qbit/go
1
0
Fork 0
mirror of https://github.com/golang/go synced 2024-11-26 04:47:57 -07:00
Code Releases Activity

cmd/compile: permit indices of certain non-constant shifts

Browse Source 
Per the decision for #14844, index expressions that are non-constant
shifts where the LHS operand is representable as an int are now valid.

Fixes #21693.

Change-Id: Ifafad2c0c65975e0200ce7e28d1db210e0eacd9d
Reviewed-on: https://go-review.googlesource.com/81277
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This commit is contained in:
Robert Griesemer 2017-11-30 15:47:46 -08:00
parent aaccb3834c
commit 088a9ad543
2 changed files with 10 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
src/cmd/compile/internal/gc/typecheck.go
View File

@ -243,21 +243,15 @@ func callrecvlist(l Nodes) bool {
}
// indexlit implements typechecking of untyped values as
// array/slice indexes. It is equivalent to defaultlit
// except for constants of numerical kind, which are acceptable
// whenever they can be represented by a value of type int.
// array/slice indexes. It is almost equivalent to defaultlit
// but also accepts untyped numeric values representable as
// value of type int (see also checkmake for comparison).
// The result of indexlit MUST be assigned back to n, e.g.
// n.Left = indexlit(n.Left)
func indexlit(n *Node) *Node {
if n == nil || !n.Type.IsUntyped() {
return n
if n != nil && n.Type != nil && n.Type.Etype == TIDEAL {
return defaultlit(n, types.Types[TINT])
}
switch consttype(n) {
case CTINT, CTRUNE, CTFLT, CTCPLX:
n = defaultlit(n, types.Types[TINT])
}
n = defaultlit(n, nil)
return n
}
@ -3783,6 +3777,10 @@ func checkmake(t *types.Type, arg string, n *Node) bool {
}
// defaultlit is necessary for non-constants too: n might be 1.1<<k.
// TODO(gri) The length argument requirements for (array/slice) make
// are the same as for index expressions. Factor the code better;
// for instance, indexlit might be called here and incorporate some
// of the bounds checks done for make.
n = defaultlit(n, types.Types[TINT])
return true

3
test/shift1.go
View File

@ -152,8 +152,7 @@ func _() {
var a []int
_ = a[1<<s]
_ = a[1.]
// For now, the spec disallows these. We may revisit past Go 1.1.
_ = a[1.<<s] // ERROR "integer|shift of type float64"
_ = a[1.<<s]
_ = a[1.1<<s] // ERROR "integer|shift of type float64"
_ = make([]int, 1)