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util/deephash: simplify typeIsRecursive (#5385)

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Any type that is memory hashable must not be recursive since
there are definitely no pointers involved to make a cycle.

Signed-off-by: Joe Tsai <joetsai@digital-static.net>
This commit is contained in:
Joe Tsai 2022-08-15 23:29:06 -07:00 committed by GitHub
parent 23ec3c104a
commit d53eb6fa11
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 11 additions and 32 deletions
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43
util/deephash/deephash.go
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@ -648,31 +648,7 @@ func typeIsRecursive(t reflect.Type) bool {
var visitType func(t reflect.Type) (isRecursiveSoFar bool)
visitType = func(t reflect.Type) (isRecursiveSoFar bool) {
switch t.Kind() {
case reflect.Bool,
reflect.Int,
reflect.Int8,
reflect.Int16,
reflect.Int32,
reflect.Int64,
reflect.Uint,
reflect.Uint8,
reflect.Uint16,
reflect.Uint32,
reflect.Uint64,
reflect.Uintptr,
reflect.Float32,
reflect.Float64,
reflect.Complex64,
reflect.Complex128,
reflect.String,
reflect.UnsafePointer,
reflect.Func:
return false
}
if t.Size() == 0 {
return false
}
// Check whether we have seen this type before.
if inStack[t] {
return true
}
@ -681,9 +657,18 @@ func typeIsRecursive(t reflect.Type) bool {
delete(inStack, t)
}()
// Any type that is memory hashable must not be recursive since
// cycles can only occur if pointers are involved.
if canMemHash(t) {
return false
}
// Recursively check types that may contain pointers.
switch t.Kind() {
default:
panic("unhandled kind " + t.Kind().String())
case reflect.String, reflect.UnsafePointer, reflect.Func:
return false
case reflect.Interface:
// Assume the worst for now. TODO(bradfitz): in some cases
// we should be able to prove that it's not recursive. Not worth
@ -692,12 +677,7 @@ func typeIsRecursive(t reflect.Type) bool {
case reflect.Array, reflect.Chan, reflect.Pointer, reflect.Slice:
return visitType(t.Elem())
case reflect.Map:
if visitType(t.Key()) {
return true
}
if visitType(t.Elem()) {
return true
}
return visitType(t.Key()) || visitType(t.Elem())
case reflect.Struct:
if t.String() == "intern.Value" {
// Otherwise its interface{} makes this return true.
@ -710,7 +690,6 @@ func typeIsRecursive(t reflect.Type) bool {
}
return false
}
return false
}
return visitType(t)
}