In C backend, illegal access to mutable var is not detected

[fridis]

This example

m : mutate is
s := m.go (() -> m.env.new 0)
_ := s.get
say "*** failed, should have panicked ***"

correctly panics using the JVM backend

 > ../../bin/fz test_local_mutate.fz
*** panic: *** invalid mutate for Type of 'm'

But does not with the C backend

 > ../../bin/fz -c test_local_mutate.fz && ./universe 
*** failed, should have panicked ***

[michaellilltokiwa]

Problem is that getEffectForce for effect clazz m returns null which is then pushed to stack, stopping further interpretation.

// code for clazz#10639 m.type.unsafe_get:
fzT_m fzC_m_oHtype_w_m__unsafe_u_get()
{
  start:
  {
    // cur does not escape, alloc on stack
    fzT_m_oHtype_w_m__unsafe_u_get fzCur;
    memset(&fzCur,0,sizeof fzCur);
    // 805306709: Env
    if (!fzThrd_effectsEnvironment->fzEnvInstalled_11572)
    {
      fprintf(stderr,"*** effect %s not present in current environment\012","m");
      exit(1);
    }
    // 805306710: Box m => m
    // Box is a NOP, clazz is already a ref
    // 805306711: Current
    // 805306712: Assign to m.type.unsafe_get.#result
    // access to Assign to m.type.unsafe_get.#result eliminated
    return fzCur.fzF_0__Hresult;
  }
}

and then here the tagging code is missing since unsafe_get is wrongly considered to always result in void:

// code for clazz#10619 m.type.get_if_installed:
fzT_option_w_m fzC__L10619m_oHtype_w__nstalled()
{
  start:
  {
    // cur does not escape, alloc on stack
    fzT__L10619m_oHtype_w__nstalled fzCur;
    memset(&fzCur,0,sizeof fzCur);
    // 805306698: Current
    // 805306699: Call m.type.get_if_installed.#^effect.type.get_if_installed(outer m.type.get_if_installed) m.type
    // access to Call m.type.get_if_installed.#^effect.type.get_if_installed(outer m.type.get_if_installed) m.type eliminated
    // 805306700: Call m.type.is_installed#1 m(outer m.type) bool
    fzT_bool fzM_0;
    fzM_0 = fzC__L10609m_oHtype_w__lled_w_m();
    // 805306701: Match 0=>l318 1=>l325
    switch (fzM_0.fzTag)
    {
      case 1/* TRUE */:
      {
        // 805306686: Current
        // 805306687: Call m.type.get_if_installed.#^effect.type.get_if_installed(outer m.type.get_if_installed) m.type
        // access to Call m.type.get_if_installed.#^effect.type.get_if_installed(outer m.type.get_if_installed) m.type eliminated
        // 805306688: Call m.type.unsafe_get(outer m.type) m
        fzT_m fzM_1;
        fzM_1 = fzC_m_oHtype_w_m__unsafe_u_get();
        break;
      }
      case 0/* FALSE */:
      {
        // 805306693: Call nil(outer universe) nil
        fzC_nil();
        // 805306694: Tag
        // Tag a value to be of choice type option m static value type nil
        fzT_option_w_m fzM_2;
        fzM_2.fzTag = 1;
        // unit type assignment to fzM_2.fzChoice.v1
        // 805306695: Current
        // 805306696: Assign to m.type.get_if_installed.#exprResult1102
        fzCur.fzF_2__HexprResult1102 = fzM_2;
        break;
      }
    }
    // 805306704: Current
    // 805306705: Call m.type.get_if_installed.#exprResult1102(outer m.type.get_if_installed) option m
    // 805306706: Current
    // 805306707: Assign to m.type.get_if_installed.#result
    fzCur.fzF_0__Hresult = fzCur.fzF_2__HexprResult1102;
    return fzCur.fzF_0__Hresult;
  }
}

So the jvm backend works by chance only.