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package typeutil
import (
"errors"
"go/types"
"golang.org/x/exp/typeparams"
)
type TypeSet struct {
Terms []*types.Term
empty bool
}
func NewTypeSet(typ types.Type) TypeSet {
terms, err := typeparams.NormalTerms(typ)
if err != nil {
if errors.Is(err, typeparams.ErrEmptyTypeSet) {
return TypeSet{nil, true}
} else {
// We couldn't determine the type set. Assume it's all types.
return TypeSet{nil, false}
}
}
return TypeSet{terms, false}
}
// CoreType returns the type set's core type, or nil if it has none.
// The function only looks at type terms and may thus return core types for some empty type sets, such as
// 'interface { map[int]string; foo() }'
func (ts TypeSet) CoreType() types.Type {
if len(ts.Terms) == 0 {
// Either the type set is empty, or it isn't constrained. Either way it doesn't have a core type.
return nil
}
typ := ts.Terms[0].Type().Underlying()
for _, term := range ts.Terms[1:] {
ut := term.Type().Underlying()
if types.Identical(typ, ut) {
continue
}
ch1, ok := typ.(*types.Chan)
if !ok {
return nil
}
ch2, ok := ut.(*types.Chan)
if !ok {
return nil
}
if ch1.Dir() == types.SendRecv {
// typ is currently a bidirectional channel. The term's type is either also bidirectional, or
// unidirectional. Use the term's type.
typ = ut
} else if ch2.Dir() == types.SendRecv {
// typ is currently a unidirectional channel and the term's type is bidirectional, which means it has no
// effect.
continue
} else if ch1.Dir() != ch2.Dir() {
// typ is not bidirectional and typ and term disagree about the direction
return nil
}
}
return typ
}
// CoreType is a wrapper for NewTypeSet(typ).CoreType()
func CoreType(typ types.Type) types.Type {
return NewTypeSet(typ).CoreType()
}
// All calls fn for each term in the type set and reports whether all invocations returned true.
// If the type set is empty or unconstrained, All immediately returns false.
func (ts TypeSet) All(fn func(*types.Term) bool) bool {
if len(ts.Terms) == 0 {
return false
}
for _, term := range ts.Terms {
if !fn(term) {
return false
}
}
return true
}
// Any calls fn for each term in the type set and reports whether any invocation returned true.
// It stops after the first call that returned true.
func (ts TypeSet) Any(fn func(*types.Term) bool) bool {
for _, term := range ts.Terms {
if fn(term) {
return true
}
}
return false
}
// All is a wrapper for NewTypeSet(typ).All(fn).
func All(typ types.Type, fn func(*types.Term) bool) bool {
return NewTypeSet(typ).All(fn)
}
// Any is a wrapper for NewTypeSet(typ).Any(fn).
func Any(typ types.Type, fn func(*types.Term) bool) bool {
return NewTypeSet(typ).Any(fn)
}
func IsSlice(term *types.Term) bool {
_, ok := term.Type().Underlying().(*types.Slice)
return ok
}
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