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go/parser: check presence of 2nd and 3rd index in 3-index slice

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Fixes #7305.

LGTM=adonovan
R=bradfitz, adonovan
CC=golang-codereviews
https://golang.org/cl/58950045
This commit is contained in:
Robert Griesemer 2014-02-11 13:40:37 -08:00
parent 85e4cb2f10
commit 13a5958db3
2 changed files with 26 additions and 5 deletions
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25
src/pkg/go/parser/parser.go
View File

@ -1168,16 +1168,19 @@ func (p *parser) parseIndexOrSlice(x ast.Expr) ast.Expr {
defer un(trace(p, "IndexOrSlice"))
}
const N = 3 // change the 3 to 2 to disable 3-index slices
lbrack := p.expect(token.LBRACK)
p.exprLev++
var index [3]ast.Expr // change the 3 to 2 to disable slice expressions w/ cap
var index [N]ast.Expr
var colons [N - 1]token.Pos
if p.tok != token.COLON {
index[0] = p.parseRhs()
}
ncolons := 0
for p.tok == token.COLON && ncolons < len(index)-1 {
p.next()
for p.tok == token.COLON && ncolons < len(colons) {
colons[ncolons] = p.pos
ncolons++
p.next()
if p.tok != token.COLON && p.tok != token.RBRACK && p.tok != token.EOF {
index[ncolons] = p.parseRhs()
}
@ -1187,7 +1190,21 @@ func (p *parser) parseIndexOrSlice(x ast.Expr) ast.Expr {
if ncolons > 0 {
// slice expression
return &ast.SliceExpr{X: x, Lbrack: lbrack, Low: index[0], High: index[1], Max: index[2], Slice3: ncolons == 2, Rbrack: rbrack}
slice3 := false
if ncolons == 2 {
slice3 = true
// Check presence of 2nd and 3rd index here rather than during type-checking
// to prevent erroneous programs from passing through gofmt (was issue 7305).
if index[1] == nil {
p.error(colons[0], "2nd index required in 3-index slice")
index[1] = &ast.BadExpr{From: colons[0] + 1, To: colons[1]}
}
if index[2] == nil {
p.error(colons[1], "3rd index required in 3-index slice")
index[2] = &ast.BadExpr{From: colons[1] + 1, To: rbrack}
}
}
return &ast.SliceExpr{X: x, Lbrack: lbrack, Low: index[0], High: index[1], Max: index[2], Slice3: slice3, Rbrack: rbrack}
}
return &ast.IndexExpr{X: x, Lbrack: lbrack, Index: index[0], Rbrack: rbrack}

6
src/pkg/go/parser/short_test.go
View File

@ -76,7 +76,11 @@ var invalids = []string{
`package p; func f() { _ = x = /* ERROR "expected '=='" */ 0 {}};`,
`package p; func f() { _ = 1 == func()int { var x bool; x = x = /* ERROR "expected '=='" */ true; return x }() };`,
`package p; func f() { var s []int; _ = s[] /* ERROR "expected operand" */ };`,
`package p; func f() { var s []int; _ = s[::: /* ERROR "expected ']'" */ ] };`,
`package p; func f() { var s []int; _ = s[i:j: /* ERROR "3rd index required" */ ] };`,
`package p; func f() { var s []int; _ = s[i: /* ERROR "2nd index required" */ :k] };`,
`package p; func f() { var s []int; _ = s[i: /* ERROR "2nd index required" */ :] };`,
`package p; func f() { var s []int; _ = s[: /* ERROR "2nd index required" */ :] };`,
`package p; func f() { var s []int; _ = s[: /* ERROR "2nd index required" */ ::] };`,
`package p; func f() { var s []int; _ = s[i:j:k: /* ERROR "expected ']'" */ l] };`,
}