_, ok := Unalias(t).(*TypeParam)
	return ok
}

// hasEmptyTypeset reports whether t is a type parameter with an empty type set.
// The function does not force the computation of the type set and so is safe to
// use anywhere, but it may report a false negative if the type set has not been
// computed yet.
func hasEmptyTypeset(t Type) bool {
	if tpar, _ := Unalias(t).(*TypeParam); tpar != nil && tpar.bound != nil {

	_, ok := Unalias(t).(*TypeParam)
	return ok
}

// hasEmptyTypeset reports whether t is a type parameter with an empty type set.
// The function does not force the computation of the type set and so is safe to
// use anywhere, but it may report a false negative if the type set has not been
// computed yet.
func hasEmptyTypeset(t Type) bool {
	if tpar, _ := Unalias(t).(*TypeParam); tpar != nil && tpar.bound != nil {

				buf.WriteString(" constrained by ")
				WriteType(&buf, tpar.bound, qf) // do not compute interface type sets here
				// If we have the type set and it's empty, say so for better error messages.
				if hasEmptyTypeset(tpar) {
					buf.WriteString(" with empty type set")
				}
			}
		} else {
			buf.WriteString(" with invalid type")
		}
	}

	// )
	if expr != "" {
		buf.WriteByte(')')
	}

				buf.WriteString(" constrained by ")
				WriteType(&buf, tpar.bound, qf) // do not compute interface type sets here
				// If we have the type set and it's empty, say so for better error messages.
				if hasEmptyTypeset(tpar) {
					buf.WriteString(" with empty type set")
				}
			}
		} else {
			buf.WriteString(" with invalid type")
		}
	}

	// )
	if expr != "" {
		buf.WriteByte(')')
	}