2024-07-10: Fuzion July Update

A long list of improvements to all parts for Fuzion. Among the many minor language and library improvements the new handling of pre-conditions as effects and support for inheritance of pre-conditions of redefined features is maybe the most important one.

• Fuzion language

  • Make use of redef mandatory when implementing abstract features (#3228, #3213, #3218).

    So redef is required now, e.g., in this code:

      new_line : String is
        public redef utf8 => [u8 10]
            

    This avoids bugs due to accidental redefinition and underlines the fact that redefinition includes inheritance of pre- and post-conditions.

  • Precondition are now syntax sugar that uses effects (#3260). This permits code to handle pre-condition failures as in

      v := fuzion.runtime.pre_fault
        .try ()->
          a := i32 1000000
          a*a
        .catch s->
          say "precondition failed $s"
          -1
            

    If debug is enabled, this will result in printing that the precondition of `infix *` did not hold due to the overflow caused by the code.

    Internally, what happens is that code with a precondition like

      feat(a t)
        pre cc
      => code
    
      r := feat v
            

    will be compiled into

      feat(a t)
      => code
    
      pre_feat(a t) =>
        if !cc then
          fuzion.runtime.pre_fault.cause "cc"
    
      pre_and_call_feat(a t) =>
        pre_feat a
        feat a
    
      r := pre_and_call_feat  v
            

    And calls to feat will be replaced by calls to pre_and_call_feat.

    This change resulted in a significant simplification of the Fuzion middle end and back ends, code related to pre- and post-conditions could be removed.

  • Precondition inheritance is now supported (#3260): Preconditions in redefined features can only be weakened.

  • use keyword (for/do/while/until) as reference for indentation (#3177). This avoids errors as in

      for i := 0, i+1
      until i > 3 do
        say "hey!"
            

    which used to be parsed as two loops (the second one being do say "hey!", now causes an error.

  • remove intrinsic_contructor features (#3062), using instrinsic instead.

  • Fuzion no longer permits silently ignoring a result (#3095). If feat returns a result that is no unit or void, calling feat will cause an error:

      feat     # ignoring result causes an error
            

    we need to use the result and have to ignore it explicitly, e.g., by

      ignore := feat  # assign result to a dummy field is ok
      _ := feat       # assign result to _ is also ok
            

  • Chained-boolean operations like a <= b <= c are now restricted to infix operators=, <=, etc., this avoids broken code like 8 %% 5 = 3 to cause a compile time error (#3264)

• Base library

  • New base library features

    • circular buffer (#3186)

    • buffered writer (#3269)

    • fallible effect is an abstract parent intended for effects that may fail abruptly like fault, pre- and post-conditions, panic, etc. (#3157)

  • Changes related to precondition features #3260: added contract_fault (#3184), fixed preconditions of numeric operator (#3283)-

  • Changes to the following standard library features

    • change exit(handler, code) to return unit (#3173)

    • change visibility of Random_Handler (#3265)

    • cleanup, rename foldf_list to foldf (#3240)

    • hide f16/f128 for now (#3148)

    • process, add with_out/with_err (#3146)

    • remove set from buffered.reader (#3263)

• Parser

  • cleanup: Add Num to methods and fields related to numeric literals (#3277)

  • improve syntax error on wrong set usage. (#3262)

  • lexer: raise error if num literal is followed by letters. (#3258)

  • Fix issue parsing tuples (#3242), it is no longer required to use double parentheses in code like

      f(x option ((i32,i32))) => ...
            

    which can now be written as

      f(x option (i32,i32)) => ...
            

• Front end

  • fix cryptic feature names in err output (#3155)

  • fix reproducibility of order of parsing of source files (#3188)

  • Code cleanup

    • cleanup loop code (#3279)

    • Delay calls to AbstractType.checkChoice to the types checking phase (#3197)

    • make error handling for types more fault tolerant (#3183)

    • move choiceTypeCheck from type inf to type check (#3154)

    • remove unique anonymous feature id (#3174)

    • refine lookup0 to consider the scope of definition/usage of a feature (#3112)

  • Bug Fixes

    • fix NPE in Block.checkTypes (#3226)

    • Fix post-condition failure on fuzion-lang.dev's design/examples/arg_choice.fz (#3193)

    • fix unjustified "Block must end with a result expression" (#3271)

    • In containsThisType: Fix check-fail on call to outer() on type parameter (#3181)

    • Workaround for #3160 for nested and inherited type features (#3182)

• Middle end

  • air: do not automatically mark ref results from intrinsics as instantiated (#3200)

  • air: for intrinsic constructors mark outers as instantiated as well (#3206)

  • air: in abstractCalled-check use isCalled instead of isInstantiated (#3061)

  • dfa: Use StringBuilder instead of say in showWhy (#3195)

  • fuir: move addClasses to constructor (#3145)

• JVM back end

  • be/jvm/int: workaround f64 e^1.0 != e (#3239)

• C back end

  • fix "use of an empty initializer is a C23 extension" (#3139, #3209)

  • fix JAVA_HOME and jvm.dll-path on windows (#3210)

  • fix switch-expr in fzE_call_v0/fzE_call_s0 (#3231)

  • fix test process on windows (#3198)

  • fix void function should not return void expression (#3227)

  • improve c11 compat., no empty initializer (#3190)

  • win.c remove some includes (#3215)

• Interpreter back end

  • improve thread safety (#3252)

• Tests

  • add regression tests (#3153, #3205, #3273)

  • add test for tail recursion #1588 (#3212)

  • for simple tests, pre-process err output to avoid common false pos errors (#3185)

  • remove skip file from test fz_cmd (#3272)

  • improve segfault handling (#3256)

  • increase stack size (#3257)

  • utf8 output on Windows: add workaround for #2586 (#3175)

  • fix trailing CR handling for windows test runs (#3236)

  • renamed dfa.mk as compile.mk (#3268)

Cheers,

--The Fuzion Team.