f.walk(n.Body, ctxStmt, visit)
	case *ast.SelectStmt:
		f.walk(n.Body, ctxStmt, visit)
	case *ast.ForStmt:
		f.walk(n.Init, ctxStmt, visit)
		f.walk(&n.Cond, ctxExpr, visit)
		f.walk(n.Post, ctxStmt, visit)
		f.walk(n.Body, ctxStmt, visit)
	case *ast.RangeStmt:
		f.walk(&n.Key, ctxExpr, visit)
		f.walk(&n.Value, ctxExpr, visit)
		f.walk(&n.X, ctxExpr, visit)
		f.walk(n.Body, ctxStmt, visit)

<p>
A "for" statement with a ForClause is also controlled by its condition, but
additionally it may specify an <i>init</i>
and a <i>post</i> statement, such as an assignment,
an increment or decrement statement. The init statement may be a
<a href="#Short_variable_declarations">short variable declaration</a>, but the post statement must not.
Variables declared by the init statement are re-used in each iteration.
</p>

<pre class="ebnf">

In an external link, cmd/link will create a temporary directory, write any
host object files found in package archives to that directory (renamed
to avoid conflicts), write the go.o file to that directory, and invoke
the host linker. The default value for the host linker is $CC, split
into fields, or else "gcc". The specific host linker command line can
be overridden using command line flags: cmd/link -extld=clang

of Go values and free that space manually all at once, safely. The purpose
of this functionality is to improve efficiency: manually freeing memory
before a garbage collection delays that cycle. Less frequent cycles means
the CPU cost of the garbage collector is incurred less frequently.

This functionality in this package is mostly captured in the Arena type.
Arenas allocate large chunks of memory for Go values, so they're likely to

	VGATHERQPD (DX)(Z23*1),K1,Z15 // 6272fd41933c3a
	// EVEX: VCVTPD2DQ with Y suffix (VL=2).
	VCVTPD2DQY (BX), X20  // 62e1ff28e623
	VCVTPD2DQY (R11), X30 // 6241ff28e633
	// XED encoder uses EVEX.X=0 for these; most x86 tools use EVEX.X=1.
	// Either way is OK.
	VMOVQ SP, X20  // 62e1fd086ee4 or 62a1fd086ee4
	VMOVQ BP, X20  // 62e1fd086ee5 or 62a1fd086ee5
	VMOVQ R14, X20 // 62c1fd086ee6 or 6281fd086ee6

	}
	defer func() {
		s := recover()
		if s == nil {
			t.Fatal("did not panic")
		}
		if s.(string) != "callback panic" {
			t.Fatal("wrong panic:", s)
		}
		if !lockedOSThread() {
			t.Fatal("lost lock on OS thread after panic")
		}
	}()
	nestedCall(func() { panic("callback panic") })
	panic("nestedCall returned")
}

// Callback with zero arguments used to make the stack misaligned,

	VST1.P	[V4.S4,V5.S4], 48(R1)                            // ERROR "invalid post-increment offset"
	VST1.P	[V4.S4], 8(R1)                                   // ERROR "invalid post-increment offset"
	VLD1.P	32(R1), [V8.S4, V9.S4, V10.S4]                   // ERROR "invalid post-increment offset"
	VLD1.P	48(R1), [V7.S4, V8.S4, V9.S4, V10.S4]            // ERROR "invalid post-increment offset"

<p>
A "for" statement with a ForClause is also controlled by its condition, but
additionally it may specify an <i>init</i>
and a <i>post</i> statement, such as an assignment,
an increment or decrement statement. The init statement may be a
<a href="#Short_variable_declarations">short variable declaration</a>, but the post statement must not.
</p>

<pre class="ebnf">
ForClause = [ InitStmt ] ";" [ Condition ] ";" [ PostStmt ] .

// the subslices between those separators.
// If sep is empty, SplitN splits after each UTF-8 sequence.
// The count determines the number of subslices to return:
//
//	n > 0: at most n subslices; the last subslice will be the unsplit remainder.
//	n == 0: the result is nil (zero subslices)
//	n < 0: all subslices
//
// To split around the first instance of a separator, see Cut.

	}
	fmt.Fprintf(os.Stderr, "%s:%d: %s", in.File(), in.Line(), fmt.Sprintln(args...))
	os.Exit(1)
}

// expectText is like Error but adds "got XXX" where XXX is a quoted representation of the most recent token.
func (in *Input) expectText(args ...interface{}) {
	in.Error(append(args, "; got", strconv.Quote(in.Stack.Text()))...)
}

// enabled reports whether the input is enabled by an ifdef, or is at the top level.