Solidity - v0.8.21

The release is still in progress and the binaries may not yet be available from all sources.

Changelog

Important Bugfixes:
* Code Generator: Always generate code for the expression in <expression>.selector in the legacy code generation pipeline.
* Yul Optimizer: Fix FullInliner step (i) not preserving the evaluation order of arguments passed into inlined functions in code that is not in expression-split form (i.e. when using a custom optimizer sequence in which the step not preceded by ExpressionSplitter (x)).

Language Features:
* Allow qualified access to events from other contracts.
* Relax restrictions on initialization of immutable variables. Reads and writes may now happen at any point at construction time outside of functions and modifiers. Explicit initialization is no longer mandatory.

Compiler Features:
* Commandline Interface: Add --ast-compact-json output in assembler mode.
* Commandline Interface: Add --ir-ast-json and --ir-optimized-ast-json outputs for Solidity input, providing AST in compact JSON format for IR and optimized IR.
* Commandline Interface: Respect --optimize-yul and --no-optimize-yul in compiler mode and accept them in assembler mode as well. --optimize --no-optimize-yul combination now allows enabling EVM assembly optimizer without enabling Yul optimizer.
* EWasm: Remove EWasm backend.
* Parser: Introduce pragma experimental solidity, which will enable an experimental language mode that in particular has no stability guarantees between non-breaking releases and is not suited for production use.
* SMTChecker: Add --model-checker-print-query CLI option and settings.modelChecker.printQuery JSON option to output the SMTChecker queries in the SMTLIB2 format. This requires using smtlib2 solver only.
* Standard JSON Interface: Add ast file-level output for Yul input.
* Standard JSON Interface: Add irAst and irOptimizedAst contract-level outputs for Solidity input, providing AST in compact JSON format for IR and optimized IR.
* Yul Optimizer: Remove experimental ReasoningBasedSimplifier optimization step.
* Yul Optimizer: Stack-to-memory mover is now enabled by default whenever possible for via IR code generation and pure Yul compilation.

Bugfixes:
* Code Generator: Disallow complex expressions whose results are types, built-ins, modules or some unassignable functions. The legacy code generation pipeline would not actually evaluate them, discarding any side-effects they might have.
* Code Generator: Fix not entirely deterministic order of functions in unoptimized Yul output. The choice of C++ compiler in some cases would result in different (but equivalent) bytecode (especially from native binaries vs emscripten binaries).
* Commandline Interface: Fix internal error when using --stop-after parsing and requesting some of the outputs that require full analysis or compilation.
* Commandline Interface: It is no longer possible to specify both --optimize-yul and --no-optimize-yul at the same time.
* SMTChecker: Fix encoding of side-effects inside if and ternary conditionalstatements in the BMC engine.
* SMTChecker: Fix false negative when a verification target can be violated only by trusted external call from another public function.
* SMTChecker: Fix generation of invalid SMT-LIB2 scripts in BMC engine with trusted mode for external calls when CHC engine times out.
* SMTChecker: Fix internal error caused by incorrectly classifying external function call using function pointer as a public getter.
* SMTChecker: Fix internal error caused by using external identifier to encode member access to functions that take an internal function as a parameter.
* Standard JSON Interface: Fix an incomplete AST being returned when analysis is interrupted by certain kinds of fatal errors.
* Type Checker: Disallow using certain unassignable function types in complex expressions.
* Type Checker: Function declaration types referring to different declarations are no longer convertible to each other.
* Yul Optimizer: Ensure that the assignment of memory slots for variables moved to memory does not depend on AST IDs that may depend on whether additional files are included during compilation.
* Yul Optimizer: Fix FullInliner step not ignoring code that is not in expression-split form.
* Yul Optimizer: Fix optimized IR being unnecessarily passed through the Yul optimizer again before bytecode generation.

AST Changes:
* AST: Add the experimentalSolidity field to the SourceUnit nodes, which indicate whether the experimental parsing mode has been enabled via pragma experimental solidity.

We especially thank all the contributors that made this release possible:

Alejandro Criado-Pérez, Alexander Arlt, Alexandre Ferreira, Bhargava Shastry, Cliff Syner, Daniel, Daniel Kirchner, David Bar-On, GiokaMarkella, Jun Zhang, Kaan Uzdoğan, Kamil Śliwak, Leo Alt, Martin Blicha, Matheus Aguiar, Nikola Matić, Nuno Santos, Paul Wackerow, Pawel Gebal, johnnygee19, minaminao, r0qs