)

type MainModuleSet struct {
	// versions are the module.Version values of each of the main modules.
	// For each of them, the Path fields are ordinary module paths and the Version
	// fields are empty strings.
	// versions is clipped (len=cap).
	versions []module.Version

	// modRoot maps each module in versions to its absolute filesystem path.
	modRoot map[module.Version]string

// and may rely on it not to be modified.
func (mg *ModuleGraph) RequiredBy(m module.Version) (reqs []module.Version, ok bool) {
	return mg.g.RequiredBy(m)
}

// Selected returns the selected version of the module with the given path.
//
// If no version is selected, Selected returns version "none".
func (mg *ModuleGraph) Selected(path string) (version string) {
	return mg.g.Selected(path)
}

			return path, version, fmt.Errorf("invalid %s path: %v", adj, err)
		}
	}
	if path != arg && !allowedVersionArg(version) {
		return path, version, fmt.Errorf("invalid %s version: %q", adj, version)
	}
	return path, version, nil
}

// flagEditworkReplace implements the -replace flag.
func flagEditworkReplace(arg string) {
	before, after, found := strings.Cut(arg, "=")
	if !found {

				// versions older than what is listed in the go.mod file.
				compatVersion = goVersion
			}
		}
		if gover.Compare(compatVersion, goVersion) > 0 {
			// Each version of the Go toolchain knows how to interpret go.mod and
			// go.sum files produced by all previous versions, so a compatibility
			// version higher than the go.mod version adds nothing.
			compatVersion = goVersion
		}

				}
				if len(packages) == 0 {
					// curM at its original version contains a path matching q.pattern,
					// but at rev.Version it does not, so (somewhat paradoxically) if
					// we changed the version of curM it would no longer match the query.
					var version any = m
					if rev.Version != q.version {
						version = fmt.Sprintf("%s@%s (%s)", m.Path, q.version, m.Version)
					}

//
// The -dropreplace=old[@v] flag drops a replacement of the given
// module path and version pair. If the @v is omitted, a replacement without
// a version on the left side is dropped.
//
// The -retract=version and -dropretract=version flags add and drop a
// retraction on the given version. The version may be a single version

)

// allowVersion reports whether the current package at the given position
// is allowed to use version v. If the position is unknown, the specified
// module version (Config.GoVersion) is used. If that version is invalid,
// allowVersion returns true.
func (check *Checker) allowVersion(at poser, v goVersion) bool {
	fileVersion := check.conf.GoVersion
	if pos := at.Pos(); pos.IsKnown() {

func convT(typ *byte, elem *any) unsafe.Pointer

// Same as convT, for types with no pointers in them.
func convTnoptr(typ *byte, elem *any) unsafe.Pointer

// Specialized versions of convT for specific types.
// These functions take concrete types in the runtime. But they may
// be used for a wider range of types, which have the same memory
// layout as the parameter type. The compiler converts the

// data is the go.mod content.
func checkGoMod(path, version string, data []byte) error {
	h, err := goModSum(data)
	if err != nil {
		return &module.ModuleError{Path: path, Version: version, Err: fmt.Errorf("verifying go.mod: %v", err)}
	}

	return checkModSum(module.Version{Path: path, Version: version + "/go.mod"}, h)
}

// checkModSum checks that the recorded checksum for mod is h.
//

means that if a header file foo/bar.h exists both in the source
directory and also in the system include directory (or some other place
specified by a -I flag), then "#include <foo/bar.h>" will always find the
local version in preference to any other version.

The cgo tool is enabled by default for native builds on systems where
it is expected to work. It is disabled by default when cross-compiling