if updated {
			// Create a new instance and populate the context to avoid endless
			// recursion. The position used here is irrelevant because validation only
			// occurs on t (we don't call validType on named), but we use subst.pos to
			// help with debugging.
			return subst.check.instance(subst.pos, orig, targs, subst.expanding, subst.ctxt)
		}

	case *TypeParam:
		return subst.smap.lookup(t)

		if updated {
			// Create a new instance and populate the context to avoid endless
			// recursion. The position used here is irrelevant because validation only
			// occurs on t (we don't call validType on named), but we use subst.pos to
			// help with debugging.
			return subst.check.instance(subst.pos, orig, targs, subst.expanding, subst.ctxt)
		}

	case *TypeParam:
		return subst.smap.lookup(t)

	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 *ast.Field

	"typeterm.go":      nil,
	"typestring.go":    nil,
	"under.go":         nil,
	"unify.go":         fixSprintf,
	"universe.go":      fixGlobalTypVarDecl,
	"util_test.go":     fixTokenPos,
	"validtype.go":     func(f *ast.File) { fixTokenPos(f); renameSelectors(f, "Trace->_Trace") },
}

// TODO(gri) We should be able to make these rewriters more configurable/composable.
//           For now this is a good starting point.

	obj   *TypeName // corresponding declared object for declared types; see above for instantiated types

	// fromRHS holds the type (on RHS of declaration) this *Named type is derived
	// from (for cycle reporting). Only used by validType, and therefore does not
	// require synchronization.
	fromRHS Type

	// information for instantiated types; nil otherwise
	inst *instance

	mu         sync.Mutex     // guards all fields below

	obj   *TypeName // corresponding declared object for declared types; see above for instantiated types

	// fromRHS holds the type (on RHS of declaration) this *Named type is derived
	// from (for cycle reporting). Only used by validType, and therefore does not
	// require synchronization.
	fromRHS Type

	// information for instantiated types; nil otherwise
	inst *instance

	mu         sync.Mutex     // guards all fields below