// Issue 20185: type switching on untyped values (e.g. nil or consts)
// caused an internal compiler error.

package p

func F() {
	switch t := nil.(type) { // ERROR "cannot type switch on non-interface value|not an interface"
	default:
		_ = t
	}
}

const x = 1

func G() {
	switch t := x.(type) { // ERROR "cannot type switch on non-interface value|declared and not used|not an interface"

func (e *TooNewError) Is(err error) bool {
	return err == ErrTooNew
}

// A Switcher provides the ability to switch to a new toolchain in response to TooNewErrors.
// See [cmd/go/internal/toolchain.Switcher] for documentation.
type Switcher interface {
	Error(err error)
	Switch(ctx context.Context)

# Using an old Go version, fails during module loading, but we rewrite the error to the
# same one a switching version would use, without the auto-switch.
# This is a misconfigured system that should not arise in practice.
env TESTGO_VERSION=go1.21.1
env TESTGO_VERSION_SWITCH=switch
cp go.work go.work.orig
! go list

// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Issue 19977: multiple error messages when type switching on an undefined

package foo

func Foo() {
	switch x := a.(type) { // ERROR "undefined: a|reference to undefined name .*a"
	default:
		_ = x
	}

		rng = rng.next(predictable)
		switch a[rng.value()&7].(type) {
		case SI0:
			n += 1
		case SI1:
			n += 2
		case SI2:
			n += 3
		case SI3:
			n += 4
		case SI4:
			n += 5
		case SI5:
			n += 6
		case SI6:
			n += 7
		case SI7:
			n += 8
		}
	}
	sink = n
}

// A simple random number generator used to make switches conditionally predictable.
type rng uint64

			targets []ast.Expr          // interfaces T in v.(T)
		)
		switch n := n.(type) {
		case *ast.TypeAssertExpr:
			// take care of v.(type) in *ast.TypeSwitchStmt
			if n.Type == nil {
				return
			}
			assert = n
			targets = append(targets, n.Type)
		case *ast.TypeSwitchStmt:
			// retrieve type assertion from type switch's 'assign' field
			switch t := n.Assign.(type) {
			case *ast.ExprStmt:

	if haveExplicitArgs || modload.WorkFilePath() != "" {
		var sw toolchain.Switcher
		// Add errors to the Switcher in deterministic order so that they will be
		// logged deterministically.
		for _, m := range mods {
			if erri, ok := downloadErrs.Load(m); ok {
				sw.Error(erri.(error))
			}
		}
		// Only call sw.Switch if it will actually switch.
		// Otherwise, we may want to write the errors as JSON

env TESTGO_VERSION=go1.21.0
env TESTGO_VERSION_SWITCH=switch

# If the main module's go.mod file lists a version lower than the version
# required by its dependencies, the commands that fetch and diagnose the module
# graph (such as 'go mod graph' and 'go mod verify') should fail explicitly:
# they can't interpret the graph themselves, and they aren't allowed to update
# the go.mod file to record a specific, stable toolchain version that can.

! go mod verify

	OIF:         -1,
	OLABEL:      -1,
	OGO:         -1,
	ORANGE:      -1,
	ORETURN:     -1,
	OSELECT:     -1,
	OSWITCH:     -1,

	OEND: 0,
}

// StmtWithInit reports whether op is a statement with an explicit init list.
func StmtWithInit(op Op) bool {
	switch op {
	case OIF, OFOR, OSWITCH:
		return true
	}
	return false
}

func stmtFmt(n Node, s fmt.State) {

	// if g == g0 call badmcall
	Get g
	Get R2
	I64Eq
	If
		JMP runtime·badmcall(SB)
	End

	// switch to g0's stack
	I64Load (g_sched+gobuf_sp)(R2)
	I64Const $8
	I64Sub
	I32WrapI64
	Set SP

	// set arg to current g
	MOVD g, 0(SP)

	// switch to g0
	MOVD R2, g

	// call fn
	Get CTXT
	I32WrapI64
	I64Load $0
	CALL

	Get SP
	I32Const $8
	I32Add