integration: add function pointer integration test (#205)

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

crates/integration/contracts/FunctionPointer.sol

@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8;
+
+/* runner.json
+{
+    "differential": true,
+    "actions": [
+        {
+            "Instantiate": {
+                "code": {
+                    "Solidity": {
+                        "contract": "FunctionPointer"
+                    }
+                }
+            }
+        },
+        {
+            "Call": {
+                "dest": {
+                    "Instantiated": 0
+                },
+                "data": "26121ff0"
+            }
+        }
+    ]
+}
+*/
+
+contract FunctionPointer {
+    bool public flag = false;
+
+    function f0() public {
+        flag = true;
+    }
+
+    function f() public returns (bool) {
+        function() internal x = f0;
+        x();
+        return flag;
+    }
+}

crates/integration/src/tests.rs

@@ -54,6 +54,7 @@ test_spec!(coinbase, "Coinbase", "Coinbase.sol");
 test_spec!(create2, "CreateB", "Create2.sol");
 test_spec!(transfer, "Transfer", "Transfer.sol");
 test_spec!(send, "Send", "Send.sol");
+test_spec!(function_pointer, "FunctionPointer", "FunctionPointer.sol");
 
 fn instantiate(path: &str, contract: &str) -> Vec<SpecsAction> {
     vec![Instantiate {