2025-04-11: Fuzion April Update

Last month, the focus has shifted towards a number of minor Fuzion language improvements, cleaning up syntax sugar that was rarely used, disallowing confusing syntax and improving type inference.

Furthermore, important progress is happening on the native interface.

• General

  • We are happy to welcome Nina Hinkkanen from Finland for an internship until May at Tokiwa Software GmbH!

• Fuzion language

  • remove of keyword (#4983). The syntax sugar of the form

      fruit : choice of apple, pear, banana.
            

    now has to be written as

      apple is
      pear is
      banana is
      fruit : choice apple pear banana is
            

  • remove full stop (#4979). Empty feature declarations like

      point2D (x, y i32).
      point3D (x, y, z i32).
            

    now have to be written using is, even if nothing follows:

      point2D (x, y i32) is
      point3D (x, y, z i32) is
            

  • require is keyword for anonymous feature declaration (#4956), i.e., instead of

      nul String =>
        ref : String
          public redef utf8 Sequence u8 => [u8 0]
            

    the new syntax is:

      nul String =>
        ref : String is
          public redef utf8 Sequence u8 => [u8 0]
            

  • the code of an anonymous feature now must be indented further than ref (#4976). So instead of

      nul String := ref : String is
          public redef utf8 Sequence u8 => [u8 0]
            

    we now require

      nul String := ref : String is
                      public redef utf8 Sequence u8 => [u8 0]
            

    or

      nul String :=
        ref : String is
          public redef utf8 Sequence u8 => [u8 0]
            

  • Restrict possibilities for indentation of else (#4948), disallowing confusing cases such as

      if c0 then "-true-"
            else if c1 then "-false::true-"
      else       "-false::false-"    # 1. should flag an error: inconsistent indentation
            

    or

      if c0 then "-true-"
      else if c1 then "-false::true-"
           else if c2       "-false::false::true-"
      else             "-false::false::false-" # 2. should flag an error: inconsistent indentation
            

  • forbid setting argument visibility on non constructor features (#4904)

  • Enable partial application for string literals, numeric literals and operator calls (#4867). This avoids the explicit use of lambda: instead of

      log_string(s ()->String) => if logging then say s()
      log_i32(s ()->i32) => log_string ()->"i32:{i()}"
      log ()->"test"
      log ()->4711
            

    one can now write

      log_string(s ()->String) => if logging then say s()
      log_i32(s ()->i32) => log_string "i32:{i()}"
      log "test"
      log 4711
            

  • improve type inference for calls to flat_map, bind where the type parameter must be inferred from the type parameter of a lambda result (#4916). This simplifies code like

      say ([1,2,3].flat_map i32 x->[x,x])
            

    to

      say ([1,2,3].flat_map x->[x,x])
            

  • allow fixed implementation alongside abstract feature declaration(#4934)

  • redefined features no longer inherit visibility of original feature (#4915)

  • partial application now works for select (#4936). This is very useful for accessing elements in a tuple, e.g., as follows:

    The following code sums up the first elements of a Sequence of tuples, resulting in 8:

      say ([(3,4),(5,6)].map (.0) |> .sum)
            

    while this sums up the second elements of a Sequence of tuples, resulting in 10:

      say ([(3,4),(5,6)].map (.1) |> .sum)
            

    This can also be used for nested tuples

      say <| [(".0",(".1.0", ".1.1"))].map (.1.0)
      say <| [(".0", ((".1.0.0", ".1.0.1"), ".1.1"))].map (.1.0.1)
            

    or tuples of arrays

      say <| [(0,[1,2,3],0), (1, [4,5,6], 1)].map (.1[2])
            

    or with subsequent calls

      say <| [("a","b","c"), ("d","e","f")].map (.2.as_string)
            

• fz command

  • fz: option -saveLib of the fz command is now called -save-module (#4888)

• Base library

  • New base library features

    • time: add skeleton implementation for calendar_duration (#4905)

    • time/calendar_duration: implement as_string (#4939)

    • time/date_time: use month and day arguments instead of day in year (#4872)

    • added Mutable_Hash_Map (#4873)

  • Changes to the following standard library features

    • When reading form io.stdin, no longer block until EOF/ctrl-D to allow interactive input terminated with the return key(#4894)

• Documentation

  • fix display of constraint for type parameters (#4881)

  • make API sources link configurable (#4930)

• Parser

  • create better error when parsing numeric literals like 1e3 with lowercase exponent indicator (#4923)

  • fix ebnf grammar that contained reference to non-existing rule op, which is now OPERATOR (#4951)

• Front End

  • resolveSyntacticSugar2, performance enhancements (#4921)

  • bug fixes

    • Match.typeForInferencing return null on error (#4919)

    • fix NPE in Select.toString (#4958)

    • fix NullPointerException for target of Select (#4960)

    • suppress subsequent errors in case of type inference of lambda error (#4931)

    • add check for argument and result types of native features (#4850)

    • allow setting feature name for features with arguments (#4969)

    • do not implicitly assume result type to be void (#4974)

    • fix class cast exception (#4968)

    • fix issue with type inference of inheritance call of cotypes (#4891)

    • fix logic in isExtensionFeature (#4889)

    • fix type parameter inference for inheritance call (#4890)

• Middle End

  • dfa: genericResult return null if result is void (#4876)

  • dfa: native, dummy call function args (#4878)

  • fuir: add convenience method, fuir clazzNativeName (#4848)

  • fuir: isTailCall return true if site always results in void (#4243)

• Back Ends

  • native: add upcalls, i.e., passing Fuzion function for callback to native code (#4926)

• Build

  • now shows reason if test was canceled because of timeout or stack limit (#4954)

  • now shows the slowest tests after a test run (#4973)

• Tests

  • fix test sqlite on windows (#4982)

  • add regression test for #2489, partial application with type inference (#4871)

• Windows

  • fix error: 'poll.h' file not found (#4977)

Cheers,

--The Fuzion Team.