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go/types, types2: add check for map value completeness in IndexExpr

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An index expression can also go from map[K]V to V. Since V could be
incomplete (due to some admittedly contrived syntax), we need a
check.

Change-Id: I03ffbfc0e5bcc9129591d60dfbaa5fafcf8fb183
Reviewed-on: https://go-review.googlesource.com/c/go/+/737620
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Mark Freeman <markfreeman@google.com>
This commit is contained in:
Mark Freeman
2026-01-20 14:23:19 -05:00
committed by Gopher Robot
parent 8ca47fab42
commit a977717393
3 changed files with 32 additions and 10 deletions
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20
src/cmd/compile/internal/types2/index.go
View File

@@ -52,11 +52,21 @@ func (check *Checker) indexExpr(x *operand, e *syntax.IndexExpr) (isFuncInst boo
x.mode = invalid
return false
}
// Additionally, if x.typ is a pointer to an array type, indexing implicitly dereferences the value, meaning
// its base type must also be complete.
if p, ok := x.typ.Underlying().(*Pointer); ok && !check.isComplete(p.base) {
x.mode = invalid
return false
switch typ := x.typ.Underlying().(type) {
case *Pointer:
// Additionally, if x.typ is a pointer to an array type, indexing implicitly dereferences the value, meaning
// its base type must also be complete.
if !check.isComplete(typ.base) {
x.mode = invalid
return false
}
case *Map:
// Lastly, if x.typ is a map type, indexing must produce a value of a complete type, meaning
// its element type must also be complete.
if !check.isComplete(typ.elem) {
x.mode = invalid
return false
}
}
// ordinary index expression

20
src/go/types/index.go
View File

@@ -53,11 +53,21 @@ func (check *Checker) indexExpr(x *operand, e *indexedExpr) (isFuncInst bool) {
x.mode = invalid
return false
}
// Additionally, if x.typ is a pointer to an array type, indexing implicitly dereferences the value, meaning
// its base type must also be complete.
if p, ok := x.typ.Underlying().(*Pointer); ok && !check.isComplete(p.base) {
x.mode = invalid
return false
switch typ := x.typ.Underlying().(type) {
case *Pointer:
// Additionally, if x.typ is a pointer to an array type, indexing implicitly dereferences the value, meaning
// its base type must also be complete.
if !check.isComplete(typ.base) {
x.mode = invalid
return false
}
case *Map:
// Lastly, if x.typ is a map type, indexing must produce a value of a complete type, meaning
// its element type must also be complete.
if !check.isComplete(typ.elem) {
x.mode = invalid
return false
}
}
// ordinary index expression

2
src/internal/types/testdata/check/cycles6.go vendored
View File

@@ -69,3 +69,5 @@ type T11 /* ERROR "invalid recursive type" */ [unsafe.Sizeof(new(T11)[:])]int
type T12 /* ERROR "invalid recursive type" */ [unsafe.Sizeof(T12{}[42])]int
// index on pointer (case 3)
type T13 /* ERROR "invalid recursive type" */ [unsafe.Sizeof(new(T13)[42])]int
// index on map (case 1)
type T14 /* ERROR "invalid recursive type" */ [unsafe.Sizeof((*new(map[int]T14))[42])]int