func close(c chan<- Type)

// The panic built-in function stops normal execution of the current
// goroutine. When a function F calls panic, normal execution of F stops
// immediately. Any functions whose execution was deferred by F are run in
// the usual way, and then F returns to its caller. To the caller G, the
// invocation of F then behaves like a call to panic, terminating G's

At that point, the program is terminated and the error
condition is reported, including the value of the argument to <code>panic</code>.
This termination sequence is called <i>panicking</i>.
</p>

<pre>
panic(42)
panic("unreachable")
panic(Error("cannot parse"))
</pre>

<p>
The <code>recover</code> function allows a program to manage behavior
of a panicking goroutine.

func (r *Reader) WriteTo(w io.Writer) (n int64, err error) {
	r.prevRune = -1
	if r.i >= int64(len(r.s)) {
		return 0, nil
	}
	b := r.s[r.i:]
	m, err := w.Write(b)
	if m > len(b) {
		panic("bytes.Reader.WriteTo: invalid Write count")
	}
	r.i += int64(m)
	n = int64(m)
	if m != len(b) && err == nil {
		err = io.ErrShortWrite
	}
	return
}

	if count == 0 {
		return []byte{}
	}

	// Since we cannot return an error on overflow,
	// we should panic if the repeat will generate an overflow.
	// See golang.org/issue/16237.
	if count < 0 {
		panic("bytes: negative Repeat count")
	}
	if len(b) >= maxInt/count {
		panic("bytes: Repeat output length overflow")
	}
	n := len(b) * count

	if len(b) == 0 {
		return []byte{}
	}

		pkgPrefix:   pkgPrefix,
	}
}

// panicOnError is enabled when testing to abort execution on the first error
// and turn it into a recoverable panic.
var panicOnError bool

func (p *Parser) errorf(format string, args ...interface{}) {
	if panicOnError {
		panic(fmt.Errorf(format, args...))
	}
	if p.lineNum == p.errorLine {
		// Only one error per line.
		return
	}
	p.errorLine = p.lineNum
	if p.lex != nil {

			name:   name,
			args:   nil,
			tokens: Tokenize(value),
		}
	}
	return macros
}

var panicOnError bool // For testing.

func (in *Input) Error(args ...interface{}) {
	if panicOnError {
		panic(fmt.Errorf("%s:%d: %s", in.File(), in.Line(), fmt.Sprintln(args...)))
	}
	fmt.Fprintf(os.Stderr, "%s:%d: %s", in.File(), in.Line(), fmt.Sprintln(args...))
	os.Exit(1)
}

func TestDontLoopForever(t *testing.T) {
	s := NewScanner(strings.NewReader("abc"))
	s.Split(loopAtEOFSplit)
	// Expect a panic
	defer func() {
		err := recover()
		if err == nil {
			t.Fatal("should have panicked")
		}
		if msg, ok := err.(string); !ok || !strings.Contains(msg, "empty tokens") {
			panic(err)
		}
	}()
	for count := 0; s.Scan(); count++ {
		if count > 1000 {
			t.Fatal("looping")
		}
	}

}

func (w *Walker) emitf(format string, args ...any) {
	f := strings.Join(w.scope, ", ") + ", " + fmt.Sprintf(format, args...)
	if strings.Contains(f, "\n") {
		panic("feature contains newlines: " + f)
	}

	if _, dup := w.features[f]; dup {
		panic("duplicate feature inserted: " + f)
	}
	w.features[f] = true

	if verbose {
		log.Printf("feature: %s", f)
	}
}

	if b.r > 0 {
		copy(b.buf, b.buf[b.r:b.w])
		b.w -= b.r
		b.r = 0
	}

	if b.w >= len(b.buf) {
		panic("bufio: tried to fill full buffer")
	}

	// Read new data: try a limited number of times.
	for i := maxConsecutiveEmptyReads; i > 0; i-- {
		n, err := b.rd.Read(b.buf[b.w:])
		if n < 0 {
			panic(errNegativeRead)
		}
		b.w += n
		if err != nil {
			b.err = err
			return
		}
		if n > 0 {

If <code>list</code> pointed to a cyclic list,
then the original program would never access <code>*p</code> or <code>*q</code>,
but the rewritten program would.
(Moving `*p` ahead would be safe if the compiler can prove `*p` will not panic;
moving `*q` ahead would also require the compiler proving that no other
goroutine can access `*q`.)
</p>

<p>
Not introducing data races also means not assuming that called functions