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cue/ast: add walkNilable and applyNilable helpers
To avoid the repetition of explicit nil checks.
Overall we don't save that many lines of code, but what matters
is that saving repetition reduces the chances for human mistakes,
like using different fields for the nil check and the recursing call.
Signed-off-by: Daniel Martí <mvdan@mvdan.cc>
Change-Id: Ic1aacaf86bc3a7f1d93948e1c1709334c1f2fadf
Reviewed-on: https://cue.gerrithub.io/c/cue-lang/cue/+/1227720
Reviewed-by: Roger Peppe <rogpeppe@gmail.com>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
+47
-55
+26
-28
cue/ast/astutil/apply.go
+26
-28
cue/ast/astutil/apply.go
···
317
317
return c.decls
318
318
}
319
319
320
-
func apply[N ast.Node](v applyVisitor, parent Cursor, nodePtr *N) {
320
+
type nilableNode interface {
321
+
ast.Node
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+
comparable // pointer nodes, which can be compared to nil
323
+
}
324
+
325
+
func applyIfNotNil[N nilableNode](v applyVisitor, parent Cursor, nodePtr *N) {
326
+
var zero N // nil
327
+
if *nodePtr != zero {
328
+
apply(v, parent, nodePtr)
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+
}
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+
}
331
+
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+
func apply[N nilableNode](v applyVisitor, parent Cursor, nodePtr *N) {
321
333
node := *nodePtr
334
+
var zero N // nil
335
+
if node == zero {
336
+
panic("unexpected nil node; malformed syntax tree?")
337
+
}
322
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c := newCursor(parent, node, nodePtr)
323
339
applyCursor(v, c)
324
340
if c.modified && parent != nil {
···
381
397
case *ast.Field:
382
398
beforeValue = n.Value
383
399
apply(v, c, &n.Label)
384
-
if n.Alias != nil {
385
-
apply(v, c, &n.Alias)
386
-
}
387
-
if n.Value != nil {
388
-
apply(v, c, &n.Value)
389
-
}
400
+
applyIfNotNil(v, c, &n.Alias)
401
+
applyIfNotNil(v, c, &n.Value)
390
402
applyList(v, c, n.Attrs)
391
403
392
404
case *ast.StructLit:
···
403
415
applyList(v, c, n.Elts)
404
416
405
417
case *ast.Ellipsis:
406
-
if n.Type != nil {
407
-
apply(v, c, &n.Type)
408
-
}
418
+
applyIfNotNil(v, c, &n.Type)
409
419
410
420
case *ast.ParenExpr:
411
421
apply(v, c, &n.X)
···
420
430
421
431
case *ast.SliceExpr:
422
432
apply(v, c, &n.X)
423
-
if n.Low != nil {
424
-
apply(v, c, &n.Low)
425
-
}
426
-
if n.High != nil {
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-
apply(v, c, &n.High)
428
-
}
433
+
applyIfNotNil(v, c, &n.Low)
434
+
applyIfNotNil(v, c, &n.High)
429
435
430
436
case *ast.CallExpr:
431
437
apply(v, c, &n.Fun)
···
443
449
444
450
// Declarations
445
451
case *ast.ImportSpec:
446
-
if n.Name != nil {
447
-
apply(v, c, &n.Name)
448
-
}
452
+
applyIfNotNil(v, c, &n.Name)
449
453
apply(v, c, &n.Path)
450
454
451
455
case *ast.BadDecl:
···
466
470
apply(v, c, &n.Expr)
467
471
468
472
case *ast.PostfixAlias:
469
-
if n.Label != nil {
470
-
apply(v, c, &n.Label)
471
-
}
472
-
if n.Field != nil {
473
-
apply(v, c, &n.Field)
474
-
}
473
+
applyIfNotNil(v, c, &n.Label)
474
+
applyIfNotNil(v, c, &n.Field)
475
475
476
476
case *ast.Comprehension:
477
477
applyList(v, c, n.Clauses)
···
485
485
apply(v, c, &n.Name)
486
486
487
487
case *ast.ForClause:
488
-
if n.Key != nil {
489
-
apply(v, c, &n.Key)
490
-
}
488
+
applyIfNotNil(v, c, &n.Key)
491
489
apply(v, c, &n.Value)
492
490
apply(v, c, &n.Source)
493
491
+21
-27
cue/ast/walk.go
+21
-27
cue/ast/walk.go
···
18
18
"fmt"
19
19
)
20
20
21
+
type nilableNode interface {
22
+
Node
23
+
comparable // pointer nodes, which can be compared to nil
24
+
}
25
+
26
+
func walkIfNotNil[N nilableNode](node N, before func(Node) bool, after func(Node)) {
27
+
var zero N // nil
28
+
if node != zero {
29
+
Walk(node, before, after)
30
+
}
31
+
}
32
+
21
33
func walkList[N Node](list []N, before func(Node) bool, after func(Node)) {
22
34
for _, node := range list {
23
35
Walk(node, before, after)
···
53
65
54
66
case *Field:
55
67
Walk(n.Label, before, after)
56
-
if n.Alias != nil {
57
-
Walk(n.Alias, before, after)
58
-
}
59
-
if n.Value != nil {
60
-
Walk(n.Value, before, after)
61
-
}
68
+
walkIfNotNil(n.Alias, before, after)
69
+
walkIfNotNil(n.Value, before, after)
62
70
walkList(n.Attrs, before, after)
63
71
64
72
case *Func:
···
79
87
walkList(n.Elts, before, after)
80
88
81
89
case *Ellipsis:
82
-
if n.Type != nil {
83
-
Walk(n.Type, before, after)
84
-
}
90
+
walkIfNotNil(n.Type, before, after)
85
91
86
92
case *ParenExpr:
87
93
Walk(n.X, before, after)
···
96
102
97
103
case *SliceExpr:
98
104
Walk(n.X, before, after)
99
-
if n.Low != nil {
100
-
Walk(n.Low, before, after)
101
-
}
102
-
if n.High != nil {
103
-
Walk(n.High, before, after)
104
-
}
105
+
walkIfNotNil(n.Low, before, after)
106
+
walkIfNotNil(n.High, before, after)
105
107
106
108
case *CallExpr:
107
109
Walk(n.Fun, before, after)
···
119
121
120
122
// Declarations
121
123
case *ImportSpec:
122
-
if n.Name != nil {
123
-
Walk(n.Name, before, after)
124
-
}
124
+
walkIfNotNil(n.Name, before, after)
125
125
Walk(n.Path, before, after)
126
126
127
127
case *BadDecl:
···
142
142
Walk(n.Expr, before, after)
143
143
144
144
case *PostfixAlias:
145
-
if n.Label != nil {
146
-
Walk(n.Label, before, after)
147
-
}
148
-
if n.Field != nil {
149
-
Walk(n.Field, before, after)
150
-
}
145
+
walkIfNotNil(n.Label, before, after)
146
+
walkIfNotNil(n.Field, before, after)
151
147
152
148
case *Comprehension:
153
149
walkList(n.Clauses, before, after)
···
161
157
Walk(n.Name, before, after)
162
158
163
159
case *ForClause:
164
-
if n.Key != nil {
165
-
Walk(n.Key, before, after)
166
-
}
160
+
walkIfNotNil(n.Key, before, after)
167
161
Walk(n.Value, before, after)
168
162
Walk(n.Source, before, after)
169
163