reflect: add TypeAssert[T]
This implementation is zero-alloc when T is a concrete type,
allocates when val contains a method or when T is a interface
and Value was obtained for example through Elem(), in which case
it has to be allocated to avoid sharing the same memory.
goos: linux
goarch: amd64
pkg: reflect
cpu: AMD Ryzen 5 4600G with Radeon Graphics
│ /tmp/bench2 │
│ sec/op │
TypeAssert/TypeAssert[int](int)-12 2.725n ± 1%
TypeAssert/TypeAssert[uint8](int)-12 2.599n ± 1%
TypeAssert/TypeAssert[fmt.Stringer](reflect_test.testTypeWithMethod)-12 8.470n ± 0%
TypeAssert/TypeAssert[fmt.Stringer](*reflect_test.testTypeWithMethod)-12 8.460n ± 1%
TypeAssert/TypeAssert[interface_{}](int)-12 4.181n ± 1%
TypeAssert/TypeAssert[interface_{}](reflect_test.testTypeWithMethod)-12 4.178n ± 1%
TypeAssert/TypeAssert[time.Time](time.Time)-12 2.839n ± 0%
TypeAssert/TypeAssert[func()_string](func()_string)-12 151.1n ± 1%
geomean 6.645n
│ /tmp/bench2 │
│ B/op │
TypeAssert/TypeAssert[int](int)-12 0.000 ± 0%
TypeAssert/TypeAssert[uint8](int)-12 0.000 ± 0%
TypeAssert/TypeAssert[fmt.Stringer](reflect_test.testTypeWithMethod)-12 0.000 ± 0%
TypeAssert/TypeAssert[fmt.Stringer](*reflect_test.testTypeWithMethod)-12 0.000 ± 0%
TypeAssert/TypeAssert[interface_{}](int)-12 0.000 ± 0%
TypeAssert/TypeAssert[interface_{}](reflect_test.testTypeWithMethod)-12 0.000 ± 0%
TypeAssert/TypeAssert[time.Time](time.Time)-12 0.000 ± 0%
TypeAssert/TypeAssert[func()_string](func()_string)-12 72.00 ± 0%
geomean ¹
Fixes #62121
Change-Id: I0911c70c5966672c930d387438643f94a40441c4
GitHub-Last-Rev:
ce89a53097b53fc59ff3ce3996917f8484ad3967
GitHub-Pull-Request: golang/go#71639
Reviewed-on: https://go-review.googlesource.com/c/go/+/648056
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>