From a2ad47441eeff3c8cac063670dc51e81e32c9005 Mon Sep 17 00:00:00 2001
From: Christian <c@ethdev.com>
Date: Mon, 1 Dec 2014 17:32:10 +0100
Subject: [PATCH] Disallow assignments to structs and mappings.

---
 AST.cpp | 12 ++++++++----
 AST.h   | 16 +++++++++++-----
 2 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/AST.cpp b/AST.cpp
index 5c07ec80e..4bd0b2c0e 100644
--- a/AST.cpp
+++ b/AST.cpp
@@ -378,6 +378,9 @@ void Assignment::checkTypeRequirements()
 {
 	m_leftHandSide->checkTypeRequirements();
 	m_leftHandSide->requireLValue();
+	//@todo later, assignments to structs might be possible, but not to mappings
+	if (!m_leftHandSide->getType()->isValueType() && !m_leftHandSide->isLocalLValue())
+		BOOST_THROW_EXCEPTION(createTypeError("Assignment to non-local non-value lvalue."));
 	m_rightHandSide->expectType(*m_leftHandSide->getType());
 	m_type = m_leftHandSide->getType();
 	if (m_assigmentOperator != Token::ASSIGN)
@@ -403,7 +406,7 @@ void Expression::expectType(Type const& _expectedType)
 
 void Expression::requireLValue()
 {
-	if (!isLvalue())
+	if (!isLValue())
 		BOOST_THROW_EXCEPTION(createTypeError("Expression has to be an lvalue."));
 	m_lvalueRequested = true;
 }
@@ -495,7 +498,8 @@ void MemberAccess::checkTypeRequirements()
 	m_type = type.getMemberType(*m_memberName);
 	if (!m_type)
 		BOOST_THROW_EXCEPTION(createTypeError("Member \"" + *m_memberName + "\" not found in " + type.toString()));
-	m_isLvalue = (type.getCategory() == Type::Category::STRUCT && m_type->getCategory() != Type::Category::MAPPING);
+	//@todo later, this will not always be STORAGE
+	m_lvalue = type.getCategory() == Type::Category::STRUCT ? LValueType::STORAGE : LValueType::NONE;
 }
 
 void IndexAccess::checkTypeRequirements()
@@ -507,7 +511,7 @@ void IndexAccess::checkTypeRequirements()
 	MappingType const& type = dynamic_cast<MappingType const&>(*m_base->getType());
 	m_index->expectType(*type.getKeyType());
 	m_type = type.getValueType();
-	m_isLvalue = m_type->getCategory() != Type::Category::MAPPING;
+	m_lvalue = LValueType::STORAGE;
 }
 
 void Identifier::checkTypeRequirements()
@@ -521,7 +525,7 @@ void Identifier::checkTypeRequirements()
 		if (!variable->getType())
 			BOOST_THROW_EXCEPTION(createTypeError("Variable referenced before type could be determined."));
 		m_type = variable->getType();
-		m_isLvalue = true;
+		m_lvalue = variable->isLocalVariable() ? LValueType::LOCAL : LValueType::STORAGE;
 		return;
 	}
 	//@todo can we unify these with TypeName::toType()?
diff --git a/AST.h b/AST.h
index 68b5c8b80..87bc3cd40 100644
--- a/AST.h
+++ b/AST.h
@@ -242,6 +242,8 @@ public:
 	std::shared_ptr<Type const> const& getType() const { return m_type; }
 	void setType(std::shared_ptr<Type const> const& _type) { m_type = _type; }
 
+	bool isLocalVariable() const { return !!dynamic_cast<FunctionDefinition*>(getScope()); }
+
 private:
 	ASTPointer<TypeName> m_typeName; ///< can be empty ("var")
 
@@ -526,12 +528,16 @@ private:
  */
 class Expression: public ASTNode
 {
+protected:
+	enum class LValueType { NONE, LOCAL, STORAGE };
+
 public:
-	Expression(Location const& _location): ASTNode(_location), m_isLvalue(false), m_lvalueRequested(false) {}
+	Expression(Location const& _location): ASTNode(_location), m_lvalue(LValueType::NONE), m_lvalueRequested(false) {}
 	virtual void checkTypeRequirements() = 0;
 
 	std::shared_ptr<Type const> const& getType() const { return m_type; }
-	bool isLvalue() const { return m_isLvalue; }
+	bool isLValue() const { return m_lvalue != LValueType::NONE; }
+	bool isLocalLValue() const { return m_lvalue == LValueType::LOCAL; }
 
 	/// Helper function, infer the type via @ref checkTypeRequirements and then check that it
 	/// is implicitly convertible to @a _expectedType. If not, throw exception.
@@ -546,9 +552,9 @@ public:
 protected:
 	//! Inferred type of the expression, only filled after a call to checkTypeRequirements().
 	std::shared_ptr<Type const> m_type;
-	//! Whether or not this expression is an lvalue, i.e. something that can be assigned to.
-	//! This is set during calls to @a checkTypeRequirements()
-	bool m_isLvalue;
+	//! If this expression is an lvalue (i.e. something that can be assigned to) and is stored
+	//! locally or in storage. This is set during calls to @a checkTypeRequirements()
+	LValueType m_lvalue;
 	//! Whether the outer expression requested the address (true) or the value (false) of this expression.
 	bool m_lvalueRequested;
 };