示例#1
0
文件: c-path.c 项目: kjanz1899/ren-c
//
//  Do_Path_Throws: C
//
// Evaluate an ANY_PATH! REBVAL, starting from the index position of that
// path value and continuing to the end.
//
// The evaluator may throw because GROUP! is evaluated, e.g. `foo/(throw 1020)`
//
// If label_sym is passed in as being non-null, then the caller is implying
// readiness to process a path which may be a function with refinements.
// These refinements will be left in order on the data stack in the case
// that `out` comes back as IS_FUNCTION().
//
// If `opt_setval` is given, the path operation will be done as a "SET-PATH!"
// if the path evaluation did not throw or error.  HOWEVER the set value
// is NOT put into `out`.  This provides more flexibility on performance in
// the evaluator, which may already have the `val` where it wants it, and
// so the extra assignment would just be overhead.
//
// !!! Path evaluation is one of the parts of R3-Alpha that has not been
// vetted very heavily by Ren-C, and needs a review and overhaul.
//
REBOOL Do_Path_Throws(
    REBVAL *out,
    REBSYM *label_sym,
    const REBVAL *path,
    REBVAL *opt_setval
) {
    REBPVS pvs;
    REBDSP dsp_orig = DSP;

    assert(ANY_PATH(path));

    // !!! There is a bug in the dispatch such that if you are running a
    // set path, it does not always assign the output, because it "thinks you
    // aren't going to look at it".  This presumably originated from before
    // parens were allowed in paths, and neglects cases like:
    //
    //     foo/(throw 1020): value
    //
    // We always have to check to see if a throw occurred.  Until this is
    // streamlined, we have to at minimum set it to something that is *not*
    // thrown so that we aren't testing uninitialized memory.  A safe trash
    // will do, which is unset in release builds.
    //
    if (opt_setval)
        SET_TRASH_SAFE(out);

    // None of the values passed in can live on the data stack, because
    // they might be relocated during the path evaluation process.
    //
    assert(!IN_DATA_STACK(out));
    assert(!IN_DATA_STACK(path));
    assert(!opt_setval || !IN_DATA_STACK(opt_setval));

    // Not currently robust for reusing passed in path or value as the output
    assert(out != path && out != opt_setval);

    assert(!opt_setval || !THROWN(opt_setval));

    // Initialize REBPVS -- see notes in %sys-do.h
    //
    pvs.opt_setval = opt_setval;
    pvs.store = out;
    pvs.orig = path;
    pvs.item = VAL_ARRAY_AT(pvs.orig); // may not be starting at head of PATH!

    // Seed the path evaluation process by looking up the first item (to
    // get a datatype to dispatch on for the later path items)
    //
    if (IS_WORD(pvs.item)) {
        pvs.value = GET_MUTABLE_VAR_MAY_FAIL(pvs.item);
        if (IS_UNSET(pvs.value))
            fail (Error(RE_NO_VALUE, pvs.item));
    }
    else {
        // !!! Ideally there would be some way to protect pvs.value during
        // successive path dispatches to make sure it does not get written.
        // This is semi-dangerously giving pvs.value a reference into the
        // input path, which should not be modified!

        pvs.value = VAL_ARRAY_AT(pvs.orig);
    }

    // Start evaluation of path:
    if (IS_END(pvs.item + 1)) {
        // If it was a single element path, return the value rather than
        // try to dispatch it (would cause a crash at time of writing)
        //
        // !!! Is this the desired behavior, or should it be an error?
    }
    else if (Path_Dispatch[VAL_TYPE_0(pvs.value)]) {
        REBOOL threw = Next_Path_Throws(&pvs);

        // !!! See comments about why the initialization of out is necessary.
        // Without it this assertion can change on some things:
        //
        //     t: now
        //     t/time: 10:20:03
        //
        // (It thinks pvs.value has its THROWN bit set when it completed
        // successfully.  It was a PE_USE_STORE case where pvs.value was reset to
        // pvs.store, and pvs.store has its thrown bit set.  Valgrind does not
        // catch any uninitialized variables.)
        //
        // There are other cases that do trip valgrind when omitting the
        // initialization, though not as clearly reproducible.
        //
        assert(threw == THROWN(pvs.value));

        if (threw) return TRUE;

        // Check for errors:
        if (NOT_END(pvs.item + 1) && !IS_FUNCTION(pvs.value)) {
            // Only function refinements should get by this line:
            fail (Error(RE_INVALID_PATH, pvs.orig, pvs.item));
        }
    }
    else if (!IS_FUNCTION(pvs.value))
        fail (Error(RE_BAD_PATH_TYPE, pvs.orig, Type_Of(pvs.value)));

    if (opt_setval) {
        // If SET then we don't return anything
        assert(IS_END(pvs.item) + 1);
        return FALSE;
    }

    // If storage was not used, then copy final value back to it:
    if (pvs.value != pvs.store) *pvs.store = *pvs.value;

    assert(!THROWN(out));

    // Return 0 if not function or is :path/word...
    if (!IS_FUNCTION(pvs.value)) {
        assert(IS_END(pvs.item) + 1);
        return FALSE;
    }

    if (label_sym) {
        REBVAL refinement;
        VAL_INIT_WRITABLE_DEBUG(&refinement);

        // When a function is hit, path processing stops as soon as the
        // processed sub-path resolves to a function. The path is still sitting
        // on the position of the last component of that sub-path. Usually,
        // this last component in the sub-path is a word naming the function.
        //
        if (IS_WORD(pvs.item)) {
            *label_sym = VAL_WORD_SYM(pvs.item);
        }
        else {
            // In rarer cases, the final component (completing the sub-path to
            // the function to call) is not a word. Such as when you use a path
            // to pick by index out of a block of functions:
            //
            //      functions: reduce [:add :subtract]
            //      functions/1 10 20
            //
            // Or when you have an immediate function value in a path with a
            // refinement. Tricky to make, but possible:
            //
            //      do reduce [
            //          to-path reduce [:append 'only] [a] [b]
            //      ]
            //

            // !!! When a function was not invoked through looking up a word
            // (or a word in a path) to use as a label, there were once three
            // different alternate labels used.  One was SYM__APPLY_, another
            // was ROOT_NONAME, and another was to be the type of the function
            // being executed.  None are fantastic, we do the type for now.

            *label_sym = SYM_FROM_KIND(VAL_TYPE(pvs.value));
        }

        // Move on to the refinements (if any)
        ++pvs.item;

        // !!! Currently, the mainline path evaluation "punts" on refinements.
        // When it finds a function, it stops the path evaluation and leaves
        // the position pvs.path before the list of refinements.
        //
        // A more elegant solution would be able to process and notice (for
        // instance) that `:APPEND/ONLY` should yield a function value that
        // has been specialized with a refinement.  Path chaining should thus
        // be able to effectively do this and give the refined function object
        // back to the evaluator or other client.
        //
        // If a label_sym is passed in, we recognize that a function dispatch
        // is going to be happening.  We do not want to pay to generate the
        // new series that would be needed to make a temporary function that
        // will be invoked and immediately GC'd  So we gather the refinements
        // on the data stack.
        //
        // This code simulates that path-processing-to-data-stack, but it
        // should really be something in dispatch iself.  In any case, we put
        // refinements on the data stack...and caller knows refinements are
        // from dsp_orig to DSP (thanks to accounting, all other operations
        // should balance!)

        for (; NOT_END(pvs.item); ++pvs.item) { // "the refinements"
            if (IS_NONE(pvs.item)) continue;

            if (IS_GROUP(pvs.item)) {
                // Note it is not legal to use the data stack directly as the
                // output location for a DO (might be resized)

                if (DO_VAL_ARRAY_AT_THROWS(&refinement, pvs.item)) {
                    *out = refinement;
                    DS_DROP_TO(dsp_orig);
                    return TRUE;
                }
                if (IS_NONE(&refinement)) continue;
                DS_PUSH(&refinement);
            }
            else if (IS_GET_WORD(pvs.item)) {
                DS_PUSH_TRASH;
                *DS_TOP = *GET_OPT_VAR_MAY_FAIL(pvs.item);
                if (IS_NONE(DS_TOP)) {
                    DS_DROP;
                    continue;
                }
            }
            else DS_PUSH(pvs.item);

            // Whatever we were trying to use as a refinement should now be
            // on the top of the data stack, and only words are legal ATM
            //
            if (!IS_WORD(DS_TOP))
                fail (Error(RE_BAD_REFINE, DS_TOP));

            // Go ahead and canonize the word symbol so we don't have to
            // do it each time in order to get a case-insenstive compare
            //
            INIT_WORD_SYM(DS_TOP, SYMBOL_TO_CANON(VAL_WORD_SYM(DS_TOP)));
        }

        // To make things easier for processing, reverse the refinements on
        // the data stack (we needed to evaluate them in forward order).
        // This way we can just pop them as we go, and know if they weren't
        // all consumed if it doesn't get back to `dsp_orig` by the end.

        if (dsp_orig != DSP) {
            REBVAL *bottom = DS_AT(dsp_orig + 1);
            REBVAL *top = DS_TOP;
            while (top > bottom) {
                refinement = *bottom;
                *bottom = *top;
                *top = refinement;

                top--;
                bottom++;
            }
        }
    }
    else {
        // !!! Historically this just ignores a result indicating this is a
        // function with refinements, e.g. ':append/only'.  However that
        // ignoring seems unwise.  It should presumably create a modified
        // function in that case which acts as if it has the refinement.
        //
        // If the caller did not pass in a label pointer we assume they are
        // likely not ready to process any refinements.
        //
        if (NOT_END(pvs.item + 1))
            fail (Error(RE_TOO_LONG)); // !!! Better error or add feature
    }

    return FALSE;
}
示例#2
0
//
//  For_Each_Unspecialized_Param: C
//
// We have to take into account specialization of refinements in order to know
// the correct order.  If someone has:
//
//     foo: func [a [integer!] /b [integer!] /c [integer!]] [...]
//
// They can partially specialize this as :foo/c/b.  This makes it seem to the
// caller a function originally written with spec:
//
//     [a [integer!] c [integer!] b [integer!]]
//
// But the frame order doesn't change; the information for knowing the order
// is encoded with instructions occupying the non-fully-specialized slots.
// (See %c-specialize.c for a description of the mechanic.)
//
// The true order could be cached when the function is generated, but to keep
// things "simple" we capture the behavior in this routine.
//
// Unspecialized parameters are visited in two passes: unsorted, then sorted.
//
void For_Each_Unspecialized_Param(
    REBACT *act,
    PARAM_HOOK hook,
    void *opaque
){
    REBDSP dsp_orig = DSP;

    // Do an initial scan to push the partial refinements in the reverse
    // order that they apply.  While walking the parameters in a potentially
    // "unsorted" fashion, offer them to the passed-in hook in case it has a
    // use for this first pass (e.g. just counting, to make an array big
    // enough to hold what's going to be given to it in the second pass.

    REBVAL *param = ACT_PARAMS_HEAD(act);
    REBVAL *special = ACT_SPECIALTY_HEAD(act);

    REBCNT index = 1;
    for (; NOT_END(param); ++param, ++special, ++index) {
        if (Is_Param_Hidden(param))
            continue;  // specialized out, not in interface

        Reb_Param_Class pclass = VAL_PARAM_CLASS(param);
        if (pclass == REB_P_RETURN or pclass == REB_P_LOCAL)
            continue;  // locals not in interface

        if (not hook(param, false, opaque)) { // false => unsorted pass
            DS_DROP_TO(dsp_orig);
            return;
        }

        if (IS_SYM_WORD(special)) {
            assert(TYPE_CHECK(param, REB_TS_REFINEMENT));
            Move_Value(DS_PUSH(), special);
        }
    }

    // Refinements are now on stack such that topmost is first in-use
    // specialized refinement.

    // Now second loop, where we print out just the normal args.
    //
    param = ACT_PARAMS_HEAD(act);
    for (; NOT_END(param); ++param) {
        if (Is_Param_Hidden(param))
            continue;

        if (TYPE_CHECK(param, REB_TS_REFINEMENT))
            continue;

        Reb_Param_Class pclass = VAL_PARAM_CLASS(param);
        if (pclass == REB_P_LOCAL or pclass == REB_P_RETURN)
            continue;

        if (not hook(param, true, opaque)) { // true => sorted pass
            DS_DROP_TO(dsp_orig);
            return;
        }
    }

    // Now jump around and take care of the partial refinements.

    DECLARE_LOCAL (unrefined);

    REBDSP dsp = DSP;  // highest priority are at *top* of stack, go downward
    while (dsp != dsp_orig) {
        param = ACT_PARAM(act, VAL_WORD_INDEX(DS_AT(dsp)));
        --dsp;

        Move_Value(unrefined, param);
        assert(TYPE_CHECK(unrefined, REB_TS_REFINEMENT));
        TYPE_CLEAR(unrefined, REB_TS_REFINEMENT);

        PUSH_GC_GUARD(unrefined);
        bool cancel = not hook(unrefined, true, opaque);  // true => sorted
        DROP_GC_GUARD(unrefined);

        if (cancel) {
            DS_DROP_TO(dsp_orig);
            return;
        }
    }

    // Finally, output any fully unspecialized refinements

    param = ACT_PARAMS_HEAD(act);

    for (; NOT_END(param); ++param) {
        if (Is_Param_Hidden(param))
            continue;

        if (not TYPE_CHECK(param, REB_TS_REFINEMENT))
            continue;

        dsp = dsp_orig;
        while (dsp != DSP) {
            ++dsp;
            if (SAME_STR(
                VAL_WORD_SPELLING(DS_AT(dsp)),
                VAL_PARAM_SPELLING(param)
            )){
                goto continue_unspecialized_loop;
            }
        }

        if (not hook(param, true, opaque)) {  // true => sorted pass
            DS_DROP_TO(dsp_orig);
            return; // stack should be balanced here
        }

      continue_unspecialized_loop:
        NOOP;
    }

    DS_DROP_TO(dsp_orig);
}
示例#3
0
//
//  Make_Context_For_Action_Push_Partials: C
//
// This creates a FRAME! context with NULLED cells in the unspecialized slots
// that are available to be filled.  For partial refinement specializations
// in the action, it will push the refinement to the stack.  In this way it
// retains the ordering information implicit in the partial refinements of an
// action's existing specialization.
//
// It is able to take in more specialized refinements on the stack.  These
// will be ordered *after* partial specializations in the function already.
// The caller passes in the stack pointer of the lowest priority refinement,
// which goes up to DSP for the highest of those added specializations.
//
// Since this is walking the parameters to make the frame already--and since
// we don't want to bind to anything specialized out (including the ad-hoc
// refinements added on the stack) we go ahead and collect bindings from the
// frame if needed.
//
REBCTX *Make_Context_For_Action_Push_Partials(
    const REBVAL *action,  // need ->binding, so can't just be a REBACT*
    REBDSP lowest_ordered_dsp,  // caller can add refinement specializations
    struct Reb_Binder *opt_binder,
    REBFLGS prep  // cell formatting mask bits, result managed if non-stack
){
    REBDSP highest_ordered_dsp = DSP;

    REBACT *act = VAL_ACTION(action);

    REBCNT num_slots = ACT_NUM_PARAMS(act) + 1;  // +1 is for CTX_ARCHETYPE()
    REBARR *varlist = Make_Array_Core(num_slots, SERIES_MASK_VARLIST);

    REBVAL *rootvar = RESET_CELL(
        ARR_HEAD(varlist),
        REB_FRAME,
        CELL_MASK_CONTEXT
    );
    INIT_VAL_CONTEXT_VARLIST(rootvar, varlist);
    INIT_VAL_CONTEXT_PHASE(rootvar, VAL_ACTION(action));
    INIT_BINDING(rootvar, VAL_BINDING(action));

    const REBVAL *param = ACT_PARAMS_HEAD(act);
    REBVAL *arg = rootvar + 1;
    const REBVAL *special = ACT_SPECIALTY_HEAD(act);  // of exemplar/paramlist

    REBCNT index = 1; // used to bind REFINEMENT! values to parameter slots

    REBCTX *exemplar = ACT_EXEMPLAR(act); // may be null
    if (exemplar)
        assert(special == CTX_VARS_HEAD(exemplar));
    else
        assert(special == ACT_PARAMS_HEAD(act));

    for (; NOT_END(param); ++param, ++arg, ++special, ++index) {
        arg->header.bits = prep;

        if (Is_Param_Hidden(param)) {  // specialized out
            assert(GET_CELL_FLAG(special, ARG_MARKED_CHECKED));
            Move_Value(arg, special); // doesn't copy ARG_MARKED_CHECKED
            SET_CELL_FLAG(arg, ARG_MARKED_CHECKED);

          continue_specialized:

            assert(not IS_NULLED(arg));
            assert(GET_CELL_FLAG(arg, ARG_MARKED_CHECKED));
            continue;  // Eval_Core() double-checks type in debug build
        }

        assert(NOT_CELL_FLAG(special, ARG_MARKED_CHECKED));

        REBSTR *canon = VAL_PARAM_CANON(param);  // for adding to binding
        if (not TYPE_CHECK(param, REB_TS_REFINEMENT)) {  // nothing to push

          continue_unspecialized:

            assert(arg->header.bits == prep);
            Init_Nulled(arg);
            if (opt_binder) {
                if (not Is_Param_Unbindable(param))
                    Add_Binder_Index(opt_binder, canon, index);
            }
            continue;
        }

        // Unspecialized refinement slots may have an SYM-WORD! in them that
        // reflects a partial that needs to be pushed to the stack.  (They
        // are in *reverse* order of use.)

        assert(
            (special == param and IS_PARAM(special))
            or (IS_SYM_WORD(special) or IS_NULLED(special))
        );

        if (IS_SYM_WORD(special)) {
            REBCNT partial_index = VAL_WORD_INDEX(special);
            Init_Any_Word_Bound( // push a SYM-WORD! to data stack
                DS_PUSH(),
                REB_SYM_WORD,
                VAL_STORED_CANON(special),
                exemplar,
                partial_index
            );
        }

        // Unspecialized or partially specialized refinement.  Check the
        // passed-in refinements on the stack for usage.
        //
        REBDSP dsp = highest_ordered_dsp;
        for (; dsp != lowest_ordered_dsp; --dsp) {
            REBVAL *ordered = DS_AT(dsp);
            if (VAL_STORED_CANON(ordered) != canon)
                continue;  // just continuing this loop

            assert(not IS_WORD_BOUND(ordered));  // we bind only one
            INIT_BINDING(ordered, varlist);
            INIT_WORD_INDEX_UNCHECKED(ordered, index);

            if (not Is_Typeset_Invisible(param))  // needs argument
                goto continue_unspecialized;

            // If refinement named on stack takes no arguments, then it can't
            // be partially specialized...only fully, and won't be bound:
            //
            //     specialize 'append/only [only: false]  ; only not bound
            //
            Init_Word(arg, VAL_STORED_CANON(ordered));
            Refinify(arg);
            SET_CELL_FLAG(arg, ARG_MARKED_CHECKED);
            goto continue_specialized;
        }

        goto continue_unspecialized;
    }

    TERM_ARRAY_LEN(varlist, num_slots);
    MISC_META_NODE(varlist) = nullptr;  // GC sees this, we must initialize

    // !!! Can't pass SERIES_FLAG_STACK_LIFETIME into Make_Array_Core(),
    // because TERM_ARRAY_LEN won't let it set stack array lengths.
    //
    if (prep & CELL_FLAG_STACK_LIFETIME)
        SET_SERIES_FLAG(varlist, STACK_LIFETIME);

    INIT_CTX_KEYLIST_SHARED(CTX(varlist), ACT_PARAMLIST(act));
    return CTX(varlist);
}
示例#4
0
//
//  Specialize_Action_Throws: C
//
// Create a new ACTION! value that uses the same implementation as another,
// but just takes fewer arguments or refinements.  It does this by storing a
// heap-based "exemplar" FRAME! in the specialized action; this stores the
// values to preload in the stack frame cells when it is invoked.
//
// The caller may provide information on the order in which refinements are
// to be specialized, using the data stack.  These refinements should be
// pushed in the *reverse* order of their invocation, so append/dup/part
// has /DUP at DS_TOP, and /PART under it.  List stops at lowest_ordered_dsp.
//
bool Specialize_Action_Throws(
    REBVAL *out,
    REBVAL *specializee,
    REBSTR *opt_specializee_name,
    REBVAL *opt_def, // !!! REVIEW: binding modified directly (not copied)
    REBDSP lowest_ordered_dsp
){
    assert(out != specializee);

    struct Reb_Binder binder;
    if (opt_def)
        INIT_BINDER(&binder);

    REBACT *unspecialized = VAL_ACTION(specializee);

    // This produces a context where partially specialized refinement slots
    // will be on the stack (including any we are adding "virtually", from
    // the current DSP down to the lowest_ordered_dsp).
    //
    REBCTX *exemplar = Make_Context_For_Action_Push_Partials(
        specializee,
        lowest_ordered_dsp,
        opt_def ? &binder : nullptr,
        CELL_MASK_NON_STACK
    );
    Manage_Array(CTX_VARLIST(exemplar)); // destined to be managed, guarded

    if (opt_def) { // code that fills the frame...fully or partially
        //
        // Bind all the SET-WORD! in the body that match params in the frame
        // into the frame.  This means `value: value` can very likely have
        // `value:` bound for assignments into the frame while `value` refers
        // to whatever value was in the context the specialization is running
        // in, but this is likely the more useful behavior.
        //
        // !!! This binds the actual arg data, not a copy of it--following
        // OBJECT!'s lead.  However, ordinary functions make a copy of the
        // body they are passed before rebinding.  Rethink.

        // See Bind_Values_Core() for explanations of how the binding works.

        Bind_Values_Inner_Loop(
            &binder,
            VAL_ARRAY_AT(opt_def),
            exemplar,
            FLAGIT_KIND(REB_SET_WORD), // types to bind (just set-word!)
            0, // types to "add midstream" to binding as we go (nothing)
            BIND_DEEP
        );

        // !!! Only one binder can be in effect, and we're calling arbitrary
        // code.  Must clean up now vs. in loop we do at the end.  :-(
        //
        RELVAL *key = CTX_KEYS_HEAD(exemplar);
        REBVAL *var = CTX_VARS_HEAD(exemplar);
        for (; NOT_END(key); ++key, ++var) {
            if (Is_Param_Unbindable(key))
                continue; // !!! is this flag still relevant?
            if (Is_Param_Hidden(key)) {
                assert(GET_CELL_FLAG(var, ARG_MARKED_CHECKED));
                continue;
            }
            if (GET_CELL_FLAG(var, ARG_MARKED_CHECKED))
                continue; // may be refinement from stack, now specialized out
            Remove_Binder_Index(&binder, VAL_KEY_CANON(key));
        }
        SHUTDOWN_BINDER(&binder);

        // Run block and ignore result (unless it is thrown)
        //
        PUSH_GC_GUARD(exemplar);
        bool threw = Do_Any_Array_At_Throws(out, opt_def, SPECIFIED);
        DROP_GC_GUARD(exemplar);

        if (threw) {
            DS_DROP_TO(lowest_ordered_dsp);
            return true;
        }
    }

    REBVAL *rootkey = CTX_ROOTKEY(exemplar);

    // Build up the paramlist for the specialized function on the stack.
    // The same walk used for that is used to link and process REB_X_PARTIAL
    // arguments for whether they become fully specialized or not.

    REBDSP dsp_paramlist = DSP;
    Move_Value(DS_PUSH(), ACT_ARCHETYPE(unspecialized));

    REBVAL *param = rootkey + 1;
    REBVAL *arg = CTX_VARS_HEAD(exemplar);

    REBDSP ordered_dsp = lowest_ordered_dsp;

    for (; NOT_END(param); ++param, ++arg) {
        if (TYPE_CHECK(param, REB_TS_REFINEMENT)) {
            if (IS_NULLED(arg)) {
                //
                // A refinement that is nulled is a candidate for usage at the
                // callsite.  Hence it must be pre-empted by our ordered
                // overrides.  -but- the overrides only apply if their slot
                // wasn't filled by the user code.  Yet these values we are
                // putting in disrupt that detection (!), so use another
                // flag (PUSH_PARTIAL) to reflect this state.
                //
                while (ordered_dsp != dsp_paramlist) {
                    ++ordered_dsp;
                    REBVAL *ordered = DS_AT(ordered_dsp);

                    if (not IS_WORD_BOUND(ordered))  // specialize 'print/asdf
                        fail (Error_Bad_Refine_Raw(ordered));

                    REBVAL *slot = CTX_VAR(exemplar, VAL_WORD_INDEX(ordered));
                    if (
                        IS_NULLED(slot) or GET_CELL_FLAG(slot, PUSH_PARTIAL)
                    ){
                        // It's still partial, so set up the pre-empt.
                        //
                        Init_Any_Word_Bound(
                            arg,
                            REB_SYM_WORD,
                            VAL_STORED_CANON(ordered),
                            exemplar,
                            VAL_WORD_INDEX(ordered)
                        );
                        SET_CELL_FLAG(arg, PUSH_PARTIAL);
                        goto unspecialized_arg;
                    }
                    // Otherwise the user filled it in, so skip to next...
                }

                goto unspecialized_arg;  // ran out...no pre-empt needed
            }

            if (GET_CELL_FLAG(arg, ARG_MARKED_CHECKED)) {
                assert(
                    IS_BLANK(arg)
                    or (
                        IS_REFINEMENT(arg)
                        and (
                            VAL_REFINEMENT_SPELLING(arg)
                            == VAL_PARAM_SPELLING(param)
                        )
                    )
                );
            }
            else
                Typecheck_Refinement_And_Canonize(param, arg);

            goto specialized_arg_no_typecheck;
        }

        switch (VAL_PARAM_CLASS(param)) {
          case REB_P_RETURN:
          case REB_P_LOCAL:
            assert(IS_NULLED(arg)); // no bindings, you can't set these
            goto unspecialized_arg;

          default:
            break;
        }

        // It's an argument, either a normal one or a refinement arg.

        if (not IS_NULLED(arg))
            goto specialized_arg_with_check;

    unspecialized_arg:

        assert(NOT_CELL_FLAG(arg, ARG_MARKED_CHECKED));
        assert(
            IS_NULLED(arg)
            or (IS_SYM_WORD(arg) and TYPE_CHECK(param, REB_TS_REFINEMENT))
        );
        Move_Value(DS_PUSH(), param);
        continue;

    specialized_arg_with_check:

        // !!! If argument was previously specialized, should have been type
        // checked already... don't type check again (?)
        //
        if (Is_Param_Variadic(param))
            fail ("Cannot currently SPECIALIZE variadic arguments.");

        if (TYPE_CHECK(param, REB_TS_DEQUOTE_REQUOTE) and IS_QUOTED(arg)) {
            //
            // Have to leave the quotes on, but still want to type check.

            if (not TYPE_CHECK(param, CELL_KIND(VAL_UNESCAPED(arg))))
                fail (arg); // !!! merge w/Error_Invalid_Arg()
        }
        else if (not TYPE_CHECK(param, VAL_TYPE(arg)))
            fail (arg); // !!! merge w/Error_Invalid_Arg()

       SET_CELL_FLAG(arg, ARG_MARKED_CHECKED);

    specialized_arg_no_typecheck:

        // Specialized-out arguments must still be in the parameter list,
        // for enumeration in the evaluator to line up with the frame values
        // of the underlying function.

        assert(GET_CELL_FLAG(arg, ARG_MARKED_CHECKED));
        Move_Value(DS_PUSH(), param);
        TYPE_SET(DS_TOP, REB_TS_HIDDEN);
        continue;
    }

    REBARR *paramlist = Pop_Stack_Values_Core(
        dsp_paramlist,
        SERIES_MASK_PARAMLIST
            | (SER(unspecialized)->header.bits & PARAMLIST_MASK_INHERIT)
    );
    Manage_Array(paramlist);
    RELVAL *rootparam = ARR_HEAD(paramlist);
    VAL_ACT_PARAMLIST_NODE(rootparam) = NOD(paramlist);

    // Everything should have balanced out for a valid specialization
    //
    while (ordered_dsp != DSP) {
        ++ordered_dsp;
        REBVAL *ordered = DS_AT(ordered_dsp);
        if (not IS_WORD_BOUND(ordered))  // specialize 'print/asdf
            fail (Error_Bad_Refine_Raw(ordered));

        REBVAL *slot = CTX_VAR(exemplar, VAL_WORD_INDEX(ordered));
        assert(not IS_NULLED(slot) and NOT_CELL_FLAG(slot, PUSH_PARTIAL));
        UNUSED(slot);
    }
    DS_DROP_TO(lowest_ordered_dsp);

    // See %sysobj.r for `specialized-meta:` object template

    REBVAL *example = Get_System(SYS_STANDARD, STD_SPECIALIZED_META);

    REBCTX *meta = Copy_Context_Shallow_Managed(VAL_CONTEXT(example));

    Init_Nulled(CTX_VAR(meta, STD_SPECIALIZED_META_DESCRIPTION)); // default
    Move_Value(
        CTX_VAR(meta, STD_SPECIALIZED_META_SPECIALIZEE),
        specializee
    );
    if (not opt_specializee_name)
        Init_Nulled(CTX_VAR(meta, STD_SPECIALIZED_META_SPECIALIZEE_NAME));
    else
        Init_Word(
            CTX_VAR(meta, STD_SPECIALIZED_META_SPECIALIZEE_NAME),
            opt_specializee_name
        );

    MISC_META_NODE(paramlist) = NOD(meta);

    REBACT *specialized = Make_Action(
        paramlist,
        &Specializer_Dispatcher,
        ACT_UNDERLYING(unspecialized), // same underlying action as this
        exemplar, // also provide a context of specialization values
        1 // details array capacity
    );
    assert(CTX_KEYLIST(exemplar) == ACT_PARAMLIST(unspecialized));

    assert(
        GET_ACTION_FLAG(specialized, IS_INVISIBLE)
        == GET_ACTION_FLAG(unspecialized, IS_INVISIBLE)
    );

    // The "body" is the FRAME! value of the specialization.  It takes on the
    // binding we want to use (which we can't put in the exemplar archetype,
    // that binding has to be UNBOUND).  It also remembers the original
    // action in the phase, so Specializer_Dispatcher() knows what to call.
    //
    RELVAL *body = ARR_HEAD(ACT_DETAILS(specialized));
    Move_Value(body, CTX_ARCHETYPE(exemplar));
    INIT_BINDING(body, VAL_BINDING(specializee));
    INIT_VAL_CONTEXT_PHASE(body, unspecialized);

    Init_Action_Unbound(out, specialized);
    return false; // code block did not throw
}