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package parse
import "fmt"
// checkParseTree checks whether the parse tree part of a Node is well-formed.
func checkParseTree(n Node) error {
children := Children(n)
if len(children) == 0 {
return nil
}
// Parent pointers of all children should point to me.
for i, ch := range children {
if Parent(ch) != n {
return fmt.Errorf("parent of child %d (%s) is wrong: %s", i, summary(ch), summary(n))
}
}
// The Begin of the first child should be equal to mine.
if children[0].Range().From != n.Range().From {
return fmt.Errorf("gap between node and first child: %s", summary(n))
}
// The End of the last child should be equal to mine.
nch := len(children)
if children[nch-1].Range().To != n.Range().To {
return fmt.Errorf("gap between node and last child: %s", summary(n))
}
// Consecutive children have consecutive position ranges.
for i := 0; i < nch-1; i++ {
if children[i].Range().To != children[i+1].Range().From {
return fmt.Errorf("gap between child %d and %d of: %s", i, i+1, summary(n))
}
}
// Check children recursively.
for _, ch := range Children(n) {
err := checkParseTree(ch)
if err != nil {
return err
}
}
return nil
}
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