if T == nil {
					check.errorf(x, UntypedNilUse, "use of untyped nil in %s", context)
					x.mode = invalid
					return
				}
			} else if T == nil || isNonTypeParamInterface(T) {
				target = Default(x.typ)
			}
		} else { // go/types
			if T == nil || isNonTypeParamInterface(T) {
				if T == nil && x.typ == Typ[UntypedNil] {
					check.errorf(x, UntypedNilUse, "use of untyped nil in %s", context)
					x.mode = invalid
					return

}

// IsInterface reports whether t is an interface type.
func IsInterface(t Type) bool {
	_, ok := under(t).(*Interface)
	return ok
}

// isNonTypeParamInterface reports whether t is an interface type but not a type parameter.
func isNonTypeParamInterface(t Type) bool {
	return !isTypeParam(t) && IsInterface(t)
}

// isTypeParam reports whether t is a type parameter.
func isTypeParam(t Type) bool {

				if T == nil {
					check.errorf(x, UntypedNilUse, "use of untyped nil in %s", context)
					x.mode = invalid
					return
				}
			} else if T == nil || isNonTypeParamInterface(T) {
				target = Default(x.typ)
			}
		} else { // go/types
			if T == nil || isNonTypeParamInterface(T) {
				if T == nil && x.typ == Typ[UntypedNil] {
					check.errorf(x, UntypedNilUse, "use of untyped nil in %s", context)
					x.mode = invalid
					return

}

// IsInterface reports whether t is an interface type.
func IsInterface(t Type) bool {
	_, ok := under(t).(*Interface)
	return ok
}

// isNonTypeParamInterface reports whether t is an interface type but not a type parameter.
func isNonTypeParamInterface(t Type) bool {
	return !isTypeParam(t) && IsInterface(t)
}

// isTypeParam reports whether t is a type parameter.
func isTypeParam(t Type) bool {