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Update changes for 0.6.0
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chriseth
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@ -9,29 +9,43 @@ For the full list check
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`the release changelog <https://github.com/ethereum/solidity/releases/tag/v0.6.0>`_.
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Syntactic Only Changes
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======================
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Changes the Compiler Might not Warn About
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=========================================
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This section lists purely syntactic changes that do not affect the behavior of existing code.
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This section lists changes where the behaviour of your code might
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change without the compiler telling you about it.
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* Conversions from external function types to ``address`` are now disallowed. Instead external
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function types have a member called ``address``, similar to the existing ``selector`` member.
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* Conversions from ``address`` to ``address payable`` are now possible via ``payable(x)``, where
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``x`` must be of type ``address``.
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* The resulting type of an exponentiation is the type of the base. It used to be the smallest type
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that can hold both the type of the base and the type of the exponent, as with symmentric
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operations. Additionally, signed types are allowed for the base of the exponetation.
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* Function ``push(value)`` for dynamic storage arrays do not return the new length anymore.
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Explicitness Requirements
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=========================
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This section lists changes where the code now needs to be more explicit,
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but the semantics to do not change.
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For most of the topics the compiler will provide suggestions.
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* Functions can now only be overridden when they are either marked with the
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``virtual`` keyword or defined in an interface. Functions without
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implementation outside an interface have to be marked ``virtual``.
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When overriding a function or modifier, the new keyword ``override``
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must be used. When overriding a function or modifier defined in multiple
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parallel bases, all bases must be listed in parentheses after the keyword
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like so: ``override(Base1, Base2)``.
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* Member-access to ``length`` of arrays is now always read-only, even for storage arrays. It is no
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longer possible to resize storage arrays assigning a new value to their length. Use ``push()``,
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``push(value)`` or ``pop()`` instead, or assign a full array, which will of course overwrite existing content.
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The reason behind this is to prevent storage collisions by gigantic
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storage arrays.
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* The new keyword ``abstract`` can be used to mark contracts as abstract. It has to be used
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if a contract does not implement all its functions.
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* Libraries have to implement all their functions, not only the internal ones.
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* Member-access to ``length`` of arrays is now always read-only, even for storage arrays. It's no
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longer possible to resize storage arrays assigning a new value to their length. Use ``push()``,
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``push(value)`` or ``pop()`` instead, or assign a full array, which will of course overwrite existing content.
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* New reserved keywords: ``override``, ``receive``, and ``virtual``.
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* The names of variables declared in inline assembly may no longer end in ``_slot`` or ``_offset``.
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* Variable declarations in inline assembly may no longer shadow any declaration outside the inline assembly block.
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@ -43,21 +57,16 @@ This section lists purely syntactic changes that do not affect the behavior of e
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the same name in any of its bases.
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Semantic Only Changes
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=====================
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This section lists the changes that are semantic-only, thus potentially
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hiding new and different behavior in existing code.
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Semantic and Syntactic Changes
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==============================
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This section highlights changes that affect syntax and semantics.
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This section lists changes where you have to modify your code
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and it does something else afterwards.
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* The resulting type of an exponentiation is the type of the base. It used to be the smallest type
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that can hold both the type of the base and the type of the exponent, as with symmentric
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operations. Additionally, signed types are allowed for the base of the exponetation.
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* Conversions from external function types to ``address`` are now disallowed. Instead external
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function types have a member called ``address``, similar to the existing ``selector`` member.
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* The function ``push(value)`` for dynamic storage arrays does not return the new length anymore (it returns nothing).
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* The unnamed function commonly referred to as "fallback function" was split up into a new
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fallback function that is defined using the ``fallback`` keyword and a receive ether function
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@ -72,13 +81,21 @@ This section highlights changes that affect syntax and semantics.
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not matching any other function which send value will revert. You should only need to
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implement the new fallback function if you are following an upgrade or proxy pattern.
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* Functions can now only be overridden when they are either marked with the
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``virtual`` keyword or defined in an interface. Functions without
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implementation outside an interface have to be marked ``virtual``.
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When overriding a function or modifier, the new keyword ``override``
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must be used. When overriding a function or modifier defined in multiple
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parallel bases, all bases must be listed in parentheses after the keyword
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like so: ``override(Base1, Base2)``.
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New Features
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============
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This section lists things that were not possible prior to Solidity 0.6.0
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or at least more difficult.
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* The :ref:`try/catch statement <try-catch>` allows you to react on failed external calls.
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* ``struct`` and ``enum`` types can be declared at file level.
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* Array slices can be used for calldata arrays, for example ``abi.decode(msg.data[4:], (uint, uint))``
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is a low-level way to decode the function call payload.
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* Natspec supports multiple return parameters in dev documentation, enforcing the same naming check as ``@param``.
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* Yul and Inline Assembly have a new statement called ``leave`` that exits the current function.
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* Conversions from ``address`` to ``address payable`` are now possible via ``payable(x)``, where
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``x`` must be of type ``address``.
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How to update your code
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@ -88,7 +105,9 @@ This section gives detailed instructions on how to update prior code for every b
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* Change ``address(f)`` to ``f.address`` for ``f`` being of external function type.
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* Replace ``function () external [payable] { ... }`` by either ``receive() external payable { ... }``, ``fallback() external [payable] { ... }`` or both. Prefer using a ``receive`` function only, whenever possible.
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* Replace ``function () external [payable] { ... }`` by either ``receive() external payable { ... }``,
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``fallback() external [payable] { ... }`` or both. Prefer
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using a ``receive`` function only, whenever possible.
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* Change ``uint length = array.push(value)`` to ``array.push(value);``. The new length can be
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accessed via ``array.length``.
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@ -102,27 +121,11 @@ This section gives detailed instructions on how to update prior code for every b
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parameters like so: ``@return value The return value.``. You can mix named and un-named return parameters
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documentation so long as the notices are in the order they appear in the tuple return type.
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* Choose unique identifiers for variable declarations in inline assembly that do not conflict with declartions outside the inline assembly block.
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* Add ``virtual`` to every non-interface function you intend to override. Add ``virtual`` to all functions without implementation outside interfaces. 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.
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New Features
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============
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* The :ref:`try/catch statement <try-catch>` allows you to react on failed external calls.
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* Natspec supports multiple return parameters in dev documentation, enforcing the same naming check as ``@param``.
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* Yul and Inline Assembly have a new statement called ``leave`` that exits the current function.
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Deprecated Elements
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===================
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This section lists changes that deprecate prior features or syntax.
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.. _interoperability_060:
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Interoperability With Older Contracts
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=====================================
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* Choose unique identifiers for variable declarations in inline assembly that do not conflict
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with declartions outside the inline assembly block.
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* Add ``virtual`` to every non-interface function you intend to override. Add ``virtual``
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to all functions without implementation outside interfaces. For single inheritance, add
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``override`` to every overriding function. For multiple inheritance, add ``override(A, B, ..)``,
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where you list all contracts that define the overridden function in the parentheses. When
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multiple bases define the same function, the inheriting contract must override all conflicting functions.
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