// command line. Recommend 'go mod download' for the modules that could
		// provide the package, since that shouldn't change go.mod.
		if len(e.mods) > 0 {
			args := make([]string, len(e.mods))
			for i, mod := range e.mods {
				args[i] = mod.Path
			}
			hint = fmt.Sprintf("; to add:\n\tgo mod download %s", strings.Join(args, " "))
		}
	} else {

	Short:     "edit go.mod from tools or scripts",
	Long: `
Edit provides a command-line interface for editing go.mod,
for use primarily by tools or scripts. It reads only go.mod;
it does not look up information about the modules involved.
By default, edit reads and writes the go.mod file of the main module,
but a different target file can be specified after the editing flags.

		indirect bool
	}
	need := make(map[string]elem)
	for _, r := range req {
		if prev, dup := need[r.Mod.Path]; dup && prev.version != r.Mod.Version {
			panic(fmt.Errorf("SetRequire called with conflicting versions for path %s (%s and %s)", r.Mod.Path, prev.version, r.Mod.Version))
		}
		need[r.Mod.Path] = elem{r.Mod.Version, r.Indirect}
	}

	// Update or delete the existing Require entries to preserve

		}
	}

	// Not v2/go.mod, so it's either go.mod or nothing. Which is it?
	if found1 {
		// Explicit go.mod with matching major version ok.
		return rev, r.codeDir, gomod1, nil
	}
	if err1 == nil {
		// Explicit go.mod with non-matching major version disallowed.
		suffix := ""
		if file2 != "" {
			suffix = fmt.Sprintf(" (and ...%s/go.mod does not exist)", r.pathMajor)
		}
		if mpath1 == "" {

		mod = readString(x, ptrSize, readPtr, readPtr(data[16+ptrSize:]))
	}
	if vers == "" {
		return "", "", errNotGoExe
	}
	if len(mod) >= 33 && mod[len(mod)-17] == '\n' {
		// Strip module framing: sentinel strings delimiting the module info.
		// These are cmd/go/internal/modload.infoStart and infoEnd.
		mod = mod[16 : len(mod)-16]
	} else {
		mod = ""
	}

	return vers, mod, nil

		if plus && suffix != "auto" && suffix != "path" {
			base.Fatalf("invalid GOTOOLCHAIN %q: only version suffixes are +auto and +path", gotoolchain)
		}
		mode = suffix
	}

	gotoolchain = minToolchain
	if (mode == "auto" || mode == "path") && !goInstallVersion() {
		// Read go.mod to find new minimum and suggested toolchain.
		file, goVers, toolchain := modGoToolchain()
		gover.Startup.AutoFile = file
		if toolchain == "default" {

}

// Subtract sets s = x - y mod l, and returns s.
func (s *Scalar) Subtract(x, y *Scalar) *Scalar {
	// s = -1 * y + x mod l
	fiatScalarSub(&s.s, &x.s, &y.s)
	return s
}

// Negate sets s = -x mod l, and returns s.
func (s *Scalar) Negate(x *Scalar) *Scalar {
	// s = -1 * x + 0 mod l
	fiatScalarOpp(&s.s, &x.s)
	return s
}

// Multiply sets s = x * y mod l, and returns s.
func (s *Scalar) Multiply(x, y *Scalar) *Scalar {

		}

		// m = c ^ Dp mod p
		m = bigmod.NewNat().Exp(t0.Mod(c, P), priv.Precomputed.Dp.Bytes(), P)
		// m2 = c ^ Dq mod q
		m2 := bigmod.NewNat().Exp(t0.Mod(c, Q), priv.Precomputed.Dq.Bytes(), Q)
		// m = m - m2 mod p
		m.Sub(t0.Mod(m2, P), P)
		// m = m * Qinv mod p
		m.Mul(Qinv, P)
		// m = m * q mod N
		m.ExpandFor(N).Mul(t0.Mod(Q.Nat(), N), N)
		// m = m + m2 mod N
		m.Add(m2.ExpandFor(N), N)
	}

		needSubtraction = not(choice(borrow)) | choice(carry)
	}
	return x.assign(needSubtraction, d)
}

// Mod calculates out = x mod m.
//
// This works regardless how large the value of x is.
//
// The output will be resized to the size of m and overwritten.
func (out *Nat) Mod(x *Nat, m *Modulus) *Nat {
	out.resetFor(m)
	// Working our way from the most significant to the least significant limb,

// We stopped trying to auto-generate the go.mod files. Now we use a trivial
// go.mod with only a module line, and we've dropped the version prefix
// entirely. If we see a version prefix, that means we're looking at an old copy
// and should ignore it.
var oldVgoPrefix = []byte("//vgo 0.0.")

// readDiskGoMod reads a cached go.mod file from disk,