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go/types: preserve untyped constants on the RHS of a shift expression

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CL 291316 fixed go/types to verify that untyped shift counts are
representable by uint, but as a side effect also converted their types
to uint.

Rearrange the logic to keep the check for representability, but not
actually convert untyped integer constants. Untyped non-integer
constants are still converted, to preserve the behavior of 1.16. This
behavior for non-integer types is a bug, filed as #47410.

Updates #47410
Fixes #47243

Change-Id: I5eab4aab35b97f932fccdee2d4a18623ee2ccad5
Reviewed-on: https://go-review.googlesource.com/c/go/+/337529
Trust: Robert Findley <rfindley@google.com>
Trust: Robert Griesemer <gri@golang.org>
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:
Rob Findley 2021-07-26 16:33:44 -04:00 committed by Robert Findley
parent 840e583ff3
commit 33ff155970
3 changed files with 44 additions and 9 deletions
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12
src/go/types/api_test.go
View file

@ -322,6 +322,18 @@ func TestTypesInfo(t *testing.T) {
`[][]struct{}`,
},
// issue 47243
{`package issue47243_a; var x int32; var _ = x << 3`, `3`, `untyped int`},
{`package issue47243_b; var x int32; var _ = x << 3.`, `3.`, `uint`}, // issue 47410: should be untyped float
{`package issue47243_c; var x int32; var _ = 1 << x`, `1 << x`, `int`},
{`package issue47243_d; var x int32; var _ = 1 << x`, `1`, `int`},
{`package issue47243_e; var x int32; var _ = 1 << 2`, `1`, `untyped int`},
{`package issue47243_f; var x int32; var _ = 1 << 2`, `2`, `untyped int`},
{`package issue47243_g; var x int32; var _ = int(1) << 2`, `2`, `untyped int`},
{`package issue47243_h; var x int32; var _ = 1 << (2 << x)`, `1`, `int`},
{`package issue47243_i; var x int32; var _ = 1 << (2 << x)`, `(2 << x)`, `untyped int`},
{`package issue47243_j; var x int32; var _ = 1 << (2 << x)`, `2`, `untyped int`},
// tests for broken code that doesn't parse or type-check
{broken + `x0; func _() { var x struct {f string}; x.f := 0 }`, `x.f`, `string`},
{broken + `x1; func _() { var z string; type x struct {f string}; y := &x{q: z}}`, `z`, `string`},

7
src/go/types/check_test.go
View file

@ -344,6 +344,13 @@ func TestIssue46453(t *testing.T) {
checkFiles(t, nil, "", []string{"issue46453.go"}, [][]byte{[]byte(src)}, false, nil)
}
func TestIssue47243_TypedRHS(t *testing.T) {
// The RHS of the shift expression below overflows uint on 32bit platforms,
// but this is OK as it is explicitly typed.
const src = "package issue47243\n\nvar a uint64; var _ = a << uint64(4294967296)" // uint64(1<<32)
checkFiles(t, &StdSizes{4, 4}, "", []string{"p.go"}, [][]byte{[]byte(src)}, false, nil)
}
func TestCheck(t *testing.T) { DefPredeclaredTestFuncs(); testDir(t, "check") }
func TestExamples(t *testing.T) { testDir(t, "examples") }
func TestFixedbugs(t *testing.T) { testDir(t, "fixedbugs") }

34
src/go/types/expr.go
View file

@ -778,32 +778,48 @@ func (check *Checker) shift(x, y *operand, e ast.Expr, op token.Token) {
// spec: "The right operand in a shift expression must have integer type
// or be an untyped constant representable by a value of type uint."
// Provide a good error message for negative shift counts.
// Check that constants are representable by uint, but do not convert them
// (see also issue #47243).
if y.mode == constant_ {
// Provide a good error message for negative shift counts.
yval := constant.ToInt(y.val) // consider -1, 1.0, but not -1.1
if yval.Kind() == constant.Int && constant.Sign(yval) < 0 {
check.invalidOp(y, _InvalidShiftCount, "negative shift count %s", y)
x.mode = invalid
return
}
if isUntyped(y.typ) {
// Caution: Check for representability here, rather than in the switch
// below, because isInteger includes untyped integers (was bug #43697).
check.representable(y, Typ[Uint])
if y.mode == invalid {
x.mode = invalid
return
}
}
}
// Caution: Check for isUntyped first because isInteger includes untyped
// integers (was bug #43697).
if isUntyped(y.typ) {
// Check that RHS is otherwise at least of integer type.
switch {
case isInteger(y.typ):
if !isUnsigned(y.typ) && !check.allowVersion(check.pkg, 1, 13) {
check.invalidOp(y, _InvalidShiftCount, "signed shift count %s requires go1.13 or later", y)
x.mode = invalid
return
}
case isUntyped(y.typ):
// This is incorrect, but preserves pre-existing behavior.
// See also bug #47410.
check.convertUntyped(y, Typ[Uint])
if y.mode == invalid {
x.mode = invalid
return
}
} else if !isInteger(y.typ) {
default:
check.invalidOp(y, _InvalidShiftCount, "shift count %s must be integer", y)
x.mode = invalid
return
} else if !isUnsigned(y.typ) && !check.allowVersion(check.pkg, 1, 13) {
check.invalidOp(y, _InvalidShiftCount, "signed shift count %s requires go1.13 or later", y)
x.mode = invalid
return
}
if x.mode == constant_ {