
+// Verifies that the transmute cast evaluates concretely.
+
+struct Thing { payload: i16 }
+
+fn main() {
+    let a = [Thing { payload: 1 }, Thing { payload: 2 }, Thing { payload: 3 }];
+    let p = &a as *const Thing;
+    let p1 = unsafe { p.add(1) };
+
+    let two = unsafe { (*p1).payload };
+    assert!(two == 2);
+}

kmir/src/tests/integration/data/prove-rs/interior-mut3.rs

@@ -0,0 +1,11 @@
+use std::cell::UnsafeCell;
+
+fn main() {
+    let data = UnsafeCell::new(0);
+    
+    unsafe {
+        *data.get() += 42;
+    }
+    
+    assert!(data.into_inner() == 42)
+}

kmir/src/tests/integration/data/prove-rs/local-raw.rs

@@ -0,0 +1,5 @@
+fn main() {
+    let mut x: u32 = 3;
+    let y: *mut u32 = &mut x;
+    unsafe { *y = 0; }
+}

kmir/src/tests/integration/data/prove-rs/ptr-through-wrapper.rs

@@ -0,0 +1,19 @@
+struct Wrapper<T>(T);
+
+fn main() {
+    let i = 32_i32;
+
+    unsafe {
+        let p_i = &i as *const i32;
+        assert!(32 == *p_i);
+
+        let p_w = p_i as *const Wrapper<i32>;
+        assert!(32 == (*p_w).0);
+
+        let p_ww = p_w as *const Wrapper<Wrapper<i32>>;
+        assert!(32 == (*p_ww).0.0);
+
+        let p_ii = p_ww as *const i32;
+        assert!(32 == *p_ii);
+    }
+}

kmir/src/tests/integration/data/prove-rs/ptr_offset.rs

@@ -0,0 +1,11 @@
+struct Thing {payload: i16}
+
+fn main() {
+
+    let a = [Thing{payload: 1}, Thing{payload: 2}, Thing{payload:3}];
+    let p = &a as *const Thing;
+    let p1 = unsafe { p.add(1) };
+
+    let two = unsafe { (*p1).payload };
+    assert!(two == 2);
+}

kmir/src/tests/integration/data/prove-rs/raw-ptr-cast.rs

@@ -0,0 +1,10 @@
+fn main() {
+    let mut data = 11;
+    let ptr = &data as *const i32;
+
+    let ptr_mut = &mut data as *mut i32;
+    unsafe {
+        (*ptr_mut) = 44;
+        assert_eq!(44, *ptr);
+    }
+}

kmir/src/tests/integration/data/prove-rs/ref-ptr-cast-elem-offset.rs

@@ -0,0 +1,11 @@
+// ptr-cast-elem-offset-fail.rs
+fn main() {
+    let arr: [i32; 2] = [42, 84];
+    let r_arr = &arr;
+    let p_arr = r_arr as *const i32;
+    
+    unsafe {
+        let p_arr_offset = p_arr.offset(1);
+        assert!(*p_arr_offset == 84);
+    }
+}

kmir/src/tests/integration/data/prove-rs/ref-ptr-cast-elem.rs

@@ -0,0 +1,9 @@
+fn main() {
+    let arr: [i32; 1] = [42];
+    let r_arr = &arr;
+    let p_arr = r_arr as *const i32;
+    
+    unsafe {
+        assert!(*p_arr == 42);
+    }
+}