// only in debug mode.
		if debug {
			panic("validType0(nil)")
		}

	case *Array:
		return check.validType0(pos, t.elem, nest, path)

	case *Struct:
		for _, f := range t.fields {
			if !check.validType0(pos, f.typ, nest, path) {
				return false
			}
		}

	case *Union:
		for _, t := range t.terms {
			if !check.validType0(pos, t.typ, nest, path) {
				return false
			}
		}

		// only in debug mode.
		if debug {
			panic("validType0(nil)")
		}

	case *Array:
		return check.validType0(pos, t.elem, nest, path)

	case *Struct:
		for _, f := range t.fields {
			if !check.validType0(pos, f.typ, nest, path) {
				return false
			}
		}

	case *Union:
		for _, t := range t.terms {
			if !check.validType0(pos, t.typ, nest, path) {
				return false
			}
		}

        T8 interface { T7; T7 }
        T9 interface { T8; T8 }

        // TODO(gri) Enable this longer test once we have found a solution
        //           for the incorrect optimization in the validType check
        //           (see TODO in validtype.go).
        // T10 interface { T9; T9 }
        // T11 interface { T10; T10 }
        // T12 interface { T11; T11 }
        // T13 interface { T12; T12 }
        // T14 interface { T13; T13 }

			}
		}

		// TODO(rfindley): remove this call: we don't need to call validType here,
		// as cycles can only occur for types used inside a Named type declaration,
		// and so it suffices to call validType from declared types.
		check.validType(inst)
	}).describef(ix, "resolve instance %s", inst)

	return inst
}

			}
		}

		// TODO(rfindley): remove this call: we don't need to call validType here,
		// as cycles can only occur for types used inside a Named type declaration,
		// and so it suffices to call validType from declared types.
		check.validType(inst)
	}).describef(x, "resolve instance %s", inst)

	return inst
}

		}()
	}

	// An infinitely expanding interface (due to a cycle) is detected
	// elsewhere (Checker.validType), so here we simply assume we only
	// have valid interfaces. Mark the interface as complete to avoid
	// infinite recursion if the validType check occurs later for some
	// reason.
	ityp.tset = &_TypeSet{terms: allTermlist} // TODO(gri) is this sufficient?

		}()
	}

	// An infinitely expanding interface (due to a cycle) is detected
	// elsewhere (Checker.validType), so here we simply assume we only
	// have valid interfaces. Mark the interface as complete to avoid
	// infinite recursion if the validType check occurs later for some
	// reason.
	ityp.tset = &_TypeSet{terms: allTermlist} // TODO(gri) is this sufficient?

	impMap  map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
	// see TODO in validtype.go
	// valids  instanceLookup      // valid *Named (incl. instantiated) types per the validType check

	// pkgPathMap maps package names to the set of distinct import paths we've
	// seen for that name, anywhere in the import graph. It is used for

	check.later(func() {
		if t := asNamed(obj.typ); t != nil { // type may be invalid
			check.validType(t)
		}
		// If typ is local, an error was already reported where typ is specified/defined.
		_ = !versionErr && check.isImportedConstraint(rhs) && check.verifyVersionf(tdecl.Type, go1_18, "using type constraint %s", rhs)
	}).describef(obj, "validType(%s)", obj.Name())

	// First type parameter, or nil.
	var tparam0 *syntax.Field

	impMap  map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
	// see TODO in validtype.go
	// valids instanceLookup // valid *Named (incl. instantiated) types per the validType check

	// pkgPathMap maps package names to the set of distinct import paths we've
	// seen for that name, anywhere in the import graph. It is used for