// For a given struct type and (promoted) field Id, findEmbeddedField
// returns the path of implicit anonymous field selections, and the
// field index of the explicit (=outermost) selection.
//
// TODO(gri): if go/types/operand.go's lookupFieldBreadthFirst were to
// record (e.g. call a client-provided callback) the implicit field
// selection path discovered for a particular ast.SelectorExpr, we could
// eliminate this function.
//
func findPromotedField(st *types.Struct, id Id) (*anonFieldPath, int) {
// visited records the types that have been searched already.
// Invariant: keys are all *types.Named.
// (types.Type is not a sound map key in general.)
visited := make(map[types.Type]bool)
var list, next []*anonFieldPath
i := 0
st.ForEachField(func(f *types.Field) {
if f.IsAnonymous {
list = append(list, &anonFieldPath{nil, i, f})
}
i++
})
// Search the current level if there is any work to do and collect
// embedded types of the next lower level in the next list.
for {
// look for name in all types at this level
for _, node := range list {
typ := node.field.Type.Deref().(*types.Named)
if visited[typ] {
continue
}
visited[typ] = true
switch typ := typ.Underlying().(type) {
case *types.Struct:
for i, n := 0, typ.NumFields(); i < n; i++ {
f := typ.Field(i)
if MakeId(f.Name, f.Pkg) == id {
return node, i
}
}
i := 0
typ.ForEachField(func(f *types.Field) {
if f.IsAnonymous {
next = append(next, &anonFieldPath{node, i, f})
}
i++
})
}
}
if len(next) == 0 {
panic("field not found: " + id.String())
}
// No match so far.
list, next = next, list[:0] // reuse arrays
}
panic("unreachable")
}
