What's wrong with using non@safe actions which creates and
modifies some external objects?
```D
class Layer {
int index;
string name;
this(int index, string name) {
class SignalLayer : Layer {
class UserLayer : Layer {
class PCB {
Layer[] layer;
PT _deflayer(PT)(PT p) {
auto index = to!int(p.matches[0]);
switch (p.matches[2]) {
case "signal":
pcb.layer ~= new SignalLayer(index, p.matches[1]); break;
case "user":
pcb.layer ~= new UserLayer(index, p.matches[1]); break;
default:
break;
}
return p;
}
mixin(grammar(`
parser:
kicad_pcb < :l :'kicad_pcb' verzion host general page
layers
layers < :l :'layers' (deflayer {_deflayer})+ :r
deflayer < :l unum layer ('signal'|'user') :r
```
```
../.dub/packages/pegged/0.4.9/pegged/pegged/peg.d(3049,19):
Error: `@safe` function `pegged.peg.action!(wrapAround,
_deflayer).action` cannot call `@system` function
`kicad._deflayer!(ParseTree)._deflayer`
src/kicad.d(27,5): which calls `kicad.SignalLayer.this`
src/kicad.d(68,4): `kicad._deflayer!(ParseTree)._deflayer`
is declared here
src/kicad.d-mixin-83(219,289): Error: template instance
`pegged.peg.action!(wrapAround, _deflayer)` error instantiating
src/kicad.d-mixin-83(932,7): instantiated from here:
`Genericparser!(ParseTree)`
../.dub/packages/pegged/0.4.9/pegged/pegged/peg.d(544,20): Error:
none of the overloads of `layers` are callable using argument
types `(GetName)`
src/kicad.d-mixin-83(215,23): Candidates are:
`kicad.Genericparser!(ParseTree).Genericparser.parser.layers(ParseTree p)`
src/kicad.d-mixin-83(234,23):
`kicad.Genericparser!(ParseTree).Genericparser.parser.layers(string s)`
../.dub/packages/pegged/0.4.9/pegged/pegged/peg.d(1598,24):
Error: template instance `pegged.peg.getName!(layers)` error
instantiating
src/kicad.d-mixin-83(183,436): instantiated from here:
`wrapAround!(named, layers, named)`
src/kicad.d-mixin-83(932,7): instantiated from here:
`Genericparser!(ParseTree)`
```
