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go/types: better position for invalid slice indices error

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This is a port of CL 363671 from types2 to go/types. Also adjust the
error message to match types2 ("invalid" vs "swapped").

Change-Id: I662a73c915814fea14bfcb1ebde0fbf39589f022
Reviewed-on: https://go-review.googlesource.com/c/go/+/364902
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Robert Findley 2021-11-17 19:45:49 -05:00
parent 72f0976ac4
commit f1cc529429
2 changed files with 17 additions and 13 deletions
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10
src/go/types/index.go
View File

@ -310,9 +310,13 @@ func (check *Checker) sliceExpr(x *operand, e *ast.SliceExpr) {
L:
for i, x := range ind[:len(ind)-1] {
if x > 0 {
for _, y := range ind[i+1:] {
if y >= 0 && x > y {
check.errorf(inNode(e, e.Rbrack), _SwappedSliceIndices, "swapped slice indices: %d > %d", x, y)
for j, y := range ind[i+1:] {
if y >= 0 && y < x {
// The value y corresponds to the expression e.Index[i+1+j].
// Because y >= 0, it must have been set from the expression
// when checking indices and thus e.Index[i+1+j] is not nil.
at := []ast.Expr{e.Low, e.High, e.Max}[i+1+j]
check.errorf(at, _SwappedSliceIndices, "invalid slice indices: %d < %d", y, x)
break L // only report one error, ok to continue
}
}

20
src/go/types/testdata/check/expr3.src vendored
View File

@ -44,9 +44,9 @@ func indexes() {
_ = a[:10:10]
_ = a[:11 /* ERROR "index .* out of bounds" */ :10]
_ = a[:10:11 /* ERROR "index .* out of bounds" */ ]
_ = a[10:0:10] /* ERROR swapped slice indices" */
_ = a[0:10:0] /* ERROR "swapped slice indices" */
_ = a[10:0:0] /* ERROR "swapped slice indices" */
_ = a[10:0 /* ERROR "invalid slice indices" */ :10]
_ = a[0:10:0 /* ERROR "invalid slice indices" */ ]
_ = a[10:0 /* ERROR "invalid slice indices" */:0]
_ = &a /* ERROR "cannot take address" */ [:10]
pa := &a
@ -62,9 +62,9 @@ func indexes() {
_ = pa[:10:10]
_ = pa[:11 /* ERROR "index .* out of bounds" */ :10]
_ = pa[:10:11 /* ERROR "index .* out of bounds" */ ]
_ = pa[10:0:10] /* ERROR "swapped slice indices" */
_ = pa[0:10:0] /* ERROR "swapped slice indices" */
_ = pa[10:0:0] /* ERROR "swapped slice indices" */
_ = pa[10:0 /* ERROR "invalid slice indices" */ :10]
_ = pa[0:10:0 /* ERROR "invalid slice indices" */ ]
_ = pa[10:0 /* ERROR "invalid slice indices" */ :0]
_ = &pa /* ERROR "cannot take address" */ [:10]
var b [0]int
@ -82,16 +82,16 @@ func indexes() {
_ = s[: - /* ERROR "negative" */ 1]
_ = s[0]
_ = s[1:2]
_ = s[2:1] /* ERROR "swapped slice indices" */
_ = s[2:1 /* ERROR "invalid slice indices" */ ]
_ = s[2:]
_ = s[: 1 /* ERROR "overflows" */ <<100]
_ = s[1 /* ERROR "overflows" */ <<100 :]
_ = s[1 /* ERROR "overflows" */ <<100 : 1 /* ERROR "overflows" */ <<100]
_ = s[: /* ERROR "2nd index required" */ : /* ERROR "3rd index required" */ ]
_ = s[:10:10]
_ = s[10:0:10] /* ERROR "swapped slice indices" */
_ = s[0:10:0] /* ERROR "swapped slice indices" */
_ = s[10:0:0] /* ERROR "swapped slice indices" */
_ = s[10:0 /* ERROR "invalid slice indices" */ :10]
_ = s[0:10:0 /* ERROR "invalid slice indices" */ ]
_ = s[10:0 /* ERROR "invalid slice indices" */ :0]
_ = &s /* ERROR "cannot take address" */ [:10]
var m map[string]int