[SMTChecker] Refactor VariableUsage

test/libsolidity/smtCheckerTests/functions/function_inline_chain.sol

@@ -0,0 +1,41 @@
+pragma experimental SMTChecker;
+
+contract C
+{
+	uint x;
+	uint y;
+	uint z;
+
+	function f() public {
+		if (x == 1)
+			x = 2;
+		else
+			x = 1;
+		g();
+		assert(y == 1);
+	}
+
+	function g() public {
+		y = 1;
+		h();
+		assert(z == 1);
+	}
+
+	function h() public {
+		z = 1;
+		x = 1;
+		f();
+		// This fails for the following calls to the contract:
+		// h()
+		// g() h()
+		// It does not fail for f() g() h() because in that case
+		// h() will not inline f() since it already is in the callstack.
+		assert(x == 1);
+	}
+}
+// ----
+// Warning: (271-274): Assertion checker does not support recursive function calls.
+// Warning: (140-143): Assertion checker does not support recursive function calls.
+// Warning: (483-497): Assertion violation happens here
+// Warning: (201-204): Assertion checker does not support recursive function calls.
+// Warning: (483-497): Assertion violation happens here

test/libsolidity/smtCheckerTests/modifiers/modifier_assignment_outside_branch.sol

@@ -0,0 +1,19 @@
+pragma experimental SMTChecker;
+
+contract C
+{
+    uint x;
+    address owner;
+
+	modifier onlyOwner {
+        if (msg.sender == owner) _;
+    }
+
+    function f() public onlyOwner {
+    }
+
+    function g(uint y) public {
+        y = 1;
+        if (y > x) f();
+    }
+}

test/libsolidity/smtCheckerTests/modifiers/modifier_inside_branch.sol

@@ -0,0 +1,13 @@
+pragma experimental SMTChecker;
+
+contract C {
+    address owner;
+    modifier onlyOwner {
+        if (msg.sender == owner) _;
+    }
+    function g() public onlyOwner {
+    }
+    function f(uint x) public {
+        if (x > 0) g();
+    }
+}

test/libsolidity/smtCheckerTests/modifiers/modifier_inside_branch_assignment.sol

@@ -0,0 +1,23 @@
+pragma experimental SMTChecker;
+
+contract C {
+	uint x;
+	address owner;
+
+	modifier onlyOwner {
+		if (msg.sender == owner) _;
+	}
+
+	function f() public onlyOwner {
+		x = 0;
+	}
+	function g(uint y) public {
+		x = 1;
+		if (y > 0)
+			f();
+		// Fails for {y = >0, msg.sender == owner, x = 0}.
+		assert(x > 0);
+	}
+}
+// ----
+// Warning: (287-300): Assertion violation happens here

test/libsolidity/smtCheckerTests/modifiers/modifier_inside_branch_assignment_branch.sol

@@ -0,0 +1,27 @@
+pragma experimental SMTChecker;
+
+contract C {
+	uint x;
+	address owner;
+
+	modifier onlyOwner {
+		if (msg.sender == owner) {
+			require(x > 0);
+			_;
+		}
+	}
+
+	function f() public onlyOwner {
+		// Condition is always true due to `require(x > 0)` in the modifier.
+		if (x > 0)
+			x -= 1;
+	}
+	function g(uint y) public {
+		x = 2;
+		if (y > 0)
+			f();
+		assert(x > 0);
+	}
+}
+// ----
+// Warning: (266-271): Condition is always true.

test/libsolidity/smtCheckerTests/modifiers/modifier_inside_branch_assignment_multi_branches.sol

@@ -0,0 +1,35 @@
+pragma experimental SMTChecker;
+
+contract C {
+	uint x;
+	address owner;
+
+	modifier onlyOwner {
+		if (msg.sender == owner) {
+			require(x > 0);
+			_;
+		}
+	}
+
+	function f() public onlyOwner {
+		x -= 1;
+		h();
+	}
+	function h() public onlyOwner {
+		require(x < 10000);
+		x += 2;
+	}
+	function g(uint y) public {
+		require(y > 0 && y < 10000);
+		require(msg.sender == owner);
+		x = y;
+		if (y > 1) {
+			f();
+			assert(x == y + 1);
+		}
+		// Fails for {y = 0, x = 0}.
+		assert(x == 0);
+	}
+}
+// ----
+// Warning: (461-475): Assertion violation happens here