// the listed modules requiring a higher version of another), EditBuildList
// returns a *ConstraintError and leaves the build list in its previous state.
//
// On success, EditBuildList reports whether the selected version of any module
// in the build list may have been changed (possibly to or from "none") as a
// result.
func EditBuildList(ctx context.Context, add, mustSelect []module.Version) (changed bool, err error) {

		// A TooNewError can happen for 'go get go@newversion'
		// when all the required modules are old enough
		// but the command line is not.
		// TODO(bcmills): modload.EditBuildList should catch this instead,
		// and then this can be changed to base.Fatal(err).
		toolchain.SwitchOrFatal(ctx, err)
	}

	newReqs := reqsFromGoMod(modload.ModFile())
	r.reportChanges(oldReqs, newReqs)