The new [unique] package provides facilities for
canonicalizing values (like "interning" or "hash-consing").

Any value of comparable type may be canonicalized with the new
`Make[T]` function, which produces a reference to a canonical copy of
the value in the form of a `Handle[T]`.
Two `Handle[T]` are equal if and only if the values used to produce the
handles are equal, allowing programs to deduplicate values and reduce
their memory footprint.

analyzer, which flags references to symbols that are too new for the version
of Go in effect in the referring file. (The effective version is determined
by the `go` directive in the file's enclosing `go.mod` file, and
by any [`//go:build` constraints](https://pkg.go.dev/cmd/go#hdr-Build_constraints)
in the file.)

For example, it will report a diagnostic for a reference to the

are not marked with `//go:linkname` on their definitions.
Similarly, the linker disallows references to such symbols from assembly
code.
For backward compatibility, existing usages of `//go:linkname` found in
a large open-source code corpus remain supported.
Any new references to standard library internal symbols will be disallowed.

A linker command line flag `-checklinkname=0` can be used to disable