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go/parser: better error sync. if commas are missing

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R=rsc, bradfitz
CC=golang-dev
https://golang.org/cl/5756045
This commit is contained in:
Robert Griesemer 2012-03-06 11:05:16 -08:00
parent 4f25e4be02
commit 67cbe9431f
1 changed files with 18 additions and 6 deletions
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24
src/pkg/go/parser/parser.go
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@ -362,9 +362,9 @@ func (p *parser) expect(tok token.Token) token.Pos {
// expectClosing is like expect but provides a better error message
// for the common case of a missing comma before a newline.
//
func (p *parser) expectClosing(tok token.Token, construct string) token.Pos {
func (p *parser) expectClosing(tok token.Token, context string) token.Pos {
if p.tok != tok && p.tok == token.SEMICOLON && p.lit == "\n" {
p.error(p.pos, "missing ',' before newline in "+construct)
p.error(p.pos, "missing ',' before newline in "+context)
p.next()
}
return p.expect(tok)
@ -376,6 +376,18 @@ func (p *parser) expectSemi() {
}
}
func (p *parser) seesComma(context string) bool {
if p.tok == token.COMMA {
return true
}
if p.tok == token.SEMICOLON && p.lit == "\n" {
p.error(p.pos, "missing ',' before newline in "+context)
return true // "insert" the comma and continue
}
return false
}
func assert(cond bool, msg string) {
if !cond {
panic("go/parser internal error: " + msg)
@ -647,7 +659,7 @@ func (p *parser) parseVarList(isParam bool) (list []ast.Expr, typ ast.Expr) {
// accept them all for more robust parsing and complain later
for typ := p.parseVarType(isParam); typ != nil; {
list = append(list, typ)
if p.tok != token.COMMA {
if !p.seesComma("variable list") {
break
}
p.next()
@ -688,7 +700,7 @@ func (p *parser) parseParameterList(scope *ast.Scope, ellipsisOk bool) (params [
// Go spec: The scope of an identifier denoting a function
// parameter or result variable is the function body.
p.declare(field, nil, scope, ast.Var, idents...)
if p.tok != token.COMMA {
if !p.seesComma("parameter list") {
break
}
p.next()
@ -1078,7 +1090,7 @@ func (p *parser) parseCallOrConversion(fun ast.Expr) *ast.CallExpr {
ellipsis = p.pos
p.next()
}
if p.tok != token.COMMA {
if !p.seesComma("argument list") {
break
}
p.next()
@ -1118,7 +1130,7 @@ func (p *parser) parseElementList() (list []ast.Expr) {
for p.tok != token.RBRACE && p.tok != token.EOF {
list = append(list, p.parseElement(true))
if p.tok != token.COMMA {
if !p.seesComma("composite literal") {
break
}
p.next()