solidity/libsolidity/analysis/ViewPureChecker.cpp

/*
	This file is part of solidity.

	solidity is free software: you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	solidity is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
*/

#include <libsolidity/analysis/ViewPureChecker.h>

#include <libevmasm/SemanticInformation.h>

#include <libsolidity/inlineasm/AsmData.h>
#include <libsolidity/ast/ExperimentalFeatures.h>

#include <functional>

using namespace std;
using namespace dev;
using namespace dev::solidity;

namespace
{

class AssemblyViewPureChecker: public boost::static_visitor<void>
{
public:
	explicit AssemblyViewPureChecker(std::function<void(StateMutability, SourceLocation const&)> _reportMutability):
		m_reportMutability(_reportMutability) {}

	void operator()(assembly::Label const&) { }
	void operator()(assembly::Instruction const& _instruction)
	{
		checkInstruction(_instruction.location, _instruction.instruction);
	}
	void operator()(assembly::Literal const&) {}
	void operator()(assembly::Identifier const&) {}
	void operator()(assembly::FunctionalInstruction const& _instr)
	{
		checkInstruction(_instr.location, _instr.instruction);
		for (auto const& arg: _instr.arguments)
			boost::apply_visitor(*this, arg);
	}
	void operator()(assembly::ExpressionStatement const& _expr)
	{
		boost::apply_visitor(*this, _expr.expression);
	}
	void operator()(assembly::StackAssignment const&) {}
	void operator()(assembly::Assignment const& _assignment)
	{
		boost::apply_visitor(*this, *_assignment.value);
	}
	void operator()(assembly::VariableDeclaration const& _varDecl)
	{
		if (_varDecl.value)
			boost::apply_visitor(*this, *_varDecl.value);
	}
	void operator()(assembly::FunctionDefinition const& _funDef)
	{
		(*this)(_funDef.body);
	}
	void operator()(assembly::FunctionCall const& _funCall)
	{
		for (auto const& arg: _funCall.arguments)
			boost::apply_visitor(*this, arg);
	}
	void operator()(assembly::If const& _if)
	{
		boost::apply_visitor(*this, *_if.condition);
		(*this)(_if.body);
	}
	void operator()(assembly::Switch const& _switch)
	{
		boost::apply_visitor(*this, *_switch.expression);
		for (auto const& _case: _switch.cases)
		{
			if (_case.value)
				(*this)(*_case.value);
			(*this)(_case.body);
		}
	}
	void operator()(assembly::ForLoop const& _for)
	{
		(*this)(_for.pre);
		boost::apply_visitor(*this, *_for.condition);
		(*this)(_for.body);
		(*this)(_for.post);
	}
	void operator()(assembly::Block const& _block)
	{
		for (auto const& s: _block.statements)
			boost::apply_visitor(*this, s);
	}

private:
	std::function<void(StateMutability, SourceLocation const&)> m_reportMutability;
	void checkInstruction(SourceLocation _location, solidity::Instruction _instruction)
	{
		if (eth::SemanticInformation::invalidInViewFunctions(_instruction))
			m_reportMutability(StateMutability::NonPayable, _location);
		else if (eth::SemanticInformation::invalidInPureFunctions(_instruction))
			m_reportMutability(StateMutability::View, _location);
	}
};

}

bool ViewPureChecker::check()
{
	vector<ContractDefinition const*> contracts;

	for (auto const& node: m_ast)
	{
		SourceUnit const* source = dynamic_cast<SourceUnit const*>(node.get());
		solAssert(source, "");
		contracts += source->filteredNodes<ContractDefinition>(source->nodes());
	}

	// Check modifiers first to infer their state mutability.
	for (auto const& contract: contracts)
		for (ModifierDefinition const* mod: contract->functionModifiers())
			mod->accept(*this);

	for (auto const& contract: contracts)
		contract->accept(*this);

	return !m_errors;
}



bool ViewPureChecker::visit(FunctionDefinition const& _funDef)
{
	solAssert(!m_currentFunction, "");
	m_currentFunction = &_funDef;
	m_currentBestMutability = StateMutability::Pure;
	return true;
}

void ViewPureChecker::endVisit(FunctionDefinition const& _funDef)
{
	solAssert(m_currentFunction == &_funDef, "");
	if (
		m_currentBestMutability < _funDef.stateMutability() &&
		_funDef.stateMutability() != StateMutability::Payable &&
		_funDef.isImplemented() &&
		!_funDef.isConstructor() &&
		!_funDef.isFallback() &&
		!_funDef.annotation().superFunction
	)
		m_errorReporter.warning(
			_funDef.location(),
			"Function state mutability can be restricted to " + stateMutabilityToString(m_currentBestMutability)
		);
	m_currentFunction = nullptr;
}

bool ViewPureChecker::visit(ModifierDefinition const&)
{
	solAssert(m_currentFunction == nullptr, "");
	m_currentBestMutability = StateMutability::Pure;
	return true;
}

void ViewPureChecker::endVisit(ModifierDefinition const& _modifierDef)
{
	solAssert(m_currentFunction == nullptr, "");
	m_inferredMutability[&_modifierDef] = m_currentBestMutability;
}

void ViewPureChecker::endVisit(Identifier const& _identifier)
{
	Declaration const* declaration = _identifier.annotation().referencedDeclaration;
	solAssert(declaration, "");

	StateMutability mutability = StateMutability::Pure;

	bool writes = _identifier.annotation().lValueRequested;
	if (VariableDeclaration const* varDecl = dynamic_cast<VariableDeclaration const*>(declaration))
	{
		if (varDecl->isStateVariable() && !varDecl->isConstant())
			mutability = writes ? StateMutability::NonPayable : StateMutability::View;
	}
	else if (MagicVariableDeclaration const* magicVar = dynamic_cast<MagicVariableDeclaration const*>(declaration))
	{
		switch (magicVar->type()->category())
		{
		case Type::Category::Contract:
			solAssert(_identifier.name() == "this" || _identifier.name() == "super", "");
			if (!dynamic_cast<ContractType const&>(*magicVar->type()).isSuper())
				// reads the address
				mutability = StateMutability::View;
			break;
		case Type::Category::Integer:
			solAssert(_identifier.name() == "now", "");
			mutability = StateMutability::View;
			break;
		default:
			break;
		}
	}

	reportMutability(mutability, _identifier.location());
}

void ViewPureChecker::endVisit(InlineAssembly const& _inlineAssembly)
{
	AssemblyViewPureChecker{
		[=](StateMutability _mutability, SourceLocation const& _location) { reportMutability(_mutability, _location); }
	}(_inlineAssembly.operations());
}

void ViewPureChecker::reportMutability(StateMutability _mutability, SourceLocation const& _location)
{
	if (m_currentFunction && m_currentFunction->stateMutability() < _mutability)
	{
		if (_mutability == StateMutability::View)
			m_errorReporter.typeError(
				_location,
				"Function declared as pure, but this expression (potentially) reads from the "
				"environment or state and thus requires \"view\"."
			);
		else if (_mutability == StateMutability::NonPayable)
			m_errorReporter.typeError(
				_location,
				"Function declared as " +
				stateMutabilityToString(m_currentFunction->stateMutability()) +
				", but this expression (potentially) modifies the state and thus "
				"requires non-payable (the default) or payable."
			);
		else
			solAssert(false, "");

		solAssert(
			m_currentFunction->stateMutability() == StateMutability::View ||
			m_currentFunction->stateMutability() == StateMutability::Pure,
			""
		);
		m_errors = true;
	}
	if (_mutability > m_currentBestMutability)
		m_currentBestMutability = _mutability;
}

void ViewPureChecker::endVisit(FunctionCall const& _functionCall)
{
	if (_functionCall.annotation().kind != FunctionCallKind::FunctionCall)
		return;

	StateMutability mut = dynamic_cast<FunctionType const&>(*_functionCall.expression().annotation().type).stateMutability();
	// We only require "nonpayable" to call a payble function.
	if (mut == StateMutability::Payable)
		mut = StateMutability::NonPayable;
	reportMutability(mut, _functionCall.location());
}

bool ViewPureChecker::visit(MemberAccess const& _memberAccess)
{
	// Catch the special case of `this.f.selector` which is a pure expression.
	ASTString const& member = _memberAccess.memberName();
	if (
		_memberAccess.expression().annotation().type->category() == Type::Category::Function &&
		member == "selector"
	)
		if (auto const* expr = dynamic_cast<MemberAccess const*>(&_memberAccess.expression()))
			if (auto const* exprInt = dynamic_cast<Identifier const*>(&expr->expression()))
				if (exprInt->name() == "this")
					// Do not continue visiting.
					return false;
	return true;
}

void ViewPureChecker::endVisit(MemberAccess const& _memberAccess)
{
	StateMutability mutability = StateMutability::Pure;
	bool writes = _memberAccess.annotation().lValueRequested;

	ASTString const& member = _memberAccess.memberName();
	switch (_memberAccess.expression().annotation().type->category())
	{
	case Type::Category::Contract:
	case Type::Category::Integer:
		if (member == "balance" && !_memberAccess.annotation().referencedDeclaration)
			mutability = StateMutability::View;
		break;
	case Type::Category::Magic:
	{
		// we can ignore the kind of magic and only look at the name of the member
		set<string> static const pureMembers{
			"encode", "encodePacked", "encodeWithSelector", "encodeWithSignature", "data", "sig", "blockhash"
		};
		if (!pureMembers.count(member))
			mutability = StateMutability::View;
		break;
	}
	case Type::Category::Struct:
	{
		if (_memberAccess.expression().annotation().type->dataStoredIn(DataLocation::Storage))
			mutability = writes ? StateMutability::NonPayable : StateMutability::View;
		break;
	}
	case Type::Category::Array:
	{
		auto const& type = dynamic_cast<ArrayType const&>(*_memberAccess.expression().annotation().type);
		if (member == "length" && type.isDynamicallySized() && type.dataStoredIn(DataLocation::Storage))
			mutability = writes ? StateMutability::NonPayable : StateMutability::View;
		break;
	}
	default:
		break;
	}
	reportMutability(mutability, _memberAccess.location());
}

void ViewPureChecker::endVisit(IndexAccess const& _indexAccess)
{
	if (!_indexAccess.indexExpression())
		solAssert(_indexAccess.annotation().type->category() == Type::Category::TypeType, "");
	else
	{
		bool writes = _indexAccess.annotation().lValueRequested;
		if (_indexAccess.baseExpression().annotation().type->dataStoredIn(DataLocation::Storage))
			reportMutability(writes ? StateMutability::NonPayable : StateMutability::View, _indexAccess.location());
	}
}

void ViewPureChecker::endVisit(ModifierInvocation const& _modifier)
{
	solAssert(_modifier.name(), "");
	if (ModifierDefinition const* mod = dynamic_cast<decltype(mod)>(_modifier.name()->annotation().referencedDeclaration))
	{
		solAssert(m_inferredMutability.count(mod), "");
		reportMutability(m_inferredMutability.at(mod), _modifier.location());
	}
	else
		solAssert(dynamic_cast<ContractDefinition const*>(_modifier.name()->annotation().referencedDeclaration), "");
}