forked from golang/go
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathparser.go
More file actions
2153 lines (1849 loc) · 50.7 KB
/
parser.go
File metadata and controls
2153 lines (1849 loc) · 50.7 KB
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
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
// 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 parser implements a parser for Go source files. Input may be
// provided in a variety of forms (see the various Parse* functions); the
// output is an abstract syntax tree (AST) representing the Go source. The
// parser is invoked through one of the Parse* functions.
package parser
import (
"fmt"
"go/ast"
"go/scanner"
"go/token"
)
// The mode parameter to the Parse* functions is a set of flags (or 0).
// They control the amount of source code parsed and other optional
// parser functionality.
//
const (
PackageClauseOnly uint = 1 << iota // parsing stops after package clause
ImportsOnly // parsing stops after import declarations
ParseComments // parse comments and add them to AST
Trace // print a trace of parsed productions
DeclarationErrors // report declaration errors
)
// The parser structure holds the parser's internal state.
type parser struct {
file *token.File
scanner.ErrorVector
scanner scanner.Scanner
// Tracing/debugging
mode uint // parsing mode
trace bool // == (mode & Trace != 0)
indent uint // indentation used for tracing output
// Comments
comments []*ast.CommentGroup
leadComment *ast.CommentGroup // last lead comment
lineComment *ast.CommentGroup // last line comment
// Next token
pos token.Pos // token position
tok token.Token // one token look-ahead
lit string // token literal
// Non-syntactic parser control
exprLev int // < 0: in control clause, >= 0: in expression
// Ordinary identifier scopes
pkgScope *ast.Scope // pkgScope.Outer == nil
topScope *ast.Scope // top-most scope; may be pkgScope
unresolved []*ast.Ident // unresolved identifiers
imports []*ast.ImportSpec // list of imports
// Label scope
// (maintained by open/close LabelScope)
labelScope *ast.Scope // label scope for current function
targetStack [][]*ast.Ident // stack of unresolved labels
}
// scannerMode returns the scanner mode bits given the parser's mode bits.
func scannerMode(mode uint) uint {
var m uint = scanner.InsertSemis
if mode&ParseComments != 0 {
m |= scanner.ScanComments
}
return m
}
func (p *parser) init(fset *token.FileSet, filename string, src []byte, mode uint) {
p.file = fset.AddFile(filename, fset.Base(), len(src))
p.scanner.Init(p.file, src, p, scannerMode(mode))
p.mode = mode
p.trace = mode&Trace != 0 // for convenience (p.trace is used frequently)
p.next()
// set up the pkgScope here (as opposed to in parseFile) because
// there are other parser entry points (ParseExpr, etc.)
p.openScope()
p.pkgScope = p.topScope
// for the same reason, set up a label scope
p.openLabelScope()
}
// ----------------------------------------------------------------------------
// Scoping support
func (p *parser) openScope() {
p.topScope = ast.NewScope(p.topScope)
}
func (p *parser) closeScope() {
p.topScope = p.topScope.Outer
}
func (p *parser) openLabelScope() {
p.labelScope = ast.NewScope(p.labelScope)
p.targetStack = append(p.targetStack, nil)
}
func (p *parser) closeLabelScope() {
// resolve labels
n := len(p.targetStack) - 1
scope := p.labelScope
for _, ident := range p.targetStack[n] {
ident.Obj = scope.Lookup(ident.Name)
if ident.Obj == nil && p.mode&DeclarationErrors != 0 {
p.error(ident.Pos(), fmt.Sprintf("label %s undefined", ident.Name))
}
}
// pop label scope
p.targetStack = p.targetStack[0:n]
p.labelScope = p.labelScope.Outer
}
func (p *parser) declare(decl interface{}, scope *ast.Scope, kind ast.ObjKind, idents ...*ast.Ident) {
for _, ident := range idents {
assert(ident.Obj == nil, "identifier already declared or resolved")
if ident.Name != "_" {
obj := ast.NewObj(kind, ident.Name)
// remember the corresponding declaration for redeclaration
// errors and global variable resolution/typechecking phase
obj.Decl = decl
if alt := scope.Insert(obj); alt != nil && p.mode&DeclarationErrors != 0 {
prevDecl := ""
if pos := alt.Pos(); pos.IsValid() {
prevDecl = fmt.Sprintf("\n\tprevious declaration at %s", p.file.Position(pos))
}
p.error(ident.Pos(), fmt.Sprintf("%s redeclared in this block%s", ident.Name, prevDecl))
}
ident.Obj = obj
}
}
}
func (p *parser) shortVarDecl(idents []*ast.Ident) {
// Go spec: A short variable declaration may redeclare variables
// provided they were originally declared in the same block with
// the same type, and at least one of the non-blank variables is new.
n := 0 // number of new variables
for _, ident := range idents {
assert(ident.Obj == nil, "identifier already declared or resolved")
if ident.Name != "_" {
obj := ast.NewObj(ast.Var, ident.Name)
// short var declarations cannot have redeclaration errors
// and are not global => no need to remember the respective
// declaration
alt := p.topScope.Insert(obj)
if alt == nil {
n++ // new declaration
alt = obj
}
ident.Obj = alt
}
}
if n == 0 && p.mode&DeclarationErrors != 0 {
p.error(idents[0].Pos(), "no new variables on left side of :=")
}
}
// The unresolved object is a sentinel to mark identifiers that have been added
// to the list of unresolved identifiers. The sentinel is only used for verifying
// internal consistency.
var unresolved = new(ast.Object)
func (p *parser) resolve(x ast.Expr) {
// nothing to do if x is not an identifier or the blank identifier
ident, _ := x.(*ast.Ident)
if ident == nil {
return
}
assert(ident.Obj == nil, "identifier already declared or resolved")
if ident.Name == "_" {
return
}
// try to resolve the identifier
for s := p.topScope; s != nil; s = s.Outer {
if obj := s.Lookup(ident.Name); obj != nil {
ident.Obj = obj
return
}
}
// all local scopes are known, so any unresolved identifier
// must be found either in the file scope, package scope
// (perhaps in another file), or universe scope --- collect
// them so that they can be resolved later
ident.Obj = unresolved
p.unresolved = append(p.unresolved, ident)
}
// ----------------------------------------------------------------------------
// Parsing support
func (p *parser) printTrace(a ...interface{}) {
const dots = ". . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " +
". . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . "
const n = uint(len(dots))
pos := p.file.Position(p.pos)
fmt.Printf("%5d:%3d: ", pos.Line, pos.Column)
i := 2 * p.indent
for ; i > n; i -= n {
fmt.Print(dots)
}
fmt.Print(dots[0:i])
fmt.Println(a...)
}
func trace(p *parser, msg string) *parser {
p.printTrace(msg, "(")
p.indent++
return p
}
// Usage pattern: defer un(trace(p, "..."));
func un(p *parser) {
p.indent--
p.printTrace(")")
}
// Advance to the next token.
func (p *parser) next0() {
// Because of one-token look-ahead, print the previous token
// when tracing as it provides a more readable output. The
// very first token (!p.pos.IsValid()) is not initialized
// (it is token.ILLEGAL), so don't print it .
if p.trace && p.pos.IsValid() {
s := p.tok.String()
switch {
case p.tok.IsLiteral():
p.printTrace(s, p.lit)
case p.tok.IsOperator(), p.tok.IsKeyword():
p.printTrace("\"" + s + "\"")
default:
p.printTrace(s)
}
}
p.pos, p.tok, p.lit = p.scanner.Scan()
}
// Consume a comment and return it and the line on which it ends.
func (p *parser) consumeComment() (comment *ast.Comment, endline int) {
// /*-style comments may end on a different line than where they start.
// Scan the comment for '\n' chars and adjust endline accordingly.
endline = p.file.Line(p.pos)
if p.lit[1] == '*' {
// don't use range here - no need to decode Unicode code points
for i := 0; i < len(p.lit); i++ {
if p.lit[i] == '\n' {
endline++
}
}
}
comment = &ast.Comment{p.pos, p.lit}
p.next0()
return
}
// Consume a group of adjacent comments, add it to the parser's
// comments list, and return it together with the line at which
// the last comment in the group ends. An empty line or non-comment
// token terminates a comment group.
//
func (p *parser) consumeCommentGroup() (comments *ast.CommentGroup, endline int) {
var list []*ast.Comment
endline = p.file.Line(p.pos)
for p.tok == token.COMMENT && endline+1 >= p.file.Line(p.pos) {
var comment *ast.Comment
comment, endline = p.consumeComment()
list = append(list, comment)
}
// add comment group to the comments list
comments = &ast.CommentGroup{list}
p.comments = append(p.comments, comments)
return
}
// Advance to the next non-comment token. In the process, collect
// any comment groups encountered, and remember the last lead and
// line comments.
//
// A lead comment is a comment group that starts and ends in a
// line without any other tokens and that is followed by a non-comment
// token on the line immediately after the comment group.
//
// A line comment is a comment group that follows a non-comment
// token on the same line, and that has no tokens after it on the line
// where it ends.
//
// Lead and line comments may be considered documentation that is
// stored in the AST.
//
func (p *parser) next() {
p.leadComment = nil
p.lineComment = nil
line := p.file.Line(p.pos) // current line
p.next0()
if p.tok == token.COMMENT {
var comment *ast.CommentGroup
var endline int
if p.file.Line(p.pos) == line {
// The comment is on same line as the previous token; it
// cannot be a lead comment but may be a line comment.
comment, endline = p.consumeCommentGroup()
if p.file.Line(p.pos) != endline {
// The next token is on a different line, thus
// the last comment group is a line comment.
p.lineComment = comment
}
}
// consume successor comments, if any
endline = -1
for p.tok == token.COMMENT {
comment, endline = p.consumeCommentGroup()
}
if endline+1 == p.file.Line(p.pos) {
// The next token is following on the line immediately after the
// comment group, thus the last comment group is a lead comment.
p.leadComment = comment
}
}
}
func (p *parser) error(pos token.Pos, msg string) {
p.Error(p.file.Position(pos), msg)
}
func (p *parser) errorExpected(pos token.Pos, msg string) {
msg = "expected " + msg
if pos == p.pos {
// the error happened at the current position;
// make the error message more specific
if p.tok == token.SEMICOLON && p.lit[0] == '\n' {
msg += ", found newline"
} else {
msg += ", found '" + p.tok.String() + "'"
if p.tok.IsLiteral() {
msg += " " + p.lit
}
}
}
p.error(pos, msg)
}
func (p *parser) expect(tok token.Token) token.Pos {
pos := p.pos
if p.tok != tok {
p.errorExpected(pos, "'"+tok.String()+"'")
}
p.next() // make progress
return pos
}
func (p *parser) expectSemi() {
if p.tok != token.RPAREN && p.tok != token.RBRACE {
p.expect(token.SEMICOLON)
}
}
func assert(cond bool, msg string) {
if !cond {
panic("go/parser internal error: " + msg)
}
}
// ----------------------------------------------------------------------------
// Identifiers
func (p *parser) parseIdent() *ast.Ident {
pos := p.pos
name := "_"
if p.tok == token.IDENT {
name = p.lit
p.next()
} else {
p.expect(token.IDENT) // use expect() error handling
}
return &ast.Ident{pos, name, nil}
}
func (p *parser) parseIdentList() (list []*ast.Ident) {
if p.trace {
defer un(trace(p, "IdentList"))
}
list = append(list, p.parseIdent())
for p.tok == token.COMMA {
p.next()
list = append(list, p.parseIdent())
}
return
}
// ----------------------------------------------------------------------------
// Common productions
// If lhs is set, result list elements which are identifiers are not resolved.
func (p *parser) parseExprList(lhs bool) (list []ast.Expr) {
if p.trace {
defer un(trace(p, "ExpressionList"))
}
list = append(list, p.parseExpr(lhs))
for p.tok == token.COMMA {
p.next()
list = append(list, p.parseExpr(lhs))
}
return
}
func (p *parser) parseLhsList() []ast.Expr {
list := p.parseExprList(true)
switch p.tok {
case token.DEFINE:
// lhs of a short variable declaration
p.shortVarDecl(p.makeIdentList(list))
case token.COLON:
// lhs of a label declaration or a communication clause of a select
// statement (parseLhsList is not called when parsing the case clause
// of a switch statement):
// - labels are declared by the caller of parseLhsList
// - for communication clauses, if there is a stand-alone identifier
// followed by a colon, we have a syntax error; there is no need
// to resolve the identifier in that case
default:
// identifiers must be declared elsewhere
for _, x := range list {
p.resolve(x)
}
}
return list
}
func (p *parser) parseRhsList() []ast.Expr {
return p.parseExprList(false)
}
// ----------------------------------------------------------------------------
// Types
func (p *parser) parseType() ast.Expr {
if p.trace {
defer un(trace(p, "Type"))
}
typ := p.tryType()
if typ == nil {
pos := p.pos
p.errorExpected(pos, "type")
p.next() // make progress
return &ast.BadExpr{pos, p.pos}
}
return typ
}
// If the result is an identifier, it is not resolved.
func (p *parser) parseTypeName() ast.Expr {
if p.trace {
defer un(trace(p, "TypeName"))
}
ident := p.parseIdent()
// don't resolve ident yet - it may be a parameter or field name
if p.tok == token.PERIOD {
// ident is a package name
p.next()
p.resolve(ident)
sel := p.parseIdent()
return &ast.SelectorExpr{ident, sel}
}
return ident
}
func (p *parser) parseArrayType(ellipsisOk bool) ast.Expr {
if p.trace {
defer un(trace(p, "ArrayType"))
}
lbrack := p.expect(token.LBRACK)
var len ast.Expr
if ellipsisOk && p.tok == token.ELLIPSIS {
len = &ast.Ellipsis{p.pos, nil}
p.next()
} else if p.tok != token.RBRACK {
len = p.parseRhs()
}
p.expect(token.RBRACK)
elt := p.parseType()
return &ast.ArrayType{lbrack, len, elt}
}
func (p *parser) makeIdentList(list []ast.Expr) []*ast.Ident {
idents := make([]*ast.Ident, len(list))
for i, x := range list {
ident, isIdent := x.(*ast.Ident)
if !isIdent {
pos := x.(ast.Expr).Pos()
p.errorExpected(pos, "identifier")
ident = &ast.Ident{pos, "_", nil}
}
idents[i] = ident
}
return idents
}
func (p *parser) parseFieldDecl(scope *ast.Scope) *ast.Field {
if p.trace {
defer un(trace(p, "FieldDecl"))
}
doc := p.leadComment
// fields
list, typ := p.parseVarList(false)
// optional tag
var tag *ast.BasicLit
if p.tok == token.STRING {
tag = &ast.BasicLit{p.pos, p.tok, p.lit}
p.next()
}
// analyze case
var idents []*ast.Ident
if typ != nil {
// IdentifierList Type
idents = p.makeIdentList(list)
} else {
// ["*"] TypeName (AnonymousField)
typ = list[0] // we always have at least one element
p.resolve(typ)
if n := len(list); n > 1 || !isTypeName(deref(typ)) {
pos := typ.Pos()
p.errorExpected(pos, "anonymous field")
typ = &ast.BadExpr{pos, list[n-1].End()}
}
}
p.expectSemi() // call before accessing p.linecomment
field := &ast.Field{doc, idents, typ, tag, p.lineComment}
p.declare(field, scope, ast.Var, idents...)
return field
}
func (p *parser) parseStructType() *ast.StructType {
if p.trace {
defer un(trace(p, "StructType"))
}
pos := p.expect(token.STRUCT)
lbrace := p.expect(token.LBRACE)
scope := ast.NewScope(nil) // struct scope
var list []*ast.Field
for p.tok == token.IDENT || p.tok == token.MUL || p.tok == token.LPAREN {
// a field declaration cannot start with a '(' but we accept
// it here for more robust parsing and better error messages
// (parseFieldDecl will check and complain if necessary)
list = append(list, p.parseFieldDecl(scope))
}
rbrace := p.expect(token.RBRACE)
// TODO(gri): store struct scope in AST
return &ast.StructType{pos, &ast.FieldList{lbrace, list, rbrace}, false}
}
func (p *parser) parsePointerType() *ast.StarExpr {
if p.trace {
defer un(trace(p, "PointerType"))
}
star := p.expect(token.MUL)
base := p.parseType()
return &ast.StarExpr{star, base}
}
func (p *parser) tryVarType(isParam bool) ast.Expr {
if isParam && p.tok == token.ELLIPSIS {
pos := p.pos
p.next()
typ := p.tryIdentOrType(isParam) // don't use parseType so we can provide better error message
if typ == nil {
p.error(pos, "'...' parameter is missing type")
typ = &ast.BadExpr{pos, p.pos}
}
if p.tok != token.RPAREN {
p.error(pos, "can use '...' with last parameter type only")
}
return &ast.Ellipsis{pos, typ}
}
return p.tryIdentOrType(false)
}
func (p *parser) parseVarType(isParam bool) ast.Expr {
typ := p.tryVarType(isParam)
if typ == nil {
pos := p.pos
p.errorExpected(pos, "type")
p.next() // make progress
typ = &ast.BadExpr{pos, p.pos}
}
return typ
}
func (p *parser) parseVarList(isParam bool) (list []ast.Expr, typ ast.Expr) {
if p.trace {
defer un(trace(p, "VarList"))
}
// a list of identifiers looks like a list of type names
for {
// parseVarType accepts any type (including parenthesized ones)
// even though the syntax does not permit them here: we
// accept them all for more robust parsing and complain
// afterwards
list = append(list, p.parseVarType(isParam))
if p.tok != token.COMMA {
break
}
p.next()
}
// if we had a list of identifiers, it must be followed by a type
typ = p.tryVarType(isParam)
if typ != nil {
p.resolve(typ)
}
return
}
func (p *parser) parseParameterList(scope *ast.Scope, ellipsisOk bool) (params []*ast.Field) {
if p.trace {
defer un(trace(p, "ParameterList"))
}
list, typ := p.parseVarList(ellipsisOk)
if typ != nil {
// IdentifierList Type
idents := p.makeIdentList(list)
field := &ast.Field{nil, idents, typ, nil, nil}
params = append(params, field)
// Go spec: The scope of an identifier denoting a function
// parameter or result variable is the function body.
p.declare(field, scope, ast.Var, idents...)
if p.tok == token.COMMA {
p.next()
}
for p.tok != token.RPAREN && p.tok != token.EOF {
idents := p.parseIdentList()
typ := p.parseVarType(ellipsisOk)
field := &ast.Field{nil, idents, typ, nil, nil}
params = append(params, field)
// Go spec: The scope of an identifier denoting a function
// parameter or result variable is the function body.
p.declare(field, scope, ast.Var, idents...)
if p.tok != token.COMMA {
break
}
p.next()
}
} else {
// Type { "," Type } (anonymous parameters)
params = make([]*ast.Field, len(list))
for i, x := range list {
p.resolve(x)
params[i] = &ast.Field{Type: x}
}
}
return
}
func (p *parser) parseParameters(scope *ast.Scope, ellipsisOk bool) *ast.FieldList {
if p.trace {
defer un(trace(p, "Parameters"))
}
var params []*ast.Field
lparen := p.expect(token.LPAREN)
if p.tok != token.RPAREN {
params = p.parseParameterList(scope, ellipsisOk)
}
rparen := p.expect(token.RPAREN)
return &ast.FieldList{lparen, params, rparen}
}
func (p *parser) parseResult(scope *ast.Scope) *ast.FieldList {
if p.trace {
defer un(trace(p, "Result"))
}
if p.tok == token.LPAREN {
return p.parseParameters(scope, false)
}
typ := p.tryType()
if typ != nil {
list := make([]*ast.Field, 1)
list[0] = &ast.Field{Type: typ}
return &ast.FieldList{List: list}
}
return nil
}
func (p *parser) parseSignature(scope *ast.Scope) (params, results *ast.FieldList) {
if p.trace {
defer un(trace(p, "Signature"))
}
params = p.parseParameters(scope, true)
results = p.parseResult(scope)
return
}
func (p *parser) parseFuncType() (*ast.FuncType, *ast.Scope) {
if p.trace {
defer un(trace(p, "FuncType"))
}
pos := p.expect(token.FUNC)
scope := ast.NewScope(p.topScope) // function scope
params, results := p.parseSignature(scope)
return &ast.FuncType{pos, params, results}, scope
}
func (p *parser) parseMethodSpec(scope *ast.Scope) *ast.Field {
if p.trace {
defer un(trace(p, "MethodSpec"))
}
doc := p.leadComment
var idents []*ast.Ident
var typ ast.Expr
x := p.parseTypeName()
if ident, isIdent := x.(*ast.Ident); isIdent && p.tok == token.LPAREN {
// method
idents = []*ast.Ident{ident}
scope := ast.NewScope(nil) // method scope
params, results := p.parseSignature(scope)
typ = &ast.FuncType{token.NoPos, params, results}
} else {
// embedded interface
typ = x
}
p.expectSemi() // call before accessing p.linecomment
spec := &ast.Field{doc, idents, typ, nil, p.lineComment}
p.declare(spec, scope, ast.Fun, idents...)
return spec
}
func (p *parser) parseInterfaceType() *ast.InterfaceType {
if p.trace {
defer un(trace(p, "InterfaceType"))
}
pos := p.expect(token.INTERFACE)
lbrace := p.expect(token.LBRACE)
scope := ast.NewScope(nil) // interface scope
var list []*ast.Field
for p.tok == token.IDENT {
list = append(list, p.parseMethodSpec(scope))
}
rbrace := p.expect(token.RBRACE)
// TODO(gri): store interface scope in AST
return &ast.InterfaceType{pos, &ast.FieldList{lbrace, list, rbrace}, false}
}
func (p *parser) parseMapType() *ast.MapType {
if p.trace {
defer un(trace(p, "MapType"))
}
pos := p.expect(token.MAP)
p.expect(token.LBRACK)
key := p.parseType()
p.expect(token.RBRACK)
value := p.parseType()
return &ast.MapType{pos, key, value}
}
func (p *parser) parseChanType() *ast.ChanType {
if p.trace {
defer un(trace(p, "ChanType"))
}
pos := p.pos
dir := ast.SEND | ast.RECV
if p.tok == token.CHAN {
p.next()
if p.tok == token.ARROW {
p.next()
dir = ast.SEND
}
} else {
p.expect(token.ARROW)
p.expect(token.CHAN)
dir = ast.RECV
}
value := p.parseType()
return &ast.ChanType{pos, dir, value}
}
// If the result is an identifier, it is not resolved.
func (p *parser) tryIdentOrType(ellipsisOk bool) ast.Expr {
switch p.tok {
case token.IDENT:
return p.parseTypeName()
case token.LBRACK:
return p.parseArrayType(ellipsisOk)
case token.STRUCT:
return p.parseStructType()
case token.MUL:
return p.parsePointerType()
case token.FUNC:
typ, _ := p.parseFuncType()
return typ
case token.INTERFACE:
return p.parseInterfaceType()
case token.MAP:
return p.parseMapType()
case token.CHAN, token.ARROW:
return p.parseChanType()
case token.LPAREN:
lparen := p.pos
p.next()
typ := p.parseType()
rparen := p.expect(token.RPAREN)
return &ast.ParenExpr{lparen, typ, rparen}
}
// no type found
return nil
}
func (p *parser) tryType() ast.Expr {
typ := p.tryIdentOrType(false)
if typ != nil {
p.resolve(typ)
}
return typ
}
// ----------------------------------------------------------------------------
// Blocks
func (p *parser) parseStmtList() (list []ast.Stmt) {
if p.trace {
defer un(trace(p, "StatementList"))
}
for p.tok != token.CASE && p.tok != token.DEFAULT && p.tok != token.RBRACE && p.tok != token.EOF {
list = append(list, p.parseStmt())
}
return
}
func (p *parser) parseBody(scope *ast.Scope) *ast.BlockStmt {
if p.trace {
defer un(trace(p, "Body"))
}
lbrace := p.expect(token.LBRACE)
p.topScope = scope // open function scope
p.openLabelScope()
list := p.parseStmtList()
p.closeLabelScope()
p.closeScope()
rbrace := p.expect(token.RBRACE)
return &ast.BlockStmt{lbrace, list, rbrace}
}
func (p *parser) parseBlockStmt() *ast.BlockStmt {
if p.trace {
defer un(trace(p, "BlockStmt"))
}
lbrace := p.expect(token.LBRACE)
p.openScope()
list := p.parseStmtList()
p.closeScope()
rbrace := p.expect(token.RBRACE)
return &ast.BlockStmt{lbrace, list, rbrace}
}
// ----------------------------------------------------------------------------
// Expressions
func (p *parser) parseFuncTypeOrLit() ast.Expr {
if p.trace {
defer un(trace(p, "FuncTypeOrLit"))
}
typ, scope := p.parseFuncType()
if p.tok != token.LBRACE {
// function type only
return typ
}
p.exprLev++
body := p.parseBody(scope)
p.exprLev--
return &ast.FuncLit{typ, body}
}
// parseOperand may return an expression or a raw type (incl. array
// types of the form [...]T. Callers must verify the result.
// If lhs is set and the result is an identifier, it is not resolved.
//
func (p *parser) parseOperand(lhs bool) ast.Expr {
if p.trace {
defer un(trace(p, "Operand"))
}
switch p.tok {
case token.IDENT:
x := p.parseIdent()
if !lhs {
p.resolve(x)
}
return x
case token.INT, token.FLOAT, token.IMAG, token.CHAR, token.STRING:
x := &ast.BasicLit{p.pos, p.tok, p.lit}
p.next()
return x
case token.LPAREN:
lparen := p.pos
p.next()
p.exprLev++
x := p.parseRhs()
p.exprLev--
rparen := p.expect(token.RPAREN)
return &ast.ParenExpr{lparen, x, rparen}
case token.FUNC:
return p.parseFuncTypeOrLit()
default:
if typ := p.tryIdentOrType(true); typ != nil {
// could be type for composite literal or conversion
_, isIdent := typ.(*ast.Ident)
assert(!isIdent, "type cannot be identifier")
return typ
}
}
pos := p.pos
p.errorExpected(pos, "operand")
p.next() // make progress
return &ast.BadExpr{pos, p.pos}
}
func (p *parser) parseSelector(x ast.Expr) ast.Expr {
if p.trace {
defer un(trace(p, "Selector"))
}