go/src/cmd/go/internal/toolchain/switch.go

type Switcher …

// Error reports the error to the Switcher,
// which saves it for processing during Switch.
func (s *Switcher) Error(err error) { … }

// addTooNew adds any TooNew errors that can be found in err.
func (s *Switcher) addTooNew(err error) { … }

// NeedSwitch reports whether Switch would attempt to switch toolchains.
func (s *Switcher) NeedSwitch() bool { … }

// Switch decides whether to switch to a newer toolchain
// to resolve any of the saved errors.
// It switches if toolchain switches are permitted and there is at least one TooNewError.
//
// If Switch decides not to switch toolchains, it prints the errors using base.Error and returns.
//
// If Switch decides to switch toolchains but cannot identify a toolchain to use.
// it prints the errors along with one more about not being able to find the toolchain
// and returns.
//
// Otherwise, Switch prints an informational message giving a reason for the
// switch and the toolchain being invoked and then switches toolchains.
// This operation never returns.
func (s *Switcher) Switch(ctx context.Context) { … }

var counterSwitchExec …

// SwitchOrFatal attempts a toolchain switch based on the information in err
// and otherwise falls back to base.Fatal(err).
func SwitchOrFatal(ctx context.Context, err error) { … }

// NewerToolchain returns the name of the toolchain to use when we need
// to switch to a newer toolchain that must support at least the given Go version.
// See https://go.dev/doc/toolchain#switch.
//
// If the latest major release is 1.N.0, we use the latest patch release of 1.(N-1) if that's >= version.
// Otherwise we use the latest 1.N if that's allowed.
// Otherwise we use the latest release.
func NewerToolchain(ctx context.Context, version string) (string, error) { … }

// autoToolchains returns the list of toolchain versions available to GOTOOLCHAIN=auto or =min+auto mode.
func autoToolchains(ctx context.Context) ([]string, error) { … }

// pathToolchains returns the list of toolchain versions available to GOTOOLCHAIN=path or =min+path mode.
func pathToolchains(ctx context.Context) ([]string, error) { … }

// newerToolchain implements NewerToolchain where the list of choices is known.
// It is separated out for easier testing of this logic.
func newerToolchain(need string, list []string) (string, error) { … }

// HasAuto reports whether the GOTOOLCHAIN setting allows "auto" upgrades.
func HasAuto() bool { … }

// HasPath reports whether the GOTOOLCHAIN setting allows "path" upgrades.
func HasPath() bool { … }