MikePopoloski/slang v12.0 on GitHub

Language Compatibility

Added --allow-cross-auto-bin-max (included in 'vcs' compat mode) which enables the cross_auto_bin_max legacy coverage option, for compatibility with (pre-IEEE) SystemVerilog 3.1a (thanks to @hankhsu1996)
ANSI input ports without an explicit port kind (net or var) are specified by the LRM to be nets. slang instead used to default them to variables, so that cases like input int p wouldn't error (since 2-state types are not valid for nets). Now they are defaulted to nets to match the LRM, with a carve out for the 2-state net type check to suppress the error for these implicit cases only. This behavior better matches the LRM and several commercial tools. --infer-input-ports-as-vars (included by default in 'vcs' compat mode) can be used to get the old behavior. (thanks to @likeamahoney)
Embedded class covergroups are now allowed to reference class members declared later in textual order. The LRM is not clear about this but all commercial tools agree.
All integral types (not just packed arrays) are now allowed to be sliced across instance array port connections. The LRM is not clear about this but all commercial tools agree.

Notable Breaking Changes

The minimum required CMake version to build slang is now 3.28
fmtlib is now a fully private dependency of slang, to avoid introducing transitive dependencies to downstream users that otherwise have no need for it. In general it should be possible to build slang fully self-contained, so that relying on it does not balloon your dependency tree. See the docs for more details.
3rd party dependencies now require an explicit CMake option to use a local system-installed version (e.g. SLANG_USE_SYSTEM_BOOST). Previously this tried to auto-detect system installations but it caused too many issues where there happened to be a local copy that was undesirable for whatever reason.
The pyslang bindings have been ported to nanobind. For the most part downstream user scripts should continue to work the same, but there may be subtle edge cases (that are hard to enumerate or completely unknown to us).

New Features

Added support for external diagnostic waivers files for suppressing unwanted warnings (thanks to @sjalloq)
Added -Wmissing-else-clause which warns about if statements that look like they were meant to be else if based on being on the same line as a previous end keyword
Added -Wimplicit-net which warns for each implicit net that is created (thanks to @hankhsu1996)
Added -Wreal-case-eq which warns about using case equality operators ('===' and '!==') on real operands (thanks to @hankhsu1996)

Improvements

Depfiles created by --Mall and --Minclude now include system-style included files (via angle brackets) in addition to user-style (via double quotes) (thanks to @AndrewNolte)
When using --allow-toplevel-iface-ports, $static_assert constraints in a top-level module body can now pin interface port parameters to specific values or types, which is applied to the synthesized default interface instances (thanks to @AndrewNolte)
$static_assert with type reference comparisons now shows a detailed resolution chain for type aliases when the assert fails (thanks to @AndrewNolte)
Library search (with --libdir) can now parse files in parallel when threading is enabled (thanks to @ebrevdo)
Help text for the slang tool has been reformatted and improved in minor ways
Improved diagnostics for missing assignment pattern elements (thanks to @AndrewNolte)

Fixes

Fixed a potential crash when a single symbol has many (greater than 16) attributes declared (thanks to @AndrewNolte)
Fixed a bug where library search (with --libdir) could sometimes try to load and parse the same file more than once (thanks to @AndrewNolte)
Fixed spurious "unused" warnings on symbols that already have a previous error with their type resolution (thanks to @AndrewNolte)
Fixed `include files incorrectly being included in depfiles created by --Mmodule (thanks to @AndrewNolte)
Fixed a crash when using $static_assert to compare type references (thanks to @AndrewNolte)
Fixed false positives for -Wunused-but-set-property when accessing members via arrays of class handles
Fixed a crash when using super inside randomize calls on arrays of class handles
Fixed the ordering of element expressions in assignment patterns with explicit indices targeting arrays with descending indices
Fixed a parsing error where a labeled restrict property concurrent assertion was rejected
Fixed a bug that prevented interconnect nets from being used in alias directives
Fixed loop unrolling in data flow analysis to more conservatively handle loops that modify the iteration variable within their body
Fixed names explicitly imported into a package incorrectly being made visible to other units that import that package even when not re-exported
Fixed several internal assertions that could occur when recovering from invalid syntax
Fixed a malformed diagnostic for missing identifier tokens that go through the implicit net search logic
Fixed a crash when trying to analyze checkers with invalid port connections
Fixed ICE that could occur when a randsequence inside an unrolled for loop used a side-effecting index to drive an array element
Fixed ICE that could occur when analyzing a case statement over an enum that has a value with an erroneous initializer
Fixed output port initializers to count as drivers for multi-driver checking (thanks to @x-Aksara-x)
Fixed a bug where package exports that go through multiple layers of re-export from other packages would not work correctly (thanks to @AndrewNolte)
Fixed ICE during constant evaluation of tagged packed union member access with unknown tag (thanks to @EylonKrause)
Fixed ICE during constant evaluation of a queue read at one past the end (thanks to @EylonKrause)
Fixed ICE during constant evaluation of a streaming concat reorder on an irregular slice boundary (thanks to @EylonKrause)
Fixed ICE during constant evaluation of a streaming 'with' range past the array extent (thanks to @EylonKrause)
Fixed ICE during constant evaluation of string formatting using '%u/%z' with unpacked unions (thanks to @EylonKrause)
Fixed ICE during constant evaluation of string formatting using integer/char specifiers with a null handle (thanks to @EylonKrause)
Fixed ICE due to unbounded recursion of generic class specializations with changing param values (thanks to @EylonKrause)
Fixed a bug where SVInt::set() would drop high words when promoting from 2-state to 4-state, corrupting the value (thanks to @EylonKrause)
Fixed potentially incorrect instance caching when a module has an interface array port that is connected to different interface types (thanks to @hankhsu1996)
Fixed constant evaluation of string ato* methods to work correctly for inputs larger than 2^31 (thanks to @hankhsu1996)
Fixed a potential crash when using the --libext flag (thanks to @x-Aksara-x)
Fixed JSON AST serialization of randsequence productions to include the statement bodies of code blocks
Fixed -Wunused-subroutine firing on subroutines named in an export "DPI-C" directive, since the export makes them reachable from C

Tools & Bindings

pyslang

As mentioned above, the bindings have been ported to nanobind (previously using pybind11) (thanks to @jpienaar)
Fixed binding of symbols that match Python keyword names (thanks to @slide and @allRisc)
Improved performance of visiting nodes when using the lookup_table dict of callbacks (thanks to @hankhsu1996)

slang-tidy

Added a "NoCaseX" rule that warns about uses of casex (thanks to @Ozzy1423)
Added a "NoDefParam" rule that warns about uses of defparam (thanks to @Ozzy1423)
Added a "TypedefEnums" rule that warns about enums not declared via a typedef (thanks to @Ozzy1423)
Added a "TypedefStructUnion" rule that warns about structs and unions not declared via a typedef (thanks to @Ozzy1423)
Added new checks for naming of various constructs, configured via regex: cover groups, crosses, cover points, enums, structs, unions, typedefs (thanks to @Ozzy1423)
Added a "StructFieldsInSameProcess" rule that warns about struct fields being assigned from multiple processes (thanks to @spomata)
Fixed the resetIsActiveHigh config having inverted polarity, and changed default to false so that it stays consistent with the default resetName of rst_ni (thanks to @spomata)
Fixed the "OnlyAssignedOnReset" check to issue the right diagnostics (previously was erroneously using "RegisterNotAssignedOnReset") (thanks to @spomata)
Fixed the "EnforceModuleInstantiationPrefix" check to actually apply to non-top level modules (thanks to @nwistoffTT)

slang-unifdef

Added a new tool that can be used to rewrite code as if certain macros were either defined or not defined, while leaving other idefs alone (thanks to @AndrewNolte)