// A reslice past the end of a slice must stay a well-formed view of its
// parent: an empty slice, not a slice with a negative length.
//
// Moxie emits no slice bounds check - the programmer owns the indices - but
// `s[1:]` on an empty slice produced len -1, so the tree's
// `for ; len(r) > 0; r = r[1:]` loops left `r` with a negative length and the
// `if len(r) == 0` guards that follow never fired. A truncated REQ filter
// (`{"kinds":[1`) then read past the end and killed the relay.
package main

import (
	"fmt"
	"os"
)

func consume(s []byte) (n int32) {
	for ; len(s) > 0; s = s[1:] {
		if s[0] == 'x' {
			return -1
		}
	}
	return int32(len(s))
}

func main() {
	fmt.Fprintf(os.Stderr, "ok\n")
	empty := []byte{}
	after := empty[1:]
	if len(after) != 0 {
		panic("reslicing past the end must produce an empty slice")
	}
	if consume([]byte("x")) != -1 {
		panic("the loop body must still see its element")
	}
	if consume([]byte("xy")) != -1 {
		panic("consume must stop at the matching element")
	}
	if consume(nil) != 0 {
		panic("consume of nil must end immediately")
	}
	// Extending to capacity is a valid slice, not an out-of-range index.
	buf := []byte{:0:8}
	buf = push(buf, 'a', 'b')
	grown := buf[:cap(buf)]
	if len(grown) != 8 {
		panic("reslicing to capacity must keep the capacity")
	}
	grown[7] = 'z'
	if grown[7] != 'z' {
		panic("the extended view must alias the parent buffer")
	}
	// An inverted range and a cursor past the end are both empty. The indices
	// are variables because a constant inverted range is a frontend error.
	var lo byte = 3
	var hi byte = 1
	inverted := buf[lo:hi]
	if len(inverted) != 0 {
		panic("an inverted range must be empty")
	}
	past := buf[99:]
	if len(past) != 0 {
		panic("a reslice starting past the end must be empty")
	}
	// A valid middle slice is unchanged.
	mid := buf[2:5]
	if len(mid) != 3 || mid[0] != 0 {
		panic("a valid sub-slice must keep its bounds")
	}
	fmt.Fprintf(os.Stderr, "%d %d %d\n", int32(len(grown)), int32(len(inverted)), int32(len(past)))
	fmt.Fprintf(os.Stderr, "done\n")
}