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cmd/compile: simplify if statement parsing

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Somewhat notably, this means long if statement chains are now parsed
recursively, rather than iteratively.  This shouldn't be a concern
though, as several other functions (e.g., gen, typecheck, walk)
already use recursion to process the parsed if statement Node trees.

Change-Id: Ic8c12ace9021c870d60c06f5db86a48c4ec57084
Reviewed-on: https://go-review.googlesource.com/19756
Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Matthew Dempsky 2016-02-20 00:00:53 -08:00
parent 5efbdd9d10
commit 3a11c8d319
1 changed files with 6 additions and 55 deletions
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61
src/cmd/compile/internal/gc/parser.go
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@ -1064,65 +1064,16 @@ func (p *parser) if_stmt() *Node {
stmt.Nbody = p.loop_body("if clause")
l := p.elseif_list_else() // does markdcl
n := stmt
popdcl()
for nn := l; nn != nil; nn = nn.Next {
if nn.N.Op == OIF {
popdcl()
}
n.Rlist = list1(nn.N)
n = nn.N
}
return stmt
}
func (p *parser) elseif() *NodeList {
if trace && Debug['x'] != 0 {
defer p.trace("elseif")()
}
// LELSE LIF already consumed
markdcl() // matching popdcl in if_stmt
stmt := p.if_header()
if stmt.Left == nil {
Yyerror("missing condition in if statement")
}
stmt.Nbody = p.loop_body("if clause")
return list1(stmt)
}
func (p *parser) elseif_list_else() (l *NodeList) {
if trace && Debug['x'] != 0 {
defer p.trace("elseif_list_else")()
}
for p.got(LELSE) {
if p.got(LIF) {
l = concat(l, p.elseif())
if p.got(LELSE) {
if p.tok == LIF {
stmt.Rlist = list1(p.if_stmt())
} else {
l = concat(l, p.else_())
break
stmt.Rlist = list1(p.compound_stmt(true))
}
}
return l
}
func (p *parser) else_() *NodeList {
if trace && Debug['x'] != 0 {
defer p.trace("else")()
}
l := &NodeList{N: p.compound_stmt(true)}
l.End = l
return l
popdcl()
return stmt
}
// switch_stmt parses both expression and type switch statements.