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cmd/gc: do not nop-convert equivalent but different interface types.

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The cached computed interface tables are indexed by the interface
types, not by the unnamed underlying interfaces

To preserve the invariants expected by interface comparison, an
itab generated for an interface type must not be used for a value
of a different interface type even if the representation is identical.

Fixes #7207.

LGTM=rsc
R=rsc, iant, khr
CC=golang-codereviews
https://golang.org/cl/69210044
This commit is contained in:
Rémy Oudompheng 2014-02-27 08:07:50 +01:00
parent b7b844d4cd
commit e5f01aee04
2 changed files with 46 additions and 2 deletions
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6
src/cmd/gc/subr.c
View File

@ -1223,8 +1223,10 @@ assignop(Type *src, Type *dst, char **why)
// 2. src and dst have identical underlying types
// and either src or dst is not a named type or
// both are interface types.
if(eqtype(src->orig, dst->orig) && (src->sym == S || dst->sym == S || src->etype == TINTER))
// both are empty interface types.
// For assignable but different non-empty interface types,
// we want to recompute the itab.
if(eqtype(src->orig, dst->orig) && (src->sym == S || dst->sym == S || isnilinter(src)))
return OCONVNOP;
// 3. dst is an interface type and src implements dst.

42
test/cmp.go
View File

@ -35,6 +35,10 @@ func istrue(b bool) {
type T *int
type X int
func (X) x() {}
func main() {
var a []int
var b map[string]int
@ -129,6 +133,44 @@ func main() {
panic("bad m[c]")
}
// interface comparisons (issue 7207)
{
type I1 interface {
x()
}
type I2 interface {
x()
}
a1 := I1(X(0))
b1 := I1(X(1))
a2 := I2(X(0))
b2 := I2(X(1))
a3 := I1(a2)
a4 := I2(a1)
var e interface{} = X(0)
a5 := e.(I1)
a6 := e.(I2)
isfalse(a1 == b1)
isfalse(a1 == b2)
isfalse(a2 == b1)
isfalse(a2 == b2)
istrue(a1 == a2)
istrue(a1 == a3)
istrue(a1 == a4)
istrue(a1 == a5)
istrue(a1 == a6)
istrue(a2 == a3)
istrue(a2 == a4)
istrue(a2 == a5)
istrue(a2 == a6)
istrue(a3 == a4)
istrue(a3 == a5)
istrue(a3 == a6)
istrue(a4 == a5)
istrue(a4 == a6)
istrue(a5 == a6)
}
// non-interface comparisons
{
c := make(chan int)