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cmd/compile: simplify parsing of possibly absent type

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Introduce a try_ntype function which doesn't return an error upon
not finding a type. Use it instead of having separate repeated
token checks. Simpler, less code, and more efficient.

Change-Id: I81e482158b71901eb179470269349688636aa0ba
Reviewed-on: https://go-review.googlesource.com/17157
Reviewed-by: Chris Manghane <cmang@golang.org>
This commit is contained in:
Robert Griesemer 2015-11-20 17:31:33 -08:00
parent 8ab6e16cc9
commit 656a732a21
1 changed files with 34 additions and 33 deletions
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67
src/cmd/compile/internal/gc/parser.go
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@ -574,9 +574,7 @@ func (p *parser) constdcl() *NodeList {
var typ *Node
var exprs *NodeList
if p.tok != EOF && p.tok != ';' && p.tok != ')' {
if p.tok != '=' {
typ = p.ntype()
}
typ = p.try_ntype()
if p.got('=') {
exprs = p.expr_list()
}
@ -593,11 +591,9 @@ func (p *parser) typedcl() *NodeList {
name := typedcl0(p.sym())
typ := p.try_ntype()
// handle case where type is missing
var typ *Node
if p.tok != ';' {
typ = p.ntype()
} else {
if typ == nil {
p.syntax_error("in type declaration")
p.advance(';', ')')
}
@ -1754,9 +1750,8 @@ func (p *parser) dotdotdot() *Node {
}
p.want(LDDD)
switch p.tok {
case LCOMM, LFUNC, '[', LCHAN, LMAP, LSTRUCT, LINTERFACE, '*', LNAME, '@', '?', '(':
return Nod(ODDD, p.ntype(), nil)
if typ := p.try_ntype(); typ != nil {
return Nod(ODDD, typ, nil)
}
Yyerror("final argument in variadic function missing type")
@ -1769,6 +1764,22 @@ func (p *parser) ntype() *Node {
defer p.trace("ntype")()
}
if typ := p.try_ntype(); typ != nil {
return typ
}
p.syntax_error("")
p.advance()
return nil
}
// try_ntype is like ntype but it returns nil if there was no type
// instead of reporting an error.
func (p *parser) try_ntype() *Node {
if trace && Debug['x'] != 0 {
defer p.trace("try_ntype")()
}
switch p.tok {
case LCOMM:
// recvchantype
@ -1848,8 +1859,6 @@ func (p *parser) ntype() *Node {
return t
default:
p.syntax_error("")
p.advance()
return nil
}
}
@ -1859,19 +1868,13 @@ func (p *parser) chan_elem() *Node {
defer p.trace("chan_elem")()
}
switch p.tok {
case LCOMM, LFUNC,
'[', LCHAN, LMAP, LSTRUCT, LINTERFACE,
'*',
LNAME, '@', '?',
'(':
return p.ntype()
default:
p.syntax_error("missing channel element type")
// assume element type is simply absent - don't advance
return nil
if typ := p.try_ntype(); typ != nil {
return typ
}
p.syntax_error("missing channel element type")
// assume element type is simply absent - don't advance
return nil
}
// go.y:dotname (partial)
@ -2158,18 +2161,16 @@ func (p *parser) fnres() *NodeList {
defer p.trace("fnres")()
}
switch p.tok {
default:
return nil
case LCOMM, LFUNC, '[', LCHAN, LMAP, LSTRUCT, LINTERFACE, '*', LNAME, '@', '?':
result := p.ntype()
return list1(Nod(ODCLFIELD, nil, result))
case '(':
if p.tok == '(' {
result := p.param_list()
return checkarglist(result, 0)
}
if result := p.try_ntype(); result != nil {
return list1(Nod(ODCLFIELD, nil, result))
}
return nil
}
// go.y:xdcl_list