xtparams := x.TypeParams().list()
			ytparams := y.TypeParams().list()

			var targs []Type
			for i := range xtparams {
				targs = append(targs, x.TypeParams().At(i))
			}
			smap := makeSubstMap(ytparams, targs)

			var check *Checker   // ok to call subst on a nil *Checker
			ctxt := NewContext() // need a non-nil Context for the substitution below

			xtparams := x.TypeParams().list()
			ytparams := y.TypeParams().list()

			var targs []Type
			for i := range xtparams {
				targs = append(targs, x.TypeParams().At(i))
			}
			smap := makeSubstMap(ytparams, targs)

			var check *Checker   // ok to call subst on a nil *Checker
			ctxt := NewContext() // need a non-nil Context for the substitution below

			// it separately. Otherwise we can simply use the result signature's parameter
			// list.
			if adjusted {
				sigParams = check.subst(call.Pos(), sigParams, makeSubstMap(tparams[:n], targs[:n]), nil, check.context()).(*Tuple)
			} else {
				sigParams = rsig.params
			}
		}

		// compute argument signatures: instantiate if needed
		j := n

			// it separately. Otherwise we can simply use the result signature's parameter
			// list.
			if adjusted {
				sigParams = check.subst(call.Pos(), sigParams, makeSubstMap(tparams[:n], targs[:n]), nil, check.context()).(*Tuple)
			} else {
				sigParams = rsig.params
			}
		}

		// compute argument signatures: instantiate if needed
		j := n