-
Notifications
You must be signed in to change notification settings - Fork 17.7k
/
swt.go
740 lines (645 loc) · 18.5 KB
/
swt.go
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
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
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
176
177
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
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
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
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package gc
import (
"cmd/compile/internal/types"
"cmd/internal/src"
"sort"
)
// typecheckswitch typechecks a switch statement.
func typecheckswitch(n *Node) {
typecheckslice(n.Ninit.Slice(), ctxStmt)
if n.Left != nil && n.Left.Op == OTYPESW {
typecheckTypeSwitch(n)
} else {
typecheckExprSwitch(n)
}
}
func typecheckTypeSwitch(n *Node) {
n.Left.Right = typecheck(n.Left.Right, ctxExpr)
t := n.Left.Right.Type
if t != nil && !t.IsInterface() {
yyerrorl(n.Pos, "cannot type switch on non-interface value %L", n.Left.Right)
t = nil
}
// We don't actually declare the type switch's guarded
// declaration itself. So if there are no cases, we won't
// notice that it went unused.
if v := n.Left.Left; v != nil && !v.isBlank() && n.List.Len() == 0 {
yyerrorl(v.Pos, "%v declared but not used", v.Sym)
}
var defCase, nilCase *Node
var ts typeSet
for _, ncase := range n.List.Slice() {
ls := ncase.List.Slice()
if len(ls) == 0 { // default:
if defCase != nil {
yyerrorl(ncase.Pos, "multiple defaults in switch (first at %v)", defCase.Line())
} else {
defCase = ncase
}
}
for i := range ls {
ls[i] = typecheck(ls[i], ctxExpr|ctxType)
n1 := ls[i]
if t == nil || n1.Type == nil {
continue
}
var missing, have *types.Field
var ptr int
switch {
case n1.isNil(): // case nil:
if nilCase != nil {
yyerrorl(ncase.Pos, "multiple nil cases in type switch (first at %v)", nilCase.Line())
} else {
nilCase = ncase
}
case n1.Op != OTYPE:
yyerrorl(ncase.Pos, "%L is not a type", n1)
case !n1.Type.IsInterface() && !implements(n1.Type, t, &missing, &have, &ptr) && !missing.Broke():
if have != nil && !have.Broke() {
yyerrorl(ncase.Pos, "impossible type switch case: %L cannot have dynamic type %v"+
" (wrong type for %v method)\n\thave %v%S\n\twant %v%S", n.Left.Right, n1.Type, missing.Sym, have.Sym, have.Type, missing.Sym, missing.Type)
} else if ptr != 0 {
yyerrorl(ncase.Pos, "impossible type switch case: %L cannot have dynamic type %v"+
" (%v method has pointer receiver)", n.Left.Right, n1.Type, missing.Sym)
} else {
yyerrorl(ncase.Pos, "impossible type switch case: %L cannot have dynamic type %v"+
" (missing %v method)", n.Left.Right, n1.Type, missing.Sym)
}
}
if n1.Op == OTYPE {
ts.add(ncase.Pos, n1.Type)
}
}
if ncase.Rlist.Len() != 0 {
// Assign the clause variable's type.
vt := t
if len(ls) == 1 {
if ls[0].Op == OTYPE {
vt = ls[0].Type
} else if ls[0].Op != OLITERAL { // TODO(mdempsky): Should be !ls[0].isNil()
// Invalid single-type case;
// mark variable as broken.
vt = nil
}
}
// TODO(mdempsky): It should be possible to
// still typecheck the case body.
if vt == nil {
continue
}
nvar := ncase.Rlist.First()
nvar.Type = vt
nvar = typecheck(nvar, ctxExpr|ctxAssign)
ncase.Rlist.SetFirst(nvar)
}
typecheckslice(ncase.Nbody.Slice(), ctxStmt)
}
}
type typeSet struct {
m map[string][]typeSetEntry
}
type typeSetEntry struct {
pos src.XPos
typ *types.Type
}
func (s *typeSet) add(pos src.XPos, typ *types.Type) {
if s.m == nil {
s.m = make(map[string][]typeSetEntry)
}
// LongString does not uniquely identify types, so we need to
// disambiguate collisions with types.Identical.
// TODO(mdempsky): Add a method that *is* unique.
ls := typ.LongString()
prevs := s.m[ls]
for _, prev := range prevs {
if types.Identical(typ, prev.typ) {
yyerrorl(pos, "duplicate case %v in type switch\n\tprevious case at %s", typ, linestr(prev.pos))
return
}
}
s.m[ls] = append(prevs, typeSetEntry{pos, typ})
}
func typecheckExprSwitch(n *Node) {
t := types.Types[TBOOL]
if n.Left != nil {
n.Left = typecheck(n.Left, ctxExpr)
n.Left = defaultlit(n.Left, nil)
t = n.Left.Type
}
var nilonly string
if t != nil {
switch {
case t.IsMap():
nilonly = "map"
case t.Etype == TFUNC:
nilonly = "func"
case t.IsSlice():
nilonly = "slice"
case !IsComparable(t):
if t.IsStruct() {
yyerrorl(n.Pos, "cannot switch on %L (struct containing %v cannot be compared)", n.Left, IncomparableField(t).Type)
} else {
yyerrorl(n.Pos, "cannot switch on %L", n.Left)
}
t = nil
}
}
var defCase *Node
var cs constSet
for _, ncase := range n.List.Slice() {
ls := ncase.List.Slice()
if len(ls) == 0 { // default:
if defCase != nil {
yyerrorl(ncase.Pos, "multiple defaults in switch (first at %v)", defCase.Line())
} else {
defCase = ncase
}
}
for i := range ls {
setlineno(ncase)
ls[i] = typecheck(ls[i], ctxExpr)
ls[i] = defaultlit(ls[i], t)
n1 := ls[i]
if t == nil || n1.Type == nil {
continue
}
switch {
case nilonly != "" && !n1.isNil():
yyerrorl(ncase.Pos, "invalid case %v in switch (can only compare %s %v to nil)", n1, nilonly, n.Left)
case t.IsInterface() && !n1.Type.IsInterface() && !IsComparable(n1.Type):
yyerrorl(ncase.Pos, "invalid case %L in switch (incomparable type)", n1)
case assignop(n1.Type, t, nil) == 0 && assignop(t, n1.Type, nil) == 0:
if n.Left != nil {
yyerrorl(ncase.Pos, "invalid case %v in switch on %v (mismatched types %v and %v)", n1, n.Left, n1.Type, t)
} else {
yyerrorl(ncase.Pos, "invalid case %v in switch (mismatched types %v and bool)", n1, n1.Type)
}
}
// Don't check for duplicate bools. Although the spec allows it,
// (1) the compiler hasn't checked it in the past, so compatibility mandates it, and
// (2) it would disallow useful things like
// case GOARCH == "arm" && GOARM == "5":
// case GOARCH == "arm":
// which would both evaluate to false for non-ARM compiles.
if !n1.Type.IsBoolean() {
cs.add(ncase.Pos, n1, "case", "switch")
}
}
typecheckslice(ncase.Nbody.Slice(), ctxStmt)
}
}
// walkswitch walks a switch statement.
func walkswitch(sw *Node) {
// Guard against double walk, see #25776.
if sw.List.Len() == 0 && sw.Nbody.Len() > 0 {
return // Was fatal, but eliminating every possible source of double-walking is hard
}
if sw.Left != nil && sw.Left.Op == OTYPESW {
walkTypeSwitch(sw)
} else {
walkExprSwitch(sw)
}
}
// walkExprSwitch generates an AST implementing sw. sw is an
// expression switch.
func walkExprSwitch(sw *Node) {
lno := setlineno(sw)
cond := sw.Left
sw.Left = nil
// convert switch {...} to switch true {...}
if cond == nil {
cond = nodbool(true)
cond = typecheck(cond, ctxExpr)
cond = defaultlit(cond, nil)
}
// Given "switch string(byteslice)",
// with all cases being side-effect free,
// use a zero-cost alias of the byte slice.
// Do this before calling walkexpr on cond,
// because walkexpr will lower the string
// conversion into a runtime call.
// See issue 24937 for more discussion.
if cond.Op == OBYTES2STR && allCaseExprsAreSideEffectFree(sw) {
cond.Op = OBYTES2STRTMP
}
cond = walkexpr(cond, &sw.Ninit)
if cond.Op != OLITERAL {
cond = copyexpr(cond, cond.Type, &sw.Nbody)
}
lineno = lno
s := exprSwitch{
exprname: cond,
}
var defaultGoto *Node
var body Nodes
for _, ncase := range sw.List.Slice() {
label := autolabel(".s")
jmp := npos(ncase.Pos, nodSym(OGOTO, nil, label))
// Process case dispatch.
if ncase.List.Len() == 0 {
if defaultGoto != nil {
Fatalf("duplicate default case not detected during typechecking")
}
defaultGoto = jmp
}
for _, n1 := range ncase.List.Slice() {
s.Add(ncase.Pos, n1, jmp)
}
// Process body.
body.Append(npos(ncase.Pos, nodSym(OLABEL, nil, label)))
body.Append(ncase.Nbody.Slice()...)
if fall, pos := hasFall(ncase.Nbody.Slice()); !fall {
br := nod(OBREAK, nil, nil)
br.Pos = pos
body.Append(br)
}
}
sw.List.Set(nil)
if defaultGoto == nil {
br := nod(OBREAK, nil, nil)
br.Pos = br.Pos.WithNotStmt()
defaultGoto = br
}
s.Emit(&sw.Nbody)
sw.Nbody.Append(defaultGoto)
sw.Nbody.AppendNodes(&body)
walkstmtlist(sw.Nbody.Slice())
}
// An exprSwitch walks an expression switch.
type exprSwitch struct {
exprname *Node // value being switched on
done Nodes
clauses []exprClause
}
type exprClause struct {
pos src.XPos
lo, hi *Node
jmp *Node
}
func (s *exprSwitch) Add(pos src.XPos, expr, jmp *Node) {
c := exprClause{pos: pos, lo: expr, hi: expr, jmp: jmp}
if okforcmp[s.exprname.Type.Etype] && expr.Op == OLITERAL {
s.clauses = append(s.clauses, c)
return
}
s.flush()
s.clauses = append(s.clauses, c)
s.flush()
}
func (s *exprSwitch) Emit(out *Nodes) {
s.flush()
out.AppendNodes(&s.done)
}
func (s *exprSwitch) flush() {
cc := s.clauses
s.clauses = nil
if len(cc) == 0 {
return
}
// Caution: If len(cc) == 1, then cc[0] might not an OLITERAL.
// The code below is structured to implicitly handle this case
// (e.g., sort.Slice doesn't need to invoke the less function
// when there's only a single slice element).
if s.exprname.Type.IsString() && len(cc) >= 2 {
// Sort strings by length and then by value. It is
// much cheaper to compare lengths than values, and
// all we need here is consistency. We respect this
// sorting below.
sort.Slice(cc, func(i, j int) bool {
si := strlit(cc[i].lo)
sj := strlit(cc[j].lo)
if len(si) != len(sj) {
return len(si) < len(sj)
}
return si < sj
})
// runLen returns the string length associated with a
// particular run of exprClauses.
runLen := func(run []exprClause) int64 { return int64(len(strlit(run[0].lo))) }
// Collapse runs of consecutive strings with the same length.
var runs [][]exprClause
start := 0
for i := 1; i < len(cc); i++ {
if runLen(cc[start:]) != runLen(cc[i:]) {
runs = append(runs, cc[start:i])
start = i
}
}
runs = append(runs, cc[start:])
// Perform two-level binary search.
nlen := nod(OLEN, s.exprname, nil)
binarySearch(len(runs), &s.done,
func(i int) *Node {
return nod(OLE, nlen, nodintconst(runLen(runs[i-1])))
},
func(i int, nif *Node) {
run := runs[i]
nif.Left = nod(OEQ, nlen, nodintconst(runLen(run)))
s.search(run, &nif.Nbody)
},
)
return
}
sort.Slice(cc, func(i, j int) bool {
return compareOp(cc[i].lo.Val(), OLT, cc[j].lo.Val())
})
// Merge consecutive integer cases.
if s.exprname.Type.IsInteger() {
merged := cc[:1]
for _, c := range cc[1:] {
last := &merged[len(merged)-1]
if last.jmp == c.jmp && last.hi.Int64()+1 == c.lo.Int64() {
last.hi = c.lo
} else {
merged = append(merged, c)
}
}
cc = merged
}
s.search(cc, &s.done)
}
func (s *exprSwitch) search(cc []exprClause, out *Nodes) {
binarySearch(len(cc), out,
func(i int) *Node {
return nod(OLE, s.exprname, cc[i-1].hi)
},
func(i int, nif *Node) {
c := &cc[i]
nif.Left = c.test(s.exprname)
nif.Nbody.Set1(c.jmp)
},
)
}
func (c *exprClause) test(exprname *Node) *Node {
// Integer range.
if c.hi != c.lo {
low := nodl(c.pos, OGE, exprname, c.lo)
high := nodl(c.pos, OLE, exprname, c.hi)
return nodl(c.pos, OANDAND, low, high)
}
// Optimize "switch true { ...}" and "switch false { ... }".
if Isconst(exprname, CTBOOL) && !c.lo.Type.IsInterface() {
if exprname.Val().U.(bool) {
return c.lo
} else {
return nodl(c.pos, ONOT, c.lo, nil)
}
}
return nodl(c.pos, OEQ, exprname, c.lo)
}
func allCaseExprsAreSideEffectFree(sw *Node) bool {
// In theory, we could be more aggressive, allowing any
// side-effect-free expressions in cases, but it's a bit
// tricky because some of that information is unavailable due
// to the introduction of temporaries during order.
// Restricting to constants is simple and probably powerful
// enough.
for _, ncase := range sw.List.Slice() {
if ncase.Op != OCASE {
Fatalf("switch string(byteslice) bad op: %v", ncase.Op)
}
for _, v := range ncase.List.Slice() {
if v.Op != OLITERAL {
return false
}
}
}
return true
}
// hasFall reports whether stmts ends with a "fallthrough" statement.
func hasFall(stmts []*Node) (bool, src.XPos) {
// Search backwards for the index of the fallthrough
// statement. Do not assume it'll be in the last
// position, since in some cases (e.g. when the statement
// list contains autotmp_ variables), one or more OVARKILL
// nodes will be at the end of the list.
i := len(stmts) - 1
for i >= 0 && stmts[i].Op == OVARKILL {
i--
}
if i < 0 {
return false, src.NoXPos
}
return stmts[i].Op == OFALL, stmts[i].Pos
}
// walkTypeSwitch generates an AST that implements sw, where sw is a
// type switch.
func walkTypeSwitch(sw *Node) {
var s typeSwitch
s.facename = sw.Left.Right
sw.Left = nil
s.facename = walkexpr(s.facename, &sw.Ninit)
s.facename = copyexpr(s.facename, s.facename.Type, &sw.Nbody)
s.okname = temp(types.Types[TBOOL])
// Get interface descriptor word.
// For empty interfaces this will be the type.
// For non-empty interfaces this will be the itab.
itab := nod(OITAB, s.facename, nil)
// For empty interfaces, do:
// if e._type == nil {
// do nil case if it exists, otherwise default
// }
// h := e._type.hash
// Use a similar strategy for non-empty interfaces.
ifNil := nod(OIF, nil, nil)
ifNil.Left = nod(OEQ, itab, nodnil())
lineno = lineno.WithNotStmt() // disable statement marks after the first check.
ifNil.Left = typecheck(ifNil.Left, ctxExpr)
ifNil.Left = defaultlit(ifNil.Left, nil)
// ifNil.Nbody assigned at end.
sw.Nbody.Append(ifNil)
// Load hash from type or itab.
dotHash := nodSym(ODOTPTR, itab, nil)
dotHash.Type = types.Types[TUINT32]
dotHash.SetTypecheck(1)
if s.facename.Type.IsEmptyInterface() {
dotHash.Xoffset = int64(2 * Widthptr) // offset of hash in runtime._type
} else {
dotHash.Xoffset = int64(2 * Widthptr) // offset of hash in runtime.itab
}
dotHash.SetBounded(true) // guaranteed not to fault
s.hashname = copyexpr(dotHash, dotHash.Type, &sw.Nbody)
br := nod(OBREAK, nil, nil)
var defaultGoto, nilGoto *Node
var body Nodes
for _, ncase := range sw.List.Slice() {
var caseVar *Node
if ncase.Rlist.Len() != 0 {
caseVar = ncase.Rlist.First()
}
// For single-type cases, we initialize the case
// variable as part of the type assertion; but in
// other cases, we initialize it in the body.
singleType := ncase.List.Len() == 1 && ncase.List.First().Op == OTYPE
label := autolabel(".s")
jmp := npos(ncase.Pos, nodSym(OGOTO, nil, label))
if ncase.List.Len() == 0 { // default:
if defaultGoto != nil {
Fatalf("duplicate default case not detected during typechecking")
}
defaultGoto = jmp
}
for _, n1 := range ncase.List.Slice() {
if n1.isNil() { // case nil:
if nilGoto != nil {
Fatalf("duplicate nil case not detected during typechecking")
}
nilGoto = jmp
continue
}
if singleType {
s.Add(n1.Type, caseVar, jmp)
} else {
s.Add(n1.Type, nil, jmp)
}
}
body.Append(npos(ncase.Pos, nodSym(OLABEL, nil, label)))
if caseVar != nil && !singleType {
l := []*Node{
nodl(ncase.Pos, ODCL, caseVar, nil),
nodl(ncase.Pos, OAS, caseVar, s.facename),
}
typecheckslice(l, ctxStmt)
body.Append(l...)
}
body.Append(ncase.Nbody.Slice()...)
body.Append(br)
}
sw.List.Set(nil)
if defaultGoto == nil {
defaultGoto = br
}
if nilGoto == nil {
nilGoto = defaultGoto
}
ifNil.Nbody.Set1(nilGoto)
s.Emit(&sw.Nbody)
sw.Nbody.Append(defaultGoto)
sw.Nbody.AppendNodes(&body)
walkstmtlist(sw.Nbody.Slice())
}
// A typeSwitch walks a type switch.
type typeSwitch struct {
// Temporary variables (i.e., ONAMEs) used by type switch dispatch logic:
facename *Node // value being type-switched on
hashname *Node // type hash of the value being type-switched on
okname *Node // boolean used for comma-ok type assertions
done Nodes
clauses []typeClause
}
type typeClause struct {
hash uint32
body Nodes
}
func (s *typeSwitch) Add(typ *types.Type, caseVar *Node, jmp *Node) {
var body Nodes
if caseVar != nil {
l := []*Node{
nod(ODCL, caseVar, nil),
nod(OAS, caseVar, nil),
}
typecheckslice(l, ctxStmt)
body.Append(l...)
} else {
caseVar = nblank
}
// cv, ok = iface.(type)
as := nod(OAS2, nil, nil)
as.List.Set2(caseVar, s.okname) // cv, ok =
dot := nod(ODOTTYPE, s.facename, nil)
dot.Type = typ // iface.(type)
as.Rlist.Set1(dot)
as = typecheck(as, ctxStmt)
as = walkexpr(as, &body)
body.Append(as)
// if ok { goto label }
nif := nod(OIF, nil, nil)
nif.Left = s.okname
nif.Nbody.Set1(jmp)
body.Append(nif)
if !typ.IsInterface() {
s.clauses = append(s.clauses, typeClause{
hash: typehash(typ),
body: body,
})
return
}
s.flush()
s.done.AppendNodes(&body)
}
func (s *typeSwitch) Emit(out *Nodes) {
s.flush()
out.AppendNodes(&s.done)
}
func (s *typeSwitch) flush() {
cc := s.clauses
s.clauses = nil
if len(cc) == 0 {
return
}
sort.Slice(cc, func(i, j int) bool { return cc[i].hash < cc[j].hash })
// Combine adjacent cases with the same hash.
merged := cc[:1]
for _, c := range cc[1:] {
last := &merged[len(merged)-1]
if last.hash == c.hash {
last.body.AppendNodes(&c.body)
} else {
merged = append(merged, c)
}
}
cc = merged
binarySearch(len(cc), &s.done,
func(i int) *Node {
return nod(OLE, s.hashname, nodintconst(int64(cc[i-1].hash)))
},
func(i int, nif *Node) {
// TODO(mdempsky): Omit hash equality check if
// there's only one type.
c := cc[i]
nif.Left = nod(OEQ, s.hashname, nodintconst(int64(c.hash)))
nif.Nbody.AppendNodes(&c.body)
},
)
}
// binarySearch constructs a binary search tree for handling n cases,
// and appends it to out. It's used for efficiently implementing
// switch statements.
//
// less(i) should return a boolean expression. If it evaluates true,
// then cases before i will be tested; otherwise, cases i and later.
//
// base(i, nif) should setup nif (an OIF node) to test case i. In
// particular, it should set nif.Left and nif.Nbody.
func binarySearch(n int, out *Nodes, less func(i int) *Node, base func(i int, nif *Node)) {
const binarySearchMin = 4 // minimum number of cases for binary search
var do func(lo, hi int, out *Nodes)
do = func(lo, hi int, out *Nodes) {
n := hi - lo
if n < binarySearchMin {
for i := lo; i < hi; i++ {
nif := nod(OIF, nil, nil)
base(i, nif)
lineno = lineno.WithNotStmt()
nif.Left = typecheck(nif.Left, ctxExpr)
nif.Left = defaultlit(nif.Left, nil)
out.Append(nif)
out = &nif.Rlist
}
return
}
half := lo + n/2
nif := nod(OIF, nil, nil)
nif.Left = less(half)
lineno = lineno.WithNotStmt()
nif.Left = typecheck(nif.Left, ctxExpr)
nif.Left = defaultlit(nif.Left, nil)
do(lo, half, &nif.Nbody)
do(half, hi, &nif.Rlist)
out.Append(nif)
}
do(0, n, out)
}