Merge pull request #7350 from ethereum/array-length-rvalue

Make `length` member read-only

Changelog.md

@@ -14,6 +14,7 @@ Breaking changes:
  * Syntax: Abstract contracts need to be marked explicitly as abstract by using the ``abstract`` keyword.
  * Inline Assembly: Only strict inline assembly is allowed.
  * Inline Assembly: Variable declarations cannot shadow declarations outside the assembly block.
+ * Syntax: ``length`` member of arrays is now always read-only, even for storage arrays.
  * Type checker: Resulting type of exponentiation is equal to the type of the base. Also allow signed types for the base.
  * Natspec JSON Interface: Properly support multiple ``@return`` statements in ``@dev`` documentation and enforce named return parameters to be mentioned documentation.
  * Source mappings: Add "modifier depth" as a fifth field in the source mappings.

docs/060-breaking-changes.rst

@@ -26,6 +26,10 @@ This section lists purely syntactic changes that do not affect the behavior of e
 
 * Libraries have to implement all their functions, not only the internal ones.
 
+* Member-access to ``length`` of arrays is now always read-only, even for storage arrays. It's no
+  longer possible to resize storage arrays assigning a new value to their length. Use ``push()``,
+  ``push(value)`` or ``pop()`` instead, or assign a full array, which will of course overwrite existing content.
+
 * New reserved keywords: ``virtual``.
 
 * The names of variables declared in inline assembly may no longer end in ``_slot`` or ``_offset``.
@@ -75,6 +79,9 @@ This section gives detailed instructions on how to update prior code for every b
 * Change ``uint length = array.push(value)`` to ``array.push(value);``. The new length can be
   accessed via ``array.length``.
 
+* Change ``array.length++`` to ``array.push()`` to increase, and use ``pop()`` to decrease
+  the length of a storage array.
+
 * For every named return parameter in a function's ``@dev`` documentation define a ``@return``
   entry which contains the parameter's name as the first word. E.g. if you have function ``f()`` defined
   like ``function f() public returns (uint value)`` and a ``@dev`` annotating it, document its return
@@ -85,6 +92,7 @@ This section gives detailed instructions on how to update prior code for every b
 
 * Add ``virtual`` to every non-interface function you intend to override.  For single inheritance, add ``override`` to every overriding function. For multiple inheritance, add ``override(A, B, ..)``, where you list all contracts that define the overridden function in the brackets. When multiple bases define the same function, the inheriting contract must override all conflicting functions.
 
+
 New Features
 ============
 

docs/control-structures.rst

@@ -231,7 +231,7 @@ groupings of expressions.
     pragma solidity >0.4.23 <0.7.0;
 
     contract C {
-        uint[] data;
+        uint index;
 
         function f() public pure returns (uint, bool, uint) {
             return (7, true, 2);
@@ -244,7 +244,7 @@ groupings of expressions.
             // Common trick to swap values -- does not work for non-value storage types.
             (x, y) = (y, x);
             // Components can be left out (also for variable declarations).
-            (data.length, , ) = f(); // Sets the length to 7
+            (index, , ) = f(); // Sets the index to 7
         }
     }
 

docs/security-considerations.rst

@@ -278,7 +278,8 @@ a ``mapping``.
         mapping (uint => uint)[] array;
 
         function allocate(uint _newMaps) public {
-            array.length += _newMaps;
+            for (uint i = 0; i < _newMaps; i++)
+                array.push();
         }
 
         function writeMap(uint _map, uint _key, uint _value) public {

docs/types/mapping-types.rst

@@ -137,7 +137,8 @@ the ``sum`` function iterates over to sum all the values.
             if (keyIndex > 0)
                 return true;
             else {
-                keyIndex = self.keys.length++;
+                self.keys.push();
+                keyIndex = self.keys.length;
                 self.data[key].keyIndex = keyIndex + 1;
                 self.keys[keyIndex].key = key;
                 self.size++;

docs/types/reference-types.rst

@@ -59,7 +59,7 @@ Data locations are not only relevant for persistency of data, but also for the s
             x = memoryArray; // works, copies the whole array to storage
             uint[] storage y = x; // works, assigns a pointer, data location of y is storage
             y[7]; // fine, returns the 8th element
-            y.length = 2; // fine, modifies x through y
+            y.pop(); // fine, modifies x through y
             delete x; // fine, clears the array, also modifies y
             // The following does not work; it would need to create a new temporary /
             // unnamed array in storage, but storage is "statically" allocated:
@@ -215,12 +215,6 @@ Array Members
 **length**:
     Arrays have a ``length`` member that contains their number of elements.
     The length of memory arrays is fixed (but dynamic, i.e. it can depend on runtime parameters) once they are created.
-    For dynamically-sized arrays (only available for storage), this member can be assigned to resize the array.
-    Accessing elements outside the current length does not automatically resize the array and instead causes a failing assertion.
-    Increasing the length adds new zero-initialised elements to the array.
-    Reducing the length performs an implicit :ref:`delete<delete>` on each of the
-    removed elements. If you try to resize a non-dynamic array that isn't in
-    storage, you receive a ``Value must be an lvalue`` error.
 **push**:
      Dynamic storage arrays and ``bytes`` (not ``string``) have a member function called ``push`` that you can use to append an element at the end of the array.
      If no argument is given, the element will be zero-initialised and a reference to the new element is returned.
@@ -228,14 +222,11 @@ Array Members
 **pop**:
      Dynamic storage arrays and ``bytes`` (not ``string``) have a member function called ``pop`` that you can use to remove an element from the end of the array. This also implicitly calls :ref:`delete<delete>` on the removed element.
 
-.. warning::
-    If you use ``.length--`` on an empty array, it causes an underflow and
-    thus sets the length to ``2**256-1``.
-
 .. note::
-    Increasing the length of a storage array has constant gas costs because
+    Increasing the length of a storage array by calling ``push()``
-    storage is assumed to be zero-initialised, while decreasing
+    has constant gas costs because storage is zero-initialised,
-    the length has at least linear cost (but in most cases worse than linear),
+    while decreasing the length by calling ``pop()`` has at least
+    linear cost (but in most cases worse than linear),
     because it includes explicitly clearing the removed
     elements similar to calling :ref:`delete<delete>` on them.
 
@@ -295,7 +286,13 @@ Array Members
 
         function changeFlagArraySize(uint newSize) public {
             // if the new size is smaller, removed array elements will be cleared
-            m_pairsOfFlags.length = newSize;
+            if (newSize < m_pairsOfFlags.length) {
+                while (m_pairsOfFlags.length > newSize)
+                    m_pairsOfFlags.pop();
+            } else if (newSize > m_pairsOfFlags.length) {
+                while (m_pairsOfFlags.length < newSize)
+                    m_pairsOfFlags.push();
+            }
         }
 
         function clear() public {
@@ -303,7 +300,7 @@ Array Members
             delete m_pairsOfFlags;
             delete m_aLotOfIntegers;
             // identical effect here
-            m_pairsOfFlags.length = 0;
+            m_pairsOfFlags = new bool[2][](0);
         }
 
         bytes m_byteData;
@@ -312,7 +309,8 @@ Array Members
             // byte arrays ("bytes") are different as they are stored without padding,
             // but can be treated identical to "uint8[]"
             m_byteData = data;
-            m_byteData.length += 7;
+            for (uint i = 0; i < 7; i++)
+                m_byteData.push();
             m_byteData[3] = 0x08;
             delete m_byteData[2];
         }

libsolidity/analysis/TypeChecker.cpp

@@ -2398,14 +2398,7 @@ bool TypeChecker::visit(MemberAccess const& _memberAccess)
 	if (auto const* structType = dynamic_cast<StructType const*>(exprType))
 		annotation.isLValue = !structType->dataStoredIn(DataLocation::CallData);
 	else if (exprType->category() == Type::Category::Array)
-	{
+		annotation.isLValue = false;
-		auto const& arrayType(dynamic_cast<ArrayType const&>(*exprType));
-		annotation.isLValue = (
-			memberName == "length" &&
-			arrayType.location() == DataLocation::Storage &&
-			arrayType.isDynamicallySized()
-		);
-	}
 	else if (exprType->category() == Type::Category::FixedBytes)
 		annotation.isLValue = false;
 	else if (TypeType const* typeType = dynamic_cast<decltype(typeType)>(exprType))
@@ -2862,20 +2855,9 @@ void TypeChecker::requireLValue(Expression const& _expression)
 				if (structType->dataStoredIn(DataLocation::CallData))
 					return "Calldata structs are read-only.";
 			}
-			else if (auto arrayType = dynamic_cast<ArrayType const*>(type(memberAccess->expression())))
+			else if (dynamic_cast<ArrayType const*>(type(memberAccess->expression())))
-				if (
+				if (memberAccess->memberName() == "length")
-					memberAccess->memberName() == "length" ||
+					return "Member \"length\" is read-only and cannot be used to resize arrays.";
-					memberAccess->memberName() == "push"
-				)
-					switch (arrayType->location())
-					{
-						case DataLocation::Memory:
-							return "Memory arrays cannot be resized.";
-						case DataLocation::CallData:
-							return "Calldata arrays cannot be resized.";
-						case DataLocation::Storage:
-							break;
-					}
 		}
 
 		if (auto identifier = dynamic_cast<Identifier const*>(&_expression))

libsolidity/analysis/ViewPureChecker.cpp

@@ -383,7 +383,7 @@ void ViewPureChecker::endVisit(MemberAccess const& _memberAccess)
 	{
 		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;
+			mutability = StateMutability::View;
 		break;
 	}
 	default:

libsolidity/codegen/ExpressionCompiler.cpp

@@ -1565,7 +1565,8 @@ bool ExpressionCompiler::visit(MemberAccess const& _memberAccess)
 					m_context << Instruction::SWAP1 << Instruction::POP;
 					break;
 				case DataLocation::Storage:
-					setLValue<StorageArrayLength>(_memberAccess, type);
+					ArrayUtils(m_context).retrieveLength(type);
+					m_context << Instruction::SWAP1 << Instruction::POP;
 					break;
 				case DataLocation::Memory:
 					m_context << Instruction::MLOAD;

libsolidity/codegen/LValue.cpp

@@ -478,36 +478,6 @@ void StorageByteArrayElement::setToZero(SourceLocation const&, bool _removeRefer
 	m_context << Instruction::SWAP1 << Instruction::SSTORE;
 }
 
-StorageArrayLength::StorageArrayLength(CompilerContext& _compilerContext, ArrayType const& _arrayType):
-	LValue(_compilerContext, _arrayType.memberType("length")),
-	m_arrayType(_arrayType)
-{
-	solAssert(m_arrayType.isDynamicallySized(), "");
-}
-
-void StorageArrayLength::retrieveValue(SourceLocation const&, bool _remove) const
-{
-	ArrayUtils(m_context).retrieveLength(m_arrayType);
-	if (_remove)
-		m_context << Instruction::SWAP1 << Instruction::POP;
-}
-
-void StorageArrayLength::storeValue(Type const&, SourceLocation const&, bool _move) const
-{
-	if (_move)
-		m_context << Instruction::SWAP1;
-	else
-		m_context << Instruction::DUP2;
-	ArrayUtils(m_context).resizeDynamicArray(m_arrayType);
-}
-
-void StorageArrayLength::setToZero(SourceLocation const&, bool _removeReference) const
-{
-	solAssert(_removeReference, "");
-	ArrayUtils(m_context).clearDynamicArray(m_arrayType);
-}
-
-
 TupleObject::TupleObject(
 	CompilerContext& _compilerContext,
 	std::vector<std::unique_ptr<LValue>>&& _lvalues

libsolidity/codegen/LValue.h

@@ -171,31 +171,6 @@ public:
 	) const override;
 };
 
-/**
- * Reference to the "length" member of a dynamically-sized array. This is an LValue with special
- * semantics since assignments to it might reduce its length and thus arrays members have to be
- * deleted.
- */
-class StorageArrayLength: public LValue
-{
-public:
-	/// Constructs the LValue, assumes that the reference to the array head is already on the stack.
-	StorageArrayLength(CompilerContext& _compilerContext, ArrayType const& _arrayType);
-	void retrieveValue(langutil::SourceLocation const& _location, bool _remove = false) const override;
-	virtual void storeValue(
-		Type const& _sourceType,
-		langutil::SourceLocation const& _location = {},
-		bool _move = false
-	) const override;
-	virtual void setToZero(
-		langutil::SourceLocation const& _location = {},
-		bool _removeReference = true
-	) const override;
-
-private:
-	ArrayType const& m_arrayType;
-};
-
 /**
  * Tuple object that can itself hold several LValues.
  */

libsolidity/codegen/YulUtilFunctions.cpp

@@ -593,6 +593,62 @@ std::string YulUtilFunctions::resizeDynamicArrayFunction(ArrayType const& _type)
 	});
 }
 
+string YulUtilFunctions::storageArrayPopFunction(ArrayType const& _type)
+{
+	solAssert(_type.location() == DataLocation::Storage, "");
+	solAssert(_type.isDynamicallySized(), "");
+	solUnimplementedAssert(!_type.isByteArray(), "Byte Arrays not yet implemented!");
+	solUnimplementedAssert(_type.baseType()->storageBytes() <= 32, "Base type is not yet implemented.");
+
+	string functionName = "array_pop_" + _type.identifier();
+	return m_functionCollector->createFunction(functionName, [&]() {
+		return Whiskers(R"(
+			function <functionName>(array) {
+				let oldLen := <fetchLength>(array)
+				if iszero(oldLen) { invalid() }
+				let newLen := sub(oldLen, 1)
+
+				let slot, offset := <indexAccess>(array, newLen)
+				<setToZero>(slot, offset)
+
+				sstore(array, newLen)
+			})")
+			("functionName", functionName)
+			("fetchLength", arrayLengthFunction(_type))
+			("indexAccess", storageArrayIndexAccessFunction(_type))
+			("setToZero", storageSetToZeroFunction(*_type.baseType()))
+			.render();
+	});
+}
+
+string YulUtilFunctions::storageArrayPushFunction(ArrayType const& _type)
+{
+	solAssert(_type.location() == DataLocation::Storage, "");
+	solAssert(_type.isDynamicallySized(), "");
+	solUnimplementedAssert(!_type.isByteArray(), "Byte Arrays not yet implemented!");
+	solUnimplementedAssert(_type.baseType()->storageBytes() <= 32, "Base type is not yet implemented.");
+
+	string functionName = "array_push_" + _type.identifier();
+	return m_functionCollector->createFunction(functionName, [&]() {
+		return Whiskers(R"(
+			function <functionName>(array, value) -> newLen {
+				let oldLen := <fetchLength>(array)
+				if iszero(lt(oldLen, <maxArrayLength>)) { invalid() }
+				newLen := add(oldLen, 1)
+				sstore(array, newLen)
+
+				let slot, offset := <indexAccess>(array, oldLen)
+				<storeValue>(slot, offset, value)
+			})")
+			("functionName", functionName)
+			("fetchLength", arrayLengthFunction(_type))
+			("indexAccess", storageArrayIndexAccessFunction(_type))
+			("storeValue", updateStorageValueFunction(*_type.baseType()))
+			("maxArrayLength", (u256(1) << 64).str())
+			.render();
+	});
+}
+
 string YulUtilFunctions::clearStorageRangeFunction(Type const& _type)
 {
 	string functionName = "clear_storage_range_" + _type.identifier();

libsolidity/codegen/YulUtilFunctions.h

@@ -121,6 +121,14 @@ public:
 	/// signature: (array, newLen)
 	std::string resizeDynamicArrayFunction(ArrayType const& _type);
 
+	/// @returns the name of a function that reduces the size of a storage array by one element
+	/// signature: (array)
+	std::string storageArrayPopFunction(ArrayType const& _type);
+
+	/// @returns the name of a function that pushes an element to a storage array
+	/// signature: (array, value) -> newlength
+	std::string storageArrayPushFunction(ArrayType const& _type);
+
 	/// @returns the name of a function that will clear the storage area given
 	/// by the start and end (exclusive) parameters (slots).
 	/// signature: (start, end)

libsolidity/codegen/ir/IRGeneratorForStatements.cpp

@@ -642,6 +642,34 @@ void IRGeneratorForStatements::endVisit(FunctionCall const& _functionCall)
 
 			break;
 	}
+	case FunctionType::Kind::ArrayPop:
+	{
+		ArrayType const& arrayType = dynamic_cast<ArrayType const&>(
+			*dynamic_cast<MemberAccess const&>(_functionCall.expression()).expression().annotation().type
+		);
+		defineExpression(_functionCall) <<
+			m_utils.storageArrayPopFunction(arrayType) <<
+			"(" <<
+			m_context.variable(_functionCall.expression()) <<
+			")\n";
+		break;
+	}
+	case FunctionType::Kind::ArrayPush:
+	{
+		ArrayType const& arrayType = dynamic_cast<ArrayType const&>(
+			*dynamic_cast<MemberAccess const&>(_functionCall.expression()).expression().annotation().type
+		);
+		defineExpression(_functionCall) <<
+			m_utils.storageArrayPushFunction(arrayType) <<
+			"(" <<
+			m_context.variable(_functionCall.expression()) <<
+			", " << (
+				arguments.empty() ?
+				m_utils.zeroValueFunction(*arrayType.baseType()) + "()" :
+				expressionAsType(*arguments.front(), *arrayType.baseType())
+			) << ")\n";
+		break;
+	}
 	default:
 		solUnimplemented("FunctionKind " + toString(static_cast<int>(functionType->kind())) + " not yet implemented");
 	}
@@ -788,8 +816,8 @@ void IRGeneratorForStatements::endVisit(MemberAccess const& _memberAccess)
 	{
 		auto const& type = dynamic_cast<ArrayType const&>(*_memberAccess.expression().annotation().type);
 
-		solAssert(member == "length", "");
+		if (member == "length")
-
+		{
 			if (!type.isDynamicallySized())
 				defineExpression(_memberAccess) << type.length() << "\n";
 			else
@@ -800,14 +828,12 @@ void IRGeneratorForStatements::endVisit(MemberAccess const& _memberAccess)
 						//m_context << Instruction::SWAP1 << Instruction::POP;
 						break;
 					case DataLocation::Storage:
-				setLValue(_memberAccess, make_unique<IRStorageArrayLength>(
+					{
-					m_context.utils(),
+						string slot = m_context.variable(_memberAccess.expression());
-					m_context.variable(_memberAccess.expression()),
+						defineExpression(_memberAccess) <<
-					*_memberAccess.annotation().type,
+							m_utils.arrayLengthFunction(type) + "(" + slot + ")\n";
-					type
-				));
-
 						break;
+					}
 					case DataLocation::Memory:
 						defineExpression(_memberAccess) <<
 							"mload(" <<
@@ -815,6 +841,20 @@ void IRGeneratorForStatements::endVisit(MemberAccess const& _memberAccess)
 							")\n";
 						break;
 				}
+		}
+		else if (member == "pop")
+		{
+			solAssert(type.location() == DataLocation::Storage, "");
+			defineExpression(_memberAccess) << m_context.variable(_memberAccess.expression()) << "\n";
+		}
+		else if (member == "push")
+		{
+			solAssert(type.location() == DataLocation::Storage, "");
+			defineExpression(_memberAccess) << m_context.variable(_memberAccess.expression()) << "\n";
+		}
+		else
+			solAssert(false, "Invalid array member access.");
+
 		break;
 	}
 	case Type::Category::FixedBytes:

libsolidity/codegen/ir/IRLValue.cpp

@@ -148,39 +148,6 @@ string IRStorageItem::setToZero() const
 		")\n";
 }
 
-IRStorageArrayLength::IRStorageArrayLength(
-	YulUtilFunctions _utils,
-	string _slot,
-	Type const& _type,
-	ArrayType const& _arrayType
-):
-	IRLValue(std::move(_utils), &_type), m_arrayType(_arrayType), m_slot(move(_slot))
-{
-	solAssert(*m_type == *TypeProvider::uint256(), "Must be uint256!");
-}
-
-string IRStorageArrayLength::retrieveValue() const
-{
-	return m_utils.arrayLengthFunction(m_arrayType) + "(" + m_slot + ")";
-}
-
-string IRStorageArrayLength::storeValue(std::string const& _value, Type const& _type) const
-{
-	solAssert(_type == *m_type, "Different type, but might not be an error.");
-
-	return m_utils.resizeDynamicArrayFunction(m_arrayType) +
-		"(" +
-		m_slot +
-		", " +
-		_value +
-		")\n";
-}
-
-string IRStorageArrayLength::setToZero() const
-{
-	return storeValue("0", *TypeProvider::uint256());
-}
-
 IRMemoryItem::IRMemoryItem(
 	YulUtilFunctions _utils,
 	std::string _address,

libsolidity/codegen/ir/IRLValue.h

@@ -110,30 +110,6 @@ private:
 	boost::variant<std::string, unsigned> const m_offset;
 };
 
-/**
- * Reference to the "length" member of a dynamically-sized storage array. This is an LValue with special
- * semantics since assignments to it might reduce its length and thus the array's members have to be
- * deleted.
- */
-class IRStorageArrayLength: public IRLValue
-{
-public:
-	IRStorageArrayLength(
-		YulUtilFunctions _utils,
-		std::string _slot,
-		Type const& _type,
-		ArrayType const& _arrayType
-	);
-
-	std::string retrieveValue() const override;
-	std::string storeValue(std::string const& _value, Type const& _type) const override;
-	std::string setToZero() const override;
-
-private:
-	ArrayType const& m_arrayType;
-	std::string const m_slot;
-};
-
 class IRMemoryItem: public IRLValue
 {
 public:

test/compilationTests/MultiSigWallet/MultiSigWallet.sol

@@ -143,7 +143,7 @@ contract MultiSigWallet {
                 owners[i] = owners[owners.length - 1];
                 break;
             }
-        owners.length -= 1;
+        owners.pop();
         if (required > owners.length)
             changeRequirement(owners.length);
         emit OwnerRemoval(owner);

test/compilationTests/corion/moduleHandler.sol

@@ -77,7 +77,7 @@ contract moduleHandler is multiOwner, announcementTypes {
         require( success );
         if ( ! found ) {
             id = modules.length;
-            modules.length++;
+            modules.push();
         }
         modules[id] = input;
     }

test/compilationTests/corion/schelling.sol

@@ -46,7 +46,8 @@ contract schellingDB is safeMath, schellingVars {
         Constructor
     */
     constructor() public {
-        rounds.length = 2;
+        rounds.push();
+        rounds.push();
         rounds[0].blockHeight = block.number;
         currentSchellingRound = 1;
     }

test/compilationTests/milestonetracker/MilestoneTracker.sol

@@ -227,7 +227,7 @@ contract MilestoneTracker {
 
             RLP.RLPItem memory itmProposal = itrProposals.next();
 
-            Milestone storage milestone = milestones[milestones.length ++];
+            Milestone storage milestone = milestones.push();
 
             if (!itmProposal.isList()) revert();
 

test/contracts/Wallet.cpp

@@ -208,8 +208,8 @@ contract multiowned {
 			pending.yetNeeded = m_required;
 			// reset which owners have confirmed (none) - set our bitmap to 0.
 			pending.ownersDone = 0;
-			pending.index = m_pendingIndex.length++;
+			m_pendingIndex.push(_operation);
-			m_pendingIndex[pending.index] = _operation;
+			pending.index = m_pendingIndex.length - 1;
 		}
 		// determine the bit to set for this owner.
 		uint ownerIndexBit = 2**ownerIndex;

test/libsolidity/ABIDecoderTests.cpp

@@ -637,7 +637,7 @@ BOOST_AUTO_TEST_CASE(storage_ptr)
 			L.S s;
 			uint[] r;
 			function f() public returns (uint, uint, uint, uint, uint, uint) {
-				r.length = 6;
+				r = new uint[](6);
 				r[0] = 1;
 				r[1] = 2;
 				r[2] = 3;

test/libsolidity/ABIEncoderTests.cpp

@@ -429,7 +429,9 @@ BOOST_AUTO_TEST_CASE(structs)
 				s.a = 8;
 				s.b = 9;
 				s.c = 10;
-				s.sub.length = 3;
+				s.sub.push();
+				s.sub.push();
+				s.sub.push();
 				s.sub[0].x[0] = 11;
 				s.sub[1].x[0] = 12;
 				s.sub[2].x[1] = 13;
@@ -522,11 +524,10 @@ BOOST_AUTO_TEST_CASE(bool_arrays)
 			bool[4] y;
 			event E(bool[], bool[4]);
 			function f() public returns (bool[] memory, bool[4] memory) {
-				x.length = 4;
+				x.push(true);
-				x[0] = true;
+				x.push(false);
-				x[1] = false;
+				x.push(true);
-				x[2] = true;
+				x.push(false);
-				x[3] = false;
 				y[0] = true;
 				y[1] = false;
 				y[2] = true;
@@ -556,11 +557,10 @@ BOOST_AUTO_TEST_CASE(bool_arrays_split)
 			bool[4] y;
 			event E(bool[], bool[4]);
 			function store() public {
-				x.length = 4;
+				x.push(true);
-				x[0] = true;
+				x.push(false);
-				x[1] = false;
+				x.push(true);
-				x[2] = true;
+				x.push(false);
-				x[3] = false;
 				y[0] = true;
 				y[1] = false;
 				y[2] = true;
@@ -594,9 +594,8 @@ BOOST_AUTO_TEST_CASE(bytesNN_arrays)
 			bytesWIDTH[SIZE] y;
 			event E(bytes8[], bytesWIDTH[SIZE]);
 			function store() public {
-				x.length = 2;
+				x.push("abc");
-				x[0] = "abc";
+				x.push("def");
-				x[1] = "def";
 				for (uint i = 0; i < y.length; i ++)
 					y[i] = bytesWIDTH(uintUINTWIDTH(i + 1));
 			}
@@ -640,9 +639,8 @@ BOOST_AUTO_TEST_CASE(bytesNN_arrays_dyn)
 			bytesWIDTH[] y;
 			event E(bytesWIDTH[], bytes8[]);
 			function store() public {
-				x.length = 2;
+				x.push("abc");
-				x[0] = "abc";
+				x.push("def");
-				x[1] = "def";
 				for (uint i = 0; i < SIZE; i ++)
 					y.push(bytesWIDTH(uintUINTWIDTH(i + 1)));
 			}

test/libsolidity/GasMeter.cpp

@@ -133,9 +133,8 @@ BOOST_AUTO_TEST_CASE(non_overlapping_filtered_costs)
 		contract test {
 			bytes x;
 			function f(uint a) public returns (uint b) {
-				x.length = a;
 				for (; a < 200; ++a) {
-					x[a] = 0x09;
+					x.push(0x09);
 					b = a * a;
 				}
 				return f(a - 1);

test/libsolidity/SolidityEndToEndTest.cpp

@@ -1030,26 +1030,6 @@ BOOST_AUTO_TEST_CASE(multi_level_mapping)
 	)
 }
 
-BOOST_AUTO_TEST_CASE(deleteLength)
-{
-	char const* sourceCode = R"(
-		contract test {
-			uint[] x;
-			function f() public returns (uint){
-				x.length = 1;
-				x[0] = 1;
-				delete x.length;
-				return x.length;
-			}
-		}
-	)";
-	ALSO_VIA_YUL(
-		compileAndRun(sourceCode);
-		ABI_CHECK(callContractFunction("f()"), encodeArgs(0));
-		BOOST_CHECK(storageEmpty(m_contractAddress));
-	)
-}
-
 BOOST_AUTO_TEST_CASE(constructor)
 {
 	char const* sourceCode = R"(
@@ -2849,10 +2829,9 @@ BOOST_AUTO_TEST_CASE(event_really_lots_of_data_from_storage)
 			bytes x;
 			event Deposit(uint fixeda, bytes dynx, uint fixedb);
 			function deposit() public {
-				x.length = 3;
+				x.push("A");
-				x[0] = "A";
+				x.push("B");
-				x[1] = "B";
+				x.push("C");
-				x[2] = "C";
 				emit Deposit(10, x, 15);
 			}
 		}
@@ -2873,7 +2852,7 @@ BOOST_AUTO_TEST_CASE(event_really_really_lots_of_data_from_storage)
 			bytes x;
 			event Deposit(uint fixeda, bytes dynx, uint fixedb);
 			function deposit() public {
-				x.length = 31;
+				x = new bytes(31);
 				x[0] = "A";
 				x[1] = "B";
 				x[2] = "C";
@@ -3021,7 +3000,8 @@ BOOST_AUTO_TEST_CASE(event_dynamic_array_storage)
 			event E(uint[]);
 			uint[] arr;
 			function createEvent(uint x) public {
-				arr.length = 3;
+				while (arr.length < 3)
+					arr.push();
 				arr[0] = x;
 				arr[1] = x + 1;
 				arr[2] = x + 2;
@@ -3049,7 +3029,8 @@ BOOST_AUTO_TEST_CASE(event_dynamic_array_storage_v2)
 			event E(uint[]);
 			uint[] arr;
 			function createEvent(uint x) public {
-				arr.length = 3;
+				while (arr.length < 3)
+					arr.push();
 				arr[0] = x;
 				arr[1] = x + 1;
 				arr[2] = x + 2;
@@ -3077,9 +3058,8 @@ BOOST_AUTO_TEST_CASE(event_dynamic_nested_array_storage_v2)
 			event E(uint[][]);
 			uint[][] arr;
 			function createEvent(uint x) public {
-				arr.length = 2;
+				arr.push(new uint[](2));
-				arr[0].length = 2;
+				arr.push(new uint[](2));
-				arr[1].length = 2;
 				arr[0][0] = x;
 				arr[0][1] = x + 1;
 				arr[1][0] = x + 2;
@@ -3088,7 +3068,8 @@ BOOST_AUTO_TEST_CASE(event_dynamic_nested_array_storage_v2)
 			}
 		}
 	)";
-	ALSO_VIA_YUL(
+	/// TODO enable again after push(..) via yul was implemented.
+	/// ALSO_VIA_YUL()
 	compileAndRun(sourceCode);
 	u256 x(42);
 	callContractFunction("createEvent(uint256)", x);
@@ -3097,7 +3078,6 @@ BOOST_AUTO_TEST_CASE(event_dynamic_nested_array_storage_v2)
 	BOOST_CHECK(logData(0) == encodeArgs(0x20, 2, 0x40, 0xa0, 2, x, x + 1, 2, x + 2, x + 3));
 	BOOST_REQUIRE_EQUAL(numLogTopics(0), 1);
 	BOOST_CHECK_EQUAL(logTopic(0, 0), dev::keccak256(string("E(uint256[][])")));
-	);
 }
 
 BOOST_AUTO_TEST_CASE(event_indexed_string)
@@ -3108,7 +3088,8 @@ BOOST_AUTO_TEST_CASE(event_indexed_string)
 			uint[4] y;
 			event E(string indexed r, uint[4] indexed t);
 			function deposit() public {
-				bytes(x).length = 90;
+				for (uint i = 0; i < 90; i++)
+					bytes(x).push(0);
 				for (uint8 i = 0; i < 90; i++)
 					bytes(x)[i] = byte(i);
 				y[0] = 4;
@@ -3286,10 +3267,9 @@ BOOST_AUTO_TEST_CASE(keccak256_with_bytes)
 			bytes data;
 			function foo() public returns (bool)
 			{
-				data.length = 3;
+				data.push("f");
-				data[0] = "f";
+				data.push("o");
-				data[1] = "o";
+				data.push("o");
-				data[2] = "o";
 				return keccak256(data) == keccak256("foo");
 			}
 		}
@@ -3305,10 +3285,9 @@ BOOST_AUTO_TEST_CASE(iterated_keccak256_with_bytes)
 			bytes data;
 			function foo() public returns (bytes32)
 			{
-				data.length = 3;
+				data.push("x");
-				data[0] = "x";
+				data.push("y");
-				data[1] = "y";
+				data.push("z");
-				data[2] = "z";
 				return keccak256(abi.encodePacked("b", keccak256(data), "a"));
 			}
 		}
@@ -4257,7 +4236,12 @@ BOOST_AUTO_TEST_CASE(dynamic_arrays_in_storage)
 			function getID(uint index) public returns (uint) { return ids[index]; }
 			function getData(uint index) public returns (uint x, uint y) { x = data[index].x; y = data[index].y; }
 			function getLengths() public returns (uint l1, uint l2) { l1 = data.length; l2 = ids.length; }
-			function setLengths(uint l1, uint l2) public { data.length = l1; ids.length = l2; }
+			function setLengths(uint l1, uint l2) public {
+				while (data.length < l1)
+					data.push();
+				while (ids.length < l2)
+					ids.push();
+			}
 		}
 	)";
 	compileAndRun(sourceCode);
@@ -4302,13 +4286,18 @@ BOOST_AUTO_TEST_CASE(dynamic_out_of_bounds_array_access)
 	char const* sourceCode = R"(
 		contract c {
 			uint[] data;
-			function enlarge(uint amount) public returns (uint) { return data.length += amount; }
+			function enlarge(uint amount) public returns (uint) {
+				while (data.length - amount > 0)
+					data.push();
+				return data.length;
+			}
 			function set(uint index, uint value) public returns (bool) { data[index] = value; return true; }
 			function get(uint index) public returns (uint) { return data[index]; }
 			function length() public returns (uint) { return data.length; }
 		}
 	)";
-	ALSO_VIA_YUL(
+	/// TODO enable again after push(..) via yul was implemented.
+	/// ALSO_VIA_YUL()
 	compileAndRun(sourceCode);
 	ABI_CHECK(callContractFunction("length()"), encodeArgs(0));
 	ABI_CHECK(callContractFunction("get(uint256)", 3), bytes());
@@ -4319,7 +4308,6 @@ BOOST_AUTO_TEST_CASE(dynamic_out_of_bounds_array_access)
 	ABI_CHECK(callContractFunction("length()"), encodeArgs(4));
 	ABI_CHECK(callContractFunction("set(uint256,uint256)", 4, 8), bytes());
 	ABI_CHECK(callContractFunction("length()"), encodeArgs(4));
-	)
 }
 
 BOOST_AUTO_TEST_CASE(fixed_array_cleanup)
@@ -4375,14 +4363,18 @@ BOOST_AUTO_TEST_CASE(dynamic_array_cleanup)
 			uint[20] spacer;
 			uint[] dynamic;
 			function fill() public {
-				dynamic.length = 21;
+				for (uint i = 0; i < 21; ++i)
-				for (uint i = 0; i < dynamic.length; ++i) dynamic[i] = i+1;
+					dynamic.push(i + 1);
+			}
+			function halfClear() public {
+				while (dynamic.length > 5)
+					dynamic.pop();
 			}
-			function halfClear() public { dynamic.length = 5; }
 			function fullClear() public { delete dynamic; }
 		}
 	)";
-	ALSO_VIA_YUL(
+	/// TODO enable again after push(..) via yul was implemented.
+	/// ALSO_VIA_YUL()
 	compileAndRun(sourceCode);
 	BOOST_CHECK(storageEmpty(m_contractAddress));
 	ABI_CHECK(callContractFunction("fill()"), bytes());
@@ -4391,7 +4383,6 @@ BOOST_AUTO_TEST_CASE(dynamic_array_cleanup)
 	BOOST_CHECK(!storageEmpty(m_contractAddress));
 	ABI_CHECK(callContractFunction("fullClear()"), bytes());
 	BOOST_CHECK(storageEmpty(m_contractAddress));
-	);
 }
 
 BOOST_AUTO_TEST_CASE(dynamic_multi_array_cleanup)
@@ -4401,9 +4392,12 @@ BOOST_AUTO_TEST_CASE(dynamic_multi_array_cleanup)
 			struct s { uint[][] d; }
 			s[] data;
 			function fill() public returns (uint) {
-				data.length = 3;
+				while (data.length < 3)
-				data[2].d.length = 4;
+					data.push();
-				data[2].d[3].length = 5;
+				while (data[2].d.length < 4)
+					data[2].d.push();
+				while (data[2].d[3].length < 5)
+					data[2].d[3].push();
 				data[2].d[3][4] = 8;
 				return data[2].d[3][4];
 			}
@@ -4425,7 +4419,9 @@ BOOST_AUTO_TEST_CASE(array_copy_storage_storage_dyn_dyn)
 			uint[] data1;
 			uint[] data2;
 			function setData1(uint length, uint index, uint value) public {
-				data1.length = length; if (index < length) data1[index] = value;
+				data1 = new uint[](length);
+				if (index < length)
+					data1[index] = value;
 			}
 			function copyStorageStorage() public { data2 = data1; }
 			function getData2(uint index) public returns (uint len, uint val) {
@@ -4489,7 +4485,7 @@ BOOST_AUTO_TEST_CASE(array_copy_different_packing)
 			bytes8[] data1; // 4 per slot
 			bytes10[] data2; // 3 per slot
 			function test() public returns (bytes10 a, bytes10 b, bytes10 c, bytes10 d, bytes10 e) {
-				data1.length = 9;
+				data1 = new bytes8[](9);
 				for (uint i = 0; i < data1.length; ++i)
 					data1[i] = bytes8(uint64(i));
 				data2 = data1;
@@ -4608,13 +4604,15 @@ BOOST_AUTO_TEST_CASE(array_copy_storage_storage_struct)
 			Data[] data1;
 			Data[] data2;
 			function test() public returns (uint x, uint y) {
-				data1.length = 9;
+				while (data1.length < 9)
+					data1.push();
 				data1[8].x = 4;
 				data1[8].y = 5;
 				data2 = data1;
 				x = data2[8].x;
 				y = data2[8].y;
-				data1.length = 0;
+				while (data1.length > 0)
+					data1.pop();
 				data2 = data1;
 			}
 		}
@@ -4651,7 +4649,7 @@ BOOST_AUTO_TEST_CASE(array_copy_storage_abi)
 				return z;
 			}
 			function test4() public returns (uint24[][] memory) {
-				w.length = 5;
+				w = new uint24[][](5);
 				for (uint i = 0; i < 5; ++i)
 					for (uint j = 0; j < 101; ++j)
 						w[i].push(uint24(j));
@@ -4763,7 +4761,7 @@ BOOST_AUTO_TEST_CASE(array_push_packed_array)
 				x.push(3);
 				x.push(4);
 				x.push(5);
-				x.length = 4;
+				x.pop();
 				return (x[0], x[1], x[2], x[3]);
 			}
 		}
@@ -5177,7 +5175,7 @@ BOOST_AUTO_TEST_CASE(bytes_index_access)
 				return uint(uint8(data[index]));
 			}
 			function storageWrite() external returns (uint) {
-				data.length = 35;
+				data = new bytes(35);
 				data[31] = 0x77;
 				data[32] = 0x14;
 
@@ -5206,7 +5204,7 @@ BOOST_AUTO_TEST_CASE(bytes_delete_element)
 		contract c {
 			bytes data;
 			function test1() external returns (bool) {
-				data.length = 100;
+				data = new bytes(100);
 				for (uint i = 0; i < data.length; i++)
 					data[i] = byte(uint8(i));
 				delete data[94];
@@ -5290,7 +5288,10 @@ BOOST_AUTO_TEST_CASE(array_copy_including_mapping)
 			mapping(uint=>uint)[90][] large;
 			mapping(uint=>uint)[3][] small;
 			function test() public returns (uint r) {
-				large.length = small.length = 7;
+				for (uint i = 0; i < 7; i++) {
+					large.push();
+					small.push();
+				}
 				large[3][2][0] = 2;
 				large[1] = large[3];
 				small[3][2][0] = 2;
@@ -5302,13 +5303,20 @@ BOOST_AUTO_TEST_CASE(array_copy_including_mapping)
 					large[1][2][0];
 				delete small;
 				delete large;
+
+			}
+			function clear() public returns (uint, uint) {
+				for (uint i = 0; i < 7; i++) {
+					large.push();
+					small.push();
 				}
-			function clear() public returns (uint r) {
-				large.length = small.length = 7;
 				small[3][2][0] = 0;
 				large[3][2][0] = 0;
-				small.length = large.length = 0;
+				while (small.length > 0)
-				return 7;
+					small.pop();
+				while (large.length > 0)
+					large.pop();
+				return (small.length, large.length);
 			}
 		}
 	)";
@@ -5316,7 +5324,7 @@ BOOST_AUTO_TEST_CASE(array_copy_including_mapping)
 	ABI_CHECK(callContractFunction("test()"), encodeArgs(0x02000200));
 	// storage is not empty because we cannot delete the mappings
 	BOOST_CHECK(!storageEmpty(m_contractAddress));
-	ABI_CHECK(callContractFunction("clear()"), encodeArgs(7));
+	ABI_CHECK(callContractFunction("clear()"), encodeArgs(0, 0));
 	BOOST_CHECK(storageEmpty(m_contractAddress));
 }
 
@@ -6312,7 +6320,8 @@ BOOST_AUTO_TEST_CASE(accessor_involving_strings)
 			struct stringData { string a; uint b; string c; }
 			mapping(uint => stringData[]) public data;
 			function set(uint x, uint y, string calldata a, uint b, string calldata c) external returns (bool) {
-				data[x].length = y + 1;
+				while (data[x].length < y + 1)
+					data[x].push();
 				data[x][y].a = a;
 				data[x][y].b = b;
 				data[x][y].c = c;
@@ -6682,7 +6691,7 @@ BOOST_AUTO_TEST_CASE(storage_array_ref)
 		contract Store is BinarySearch {
 			uint[] data;
 			function add(uint v) public {
-				data.length++;
+				data.push(0);
 				data[data.length - 1] = v;
 			}
 			function find(uint v) public returns (uint) {
@@ -6690,7 +6699,8 @@ BOOST_AUTO_TEST_CASE(storage_array_ref)
 			}
 		}
 	)";
-	ALSO_VIA_YUL(
+	/// TODO enable again after push(..) via yul was implemented.
+	/// ALSO_VIA_YUL()
 	compileAndRun(sourceCode, 0, "Store");
 	BOOST_REQUIRE(callContractFunction("find(uint256)", u256(7)) == encodeArgs(u256(-1)));
 	BOOST_REQUIRE(callContractFunction("add(uint256)", u256(7)) == encodeArgs());
@@ -6708,7 +6718,6 @@ BOOST_AUTO_TEST_CASE(storage_array_ref)
 	ABI_CHECK(callContractFunction("find(uint256)", u256(176)), encodeArgs(u256(-1)));
 	ABI_CHECK(callContractFunction("find(uint256)", u256(0)), encodeArgs(u256(-1)));
 	ABI_CHECK(callContractFunction("find(uint256)", u256(400)), encodeArgs(u256(-1)));
-	);
 }
 
 BOOST_AUTO_TEST_CASE(memory_types_initialisation)
@@ -6796,7 +6805,8 @@ BOOST_AUTO_TEST_CASE(memory_arrays_dynamic_index_access_write)
 				return x;
 			}
 			function f() public returns (uint24[3][] memory) {
-				data[1].length = 4;
+				while (data[1].length < 4)
+					data[1].push();
 				return set(data)[1];
 			}
 		}
@@ -8291,7 +8301,8 @@ BOOST_AUTO_TEST_CASE(internal_types_in_library)
 			mapping(string => uint16[]) data;
 			function f() public returns (uint a, uint b)
 			{
-				data["abc"].length = 20;
+				while (data["abc"].length < 20)
+					data["abc"].push();
 				data["abc"][4] = 9;
 				data["abc"][17] = 3;
 				a = Lib.find(data["abc"], 9);
@@ -8556,7 +8567,8 @@ BOOST_AUTO_TEST_CASE(using_library_structs)
 			function set(Data storage _s) public
 			{
 				_s.a = 7;
-				_s.b.length = 20;
+				while (_s.b.length < 20)
+					_s.b.push();
 				_s.b[19] = 8;
 			}
 		}
@@ -8635,15 +8647,18 @@ BOOST_AUTO_TEST_CASE(short_strings)
 				if (data2.length != 51) return 4;
 				if (data2[data2.length - 1] != "a") return 5;
 				// change length: short -> short
-				data1.length = 5;
+				while (data1.length < 5)
+					data1.push();
 				if (data1.length != 5) return 6;
 				data1[4] = "4";
 				if (data1[0] != "1") return 7;
 				if (data1[4] != "4") return 8;
 				// change length: short -> long
-				data1.length = 80;
+				while (data1.length < 80)
+					data1.push();
 				if (data1.length != 80) return 9;
-				data1.length = 70;
+				while (data1.length > 70)
+					data1.pop();
 				if (data1.length != 70) return 9;
 				if (data1[0] != "1") return 10;
 				if (data1[4] != "4") return 11;
@@ -8652,20 +8667,25 @@ BOOST_AUTO_TEST_CASE(short_strings)
 				if (uint8(data1[4]) != 4 * 3) return 12;
 				if (uint8(data1[67]) != 67 * 3) return 13;
 				// change length: long -> short
-				data1.length = 22;
+				while (data1.length > 22)
+					data1.pop();
 				if (data1.length != 22) return 14;
 				if (uint8(data1[21]) != 21 * 3) return 15;
 				if (uint8(data1[2]) != 2 * 3) return 16;
 				// change length: short -> shorter
-				data1.length = 19;
+				while (data1.length > 19)
+					data1.pop();
 				if (data1.length != 19) return 17;
 				if (uint8(data1[7]) != 7 * 3) return 18;
 				// and now again to original size
-				data1.length = 22;
+				while (data1.length < 22)
+					data1.push();
 				if (data1.length != 22) return 19;
 				if (data1[21] != 0) return 20;
-				data1.length = 0;
+				while (data1.length > 0)
-				data2.length = 0;
+					data1.pop();
+				while (data2.length > 0)
+					data2.pop();
 			}
 			function copy() public returns (uint) {
 				bytes memory x = "123";
@@ -8864,8 +8884,7 @@ BOOST_AUTO_TEST_CASE(tuples)
 				return (5, 6);
 			}
 			function f() public returns (uint) {
-				data.length = 1;
+				data.push(3);
-				data[0] = 3;
 				uint a; uint b;
 				(a, b) = this.h();
 				if (a != 5 || b != 6) return 1;
@@ -8941,7 +8960,7 @@ BOOST_AUTO_TEST_CASE(destructuring_assignment)
 			uint[] y;
 			uint[] arrayData;
 			function returnsArray() public returns (uint[] memory) {
-				arrayData.length = 9;
+				arrayData = new uint[](9);
 				arrayData[2] = 5;
 				arrayData[7] = 4;
 				return arrayData;
@@ -9915,9 +9934,10 @@ BOOST_AUTO_TEST_CASE(delete_on_array_of_structs)
 			struct S { uint x; uint[] y; }
 			S[] data;
 			function f() public returns (bool) {
-				data.length = 2;
+				S storage s1 = data.push();
-				data[0].x = 2**200;
+				s1.x = 2**200;
-				data[1].x = 2**200;
+				S storage s2 = data.push();
+				s2.x = 2**200;
 				delete data;
 				return true;
 			}
@@ -11099,7 +11119,7 @@ BOOST_AUTO_TEST_CASE(copy_function_storage_array)
 			function() internal returns (uint)[] x;
 			function() internal returns (uint)[] y;
 			function test() public returns (uint) {
-				x.length = 10;
+				x = new function() internal returns (uint)[](10);
 				x[9] = a;
 				y = x;
 				return y[9]();
@@ -12009,7 +12029,8 @@ BOOST_AUTO_TEST_CASE(recursive_structs)
 				S memory s;
 				s.x = new S[](10);
 				delete s;
-				sstorage.x.length++;
+				// TODO Uncomment after implemented.
+				// sstorage.x.push();
 				delete sstorage;
 				return 1;
 			}
@@ -13292,11 +13313,15 @@ BOOST_AUTO_TEST_CASE(abi_encodePacked_from_storage)
 				return abi.encodePacked(uint8(0x01), small_fixed, uint8(0x02));
 			}
 			function sd() public returns (bytes memory) {
-				small_dyn.length = 9;
+				small_dyn.push(0xfffff1);
-				small_dyn[0] = 0xfffff1;
+				small_dyn.push(0x00);
-				small_dyn[2] = 0xfffff2;
+				small_dyn.push(0xfffff2);
-				small_dyn[5] = 0xfffff3;
+				small_dyn.push(0x00);
-				small_dyn[8] = 0xfffff4;
+				small_dyn.push(0x00);
+				small_dyn.push(0xfffff3);
+				small_dyn.push(0x00);
+				small_dyn.push(0x00);
+				small_dyn.push(0xfffff4);
 				return abi.encodePacked(uint8(0x01), small_dyn, uint8(0x02));
 			}
 			function sfs() public returns (bytes memory) {
@@ -13314,11 +13339,11 @@ BOOST_AUTO_TEST_CASE(abi_encodePacked_from_storage)
 				return abi.encodePacked(uint8(0x01), large_fixed, uint8(0x02));
 			}
 			function ld() public returns (bytes memory) {
-				large_dyn.length = 5;
+				large_dyn.push(2**248-1);
-				large_dyn[0] = 2**248-1;
+				large_dyn.push(0xfffff2);
-				large_dyn[1] = 0xfffff2;
+				large_dyn.push(2**248-2);
-				large_dyn[2] = 2**248-2;
+				large_dyn.push(0);
-				large_dyn[4] = 0xfffff4;
+				large_dyn.push(0xfffff4);
 				return abi.encodePacked(uint8(0x01), large_dyn, uint8(0x02));
 			}
 			function bytes_short() public returns (bytes memory) {
@@ -13476,9 +13501,8 @@ BOOST_AUTO_TEST_CASE(abi_encodePackedV2_structs)
 				s.b = -7;
 				s.c[0] = 2;
 				s.c[1] = 3;
-				s.d.length = 2;
+				s.d.push(-7);
-				s.d[0] = -7;
+				s.d.push(-8);
-				s.d[1] = -8;
 			}
 			function testStorage() public {
 				emit E(s);
@@ -13538,9 +13562,8 @@ BOOST_AUTO_TEST_CASE(abi_encodePackedV2_arrayOfStrings)
 			string[] x;
 			event E(string[] indexed);
 			constructor() public {
-				x.length = 2;
+				x.push("abc");
-				x[0] = "abc";
+				x.push("0123456789012345678901234567890123456789");
-				x[1] = "0123456789012345678901234567890123456789";
 			}
 			function testStorage() public {
 				emit E(x);

test/libsolidity/SolidityOptimizer.cpp

@@ -206,7 +206,8 @@ BOOST_AUTO_TEST_CASE(array_copy)
 			bytes2[] data1;
 			bytes5[] data2;
 			function f(uint x) public returns (uint l, uint y) {
-				data1.length = msg.data.length;
+				for (uint i = 0; i < msg.data.length; i++)
+					data1.push();
 				for (uint i = 0; i < msg.data.length; ++i)
 					data1[i] = msg.data[i];
 				data2 = data1;
@@ -533,16 +534,15 @@ BOOST_AUTO_TEST_CASE(inconsistency)
 			}
 
 			function trigger() public returns (uint) {
-				containers.length++;
+				Container storage container = containers.push();
-				Container storage container = containers[0];
 
 				container.values.push(Value({
 					badnum: 9000,
 					number: 0
 				}));
 
-				container.valueIndices.length++;
+				container.valueIndices.push();
-				valueIndices.length++;
+				valueIndices.push();
 
 				levelII();
 				return debug;

test/libsolidity/semanticTests/storage/accessors_mapping_for_array.sol

@@ -3,7 +3,8 @@ contract test {
     mapping(uint => uint[]) public dynamicData;
     constructor() public {
         data[2][2] = 8;
-        dynamicData[2].length = 3;
+        for (uint i = 0; i < 3; i++)
+            dynamicData[2].push();
         dynamicData[2][2] = 8;
     }
 }

test/libsolidity/semanticTests/storage/array_accessor.sol

@@ -7,13 +7,18 @@ contract test {
 
     constructor() public {
         data[0] = 8;
-        dynamicData.length = 3;
+
-        dynamicData[2] = 8;
+        dynamicData.push();
-        smallTypeData.length = 128;
+        dynamicData.push();
+        dynamicData.push(8);
+
+        smallTypeData = new uint24[](128);
         smallTypeData[1] = 22;
         smallTypeData[127] = 2;
+
         multiple_map[2][1][2].a = 3;
-        multiple_map[2][1][2].finalArray.length = 4;
+        for (uint i = 0; i < 4; i++)
+            multiple_map[2][1][2].finalArray.push();
         multiple_map[2][1][2].finalArray[3] = 5;
     }
 }

test/libsolidity/semanticTests/storage/mappings_array2d_pop_delete.sol

@@ -2,16 +2,16 @@ contract C {
 	mapping (uint => uint)[][] a;
 
 	function n1(uint key, uint value) public {
-		a.length++;
+		a.push();
 		mapping (uint => uint)[] storage b = a[a.length - 1];
-		b.length++;
+		b.push();
 		b[b.length - 1][key] = value;
 	}
 
 	function n2() public {
-		a.length++;
+		a.push();
 		mapping (uint => uint)[] storage b = a[a.length - 1];
-		b.length++;
+		b.push();
 	}
 
 	function map(uint key) public view returns (uint) {

test/libsolidity/semanticTests/storage/mappings_array_pop_delete.sol

@@ -2,12 +2,12 @@ contract C {
 	mapping (uint => uint)[] a;
 
 	function n1(uint key, uint value) public {
-		a.length++;
+		a.push();
 		a[a.length - 1][key] = value;
 	}
 
 	function n2() public {
-		a.length++;
+		a.push();
 	}
 
 	function map(uint key) public view returns (uint) {

test/libsolidity/semanticTests/structs/conversion/assignment_ignore_mapping.sol

@@ -20,8 +20,10 @@ contract Test {
         storageA.m[1] = 2;
         storageB.m[3] = 4;
         storageB.x = 5;
-        storageC.ma.length = 6;
+        for (uint i = 0; i < 6; i++)
-        storageD.a.length = 7;
+            storageC.ma.push();
+        for (uint i = 0; i < 7; i++)
+            storageD.a.push();
     }
     function run() public returns (uint, uint, uint, uint, uint, uint) {
         A memory memoryA = A();

test/libsolidity/semanticTests/structs/conversion/recursive_storage_memory.sol

@@ -2,12 +2,17 @@ contract CopyTest {
     struct Tree {
         Tree[] children;
     }
+
     Tree storageTree;
+    Tree[] children;
 
     constructor() public {
-		storageTree.children.length = 2;
+        for (uint i = 0; i < 2; i++)
-		storageTree.children[0].children.length = 23;
+            storageTree.children.push();
-		storageTree.children[1].children.length = 42;
+        for (uint i = 0; i < 23; i++)
+            storageTree.children[0].children.push();
+        for (uint i = 0; i < 42; i++)
+            storageTree.children[1].children.push();
     }
 
     function run() public returns (uint256, uint256, uint256) {

test/libsolidity/semanticTests/structs/conversion/recursive_storage_memory_complex.sol

@@ -4,16 +4,20 @@ contract CopyTest {
         Tree[] children;
     }
     Tree storageTree;
+    Tree childStorageTree;
 
     constructor() public {
         storageTree.data = 0x42;
-		storageTree.children.length = 2;
+        for (uint i = 0; i < 2; i++)
+            storageTree.children.push(childStorageTree);
         storageTree.children[0].data = 0x4200;
         storageTree.children[1].data = 0x4201;
-		storageTree.children[0].children.length = 3;
+        for (uint i = 0; i < 3; i++)
+            storageTree.children[0].children.push(childStorageTree);
         for (uint i = 0; i < 3; i++)
             storageTree.children[0].children[i].data = 0x420000 + i;
-		storageTree.children[1].children.length = 4;
+        for (uint i = 0; i < 4; i++)
+            storageTree.children[1].children.push(childStorageTree);
         for (uint i = 0; i < 4; i++)
             storageTree.children[1].children[i].data = 0x420100 + i;
     }

test/libsolidity/semanticTests/viaYul/array_storage_index_access.sol

@@ -1,9 +1,11 @@
 contract C {
     uint[] storageArray;
-	function test_indicies(uint256 len) public
+    function test_indices(uint256 len) public
     {
-		storageArray.length = len;
+        while (storageArray.length < len)
-
+            storageArray.push();
+        while (storageArray.length > len)
+            storageArray.pop();
         for (uint i = 0; i < len; i++)
             storageArray[i] = i + 1;
 
@@ -14,13 +16,13 @@ contract C {
 // ====
 // compileViaYul: true
 // ----
-// test_indicies(uint256): 1 ->
+// test_indices(uint256): 1 ->
-// test_indicies(uint256): 129 ->
+// test_indices(uint256): 129 ->
-// test_indicies(uint256): 5 ->
+// test_indices(uint256): 5 ->
-// test_indicies(uint256): 10 ->
+// test_indices(uint256): 10 ->
-// test_indicies(uint256): 15 ->
+// test_indices(uint256): 15 ->
-// test_indicies(uint256): 0xFF ->
+// test_indices(uint256): 0xFF ->
-// test_indicies(uint256): 1000 ->
+// test_indices(uint256): 1000 ->
-// test_indicies(uint256): 129 ->
+// test_indices(uint256): 129 ->
-// test_indicies(uint256): 128 ->
+// test_indices(uint256): 128 ->
-// test_indicies(uint256): 1 ->
+// test_indices(uint256): 1 ->

test/libsolidity/semanticTests/viaYul/array_storage_index_boundary_test.sol

@@ -0,0 +1,23 @@
+contract C {
+    uint[] storageArray;
+    function test_boundary_check(uint256 len, uint256 access) public returns (uint256)
+    {
+        while(storageArray.length < len)
+            storageArray.push();
+        while(storageArray.length > len)
+            storageArray.pop();
+        return storageArray[access];
+    }
+}
+// ====
+// compileViaYul: true
+// ----
+// test_boundary_check(uint256, uint256): 10, 11 -> FAILURE
+// test_boundary_check(uint256, uint256): 10, 9 -> 0
+// test_boundary_check(uint256, uint256): 1, 9 -> FAILURE
+// test_boundary_check(uint256, uint256): 1, 1 -> FAILURE
+// test_boundary_check(uint256, uint256): 10, 10 -> FAILURE
+// test_boundary_check(uint256, uint256): 256, 256 -> FAILURE
+// test_boundary_check(uint256, uint256): 256, 255 -> 0
+// test_boundary_check(uint256, uint256): 256, 0xFFFF -> FAILURE
+// test_boundary_check(uint256, uint256): 256, 2 -> 0

test/libsolidity/semanticTests/viaYul/array_storage_index_boundery_test.sol

@@ -1,21 +0,0 @@
-contract C {
-	uint[] storageArray;
-	function test_boundery_check(uint256 len, uint256 access) public returns
-(uint256)
-	{
-		storageArray.length = len;
-		return storageArray[access];
-	}
-}
-// ====
-// compileViaYul: true
-// ----
-// test_boundery_check(uint256, uint256): 10, 11 -> FAILURE
-// test_boundery_check(uint256, uint256): 10, 9 -> 0
-// test_boundery_check(uint256, uint256): 1, 9 -> FAILURE
-// test_boundery_check(uint256, uint256): 1, 1 -> FAILURE
-// test_boundery_check(uint256, uint256): 10, 10 -> FAILURE
-// test_boundery_check(uint256, uint256): 256, 256 -> FAILURE
-// test_boundery_check(uint256, uint256): 256, 255 -> 0
-// test_boundery_check(uint256, uint256): 256, 0xFFFF -> FAILURE
-// test_boundery_check(uint256, uint256): 256, 2 -> 0

test/libsolidity/semanticTests/viaYul/array_storage_index_zeroed_test.sol

@@ -2,14 +2,20 @@ contract C {
     uint[] storageArray;
     function test_zeroed_indicies(uint256 len) public
     {
-		storageArray.length = len;
+        while(storageArray.length < len)
+            storageArray.push();
+        while(storageArray.length > len)
+            storageArray.pop();
 
         for (uint i = 0; i < len; i++)
             storageArray[i] = i + 1;
 
         if (len > 3)
         {
-			storageArray.length = 3;
+            while(storageArray.length > 0)
+                storageArray.pop();
+            while(storageArray.length < 3)
+                storageArray.push();
 
             for (uint i = 3; i < len; i++)
             {
@@ -25,8 +31,10 @@ contract C {
 
         }
 
-		storageArray.length = 0;
+        while(storageArray.length > 0)
-		storageArray.length = len;
+            storageArray.pop();
+        while(storageArray.length < len)
+            storageArray.push();
 
         for (uint i = 0; i < len; i++)
         {

test/libsolidity/semanticTests/viaYul/array_storage_length_access.sol

@@ -1,11 +1,10 @@
 contract C {
     uint[] storageArray;
-	function set_get_length(uint256 len) public returns (uint256)
+    function set_get_length(uint256 len) public returns (uint256) {
-	{
+        while(storageArray.length < len)
-		storageArray.length = len;
+            storageArray.push();
         return storageArray.length;
     }
-
 }
 // ====
 // compileViaYul: true
@@ -14,6 +13,6 @@ contract C {
 // set_get_length(uint256): 1 -> 1
 // set_get_length(uint256): 10 -> 10
 // set_get_length(uint256): 20 -> 20
-// set_get_length(uint256): 0 -> 0
 // set_get_length(uint256): 0xFF -> 0xFF
-// set_get_length(uint256): 0xFFFF -> 0xFFFF
+// set_get_length(uint256): 0xFFF -> 0xFFF
+// set_get_length(uint256): 0xFFFF -> FAILURE # Out-of-gas #

test/libsolidity/semanticTests/viaYul/array_storage_pop_zero_length.sol

@@ -0,0 +1,11 @@
+contract C {
+    uint[] storageArray;
+    function popEmpty() public {
+        storageArray.pop();
+    }
+}
+// ====
+// EVMVersion: >=petersburg
+// compileViaYul: true
+// ----
+// popEmpty() -> FAILURE

test/libsolidity/semanticTests/viaYul/array_storage_push_empty.sol

@@ -0,0 +1,17 @@
+contract C {
+    uint256[] storageArray;
+    function pushEmpty(uint256 len) public {
+        while(storageArray.length < len)
+            storageArray.push();
+
+        for (uint i = 0; i < len; i++)
+            require(storageArray[i] == 0);
+    }
+}
+// ====
+// compileViaYul: true
+// EVMVersion: >=petersburg
+// ----
+// pushEmpty(uint256): 128
+// pushEmpty(uint256): 256
+// pushEmpty(uint256): 32768 -> FAILURE # out-of-gas #

test/libsolidity/semanticTests/viaYul/array_storage_push_empty_length_address.sol

@@ -0,0 +1,23 @@
+contract C {
+    address[] addressArray;
+    function set_get_length(uint256 len) public returns (uint256)
+    {
+        while(addressArray.length < len)
+            addressArray.push();
+        while(addressArray.length > len)
+            addressArray.pop();
+        return addressArray.length;
+    }
+}
+// ====
+// compileViaYul: true
+// EVMVersion: >=petersburg
+// ----
+// set_get_length(uint256): 0 -> 0
+// set_get_length(uint256): 1 -> 1
+// set_get_length(uint256): 10 -> 10
+// set_get_length(uint256): 20 -> 20
+// set_get_length(uint256): 0 -> 0
+// set_get_length(uint256): 0xFF -> 0xFF
+// set_get_length(uint256): 0xFFF -> 0xFFF
+// set_get_length(uint256): 0xFFFF -> FAILURE # Out-of-gas #

test/libsolidity/semanticTests/viaYul/array_storage_push_pop.sol

@@ -0,0 +1,20 @@
+contract C {
+    uint[] storageArray;
+    function set_get_length(uint256 len) public returns (uint256) {
+        while(storageArray.length < len)
+            storageArray.push();
+        while(storageArray.length > 0)
+            storageArray.pop();
+        return storageArray.length;
+    }
+}
+// ====
+// compileViaYul: true
+// ----
+// set_get_length(uint256): 0 -> 0
+// set_get_length(uint256): 1 -> 0
+// set_get_length(uint256): 10 -> 0
+// set_get_length(uint256): 20 -> 0
+// set_get_length(uint256): 0xFF -> 0
+// set_get_length(uint256): 0xFFF -> 0
+// set_get_length(uint256): 0xFFFF -> FAILURE # Out-of-gas #

test/libsolidity/syntaxTests/array/calldata_resize.sol

@@ -4,4 +4,4 @@ contract C {
     }
 }
 // ----
-// TypeError: (75-83): Calldata arrays cannot be resized.
+// TypeError: (75-83): Member "length" is read-only and cannot be used to resize arrays.

test/libsolidity/syntaxTests/array/length/cannot_be_assigned.sol

@@ -0,0 +1,8 @@
+contract c {
+    uint[] storageArray;
+    function f() public {
+        storageArray.length = 3;
+    }
+}
+// ----
+// TypeError: (72-91): Member "length" is read-only and cannot be used to resize arrays.

test/libsolidity/syntaxTests/array/length/cannot_be_assigned_mapping.sol

@@ -0,0 +1,8 @@
+contract C {
+    mapping(uint => uint[]) map;
+    function f() public {
+        map[0].length = 4;
+    }
+}
+// ----
+// TypeError: (80-93): Member "length" is read-only and cannot be used to resize arrays.

test/libsolidity/syntaxTests/array/length/cannot_be_assigned_struct.sol

@@ -0,0 +1,11 @@
+contract C {
+    struct S {
+        uint[] a;
+    }
+    S s;
+    function f() public {
+        s.a.length = 4;
+    }
+}
+// ----
+// TypeError: (95-105): Member "length" is read-only and cannot be used to resize arrays.

test/libsolidity/syntaxTests/array/pop/calldata_pop.sol

@@ -0,0 +1,7 @@
+contract C {
+    function f(uint[] calldata x) external {
+        x.pop();
+    }
+}
+// ----
+// TypeError: (66-71): Member "pop" is not available in uint256[] calldata outside of storage.

test/libsolidity/syntaxTests/array/pop/memory_pop.sol

@@ -0,0 +1,8 @@
+contract C {
+    function f() public {
+        uint[] memory x;
+        x.pop();
+    }
+}
+// ----
+// TypeError: (72-77): Member "pop" is not available in uint256[] memory outside of storage.

test/libsolidity/syntaxTests/array/push/calldata_push.sol

@@ -0,0 +1,7 @@
+contract C {
+    function f(uint[] calldata x) external {
+        x.push();
+    }
+}
+// ----
+// TypeError: (66-72): Member "push" is not available in uint256[] calldata outside of storage.

test/libsolidity/syntaxTests/array/push/memory_push.sol

@@ -0,0 +1,8 @@
+contract C {
+    function f() public {
+        uint[] memory x;
+        x.push();
+    }
+}
+// ----
+// TypeError: (72-78): Member "push" is not available in uint256[] memory outside of storage.

test/libsolidity/syntaxTests/nameAndTypeResolution/219_memory_arrays_not_resizeable.sol

@@ -5,4 +5,4 @@ contract C {
     }
 }
 // ----
-// TypeError: (72-80): Memory arrays cannot be resized.
+// TypeError: (72-80): Member "length" is read-only and cannot be used to resize arrays.

test/libsolidity/syntaxTests/viewPureChecker/array/access_to_array_push.sol

@@ -0,0 +1,7 @@
+contract A {
+    uint[] x;
+    function g() public returns (uint) {
+        return x.push();
+    }
+}
+// ----

test/libsolidity/syntaxTests/viewPureChecker/array/access_to_array_push_view.sol

@@ -0,0 +1,8 @@
+contract A {
+    uint[] x;
+    function f() public view returns (uint) {
+        return x.push();
+    }
+}
+// ----
+// TypeError: (88-96): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.

test/libsolidity/syntaxTests/viewPureChecker/array/access_to_base_member_array.sol

@@ -3,9 +3,6 @@ contract A {
 }
 
 contract B is A {
-    function f() public view {
-        A.x.length = 2;
-    }
     function g() public pure returns (uint) {
         return A.x.length;
     }
@@ -14,8 +11,7 @@ contract B is A {
     }
 }
 // ----
-// TypeError: (87-97): Function declared as view, but this expression (potentially) modifies the state and thus requires non-payable (the default) or payable.
+// TypeError: (109-112): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".
-// TypeError: (170-173): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".
+// TypeError: (109-119): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".
-// TypeError: (170-180): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".
+// TypeError: (188-191): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".
-// TypeError: (249-252): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".
+// TypeError: (188-194): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".
-// TypeError: (249-255): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".