qbit/go
1
0
Fork 0
mirror of https://github.com/golang/go synced 2024-11-26 17:46:57 -07:00
Code Releases Activity

reflect: disallow invoking methods on unexported embedded fields

Browse Source 
Given:

    type u struct{}
    func (u) M() {}

    type t struct { u; u2 u }

    var v = reflect.ValueOf(t{})

Package reflect allows:

    v.Method(0)          // v.M
    v.Field(0).Method(0) // v.u.M

but panics from:

    v.Field(1).Method(0) // v.u2.M

because u2 is not an exported field. However, u is not an exported
field either, so this is inconsistent.

It seems like this behavior originates from #12367, where it was
decided to allow traversing unexported embedded fields to be able to
access their exported fields, since package reflect doesn't provide an
alternative way to access promoted fields directly.

But extending that logic to promoted *methods* was inappropriate,
because package reflect's normal method handling logic already handles
promoted methods correctly. This CL corrects that mistake.

Fixes #38521.

Change-Id: If65008965f35927b4e7927cddf8614695288eb19
Reviewed-on: https://go-review.googlesource.com/c/go/+/228902
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Matthew Dempsky 2020-04-19 13:59:16 -07:00
parent 9255163091
commit 0eb694e9c2
3 changed files with 15 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
doc/go1.15.html
View File

@ -177,6 +177,18 @@ TODO
</dd>
</dl>
<dl id="reflect"><dt><a href="/pkg/reflect/">reflect</a></dt>
<dd>
<p><!-- CL 228902 -->
Package reflect now disallows accessing methods of all
non-exported fields, whereas previously it allowed accessing
those of non-exported, embedded fields. Code that relies on the
previous behavior should be updated to instead access the
corresponding promoted method of the enclosing variable.
</p>
</dd>
</dl>
<dl id="pkg-runtime"><dt><a href="/pkg/runtime/">runtime</a></dt>
<dd>
<p><!-- CL 221779 -->

4
src/reflect/all_test.go
View File

@ -3567,7 +3567,7 @@ func TestCallPanic(t *testing.T) {
i := timp(0)
v := ValueOf(T{i, i, i, i, T2{i, i}, i, i, T2{i, i}})
ok(func() { call(v.Field(0).Method(0)) }) // .t0.W
badCall(func() { call(v.Field(0).Method(0)) }) // .t0.W
badCall(func() { call(v.Field(0).Elem().Method(0)) }) // .t0.W
badCall(func() { call(v.Field(0).Method(1)) }) // .t0.w
badMethod(func() { call(v.Field(0).Elem().Method(2)) }) // .t0.w
@ -3588,7 +3588,7 @@ func TestCallPanic(t *testing.T) {
ok(func() { call(v.Field(4).Field(0).Method(0)) }) // .NamedT2.T1.Y
ok(func() { call(v.Field(4).Field(0).Elem().Method(0)) }) // .NamedT2.T1.W
ok(func() { call(v.Field(4).Field(1).Method(0)) }) // .NamedT2.t0.W
badCall(func() { call(v.Field(4).Field(1).Method(0)) }) // .NamedT2.t0.W
badCall(func() { call(v.Field(4).Field(1).Elem().Method(0)) }) // .NamedT2.t0.W
badCall(func() { call(v.Field(5).Method(0)) }) // .namedT0.W

2
src/reflect/value.go
View File

@ -1315,7 +1315,7 @@ func (v Value) Method(i int) Value {
if v.typ.Kind() == Interface && v.IsNil() {
panic("reflect: Method on nil interface value")
}
fl := v.flag & (flagStickyRO | flagIndir) // Clear flagEmbedRO
fl := v.flag.ro() | (v.flag & flagIndir)
fl |= flag(Func)
fl |= flag(i)<<flagMethodShift | flagMethod
return Value{v.typ, v.ptr, fl}