genStruct.go 20.2 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116
package gengo

import (
	"io"

	"github.com/ipld/go-ipld-prime/schema"
	"github.com/ipld/go-ipld-prime/schema/gen/go/mixins"
)

type structGenerator struct {
	AdjCfg *AdjunctCfg
	mixins.MapTraits
	PkgName string
	Type    schema.TypeStruct
}

// --- native content and specializations --->

func (g structGenerator) EmitNativeType(w io.Writer) {
	doTemplate(`
		type _{{ .Type | TypeSymbol }} struct {
			{{- range $field := .Type.Fields}}
			{{ $field | FieldSymbolLower }} _{{ $field.Type | TypeSymbol }}{{if $field.IsMaybe }}__Maybe{{end}}
			{{- end}}
		}
		type {{ .Type | TypeSymbol }} = *_{{ .Type | TypeSymbol }}
	`, w, g.AdjCfg, g)
}

func (g structGenerator) EmitNativeAccessors(w io.Writer) {
	doTemplate(`
		{{- $type := .Type -}} {{- /* ranging modifies dot, unhelpfully */ -}}
		{{- range $field := .Type.Fields }}
		func (n _{{ $type | TypeSymbol }}) Field{{ $field | FieldSymbolUpper }}()	{{ if $field.IsMaybe }}Maybe{{end}}{{ $field.Type | TypeSymbol }} {
			return &n.{{ $field | FieldSymbolLower }}
		}
		{{- end}}
	`, w, g.AdjCfg, g)
}

func (g structGenerator) EmitNativeBuilder(w io.Writer) {
	// Unclear what, if anything, goes here.
}

func (g structGenerator) EmitNativeMaybe(w io.Writer) {
	// TODO maybes need a lot of questions answered
}

// --- type info --->

func (g structGenerator) EmitTypeConst(w io.Writer) {
	doTemplate(`
		// TODO EmitTypeConst
	`, w, g.AdjCfg, g)
}

// --- TypedNode interface satisfaction --->

func (g structGenerator) EmitTypedNodeMethodType(w io.Writer) {
	doTemplate(`
		func ({{ .Type | TypeSymbol }}) Type() schema.Type {
			return nil /*TODO:typelit*/
		}
	`, w, g.AdjCfg, g)
}

func (g structGenerator) EmitTypedNodeMethodRepresentation(w io.Writer) {
	// Perhaps surprisingly, the way to get the representation node pointer
	//  does not actually depend on what the representation strategy is.
	// REVIEW: this appears to be standard even across kinds; can we extract it?
	doTemplate(`
		func (n {{ .Type | TypeSymbol }}) Representation() ipld.Node {
			return (*_{{ .Type | TypeSymbol }}__Repr)(n)
		}
	`, w, g.AdjCfg, g)
}

// --- Node interface satisfaction --->

func (g structGenerator) EmitNodeType(w io.Writer) {
	// No additional types needed.  Methods all attach to the native type.
	// We do, however, want some constants for our fields;
	//  they'll make iterators able to work faster.  So let's emit those.
	doTemplate(`
		var (
			{{- $type := .Type -}} {{- /* ranging modifies dot, unhelpfully */ -}}
			{{- range $field := .Type.Fields }}
			fieldName__{{ $type | TypeSymbol }}_{{ $field | FieldSymbolUpper }} = _String{"{{ $field.Name }}"}
			{{- end }}
		)
	`, w, g.AdjCfg, g)
}

func (g structGenerator) EmitNodeTypeAssertions(w io.Writer) {
	doTemplate(`
		var _ ipld.Node = ({{ .Type | TypeSymbol }})(&_{{ .Type | TypeSymbol }}{})
		var _ schema.TypedNode = ({{ .Type | TypeSymbol }})(&_{{ .Type | TypeSymbol }}{})
	`, w, g.AdjCfg, g)
}

func (g structGenerator) EmitNodeMethodLookupString(w io.Writer) {
	doTemplate(`
		func (n {{ .Type | TypeSymbol }}) LookupString(key string) (ipld.Node, error) {
			switch key {
			{{- range $field := .Type.Fields }}
			case "{{ $field.Name }}":
				{{- if $field.IsOptional }}
				if n.{{ $field | FieldSymbolLower }}.m == schema.Maybe_Absent {
					return ipld.Undef, nil
				}
				{{- end}}
				{{- if $field.IsNullable }}
				if n.{{ $field | FieldSymbolLower }}.m == schema.Maybe_Null {
					return ipld.Null, nil
				}
				{{- end}}
117 118
				{{- if $field.IsMaybe }}
				return {{if not (MaybeUsesPtr $field.Type) }}&{{end}}n.{{ $field | FieldSymbolLower }}.v, nil
119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134
				{{- else}}
				return &n.{{ $field | FieldSymbolLower }}, nil
				{{- end}}
			{{- end}}
			default:
				return nil, schema.ErrNoSuchField{Type: nil /*TODO*/, FieldName: key}
			}
		}
	`, w, g.AdjCfg, g)
}

func (g structGenerator) EmitNodeMethodLookup(w io.Writer) {
	doTemplate(`
		func (n {{ .Type | TypeSymbol }}) Lookup(key ipld.Node) (ipld.Node, error) {
			ks, err := key.AsString()
			if err != nil {
135
				return nil, err
136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175
			}
			return n.LookupString(ks)
		}
	`, w, g.AdjCfg, g)
}

func (g structGenerator) EmitNodeMethodMapIterator(w io.Writer) {
	// Note that the typed iterator will report absent fields.
	//  The representation iterator (if has one) however will skip those.
	doTemplate(`
		func (n {{ .Type | TypeSymbol }}) MapIterator() ipld.MapIterator {
			return &_{{ .Type | TypeSymbol }}__MapItr{n, 0}
		}

		type _{{ .Type | TypeSymbol }}__MapItr struct {
			n {{ .Type | TypeSymbol }}
			idx  int
		}

		func (itr *_{{ .Type | TypeSymbol }}__MapItr) Next() (k ipld.Node, v ipld.Node, _ error) {
			if itr.idx >= {{ len .Type.Fields }} {
				return nil, nil, ipld.ErrIteratorOverread{}
			}
			switch itr.idx {
			{{- $type := .Type -}} {{- /* ranging modifies dot, unhelpfully */ -}}
			{{- range $i, $field := .Type.Fields }}
			case {{ $i }}:
				k = &fieldName__{{ $type | TypeSymbol }}_{{ $field | FieldSymbolUpper }}
				{{- if $field.IsOptional }}
				if itr.n.{{ $field | FieldSymbolLower }}.m == schema.Maybe_Absent {
					v = ipld.Undef
					break
				}
				{{- end}}
				{{- if $field.IsNullable }}
				if itr.n.{{ $field | FieldSymbolLower }}.m == schema.Maybe_Null {
					v = ipld.Null
					break
				}
				{{- end}}
176 177
				{{- if $field.IsMaybe }}
				v = {{if not (MaybeUsesPtr $field.Type) }}&{{end}}itr.n.{{ $field | FieldSymbolLower}}.v
178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226
				{{- else}}
				v = &itr.n.{{ $field | FieldSymbolLower}}
				{{- end}}
			{{- end}}
			default:
				panic("unreachable")
			}
			itr.idx++
			return
		}
		func (itr *_{{ .Type | TypeSymbol }}__MapItr) Done() bool {
			return itr.idx >= {{ len .Type.Fields }}
		}

	`, w, g.AdjCfg, g)
}

func (g structGenerator) EmitNodeMethodLength(w io.Writer) {
	doTemplate(`
		func ({{ .Type | TypeSymbol }}) Length() int {
			return {{ len .Type.Fields }}
		}
	`, w, g.AdjCfg, g)
}

func (g structGenerator) EmitNodeMethodStyle(w io.Writer) {
	// REVIEW: this appears to be standard even across kinds; can we extract it?
	doTemplate(`
		func ({{ .Type | TypeSymbol }}) Style() ipld.NodeStyle {
			return _{{ .Type | TypeSymbol }}__Style{}
		}
	`, w, g.AdjCfg, g)
}

func (g structGenerator) EmitNodeStyleType(w io.Writer) {
	// REVIEW: this appears to be standard even across kinds; can we extract it?
	doTemplate(`
		type _{{ .Type | TypeSymbol }}__Style struct{}

		func (_{{ .Type | TypeSymbol }}__Style) NewBuilder() ipld.NodeBuilder {
			var nb _{{ .Type | TypeSymbol }}__Builder
			nb.Reset()
			return &nb
		}
	`, w, g.AdjCfg, g)
}

// --- NodeBuilder and NodeAssembler --->

227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247
func (g structGenerator) GetNodeBuilderGenerator() NodeBuilderGenerator {
	return structBuilderGenerator{
		g.AdjCfg,
		mixins.MapAssemblerTraits{
			g.PkgName,
			g.TypeName,
			"_" + g.AdjCfg.TypeSymbol(g.Type) + "__",
		},
		g.PkgName,
		g.Type,
	}
}

type structBuilderGenerator struct {
	AdjCfg *AdjunctCfg
	mixins.MapAssemblerTraits
	PkgName string
	Type    schema.TypeStruct
}

func (g structBuilderGenerator) EmitNodeBuilderType(w io.Writer) {
248 249 250 251
	doTemplate(`
		type _{{ .Type | TypeSymbol }}__Builder struct {
			_{{ .Type | TypeSymbol }}__Assembler
		}
252 253 254 255
	`, w, g.AdjCfg, g)
}
func (g structBuilderGenerator) EmitNodeBuilderMethods(w io.Writer) {
	doTemplate(`
256 257 258 259 260 261 262 263 264 265 266
		func (nb *_{{ .Type | TypeSymbol }}__Builder) Build() ipld.Node {
			if nb.state != maState_finished {
				panic("invalid state: assembler for {{ .PkgName }}.{{ .Type.Name }} must be 'finished' before Build can be called!")
			}
			return nb.w
		}
		func (nb *_{{ .Type | TypeSymbol }}__Builder) Reset() {
			var w _{{ .Type | TypeSymbol }}
			*nb = _{{ .Type | TypeSymbol }}__Builder{_{{ .Type | TypeSymbol }}__Assembler{w: &w, state: maState_initial}}
		}
	`, w, g.AdjCfg, g)
267 268 269 270 271 272 273 274 275 276 277 278 279 280 281
	// Cover up some of the assembler methods that are prepared to handle null;
	//  this saves them from having to check for a nil 'fcb'.
	//  (The MapBuilder.Finish method still has to check for nil 'fcb', though;
	//   it's far too much duplicate code to make two MapBuilder types for that.)
	doTemplate(`
		func (nb *_{{ .Type | TypeSymbol }}__Builder) AssignNull() error {
			return mixins.MapAssembler{"{{ .PkgName }}.{{ .TypeName }}"}.AssignNull()
		}
		func (nb *_{{ .Type | TypeSymbol }}__Builder) AssignNode(v ipld.Node) error {
			if nb.state != maState_initial {
				panic("misuse")
			}
			return nb.assignNode(v)
		}
	`, w, g.AdjCfg, g)
282
}
283
func (g structBuilderGenerator) EmitNodeAssemblerType(w io.Writer) {
284 285 286 287
	// - 'w' is the "**w**ip" pointer.
	// - 'state' is what it says on the tin.
	// - 's' is a bitfield for what's been **s**et.
	// - 'f' is the **f**ocused field that will be assembled next.
288 289
	// - 'z' is used to denote a null (in case we're used in a context that's acceptable).  z for **z**ilch.
	// - 'fcb' is the **f**inish **c**all**b**ack, supplied by the parent if we're a child assembler.
290 291 292 293
	doTemplate(`
		type _{{ .Type | TypeSymbol }}__Assembler struct {
			w *_{{ .Type | TypeSymbol }}
			state maState
294 295
			s int
			f int
296 297 298 299 300 301
			z bool
			fcb func() error

			{{range $field := .Type.Fields -}}
			ca_{{ $field | FieldSymbolLower }} _{{ $field.Type | TypeSymbol }}__Assembler
			{{end -}}
302
		}
303 304 305 306 307 308 309 310

		var (
			{{- $type := .Type -}} {{- /* ranging modifies dot, unhelpfully */ -}}
			{{- range $i, $field := .Type.Fields }}
			fieldBit__{{ $type | TypeSymbol }}_{{ $field | FieldSymbolUpper }} = 1 << {{ $i }}
			{{- end}}
			fieldBits__{{ $type | TypeSymbol }}_sufficient = 0 {{- range $i, $field := .Type.Fields }}{{if not $field.IsOptional }} + 1 << {{ $i }}{{end}}{{end}}
		)
311 312 313
	`, w, g.AdjCfg, g)
}
func (g structBuilderGenerator) EmitNodeAssemblerMethodBeginMap(w io.Writer) {
314 315
	// We currently disregard sizeHint.  It's not relevant to us.
	//  We could check it strictly and emit errors; presently, we don't.
316
	doTemplate(`
317
		func (na *_{{ .Type | TypeSymbol }}__Assembler) BeginMap(int) (ipld.MapAssembler, error) {
318
			return na, nil
319
		}
320 321
	`, w, g.AdjCfg, g)
}
322
func (g structBuilderGenerator) EmitNodeAssemblerMethodAssignNull(w io.Writer) {
323 324 325 326
	// All assemblers have the infrastructure and memory to potentially accept null...
	//  if used within some parent structure, the handling or the rejection of null must be supplied by the 'fcb';
	//  or if used in a NodeBuilder (where null isn't valid) this method gets overriden.
	//  We don't need a nil check for 'fcb' because all parent assemblers use it, and root builders override this method.
327 328 329 330 331 332 333 334
	//  We don't pass any args to 'fcb' because we assume it comes from something that can already see this whole struct.
	doTemplate(`
		func (na *_{{ .Type | TypeSymbol }}__Assembler) AssignNull() error {
			if na.state != maState_initial {
				panic("misuse")
			}
			na.z = true
			na.state = maState_finished
335
			return na.fcb()
336 337 338
		}
	`, w, g.AdjCfg, g)
}
339 340
func (g structBuilderGenerator) EmitNodeAssemblerMethodAssignNode(w io.Writer) {
	doTemplate(`
341
		func (na *_{{ .Type | TypeSymbol }}__Assembler) AssignNode(v ipld.Node) error {
342 343 344
			if na.state != maState_initial {
				panic("misuse")
			}
345 346 347 348 349 350
			if v.ReprKind() == ipld.ReprKind_Null {
				return na.AssignNull()
			}
			return na.assignNode(v)
		}
		func (na *_{{ .Type | TypeSymbol }}__Assembler) assignNode(v ipld.Node) error {
351 352 353
			if v2, ok := v.(*_{{ .Type | TypeSymbol }}); ok {
				*na.w = *v2
				na.state = maState_finished
354 355 356 357 358 359
				if na.fcb != nil {
					return na.fcb()
				} else {
					return nil
				}
			}
360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376
			if v.ReprKind() != ipld.ReprKind_Map {
				return ipld.ErrWrongKind{TypeName: "{{ .PkgName }}.{{ .Type.Name }}", MethodName: "AssignNode", AppropriateKind: ipld.ReprKindSet_JustMap, ActualKind: v.ReprKind()}
			}
			itr := v.MapIterator()
			for !itr.Done() {
				k, v, err := itr.Next()
				if err != nil {
					return err
				}
				if err := na.AssembleKey().AssignNode(k); err != nil {
					return err
				}
				if err := na.AssembleValue().AssignNode(v); err != nil {
					return err
				}
			}
			return na.Finish()
377 378
		}
	`, w, g.AdjCfg, g)
379 380
}
func (g structBuilderGenerator) EmitNodeAssemblerOtherBits(w io.Writer) {
381 382
	g.emitMapAssemblerMethods(w)
	g.emitKeyAssembler(w)
383 384 385 386
	for _, field := range g.Type.Fields() {
		g.emitFieldValueAssembler(field, w)
	}
}
387
func (g structBuilderGenerator) emitMapAssemblerMethods(w io.Writer) {
388
	// FUTURE: some of the setup of the child assemblers could probably be DRY'd up.
389 390 391 392 393 394 395 396 397 398 399 400 401 402
	doTemplate(`
		func (ma *_{{ .Type | TypeSymbol }}__Assembler) AssembleEntry(k string) (ipld.NodeAssembler, error) {
			if ma.state != maState_initial {
				panic("misuse")
			}
			switch k {
			{{- $type := .Type -}} {{- /* ranging modifies dot, unhelpfully */ -}}
			{{- range $i, $field := .Type.Fields }}
			case "{{ $field.Name }}":
				if ma.s & fieldBit__{{ $type | TypeSymbol }}_{{ $field | FieldSymbolUpper }} != 0 {
					return nil, ipld.ErrRepeatedMapKey{&fieldName__{{ $type | TypeSymbol }}_{{ $field | FieldSymbolUpper }}}
				}
				ma.s += fieldBit__{{ $type | TypeSymbol }}_{{ $field | FieldSymbolUpper }}
				ma.state = maState_midValue
403 404 405 406 407 408 409
				{{- if $field.IsMaybe }}
				ma.ca_{{ $field | FieldSymbolLower }}.w = {{if not (MaybeUsesPtr $field.Type) }}&{{end}}ma.w.{{ $field | FieldSymbolLower }}.v
				{{- else}}
				ma.ca_{{ $field | FieldSymbolLower }}.w = &ma.w.{{ $field | FieldSymbolLower }}
				{{- end}}
				ma.ca_{{ $field | FieldSymbolLower }}.fcb = ma.fcb_{{ $field | FieldSymbolLower }}
				return &ma.ca_{{ $field | FieldSymbolLower }}, nil
410 411
			{{- end}}
			default:
412
				return nil, ipld.ErrInvalidKey{TypeName:"{{ .PkgName }}.{{ .Type.Name }}", Key:&_String{k}}
413 414 415
			}
		}
		func (ma *_{{ .Type | TypeSymbol }}__Assembler) AssembleKey() ipld.NodeAssembler {
416 417 418 419 420
			if ma.state != maState_initial {
				panic("misuse")
			}
			ma.state = maState_midKey
			return (*_{{ .Type | TypeSymbol }}__KeyAssembler)(ma)
421 422
		}
		func (ma *_{{ .Type | TypeSymbol }}__Assembler) AssembleValue() ipld.NodeAssembler {
423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440
			if ma.state != maState_expectValue {
				panic("misuse")
			}
			ma.state = maState_midValue
			switch ma.f {
			{{- range $i, $field := .Type.Fields }}
			case {{ $i }}:
				{{- if $field.IsMaybe }}
				ma.ca_{{ $field | FieldSymbolLower }}.w = {{if not (MaybeUsesPtr $field.Type) }}&{{end}}ma.w.{{ $field | FieldSymbolLower }}.v
				{{- else}}
				ma.ca_{{ $field | FieldSymbolLower }}.w = &ma.w.{{ $field | FieldSymbolLower }}
				{{- end}}
				ma.ca_{{ $field | FieldSymbolLower }}.fcb = ma.fcb_{{ $field | FieldSymbolLower }}
				return &ma.ca_{{ $field | FieldSymbolLower }}
			{{- end}}
			default:
				panic("unreachable")
			}
441 442
		}
		func (ma *_{{ .Type | TypeSymbol }}__Assembler) Finish() error {
443 444 445
			if ma.state != maState_initial {
				panic("misuse")
			}
446
			//FIXME check if all required fields are set
447
			ma.state = maState_finished
448 449 450 451 452
			if ma.fcb != nil {
				return ma.fcb()
			} else {
				return nil
			}
453 454 455 456 457 458 459 460 461 462 463 464 465 466 467
		}
		func (ma *_{{ .Type | TypeSymbol }}__Assembler) KeyStyle() ipld.NodeStyle {
			return _String__Style{}
		}
		func (ma *_{{ .Type | TypeSymbol }}__Assembler) ValueStyle(k string) ipld.NodeStyle {
			panic("todo structbuilder mapassembler valuestyle")
		}
	`, w, g.AdjCfg, g)
}
func (g structBuilderGenerator) emitKeyAssembler(w io.Writer) {
	doTemplate(`
		type _{{ .Type | TypeSymbol }}__KeyAssembler _{{ .Type | TypeSymbol }}__Assembler
	`, w, g.AdjCfg, g)
	stubs := mixins.StringAssemblerTraits{
		g.PkgName,
468
		g.TypeName + ".KeyAssembler",
469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493
		"_" + g.AdjCfg.TypeSymbol(g.Type) + "__Key",
	}
	stubs.EmitNodeAssemblerMethodBeginMap(w)
	stubs.EmitNodeAssemblerMethodBeginList(w)
	stubs.EmitNodeAssemblerMethodAssignNull(w)
	stubs.EmitNodeAssemblerMethodAssignBool(w)
	stubs.EmitNodeAssemblerMethodAssignInt(w)
	stubs.EmitNodeAssemblerMethodAssignFloat(w)
	doTemplate(`
		func (ka *_{{ .Type | TypeSymbol }}__KeyAssembler) AssignString(k string) error {
			if ka.state != maState_midKey {
				panic("misuse")
			}
			switch k {
			{{- $type := .Type -}} {{- /* ranging modifies dot, unhelpfully */ -}}
			{{- range $i, $field := .Type.Fields }}
			case "{{ $field.Name }}":
				if ka.s & fieldBit__{{ $type | TypeSymbol }}_{{ $field | FieldSymbolUpper }} != 0 {
					return ipld.ErrRepeatedMapKey{&fieldName__{{ $type | TypeSymbol }}_{{ $field | FieldSymbolUpper }}}
				}
				ka.s += fieldBit__{{ $type | TypeSymbol }}_{{ $field | FieldSymbolUpper }}
				ka.state = maState_expectValue
				ka.f = {{ $i }}
			{{- end}}
			default:
494
				return ipld.ErrInvalidKey{TypeName:"{{ .PkgName }}.{{ .Type.Name }}", Key:&_String{k}}
495 496 497 498 499 500
			}
			return nil
		}
	`, w, g.AdjCfg, g)
	stubs.EmitNodeAssemblerMethodAssignBytes(w)
	stubs.EmitNodeAssemblerMethodAssignLink(w)
501 502 503 504 505 506 507 508
	doTemplate(`
		func (ka *_{{ .Type | TypeSymbol }}__KeyAssembler) AssignNode(v ipld.Node) error {
			if v2, err := v.AsString(); err != nil {
				return err
			} else {
				return ka.AssignString(v2)
			}
		}
509 510 511
		func (_{{ .Type | TypeSymbol }}__KeyAssembler) Style() ipld.NodeStyle {
			return _String__Style{}
		}
512
	`, w, g.AdjCfg, g)
513
}
514
func (g structBuilderGenerator) emitFieldValueAssembler(f schema.StructField, w io.Writer) {
515 516
	// TODO for Any, this should do a whole Thing;
	// TODO for any specific type, we should be able to tersely create a new type that embeds its assembler and wraps the one method that's valid for finishing its kind.
517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532

	// yes, do lets use unexported 'func()' callbacks for finishers, and thus generate WAY less types.
	// adding a word of memory to every builder?  not really.  the childbuilders would anyway for '*p' instead.  toplevels grow, true; but they frankly don't matter: 'one' doesn't show up on an asymtote.
	// is it an indirect call that can't be inlined?  yeah.  but... good lord; there's enough of them in the area already.  this one won't tip anything over.
	// one per field anyway?  probably, at least on the first pass.  easier to write; minimal consequence; can optimize size later.

	// '_MaybeT__Assembler'?  probably, yes -- the 'w' pointer has to be a different type, or things would get dumb.  ugh, every valid assign method is near-dupe but not quite.  shikata ga nai?
	// will there be '_MaybeT__ReprAssembler'?  probably, yes -- how would there not be?
	// Wild alternative: every '_T__Assembler' has a 'null bool' in addition to the 'finishCb func()'.  If used a context where null isn't valid: check it during finish.
	//  Scalar builders used as a root can do this via an overriden finisher method (literally, the AssignNull) on the Builder; easy peasy.
	//  Child assemblers can do it during the 'finishCb'.
	//  It's important to still return the possible rejection of null in the AssignNull method.
	//   But I think this shakes out: finishCb gets called at the end of *any* finisher method -- **that includes AssignNull**.
	//  If you're handling a MaybeT, the 'finishCb' can set the null state even though the '_T__Assembler' can't see the '_MaybeT.m'!
	//  Similarly: '_T__ReprAssembler' sprouts 'z bool' and 'finishCb func()' and does double duty.

533
	// Generate the finisher callbacks that we'll insert into child assemblers.
534 535 536 537 538 539 540 541 542 543 544 545 546
	//  In all cases, it's responsible for advancing the parent's state machine.
	//  If it's not a maybe:
	//   If the child assembler 'z' is true, raise error.
	//  If it's a maybe:
	//   If it's not nullable:
	//    If the child assembler 'z' is true, raise error.
	//    If the maybe uses pointer types, we copy out the pointer.
	//   If it is nullable:
	//    If the child assembler 'z' is true, set 'm' to 'Null'.
	//    If the child assembler 'z' is false:
	//     If the maybe uses pointer types, we copy out the pointer.
	//      (The pointer will not be nil.  Absent would've been on a divergent track much earlier.)
	//     (If the maybe doesn't use pointer types, the pointer is to the embed location; no action needed.)
547
	doTemplate(`
548
		func (na *_{{ .Type | TypeSymbol }}__Assembler) fcb_{{ .Field | FieldSymbolLower }}() error {
549
			{{- if .Field.IsNullable }}
550
			if na.ca_{{ .Field | FieldSymbolLower }}.z == true {
551
				na.w.{{ .Field | FieldSymbolLower }}.m = schema.Maybe_Null
552 553 554 555 556 557
			} else {
				na.w.{{ .Field | FieldSymbolLower }}.m = schema.Maybe_Value
			}
			{{- else}}
			if na.ca_{{ .Field | FieldSymbolLower }}.z == true {
				return mixins.MapAssembler{"{{ .PkgName }}.{{ .Field.Type.Name }}"}.AssignNull()
558 559
			}
			{{- end}}
560 561
			{{- if and .Field.IsOptional (not .Field.IsNullable) }}
			na.w.{{ .Field | FieldSymbolLower }}.m = schema.Maybe_Value
562
			{{- end}}
563 564
			{{- if and .Field.IsMaybe (.Field.Type | MaybeUsesPtr) }}
			na.w.{{ .Field | FieldSymbolLower }}.v = na.ca_{{ .Field | FieldSymbolLower }}.w
565
			{{- end}}
566 567 568 569 570 571 572 573 574 575 576 577 578 579 580
			na.ca_{{ .Field | FieldSymbolLower }}.w = nil
			na.state = maState_initial
			return nil
		}
	`, w, g.AdjCfg, struct {
		PkgName  string
		Type     schema.TypeStruct
		TypeName string
		Field    schema.StructField
	}{
		g.PkgName,
		g.Type,
		g.TypeName,
		f,
	})
581
}