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cmd/compile/internal/syntax: correct follow token for type parameter lists 

When parsing a type parameter declaration, parts of the code still
expected a ) as closing token. Use the correct follow token ) or ]
depending on parameter list kind.

Also, consistently use tokstring (not tok.String()) for user-facing
(error) messages.

Follow-up on comment in CL 348730.

For #43527.

Change-Id: Ib1d4feb526771a1668a54c3bb7a671f6c8a65940
Reviewed-on: https://go-review.googlesource.com/c/go/+/348742
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
This commit is contained in:
Robert Griesemer 2021-09-09 15:43:19 -07:00
parent 96ab854ab0
commit da1aa65053
2 changed files with 10 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
src/cmd/compile/internal/syntax/parser.go
View File

@ -276,7 +276,9 @@ func (p *parser) syntaxErrorAt(pos Pos, msg string) {
} }
// tokstring returns the English word for selected punctuation tokens // tokstring returns the English word for selected punctuation tokens
// for more readable error messages. // for more readable error messages. Use tokstring (not tok.String())
// for user-facing (error) messages; use tok.String() for debugging
// output.
func tokstring(tok token) string { func tokstring(tok token) string {
switch tok { switch tok {
case _Comma: case _Comma:
@ -1839,7 +1841,7 @@ func (p *parser) embeddedTerm() Expr {
} }
// ParameterDecl = [ IdentifierList ] [ "..." ] Type . // ParameterDecl = [ IdentifierList ] [ "..." ] Type .
func (p *parser) paramDeclOrNil(name *Name) *Field { func (p *parser) paramDeclOrNil(name *Name, follow token) *Field {
if trace { if trace {
defer p.trace("paramDecl")() defer p.trace("paramDecl")()
} }
@ -1893,8 +1895,8 @@ func (p *parser) paramDeclOrNil(name *Name) *Field {
return f return f
} }
p.syntaxError("expecting )") p.syntaxError("expecting " + tokstring(follow))
p.advance(_Comma, _Rparen) p.advance(_Comma, follow)
return nil return nil
} }
@ -1911,7 +1913,7 @@ func (p *parser) paramList(name *Name, close token, requireNames bool) (list []*
var named int // number of parameters that have an explicit name and type var named int // number of parameters that have an explicit name and type
var typed int // number of parameters that have an explicit type var typed int // number of parameters that have an explicit type
end := p.list(_Comma, close, func() bool { end := p.list(_Comma, close, func() bool {
par := p.paramDeclOrNil(name) par := p.paramDeclOrNil(name, close)
name = nil // 1st name was consumed if present name = nil // 1st name was consumed if present
if par != nil { if par != nil {
if debug && par.Name == nil && par.Type == nil { if debug && par.Name == nil && par.Type == nil {
@ -2211,7 +2213,7 @@ func (p *parser) header(keyword token) (init SimpleStmt, cond Expr, post SimpleS
if p.tok != _Semi { if p.tok != _Semi {
// accept potential varDecl but complain // accept potential varDecl but complain
if p.got(_Var) { if p.got(_Var) {
p.syntaxError(fmt.Sprintf("var declaration not allowed in %s initializer", keyword.String())) p.syntaxError(fmt.Sprintf("var declaration not allowed in %s initializer", tokstring(keyword)))
} }
init = p.simpleStmt(nil, keyword) init = p.simpleStmt(nil, keyword)
// If we have a range clause, we are done (can only happen for keyword == _For). // If we have a range clause, we are done (can only happen for keyword == _For).

2
src/cmd/compile/internal/syntax/testdata/tparams.go2 vendored
View File

@ -20,3 +20,5 @@ type t interface {
func f[ /* ERROR empty type parameter list */ ]() func f[ /* ERROR empty type parameter list */ ]()
func f[a, b /* ERROR missing type constraint */ ]() func f[a, b /* ERROR missing type constraint */ ]()
func f[a t, b t, c /* ERROR missing type constraint */ ]() func f[a t, b t, c /* ERROR missing type constraint */ ]()
func f[a b, /* ERROR expecting ] */ 0] ()