2026-04-14: Fuzion April Update

A focus of the current work is stabilizing the code base, removing engineering debt and fixing bugs while preparing for the development of real-time APIs through tool and API support.

• General

  • The Fuzion presentation given at Embedded World Conference in Nuremberg last month is available online.

  • We are happy to welcome Yann Glady from France who joins our team for an internship until August. Yann will be working on real-time and CPU resource related APIs for Fuzion.

• Fuzion language

  • support generic arguments as lambda targets (#6811)

    This enables type parameters for the types of lambda expressions like F in the following code

      apply(f F : i32->i32) => f 42
    
      _ := apply *2
              

    compared to using a plain lambda as in

      apply(f i32->i32) => f 42
    
      _ := apply *2
              

    this avoids passing of a reference to apply but it specializes the code of apply for each lambda it is used with avoiding the overhead of passing a value for f, avoiding heap allocation of this value and avoiding dynamic binding overhead when calling f.

• Base library

  • New library features

    • add Cons.finite for better handling of infinite lists (#6343)

    • add enhanced effect composition means (#6775)

      To instate effects e1, e2, and e3 to run code, it used to be required to instate each effect individually as in

        e1 ! ()->
          e2 ! ()->
            e3 ! code
                

      now, this can be done in one step using a tuple

        (e1, e2, e3) ! code
                

      reducing the boilerplate for effects.

    • add envir.vars.map_of(_ Sequence String) (#6753)

    • For int, implement missing fits_int... to permit conversion to smaller integer types (#6800)

    • make String.to_valid_utf8 public (#6737)

  • Changed library features

    • fix lstats (#6755)

    • make ps_map inherit from Persistent_Map (#6779)

    • do not use check for operational errors (#6791)

    • processes, close pipes on exhaustion (#6739)

    • rename Typed_Value.applyTo as Typed_Value.apply_to (#6784)

    • replaced switch.val/.get by or_panic since this clearly states the possible error this may cause (#6774)

    • stat meta_data, include path (#6767)

    • traverse, do not descend into dirs that are symlinks (#6751)

    • remove unused type pars from internal helper features tuple_zip_equals/tuple_zip_lteq (#6802)

    • Sieve_Cache, attempt to fix memory leak in fzweb by zeroing references from removed elements (#6797)

  • Removed library features

    • removed idx to use integer directly as a general index type(#6771)

• Parser

  • fix handling of multiple successive operators (#6793)

  • Permit `f.this` types to be used in preconditions by fixing bug in isFeaturePrefix (#6763)

• Front end

  • better error message in case of indentation problem, include ebnf rule name (#6683)

  • fix bug where type inference of a type params from a .this-type led to crash (#6777)

  • major cleanup untangling inheritance from type parameter application: Remove handling of inheritance from AbstractType.applyTypePars, this is now done exclusively by AbstractFeature.handDown (#6570)

  • AbstractType, remove special case concerning choices in constraintAssignableFrom (#6825)

  • add error for wrong usages of fixed modifier (#6794)

  • Call, fix crash due to wrong detection of erroneous call target (#6790)

  • check types in source code order and enhance suppressing of subsequent errors (#6841)

  • Fix front-end crash by not applying t_UNDEFINED in Call.applyToActualsAndFormalTypes (#6816)

  • fix constraint assignability checking, now enforces that type parameter on type constraint are not relaxed in redefintions (#6834)

  • fix resolving fully qualified this-types (#6837)

  • fix showing correct error, “Main feature must not be…” (#6826)

  • fix stack overflow in isAssignableFrom (#6813)

  • match, support for type constrained subject types (#6815)

  • replace type parameters in result field of postcondition feature (#6788)

  • show error on non-exhaustive destructuring (#6821) such as

      a,b := (1,2,3)
              

    which now reports Non-exhaustive destructuring is forbidden [..] Expected 3 variable names but found 2.

  • show error when choice inherits feature with contract (#6833)

  • show error when using this-type of feature we are fixed to (#6781)

  • support calling type parameter from inside type features (#6831)

  • support constraints with .this-type (#6757)

  • support for fields as target of inheritance calls (#6818)

  • support type inference from type parameter used as outer type (#6810)

• DFA

  • mark fields of result values of native features as initialized/written (#6729)

• FUIR

  • Fix crash in directParents due to this-type not replaced (#6786). Simplification of Clazz.directParents() (#6812, #6819)

• Back ends

  • be/c: use a newly started thread to run code instead of the main thread to be able to control stack size and thread parameters (#6760)

  • fix indentation in generated C code (#6746)

  • win: fix fzE_file_open, align to posix API (#6744)

  • intrinsics: remove unnecessary floating point constant intrinsics (#6768)

• Tools

  • bin/run_tests/chec_simple_example/record_simple_example: move shared process handling code to tokiwa module (#6778)

  • fix names of failed tests so that the start does not get cut off (#6750)

  • fzextract

    • add asserts ensuring size fits assumption (#6749)

    • add callback/function pointer extraction (#6730)

    • add mutate type parameter to c (#6799)

    • comment cases that differ among lin/win/macOS (#6752)

    • refine extraction heuristic (#6725)

    • slight modifications (#6742)

    • update keywords (#6809)

  • tools: add makefile target rerecord_expected_err (#6805)

  • util/Terminal: add environment variable to force ANSI output (#6747)

• Tests

  • add regression tests for #5955 (#6827), #4619 (#6838), #1207 (#6808), #4055 (#6839), #5045 (#6840), #5967 (#6832), and #6817 (#6823).

• Documentation

  • add annotation for unit types in API docs (#6769)

  • if comment of a feature is empty and this feature redefines another feature, use the redefined feature's comment. Otherwise show a warning. (#6715)

  • show pre- and postconditions in the API docs (#6776)

• Fuzion Webserver

  • add health check to docker container (#400)

  • benchmark sending change bucket (#402)

  • Jenkinsfile.bench also check out flang_dev (#403)

  • move local mutates closer to their usage (#392)

  • move login_status from util to root dir (#381)

  • move some code from util to webserver or universe (#382)

  • remove webserver.log (#383)

  • return error when password hashing fails (#380)

  • send benchmarks to influxdb (#401)

  • data sent to influx, prefix benchmark names with type (#404)

  • sort API sources alphabetically (#388)

  • src/read_file: follow symlinks when calling stat (#397)

  • src/runner: read stdout and stderr in a thread pool (#391)

  • src/session_document: drop mutability when reading TOC (#393)

  • src/session_document: implement pretty printing of Fuzion code (#385)

  • src/session_document: pretty printing: read from process before it exits (#389)

  • src/webserver: log requests that take longer than 750 ms to process (#396)

• Feeze

  • A number of improvements in the displayed data of feeze

    • CPU activity bards

    • Threads are grouped by users and processes

    • Threads may be folded per user

    • Width of thread names and scala rulers may now be adjusted.

    Here is a current screenshot:

    

  • Feeze now can be controlled via a GUI (#17)

    

Cheers,

--The Fuzion Team.