Merge pull request ethereum#8001 from ethereum/changes060

Update changes for 0.6.0

docs/060-breaking-changes.rst

@@ -9,28 +9,42 @@ For the full list check
 `the release changelog <https://github.com/ethereum/solidity/releases/tag/v0.6.0>`_.
 
 
-Syntactic Only Changes
-======================
+Changes the Compiler Might not Warn About
+=========================================
 
-This section lists purely syntactic changes that do not affect the behavior of existing code.
+This section lists changes where the behaviour of your code might
+change without the compiler telling you about it.
 
-* Conversions from external function types to ``address`` are now disallowed. Instead external
-  function types have a member called ``address``, similar to the existing ``selector`` member.
-* Conversions from ``address`` to ``address payable`` are now possible via ``payable(x)``, where
-  ``x`` must be of type ``address``.
+* The resulting type of an exponentiation is the type of the base. It used to be the smallest type
+  that can hold both the type of the base and the type of the exponent, as with symmentric
+  operations. Additionally, signed types are allowed for the base of the exponetation.
 
-* Function ``push(value)`` for dynamic storage arrays do not return the new length anymore.
 
-* The new keyword ``abstract`` can be used to mark contracts as abstract. It has to be used
-  if a contract does not implement all its functions.
+Explicitness Requirements
+=========================
 
-* Libraries have to implement all their functions, not only the internal ones.
+This section lists changes where the code now needs to be more explicit,
+but the semantics do not change.
+For most of the topics the compiler will provide suggestions.
 
-* Member-access to ``length`` of arrays is now always read-only, even for storage arrays. It's no
+* Functions can now only be overridden when they are either marked with the
+  ``virtual`` keyword or defined in an interface. Functions without
+  implementation outside an interface have to be marked ``virtual``.
+  When overriding a function or modifier, the new keyword ``override``
+  must be used. When overriding a function or modifier defined in multiple
+  parallel bases, all bases must be listed in parentheses after the keyword
+  like so: ``override(Base1, Base2)``.
+
+* Member-access to ``length`` of arrays is now always read-only, even for storage arrays. It is 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.
+  The reason behind this is to prevent storage collisions by gigantic
+  storage arrays.
 
-* New reserved keywords: ``override``, ``receive``, and ``virtual``.
+* The new keyword ``abstract`` can be used to mark contracts as abstract. It has to be used
+  if a contract does not implement all its functions.
+
+* Libraries have to implement all their functions, not only the internal ones.
 
 * The names of variables declared in inline assembly may no longer end in ``_slot`` or ``_offset``.
 
@@ -43,21 +57,16 @@ This section lists purely syntactic changes that do not affect the behavior of e
   the same name in any of its bases.
 
 
-Semantic Only Changes
-=====================
-
-This section lists the changes that are semantic-only, thus potentially
-hiding new and different behavior in existing code.
-
-
 Semantic and Syntactic Changes
 ==============================
 
-This section highlights changes that affect syntax and semantics.
+This section lists changes where you have to modify your code
+and it does something else afterwards.
 
-* The resulting type of an exponentiation is the type of the base. It used to be the smallest type
-  that can hold both the type of the base and the type of the exponent, as with symmentric
-  operations. Additionally, signed types are allowed for the base of the exponetation.
+* Conversions from external function types to ``address`` are now disallowed. Instead external
+  function types have a member called ``address``, similar to the existing ``selector`` member.
+
+* The function ``push(value)`` for dynamic storage arrays does not return the new length anymore (it returns nothing).
 
 * The unnamed function commonly referred to as "fallback function" was split up into a new
   fallback function that is defined using the ``fallback`` keyword and a receive ether function
@@ -72,13 +81,21 @@ This section highlights changes that affect syntax and semantics.
     not matching any other function which send value will revert. You should only need to
     implement the new fallback function if you are following an upgrade or proxy pattern.
 
-* Functions can now only be overridden when they are either marked with the
-  ``virtual`` keyword or defined in an interface. Functions without
-  implementation outside an interface have to be marked ``virtual``.
-  When overriding a function or modifier, the new keyword ``override``
-  must be used. When overriding a function or modifier defined in multiple
-  parallel bases, all bases must be listed in parentheses after the keyword
-  like so: ``override(Base1, Base2)``.
+
+New Features
+============
+
+This section lists things that were not possible prior to Solidity 0.6.0
+or at least were more difficult to achieve prior to Solidity 0.6.0.
+
+ * The :ref:`try/catch statement <try-catch>` allows you to react on failed external calls.
+ * ``struct`` and ``enum`` types can be declared at file level.
+ * Array slices can be used for calldata arrays, for example ``abi.decode(msg.data[4:], (uint, uint))``
+   is a low-level way to decode the function call payload.
+ * Natspec supports multiple return parameters in developer documentation, enforcing the same naming check as ``@param``.
+ * Yul and Inline Assembly have a new statement called ``leave`` that exits the current function.
+ * Conversions from ``address`` to ``address payable`` are now possible via ``payable(x)``, where
+   ``x`` must be of type ``address``.
 
 
 How to update your code
@@ -88,7 +105,9 @@ This section gives detailed instructions on how to update prior code for every b
 
 * Change ``address(f)`` to ``f.address`` for ``f`` being of external function type.
 
-* Replace ``function () external [payable] { ... }`` by either ``receive() external payable { ... }``, ``fallback() external [payable] { ... }`` or both. Prefer using a ``receive`` function only, whenever possible.
+* Replace ``function () external [payable] { ... }`` by either ``receive() external payable { ... }``,
+  ``fallback() external [payable] { ... }`` or both. Prefer
+  using a ``receive`` function only, whenever possible.
 
 * Change ``uint length = array.push(value)`` to ``array.push(value);``. The new length can be
   accessed via ``array.length``.
@@ -102,27 +121,11 @@ This section gives detailed instructions on how to update prior code for every b
   parameters like so: ``@return value The return value.``. You can mix named and un-named return parameters
   documentation so long as the notices are in the order they appear in the tuple return type.
 
-* Choose unique identifiers for variable declarations in inline assembly that do not conflict with declartions outside the inline assembly block.
-
-* 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.
-
-
-New Features
-============
-
- * The :ref:`try/catch statement <try-catch>` allows you to react on failed external calls.
- * Natspec supports multiple return parameters in dev documentation, enforcing the same naming check as ``@param``.
- * Yul and Inline Assembly have a new statement called ``leave`` that exits the current function.
-
-
-Deprecated Elements
-===================
-
-This section lists changes that deprecate prior features or syntax.
-
-
-.. _interoperability_060:
-
-Interoperability With Older Contracts
-=====================================
+* Choose unique identifiers for variable declarations in inline assembly that do not conflict
+  with declartions outside the inline assembly block.
 
+* 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 parentheses. When
+  multiple bases define the same function, the inheriting contract must override all conflicting functions.