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Solidity 0.6.0 Release Announcement

Posted by Solidity Team on December 17, 2019


This is a major breaking release of the Solidity compiler and language. Changes include explicit virtual and override keywords in inheritance, support for try/catch, splitting the fallback function into a receive Ether function and an actual fallback function and limitations on how the length of an array can be changed, among others. For a detailed explanation, please see the documentation or refer to the list below that shows every single change.

From this release on, ABIEncoderV2 is not considered experimental any more, but you still have to activate it through the pragma.

Furthermore, the Yul optimizer is automatically activated together with the regular optimizer, but you can still disable it through the detailed optimizer settings.

Breaking Changes:

  • ABI: Remove the deprecated constant and payable fields.
  • ABI: The type field is now required and no longer specified to default to function.
  • AST: Inline assembly is exported as structured JSON instead of plain string.
  • C API (libsolc): Introduce context parameter to both solidity_compile and the callback.
  • C API (libsolc): The provided callback now takes two parameters, kind and data. The callback can then be used for multiple purposes, such has file imports and SMT queries.
  • C API (libsolc): solidity_free was renamed to solidity_reset. Functions solidity_alloc and solidity_free were added.
  • C API (libsolc): solidity_compile now returns a string that must be explicitly freed via solidity_free()
  • Commandline Interface: Remove the text-based AST printer (ast).
  • Commandline Interface: Switch to the new error reporter by default. old-reporter falls back to the deprecated old error reporter.
  • Commandline Interface: Add option to disable or choose hash method between IPFS and Swarm for the bytecode metadata.
  • General: Disallow explicit conversions from external function types to address and add a member called address to them as replacement.
  • General: Enable Yul optimizer as part of standard optimization.
  • General: New reserved keywords: override, receive, and virtual.
  • General: private cannot be used together with virtual.
  • General: Split unnamed fallback functions into two cases defined using fallback() and receive().
  • Inheritance: State variable shadowing is now disallowed.
  • Inline Assembly: Only strict inline assembly is allowed.
  • Inline Assembly: Variable declarations cannot shadow declarations outside the assembly block.
  • JSON AST: Replace superFunction attribute by baseFunctions.
  • Natspec JSON Interface: Properly support multiple @return statements in @dev documentation and enforce named return parameters to be mentioned in the documentation.
  • Source mappings: Add "modifier depth" as a fifth field in the source mappings.
  • Standard JSON Interface: Add option to disable or choose hash method between IPFS and Swarm for the bytecode metadata.
  • Syntax: push(element) for dynamic storage arrays do not return the new length anymore.
  • Syntax: Abstract contracts need to be marked explicitly as abstract by using the abstract keyword.
  • 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.

Language Features:

  • Allow explicit conversions from address to address payable via payable(...).
  • Allow global enums and structs.
  • Allow public variables to override external functions.
  • Allow underscores as delimiters in hex strings.
  • Introduce syntax for array slices and implement them for dynamic calldata arrays.
  • Introduce push() for dynamic storage arrays. It returns a reference to the newly allocated element, if applicable.
  • Introduce virtual and override keywords.
  • Introduce try/catch-statement
  • Modify push(element) for dynamic storage arrays such that it does not return the new length anymore.
  • Yul: Introduce leave statement that exits the current function.
  • JSON AST: Add the function selector of each externally-visible FunctonDefinition to the AST JSON export.

Compiler Features:

  • Allow revert strings to be stripped from the binary using the revert-strings option or the settings.debug.revertStrings setting.
  • ABIEncoderV2: Do not warn about enabled ABIEncoderV2 anymore (the pragma is still needed, though).

A big thank you to all contributors who helped make this release possible!

Download the new version of Solidity here.

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