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912a638b0c
go/test/goto.go
Robert Griesemer 912a638b0c cmd/compile: check labels and branches during parse time 
Instead of a separate check control flow pass (checkcfg.go)
operating on nodes, perform this check at parse time on the
new syntax tree. Permits this check to be done concurrently,
and doesn't depend on the specifics of the symbol's dclstack
implementation anymore. The remaining dclstack uses will be
removed in a follow-up change.

- added CheckBranches Mode flag (so we can turn off the check
  if we only care about syntactic correctness, e.g. for tests)

- adjusted test/goto.go error messages: the new branches
  checker only reports if a goto jumps into a block, but not
  which block (we may want to improve this again, eventually)

- also, the new branches checker reports one variable that
  is being jumped over by a goto, but it may not be the first
  one declared (this is fine either way)

- the new branches checker reports additional errors for
  fixedbugs/issue14006.go (not crucial to avoid those errors)

- the new branches checker now correctly reports only
  variable declarations being jumped over, rather than
  all declarations (issue 8042). Added respective tests.

Fixes #8042.

Change-Id: I53b6e1bda189748e1e1fb5b765a8a64337c27d40
Reviewed-on: https://go-review.googlesource.com/39998
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
2017-04-19 00:36:34 +00:00

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// errorcheck
// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Verify goto semantics.
// Does not compile.
//
// Each test is in a separate function just so that if the
// compiler stops processing after one error, we don't
// lose other ones.
package main
var (
i, n int
x []int
c chan int
m map[int]int
s string
)
// goto after declaration okay
func _() {
x := 1
goto L
L:
_ = x
}
// goto before declaration okay
func _() {
goto L
L:
x := 1
_ = x
}
// goto across declaration not okay
func _() {
goto L // ERROR "goto L jumps over declaration of x at LINE+1|goto jumps over declaration"
x := 1 // GCCGO_ERROR "defined here"
_ = x
L:
}
// goto across declaration in inner scope okay
func _() {
goto L
{
x := 1
_ = x
}
L:
}
// goto across declaration after inner scope not okay
func _() {
goto L // ERROR "goto L jumps over declaration of x at LINE+5|goto jumps over declaration"
{
x := 1
_ = x
}
x := 1 // GCCGO_ERROR "defined here"
_ = x
L:
}
// goto across declaration in reverse okay
func _() {
L:
x := 1
_ = x
goto L
}
// error shows first offending variable
func _() {
goto L // ERROR "goto L jumps over declaration of x at LINE+1|goto L jumps over declaration of y at LINE+3|goto jumps over declaration"
x := 1 // GCCGO_ERROR "defined here"
_ = x
y := 1
_ = y
L:
}
// goto not okay even if code path is dead
func _() {
goto L // ERROR "goto L jumps over declaration of x at LINE+1|goto L jumps over declaration of y at LINE+3|goto jumps over declaration"
x := 1 // GCCGO_ERROR "defined here"
_ = x
y := 1
_ = y
return
L:
}
// goto into outer block okay
func _() {
{
goto L
}
L:
}
// goto backward into outer block okay
func _() {
L:
{
goto L
}
}
// goto into inner block not okay
func _() {
goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
{ // GCCGO_ERROR "block starts here"
L:
}
}
// goto backward into inner block still not okay
func _() {
{ // GCCGO_ERROR "block starts here"
L:
}
goto L // ERROR "goto L jumps into block starting at LINE-3|goto L jumps into block|goto jumps into block"
}
// error shows first (outermost) offending block
func _() {
goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
{
{
{ // GCCGO_ERROR "block starts here"
L:
}
}
}
}
// error prefers block diagnostic over declaration diagnostic
func _() {
goto L // ERROR "goto L jumps into block starting at LINE+3|goto L jumps into block|goto jumps into block"
x := 1
_ = x
{ // GCCGO_ERROR "block starts here"
L:
}
}
// many kinds of blocks, all invalid to jump into or among,
// but valid to jump out of
// if
func _() {
L:
if true {
goto L
}
}
func _() {
L:
if true {
goto L
} else {
}
}
func _() {
L:
if false {
} else {
goto L
}
}
func _() {
goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
if true { // GCCGO_ERROR "block starts here"
L:
}
}
func _() {
goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
if true { // GCCGO_ERROR "block starts here"
L:
} else {
}
}
func _() {
goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
if true {
} else { // GCCGO_ERROR "block starts here"
L:
}
}
func _() {
if false { // GCCGO_ERROR "block starts here"
L:
} else {
goto L // ERROR "goto L jumps into block starting at LINE-3|goto L jumps into block|goto jumps into block"
}
}
func _() {
if true {
goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
} else { // GCCGO_ERROR "block starts here"
L:
}
}
func _() {
if true {
goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
} else if false { // GCCGO_ERROR "block starts here"
L:
}
}
func _() {
if true {
goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
} else if false { // GCCGO_ERROR "block starts here"
L:
} else {
}
}
func _() {
// This one is tricky. There is an implicit scope
// starting at the second if statement, and it contains
// the final else, so the outermost offending scope
// really is LINE+1 (like in the previous test),
// even though it looks like it might be LINE+3 instead.
if true {
goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
} else if false {
} else { // GCCGO_ERROR "block starts here"
L:
}
}
/* Want to enable these tests but gofmt mangles them. Issue 1972.
func _() {
// This one is okay, because the else is in the
// implicit whole-if block and has no inner block
// (no { }) around it.
if true {
goto L
} else
L:
}
func _() {
// Still not okay.
if true { //// GCCGO_ERROR "block starts here"
L:
} else
goto L //// ERROR "goto L jumps into block starting at LINE-3|goto jumps into block"
}
*/
// for
func _() {
for {
goto L
}
L:
}
func _() {
for {
goto L
L:
}
}
func _() {
for { // GCCGO_ERROR "block starts here"
L:
}
goto L // ERROR "goto L jumps into block starting at LINE-3|goto L jumps into block|goto jumps into block"
}
func _() {
for { // GCCGO_ERROR "block starts here"
goto L
L1:
}
L:
goto L1 // ERROR "goto L1 jumps into block starting at LINE-5|goto L1 jumps into block|goto jumps into block"
}
func _() {
for i < n { // GCCGO_ERROR "block starts here"
L:
}
goto L // ERROR "goto L jumps into block starting at LINE-3|goto L jumps into block|goto jumps into block"
}
func _() {
for i = 0; i < n; i++ { // GCCGO_ERROR "block starts here"
L:
}
goto L // ERROR "goto L jumps into block starting at LINE-3|goto L jumps into block|goto jumps into block"
}
func _() {
for i = range x { // GCCGO_ERROR "block starts here"
L:
}
goto L // ERROR "goto L jumps into block starting at LINE-3|goto L jumps into block|goto jumps into block"
}
func _() {
for i = range c { // GCCGO_ERROR "block starts here"
L:
}
goto L // ERROR "goto L jumps into block starting at LINE-3|goto L jumps into block|goto jumps into block"
}
func _() {
for i = range m { // GCCGO_ERROR "block starts here"
L:
}
goto L // ERROR "goto L jumps into block starting at LINE-3|goto L jumps into block|goto jumps into block"
}
func _() {
for i = range s { // GCCGO_ERROR "block starts here"
L:
}
goto L // ERROR "goto L jumps into block starting at LINE-3|goto L jumps into block|goto jumps into block"
}
// switch
func _() {
L:
switch i {
case 0:
goto L
}
}
func _() {
L:
switch i {
case 0:
default:
goto L
}
}
func _() {
switch i {
case 0:
default:
L:
goto L
}
}
func _() {
switch i {
case 0:
default:
goto L
L:
}
}
func _() {
switch i {
case 0:
goto L
L:
;
default:
}
}
func _() {
goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
switch i {
case 0:
L: // GCCGO_ERROR "block starts here"
}
}
func _() {
goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
switch i {
case 0:
L: // GCCGO_ERROR "block starts here"
;
default:
}
}
func _() {
goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
switch i {
case 0:
default:
L: // GCCGO_ERROR "block starts here"
}
}
func _() {
switch i {
default:
goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
case 0:
L: // GCCGO_ERROR "block starts here"
}
}
func _() {
switch i {
case 0:
L: // GCCGO_ERROR "block starts here"
;
default:
goto L // ERROR "goto L jumps into block starting at LINE-4|goto L jumps into block|goto jumps into block"
}
}
// select
// different from switch. the statement has no implicit block around it.
func _() {
L:
select {
case <-c:
goto L
}
}
func _() {
L:
select {
case c <- 1:
default:
goto L
}
}
func _() {
select {
case <-c:
default:
L:
goto L
}
}
func _() {
select {
case c <- 1:
default:
goto L
L:
}
}
func _() {
select {
case <-c:
goto L
L:
;
default:
}
}
func _() {
goto L // ERROR "goto L jumps into block starting at LINE+2|goto L jumps into block|goto jumps into block"
select {
case c <- 1:
L: // GCCGO_ERROR "block starts here"
}
}
func _() {
goto L // ERROR "goto L jumps into block starting at LINE+2|goto L jumps into block|goto jumps into block"
select {
case c <- 1:
L: // GCCGO_ERROR "block starts here"
;
default:
}
}
func _() {
goto L // ERROR "goto L jumps into block starting at LINE+3|goto L jumps into block|goto jumps into block"
select {
case <-c:
default:
L: // GCCGO_ERROR "block starts here"
}
}
func _() {
select {
default:
goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
case <-c:
L: // GCCGO_ERROR "block starts here"
}
}
func _() {
select {
case <-c:
L: // GCCGO_ERROR "block starts here"
;
default:
goto L // ERROR "goto L jumps into block starting at LINE-4|goto L jumps into block|goto jumps into block"
}
}
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