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[dev.typeparams] cmd/compile/internal/types2: untyped shift counts must fit into uint

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Updates #43697.

Change-Id: If94658cb798bb0434ac3ebbf9dff504dcd59a02a
Reviewed-on: https://go-review.googlesource.com/c/go/+/283872
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
This commit is contained in:
Robert Griesemer 2021-01-14 11:50:05 -08:00
parent 67bf62d939
commit 82c3f0a358
2 changed files with 28 additions and 30 deletions
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46
src/cmd/compile/internal/types2/expr.go
View File

@ -770,14 +770,14 @@ func (check *Checker) comparison(x, y *operand, op syntax.Operator) {
}
func (check *Checker) shift(x, y *operand, e *syntax.Operation, op syntax.Operator) {
untypedx := isUntyped(x.typ)
// TODO(gri) This function seems overly complex. Revisit.
var xval constant.Value
if x.mode == constant_ {
xval = constant.ToInt(x.val)
}
if isInteger(x.typ) || untypedx && xval != nil && xval.Kind() == constant.Int {
if isInteger(x.typ) || isUntyped(x.typ) && xval != nil && xval.Kind() == constant.Int {
// The lhs is of integer type or an untyped constant representable
// as an integer. Nothing to do.
} else {
@ -789,40 +789,36 @@ func (check *Checker) shift(x, y *operand, e *syntax.Operation, op syntax.Operat
// spec: "The right operand in a shift expression must have integer type
// or be an untyped constant representable by a value of type uint."
switch {
case isInteger(y.typ):
// nothing to do
case isUntyped(y.typ):
check.convertUntyped(y, Typ[Uint])
if y.mode == invalid {
x.mode = invalid
return
}
default:
check.invalidOpf(y, "shift count %s must be integer", y)
x.mode = invalid
return
}
var yval constant.Value
// Provide a good error message for negative shift counts.
if y.mode == constant_ {
// rhs must be an integer value
// (Either it was of an integer type already, or it was
// untyped and successfully converted to a uint above.)
yval = constant.ToInt(y.val)
assert(yval.Kind() == constant.Int)
if constant.Sign(yval) < 0 {
yval := constant.ToInt(y.val) // consider -1, 1.0, but not -1.1
if yval.Kind() == constant.Int && constant.Sign(yval) < 0 {
check.invalidOpf(y, "negative shift count %s", y)
x.mode = invalid
return
}
}
// Caution: Check for isUntyped first because isInteger includes untyped
// integers (was bug #43697).
if isUntyped(y.typ) {
check.convertUntyped(y, Typ[Uint])
if y.mode == invalid {
x.mode = invalid
return
}
} else if !isInteger(y.typ) {
check.invalidOpf(y, "shift count %s must be integer", y)
x.mode = invalid
return
}
if x.mode == constant_ {
if y.mode == constant_ {
// rhs must be within reasonable bounds in constant shifts
const shiftBound = 1023 - 1 + 52 // so we can express smallestFloat64
s, ok := constant.Uint64Val(yval)
s, ok := constant.Uint64Val(y.val)
if !ok || s > shiftBound {
check.invalidOpf(y, "invalid shift count %s", y)
x.mode = invalid
@ -849,7 +845,7 @@ func (check *Checker) shift(x, y *operand, e *syntax.Operation, op syntax.Operat
}
// non-constant shift with constant lhs
if untypedx {
if isUntyped(x.typ) {
// spec: "If the left operand of a non-constant shift
// expression is an untyped constant, the type of the
// constant is what it would be if the shift expression

12
src/cmd/compile/internal/types2/testdata/shifts.src vendored
View File

@ -20,7 +20,7 @@ func shifts0() {
// This depends on the exact spec wording which is not
// done yet.
// TODO(gri) revisit and adjust when spec change is done
_ = 1<<- /* ERROR "truncated to uint" */ 1.0
_ = 1<<- /* ERROR "negative shift count" */ 1.0
_ = 1<<1075 /* ERROR "invalid shift" */
_ = 2.0<<1
_ = 1<<1.0
@ -60,11 +60,13 @@ func shifts1() {
_ uint = 1 << u
_ float32 = 1 /* ERROR "must be integer" */ << u
// for issue 14822
// issue #14822
_ = 1<<( /* ERROR "overflows uint" */ 1<<64)
_ = 1<<( /* ERROR "invalid shift count" */ 1<<64-1)
_ = 1<<( /* ERROR "invalid shift count" */ 1<<64)
_ = u<<(1<<63) // valid
_ = u<<(1<<64) // valid
// issue #43697
_ = u<<( /* ERROR "overflows uint" */ 1<<64)
_ = u<<(1<<64-1)
)
}