solidity/docs/080-breaking-changes.rst

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Solidity v0.8.0 Breaking Changes
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This section highlights the main breaking changes introduced in Solidity
version 0.8.0, along with the reasoning behind the changes and how to update
affected code.
For the full list check
`the release changelog <https://github.com/ethereum/solidity/releases/tag/v0.8.0>`_.

Semantic and Syntactic Changes
==============================

This section lists changes where you have to modify your code
and it does something else afterwards.

* Explicit conversions from negative literals and literals larger than ``type(uint160).max`` to ``address`` are now disallowed.
* Exponentiation is right associative, i.e., the expression ``a**b**c`` is parsed as ``a**(b**c)``.
  Before 0.8.0, it was parsed as ``(a**b)**c``.

Semantic only Changes
=====================

* Failing assertions (and other internal checks like division by zero) do not use the invalid opcode anymore but instead revert
  with error data equal to a function call to ``Panic(uint256)`` with an error code specific to the circumstances.

This will save gas on errors while it still allows static analysis tools to detect these situations.


Syntactic Only Changes
======================

* The global functions ``log0``, ``log1``, ``log2``, ``log3`` and ``log4`` have been removed.

These are low-level functions that were largely unused. Their behaviour can be accessed from inline assembly.