Add some tests

Author: r0qs

Diff for: test/libsolidity/semanticTests/storage/delete_overflow_bug_collision.sol

@@ -0,0 +1,27 @@
+contract CollisionTest {
+    uint256 y = 42;
+
+    function getArray() internal returns (uint256[10][1] storage x) {
+        assembly {
+            x.slot := sub(0, 1)
+        }
+    }
+
+    function f() public returns (uint256[10] memory) {
+        uint256[10][1] storage x = getArray();
+        for (uint i = 0; i < 10; i++)
+            x[0][i] = i;
+        delete x[0];
+        return x[0];
+    }
+
+    function g() public view returns (uint256) {
+        return y;
+    }
+}
+
+// ----
+// g() -> 42
+// f() -> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+// gas legacy: 170463
+// g() -> 0

Diff for: test/libsolidity/semanticTests/storage/delete_overflow_bug_partial_assignment.sol

@@ -0,0 +1,15 @@
+contract C {
+    function f() public returns (uint256[10] memory) {
+        uint256[10][1] storage x;
+        assembly { x.slot := sub(0, 1) }
+        for (uint i = 0; i < 10; i++)
+            x[0][i] = i;
+        x[0] = [11, 12, 13];
+        return x[0];
+    }
+}
+// ----
+// f() -> 11, 12, 13, 0, 0, 0, 0, 0, 0, 0
+// gas irOptimized: 181920
+// gas legacy: 200268
+// gas legacyOptimized: 181899

Diff for: test/libsolidity/semanticTests/storage/delete_overflow_bug_storage_layout.sol

@@ -0,0 +1,20 @@
+contract C layout at 2**256 - 1 {
+
+    function getArray() internal returns (uint256[10][1] storage x) {
+        assembly {
+            x.slot := sub(0, 1)
+        }
+    }
+
+    function f() public returns (uint256[10] memory) {
+        uint256[10][1] storage x = getArray();
+        for (uint i = 0; i < 10; i++)
+            x[0][i] = i;
+        delete x[0];
+        return x[0];
+    }
+}
+
+// ----
+// f() -> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+// gas legacy: 184143