ctxExpr
	ctxField
	ctxParam
	ctxAssign2 // assignment of a single expression to two variables
	ctxSwitch
	ctxTypeSwitch
	ctxFile
	ctxDecl
	ctxSpec
	ctxDefer
	ctxCall  // any function call other than ctxCall2
	ctxCall2 // function call whose result is assigned to two variables
	ctxSelector
)

// walk walks the AST x, calling visit(f, x, context) for each node.

// constant. See the Go language specification's "Length and capacity" section for
// details.
func cap(v Type) int

// The make built-in function allocates and initializes an object of type
// slice, map, or chan (only). Like new, the first argument is a type, not a
// value. Unlike new, make's return type is the same as the type of its
// argument, not a pointer to it. The specification of the result depends on
// the type:
//

		buf.WriteString("map[")
		w.writeType(buf, typ.Key())
		buf.WriteByte(']')
		w.writeType(buf, typ.Elem())

	case *types.Chan:
		var s string
		switch typ.Dir() {
		case types.SendOnly:
			s = "chan<- "
		case types.RecvOnly:
			s = "<-chan "
		case types.SendRecv:
			s = "chan "
		default:
			panic("unreachable")
		}
		buf.WriteString(s)
		w.writeType(buf, typ.Elem())

	case *types.Alias:

may be implemented as a write of each individual sub-value,
in any order.
</p>

<p>
A read <i>r</i> of a memory location <i>x</i>
holding a value
that is not larger than a machine word must observe
some write <i>w</i> such that <i>r</i> does not happen before <i>w</i>
and there is no write <i>w'</i> such that <i>w</i> happens before <i>w'</i>
and <i>w'</i> happens before <i>r</i>.

		generated output.
	-gccgo
		Generate output for the gccgo compiler rather than the
		gc compiler.
	-gccgoprefix prefix
		The -fgo-prefix option to be used with gccgo.
	-gccgopkgpath path
		The -fgo-pkgpath option to be used with gccgo.
	-gccgo_define_cgoincomplete
		Define cgo.Incomplete locally rather than importing it from
		the "runtime/cgo" package. Used for old gccgo versions.
	-godefs

}

// startDebugBridge ensures that the idevicedebugserverproxy runs on
// port 3222.
func startDebugBridge() (func(), error) {
	errChan := make(chan error, 1)
	cmd := idevCmd(exec.Command("idevicedebugserverproxy", "3222"))
	var stderr bytes.Buffer
	cmd.Stderr = &stderr
	if err := cmd.Start(); err != nil {
		return nil, fmt.Errorf("idevicedebugserverproxy: %v", err)

			// walking the tree and copying it piecewise. If the directory tree
			// contains nested modules this could push a lot of unnecessary contents,
			// but for the golang.org/x repos it seems to be significantly (~2x)
			// faster than copying one file at a time (via filepath.WalkDir),
			// apparently due to high latency in 'adb' commands.
			if err := adb("push", modDir, deviceModDir); err != nil {
				return 0, err
			}
		} else {

func (b *Buffer) Available() int { return cap(b.buf) - len(b.buf) }

// Truncate discards all but the first n unread bytes from the buffer
// but continues to use the same allocated storage.
// It panics if n is negative or greater than the length of the buffer.
func (b *Buffer) Truncate(n int) {
	if n == 0 {
		b.Reset()
		return
	}
	b.lastRead = opInvalid
	if n < 0 || n > b.Len() {
		panic("bytes.Buffer: truncation out of range")
	}

	//
	// While this format is compatible with most tar readers,
	// the format has several limitations making it unsuitable for some usages.
	// Most notably, it cannot support sparse files, files larger than 8GiB,
	// filenames larger than 256 characters, and non-ASCII filenames.
	//
	// Reference:
	//	http://pubs.opengroup.org/onlinepubs/9699919799/utilities/pax.html#tag_20_92_13_06
	FormatUSTAR

says `go` `1.20`, then the program defaults to `panicnil=1`,
matching Go 1.20 instead of Go 1.21.

Because this method of setting GODEBUG defaults was introduced only in Go 1.21,
programs listing versions of Go earlier than Go 1.20 are configured to match Go 1.20,
not the older version.

To override these defaults, a main package's source files
can include one or more `//go:debug` directives at the top of the file