cmd/compile: permit indices of certain non-constant shifts
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>
diff --git a/src/cmd/compile/internal/gc/typecheck.go b/src/cmd/compile/internal/gc/typecheck.go
index ec4db17..5285cb2 100644
--- a/src/cmd/compile/internal/gc/typecheck.go
+++ b/src/cmd/compile/internal/gc/typecheck.go
@@ -243,21 +243,15 @@
}
// 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 @@
}
// 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
diff --git a/test/shift1.go b/test/shift1.go
index c81ee51..01ecbed 100644
--- a/test/shift1.go
+++ b/test/shift1.go
@@ -152,8 +152,7 @@
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)
