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
`reflect.TypeFor` function (introduced in go1.22) from a file in a

"vendor/golang.org/x/crypto/cryptobyte". When a package with the
same path is imported from a package outside std or cmd, it will
be resolved normally. Consequently, a binary may be built with two
copies of a package at different versions if the package is
imported normally and vendored by the standard library.

Vendored packages are internally renamed with a "vendor/" prefix

	paxGNUSparseMinor     = "GNU.sparse.minor"
	paxGNUSparseSize      = "GNU.sparse.size"
	paxGNUSparseRealSize  = "GNU.sparse.realsize"
)

// basicKeys is a set of the PAX keys for which we have built-in support.
// This does not contain "charset" or "comment", which are both PAX-specific,
// so adding them as first-class features of Header is unlikely.
// Users can use the PAXRecords field to set it themselves.

// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//go:build unix

package tar

import (
	"io/fs"
	"os/user"
	"runtime"
	"strconv"
	"sync"
	"syscall"
)

func init() {
	sysStat = statUnix
}

// userMap and groupMap caches UID and GID lookups for performance reasons.

		result *= 7
	}()
	return 6
}
</pre>

<h2 id="Built-in_functions">Built-in functions</h2>

<p>
Built-in functions are
<a href="#Predeclared_identifiers">predeclared</a>.
They are called like any other function but some of them
accept a type instead of an expression as the first argument.
</p>

<p>
The built-in functions do not have standard Go types,

// The copy built-in function copies elements from a source slice into a
// destination slice. (As a special case, it also will copy bytes from a
// string to a slice of bytes.) The source and destination may overlap. Copy
// returns the number of elements copied, which will be the minimum of
// len(src) and len(dst).
func copy(dst, src []Type) int

will succeed.
Such code should use a non-blocking receive instead.

These new behaviors are only enabled when the main Go program
is in a module with a `go.mod` `go` line using Go 1.23.0 or later.
When Go 1.23 builds older programs, the old behaviors remain in effect.
The new [GODEBUG setting](/doc/godebug) [`asynctimerchan=1`](/pkg/time/#NewTimer)
can be used to revert back to asynchronous channel behaviors

</p>

<p>
Any implementation can, upon detecting a data race,
report the race and halt execution of the program.
Implementations using ThreadSanitizer
(accessed with “<code>go</code> <code>build</code> <code>-race</code>”)
do exactly this.
</p>

<p>
A read of an array, struct, or complex number
may by implemented as a read of each individual sub-value