func TestWalk(t *testing.T) {
g := ast.Grammar([]*ast.Production{
{
Name: &ast.Name{Name: "E"},
Expr: ast.Alternative([]ast.Expression{
ast.Sequence([]ast.Expression{
&ast.Name{Name: "T"},
&ast.Terminal{Terminal: "+"},
&ast.Name{Name: "T"},
}),
&ast.Name{Name: "T"},
&ast.Epsilon{Epsilon: "e"},
}),
},
{
Name: &ast.Name{Name: "T"},
Expr: ast.Alternative([]ast.Expression{
ast.Sequence([]ast.Expression{
&ast.Terminal{Terminal: "("},
&ast.Name{Name: "T"},
&ast.Terminal{Terminal: ")"},
}),
&ast.Name{Name: "T"},
}),
},
})
order := []string{
"ast.Grammar",
"*ast.Production",
"*ast.Name",
"ast.Alternative",
"ast.Sequence",
"*ast.Name",
"*ast.Terminal",
"*ast.Name",
"*ast.Name",
"*ast.Epsilon",
"*ast.Production",
"*ast.Name",
"ast.Alternative",
"ast.Sequence",
"*ast.Terminal",
"*ast.Name",
"*ast.Terminal",
"*ast.Name",
}
i := 0
ast.Walk(func(n ast.Node) bool {
if n == nil {
return false
}
if typ := reflect.TypeOf(n).String(); order[i] != typ {
t.Errorf("got %q want %q", typ, order[i])
}
i++
return true
}, g)
}
// check checks whether all productions
// used are defined.
func (p *parser) check() {
prods := make(map[string]bool)
for _, p := range p.grammar {
prods[p.Name.Name] = true
}
ast.Walk(func(n ast.Node) bool {
if n, ok := n.(*ast.Name); ok {
if _, ok := prods[n.Name]; !ok {
p.errs = append(p.errs, fmt.Errorf("%v undefined %q", n.Pos(), n.Name))
}
}
return true
}, p.grammar)
}