// so we don't write some go.mods with the "before" toolchain
		// and others with the "after" toolchain. If nothing else, that
		// discrepancy could show up in auto-recorded toolchain lines.
		changed, err := modload.EditBuildList(ctx, nil, mustSelectFor[m])
		if err != nil {
			continue
		}
		if changed {
			modload.LoadPackages(ctx, modload.PackageOpts{
				Tags:                     imports.AnyTags(),

// 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)

	// the dummy command-line-arguments module. Add a requirement on the
	// module that provides the packages named on the command line.
	if _, err := modload.EditBuildList(ctx, nil, []module.Version{rootMod}); err != nil {
		return nil, fmt.Errorf("%s: %w", args[0], err)
	}

	// Load packages for all arguments.
	pkgs := PackagesAndErrors(ctx, opts, patterns)