Fix crash for double variable declaration in the same scope.

libsolidity/analysis/DeclarationContainer.cpp

@@ -96,6 +96,11 @@ void DeclarationContainer::activateVariable(ASTString const& _name)
 	m_invisibleDeclarations.erase(_name);
 }
 
+bool DeclarationContainer::isInvisible(ASTString const& _name) const
+{
+	return m_invisibleDeclarations.count(_name);
+}
+
 bool DeclarationContainer::registerDeclaration(
 	Declaration const& _declaration,
 	ASTString const* _name,

libsolidity/analysis/DeclarationContainer.h

@@ -62,6 +62,9 @@ public:
 	/// VariableDeclarationStatements.
 	void activateVariable(ASTString const& _name);
 
+	/// @returns true if declaration is currently invisible.
+	bool isInvisible(ASTString const& _name) const;
+
 	/// @returns existing declaration names similar to @a _name.
 	/// Searches this and all parent containers.
 	std::vector<ASTString> similarNames(ASTString const& _name) const;

libsolidity/analysis/NameAndTypeResolver.cpp

@@ -156,7 +156,8 @@ bool NameAndTypeResolver::updateDeclaration(Declaration const& _declaration)
 void NameAndTypeResolver::activateVariable(string const& _name)
 {
 	solAssert(m_currentScope, "");
-	m_currentScope->activateVariable(_name);
+	if (m_currentScope->isInvisible(_name))
+		m_currentScope->activateVariable(_name);
 }
 
 vector<Declaration const*> NameAndTypeResolver::resolveName(ASTString const& _name, ASTNode const* _scope) const