[SMTChecker] Clear encoding context before engine starts

libsolidity/formal/BMC.cpp

@@ -49,6 +49,8 @@ void BMC::analyze(SourceUnit const& _source, shared_ptr<Scanner> const& _scanner
 
 	m_scanner = _scanner;
 
+	m_context.clear();
+
 	_source.accept(*this);
 
 	solAssert(m_interface->solvers() > 0, "");

libsolidity/formal/EncodingContext.cpp

@@ -44,6 +44,12 @@ void EncodingContext::reset()
 	m_assertions.clear();
 }
 
+void EncodingContext::clear()
+{
+	m_variables.clear();
+	reset();
+}
+
 /// Variables.
 
 shared_ptr<SymbolicVariable> EncodingContext::variable(solidity::VariableDeclaration const& _varDecl)

libsolidity/formal/EncodingContext.h

@@ -38,8 +38,13 @@ class EncodingContext
 public:
 	EncodingContext(std::shared_ptr<SolverInterface> _solver);
 
-	/// Resets the entire context.
+	/// Resets the entire context except for symbolic variables which stay
+	/// alive because of state variables and inlined function calls.
+	/// To be used in the beginning of a root function visit.
 	void reset();
+	/// Clears the entire context, erasing everything.
+	/// To be used before a model checking engine starts.
+	void clear();
 
 	/// Forwards variable creation to the solver.
 	Expression newVariable(std::string _name, SortPointer _sort)