argotorg · meditationduck · Apr 28, 2023 · May 4, 2023 · May 4, 2023 · May 4, 2023
diff --git a/Changelog.md b/Changelog.md
@@ -1,6 +1,7 @@
 ### 0.8.31 (unreleased)
 
 Language Features:
+ * Support for EIP-712 struct typehash via ``type(S).typehash`` for computing the keccak256 hash of the EIP-712 encoding of struct type ``S``.
 
 Compiler Features:
 * ethdebug: Experimental support for instructions and source locations under EOF.

diff --git a/docs/cheatsheet.rst b/docs/cheatsheet.rst
@@ -130,6 +130,7 @@ Type Information
 - ``type(C).creationCode`` (``bytes memory``): creation bytecode of the given contract, see :ref:`Type Information<meta-type>`.
 - ``type(C).runtimeCode`` (``bytes memory``): runtime bytecode of the given contract, see :ref:`Type Information<meta-type>`.
 - ``type(I).interfaceId`` (``bytes4``): value containing the EIP-165 interface identifier of the given interface, see :ref:`Type Information<meta-type>`.
+- ``type(S).typehash`` (``bytes32``): the typehash of the given struct type ``S``, see :ref:`Type Information<meta-type>`.
 - ``type(T).min`` (``T``): the minimum value representable by the integer type ``T``, see :ref:`Type Information<meta-type>`.
 - ``type(T).max`` (``T``): the maximum value representable by the integer type ``T``, see :ref:`Type Information<meta-type>`.
 

diff --git a/docs/units-and-global-variables.rst b/docs/units-and-global-variables.rst
@@ -404,6 +404,13 @@ for an interface type ``I``:
     interface identifier of the given interface ``I``. This identifier is defined as the ``XOR`` of all
     function selectors defined within the interface itself - excluding all inherited functions.
 
+The following properties are available for an struct type ``S``:
+
+``type(S).typehash``:
+    A ``bytes32`` value containing the `EIP-712 <https://eips.ethereum.org/EIPS/eip-712>`_
+    typehash of the given structure ``S``. This identifier is defined as ``keccak256`` of
+    structure name and all the fields with their types, wrapped in braces and separated by commas.
+
 The following properties are available for an integer type ``T``:
 
 ``type(T).min``

diff --git a/libsolidity/analysis/TypeChecker.cpp b/libsolidity/analysis/TypeChecker.cpp
@@ -210,6 +210,7 @@ TypePointers TypeChecker::typeCheckMetaTypeFunctionAndRetrieveReturnType(Functio
 			wrongType = contractType->isSuper();
 		else if (
 			typeCategory != Type::Category::Integer &&
+			typeCategory != Type::Category::Struct &&
 			typeCategory != Type::Category::Enum
 		)
 			wrongType = true;
@@ -222,7 +223,7 @@ TypePointers TypeChecker::typeCheckMetaTypeFunctionAndRetrieveReturnType(Functio
 			4259_error,
 			arguments.front()->location(),
 			"Invalid type for argument in the function call. "
-			"An enum type, contract type or an integer type is required, but " +
+			"An enum type, contract type, struct type or an integer type is required, but " +
 			type(*arguments.front())->humanReadableName() + " provided."
 		);
 
@@ -3302,6 +3303,27 @@ bool TypeChecker::visit(MemberAccess const& _memberAccess)
 			annotation.isPure = true;
 		else if (magicType->kind() == MagicType::Kind::MetaType && memberName == "interfaceId")
 			annotation.isPure = true;
+		else if (magicType->kind() == MagicType::Kind::MetaType && memberName == "typehash")
+		{
+			annotation.isPure = true;
+			auto accessedStructType = dynamic_cast<StructType const*>(magicType->typeArgument());
+			solAssert(accessedStructType, "typehash requested on a non struct type.");
+
+			// Direct recursion is already rejected by DeclarationTypeChecker,
+			// so only dynamic array based recursion can reach here. which is valid.
+
+			for (auto const& member: accessedStructType->members(currentDefinitionScope()))
+			{
+				if (!member.type->isEIP712AllowedStructMemberType())
+				{
+					m_errorReporter.typeError(
+						9518_error,
+						_memberAccess.location(),
+						"\"typehash\" cannot be used for structs with members of \"" + member.type->humanReadableName() + "\" type."
+					);
+				}
+			}
+		}
 		else if (
 			magicType->kind() == MagicType::Kind::MetaType &&
 			(memberName == "min" || memberName == "max")

diff --git a/libsolidity/analysis/ViewPureChecker.cpp b/libsolidity/analysis/ViewPureChecker.cpp
@@ -398,6 +398,7 @@ void ViewPureChecker::endVisit(MemberAccess const& _memberAccess)
 			{MagicType::Kind::MetaType, "runtimeCode"},
 			{MagicType::Kind::MetaType, "name"},
 			{MagicType::Kind::MetaType, "interfaceId"},
+			{MagicType::Kind::MetaType, "typehash"},
 			{MagicType::Kind::MetaType, "min"},
 			{MagicType::Kind::MetaType, "max"},
 		};

diff --git a/libsolidity/ast/AST.cpp b/libsolidity/ast/AST.cpp
@@ -38,6 +38,8 @@
 
 #include <functional>
 #include <utility>
+#include <numeric>
+#include <set>
 
 using namespace solidity;
 using namespace solidity::frontend;
@@ -409,6 +411,75 @@ std::vector<std::pair<ASTPointer<IdentifierPath>, std::optional<Token>>> UsingFo
 	return ranges::zip_view(m_functionsOrLibrary, m_operators) | ranges::to<std::vector>;
 }
 
+void StructDefinition::insertEip712EncodedSubtypes(std::set<std::string>& subtypes) const
+{
+	std::set<StructDefinition const*> processedStructs;
+	collectEip712SubtypesWithCycleTracking(subtypes, processedStructs, this);
+}
+
+void StructDefinition::collectEip712SubtypesWithCycleTracking(std::set<std::string>& subtypes, std::set<StructDefinition const*>& processedStructs, StructDefinition const* rootStruct) const
+{
+	if (processedStructs.count(this))
+		return;
+
+	processedStructs.insert(this);
+
+	for (auto const& member: m_members)
+	{
+		Declaration const* declaration = nullptr;
+
+		switch (member->type()->category())
+		{
+			case Type::Category::Struct:
+				declaration = member->type()->typeDefinition();
+				break;
+			case Type::Category::Array:
+				if (auto const* arrayType = dynamic_cast<ArrayType const*>(member->type()))
+					if (auto finalBaseType = dynamic_cast<StructType const*>(arrayType->finalBaseType(false)))
+					{
+						declaration = finalBaseType->typeDefinition();
+					}
+				break;
+			default:
+				continue;
+		}
+
+		if (!declaration)
+			continue;
+
+		if (auto const* structDef = dynamic_cast<StructDefinition const*>(declaration))
+			if (structDef != rootStruct)
+			{
+				subtypes.insert(structDef->eip712EncodeTypeWithoutSubtypes());
+				structDef->collectEip712SubtypesWithCycleTracking(subtypes, processedStructs, rootStruct);
+			}
+	}
+}
+
+std::string StructDefinition::eip712EncodeTypeWithoutSubtypes() const
+{
+	std::string str = name() + "(";
+	for (size_t i = 0; i < m_members.size(); i++)
+	{
+		str += i == 0 ? "" : ",";
+		str += m_members[i]->type()->eip712TypeName() + " " + m_members[i]->name();
+	}
+	return str + ")";
+}
+
+std::string StructDefinition::eip712EncodeType() const
+{
+	// std::set enables duplicates elimination and ordered enumeration
+	std::set<std::string> subtypes;
+	insertEip712EncodedSubtypes(subtypes);
+	return std::accumulate(subtypes.begin(), subtypes.end(), eip712EncodeTypeWithoutSubtypes());
+}
+
+util::h256 StructDefinition::typehash() const
+{
+	return util::keccak256(eip712EncodeType());
+}
+
 Type const* StructDefinition::type() const
 {
 	solAssert(annotation().recursive.has_value(), "Requested struct type before DeclarationTypeChecker.");

diff --git a/libsolidity/ast/AST.h b/libsolidity/ast/AST.h
@@ -777,6 +777,23 @@ class StructDefinition: public Declaration, public StructurallyDocumented, publi
 
 	std::vector<ASTPointer<VariableDeclaration>> const& members() const { return m_members; }
 
+	/// Fills set with the EIP-712 compatible struct encodings without subtypes concatenated.
+	void insertEip712EncodedSubtypes(std::set<std::string>& subtypes) const;
+
+private:
+	void collectEip712SubtypesWithCycleTracking(std::set<std::string>& subtypes, std::set<StructDefinition const*>& processedStructs, StructDefinition const* rootStruct) const;
+
+public:
+
+	/// @returns the EIP-712 compatible struct encoding but without subtypes concatenated.
+	std::string eip712EncodeTypeWithoutSubtypes() const;
+
+	/// @returns the EIP-712 compatible struct encoding with subtypes sorted and concatenated.
+	std::string eip712EncodeType() const;
+
+	/// @returns the EIP-712 compatible typehash of this struct.
+	util::h256 typehash() const;
+
 	Type const* type() const override;
 
 	bool isVisibleInDerivedContracts() const override { return true; }

diff --git a/libsolidity/ast/TypeProvider.cpp b/libsolidity/ast/TypeProvider.cpp
@@ -563,10 +563,11 @@ MagicType const* TypeProvider::meta(Type const* _type)
 	solAssert(
 		_type && (
 			_type->category() == Type::Category::Contract ||
+			_type->category() == Type::Category::Struct ||
 			_type->category() == Type::Category::Integer ||
 			_type->category() == Type::Category::Enum
 		),
-		"Only enum, contracts or integer types supported for now."
+		"Only enum, contract, struct or integer types supported for now."
 	);
 	return createAndGet<MagicType>(_type);
 }

diff --git a/libsolidity/ast/Types.cpp b/libsolidity/ast/Types.cpp
@@ -1910,6 +1910,23 @@ std::string ArrayType::canonicalName() const
 	return ret;
 }
 
+std::string ArrayType::eip712TypeName() const
+{
+	std::string ret;
+	if (isString())
+		ret = "string";
+	else if (isByteArrayOrString())
+		ret = "bytes";
+	else
+	{
+		ret = baseType()->eip712TypeName() + "[";
+		if (!isDynamicallySized())
+			ret += length().str();
+		ret += "]";
+	}
+	return ret;
+}
+
 std::string ArrayType::signatureInExternalFunction(bool _structsByName) const
 {
 	if (isByteArrayOrString())
@@ -2548,6 +2565,11 @@ std::string StructType::canonicalName() const
 	return *m_struct.annotation().canonicalName;
 }
 
+std::string StructType::eip712TypeName() const
+{
+	return this->typeDefinition()->name();
+}
+
 FunctionTypePointer StructType::constructorType() const
 {
 	TypePointers paramTypes;
@@ -2666,6 +2688,11 @@ std::string EnumType::canonicalName() const
 	return *m_enum.annotation().canonicalName;
 }
 
+std::string EnumType::eip712TypeName() const
+{
+	return "uint8";
+}
+
 size_t EnumType::numberOfMembers() const
 {
 	return m_enum.members().size();
@@ -4255,15 +4282,7 @@ MemberList::MemberMap MagicType::nativeMembers(ASTNode const*) const
 		return {};
 	case Kind::MetaType:
 	{
-		solAssert(
-			m_typeArgument && (
-					m_typeArgument->category() == Type::Category::Contract ||
-					m_typeArgument->category() == Type::Category::Integer ||
-					m_typeArgument->category() == Type::Category::Enum
-			),
-			"Only enums, contracts or integer types supported for now"
-		);
-
+		solAssert(m_typeArgument, "");
 		if (m_typeArgument->category() == Type::Category::Contract)
 		{
 			ContractDefinition const& contract = dynamic_cast<ContractType const&>(*m_typeArgument).contractDefinition();
@@ -4279,6 +4298,12 @@ MemberList::MemberMap MagicType::nativeMembers(ASTNode const*) const
 					{"name", TypeProvider::stringMemory()},
 				});
 		}
+		else if (m_typeArgument->category() == Type::Category::Struct)
+		{
+			return MemberList::MemberMap({
+				{"typehash", TypeProvider::fixedBytes(32)},
+			});
+		}
 		else if (m_typeArgument->category() == Type::Category::Integer)
 		{
 			IntegerType const* integerTypePointer = dynamic_cast<IntegerType const*>(m_typeArgument);
@@ -4295,6 +4320,10 @@ MemberList::MemberMap MagicType::nativeMembers(ASTNode const*) const
 				{"max", enumTypePointer},
 			});
 		}
+		else
+		{
+			solAssert(false, "Only enums, contracts, structs or integer types supported for now");
+		}
 	}
 	}
 	solAssert(false, "Unknown kind of magic.");