[SMTChecker] Added support for precise modeling of external calls to this.

Modeling external calls to this, since we can trust these calls.

fixed problem with transaction data not being restored after trusted external call

update to the tests

additional tests

changelog entry

added tests for external getters of this

test/libsolidity/smtCheckerTests/functions/this_external_call.sol

@@ -9,9 +9,7 @@ contract C
 	function g(uint y) public {
 		require(y < 1000);
 		this.f(y);
-		// Fails as false positive because CHC does not support `this`.
 		assert(x < 1000);
 	}
 }
 // ----
-// Warning 6328: (227-243): CHC: Assertion violation happens here.

test/libsolidity/smtCheckerTests/functions/this_external_call_2.sol

@@ -0,0 +1,16 @@
+pragma experimental SMTChecker;
+
+contract C {
+    uint a;
+    function f(uint x) public {
+        this.g(x);
+        assert(a == x);
+        assert(a != 42);
+    }
+
+    function g(uint x) public {
+        a = x;
+    }
+}
+// ----
+// Warning 6328: (141-156): CHC: Assertion violation happens here.

test/libsolidity/smtCheckerTests/functions/this_external_call_return.sol

@@ -10,9 +10,7 @@ contract C
 	function g(uint y) public {
 		require(y < 1000);
 		uint z = this.f(y);
-		// Fails as false positive because CHC does not support `this`.
 		assert(z < 1000);
 	}
 }
 // ----
-// Warning 6328: (263-279): CHC: Assertion violation happens here.

test/libsolidity/smtCheckerTests/functions/this_external_call_sender.sol

@@ -0,0 +1,28 @@
+pragma experimental SMTChecker;
+
+contract C {
+    address lastCaller;
+
+    constructor() {
+        lastCaller = msg.sender;
+    }
+
+    modifier log {
+        lastCaller = msg.sender;
+        _;
+    }
+
+    function test() log public {
+        assert(lastCaller == msg.sender);
+        this.g();
+        assert(lastCaller == address(this));
+        assert(lastCaller == msg.sender);
+        assert(lastCaller == address(0));
+    }
+
+    function g() log public {
+    }
+}
+// ----
+// Warning 6328: (347-379): CHC: Assertion violation happens here.
+// Warning 6328: (389-421): CHC: Assertion violation happens here.

test/libsolidity/smtCheckerTests/functions/this_external_call_tx_origin.sol

@@ -0,0 +1,14 @@
+pragma experimental SMTChecker;
+
+contract C {
+
+	function test() view public {
+		require(address(this) != tx.origin);
+		assert(!this.g());
+	}
+
+	function g() view public returns (bool) {
+		return msg.sender == tx.origin;
+	}
+}
+// ----

test/libsolidity/smtCheckerTests/functions/this_external_getter_1.sol

@@ -0,0 +1,12 @@
+pragma experimental SMTChecker;
+
+contract C {
+	uint public x;
+
+	function f() public view {
+		uint y = this.x();
+		assert(y == x); // This fails as false positive because of lack of support for external getters.
+	}
+}
+// ----
+// Warning 6328: (114-128): CHC: Assertion violation happens here.

test/libsolidity/smtCheckerTests/functions/this_external_getter_2.sol

@@ -0,0 +1,12 @@
+pragma experimental SMTChecker;
+
+contract C {
+	mapping (uint => uint) public map;
+
+	function f() public view {
+		uint y = this.map(2);
+		assert(y == map[2]); // This fails as false positive because of lack of support for external getters.
+	}
+}
+// ----
+// Warning 6328: (137-156): CHC: Assertion violation happens here.

test/libsolidity/smtCheckerTests/functions/this_external_getter_3.sol

@@ -0,0 +1,12 @@
+pragma experimental SMTChecker;
+
+contract C {
+	mapping (uint => mapping (uint => uint)) public map;
+
+	function f() public view {
+		uint y = this.map(2, 3);
+		assert(y == map[2][3]); // This fails as false positive because of lack of support for external getters.
+	}
+}
+// ----
+// Warning 6328: (158-180): CHC: Assertion violation happens here.

test/libsolidity/smtCheckerTests/functions/this_state.sol

@@ -6,7 +6,6 @@ contract C
     function g() public {
 		x = 0;
         this.h();
-		// Fails as false positive because CHC does not support `this`.
 		assert(x == 2);
     }
     function h() public {
@@ -14,4 +13,3 @@ contract C
     }
 }
 // ----
-// Warning 6328: (186-200): CHC: Assertion violation happens here.