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go/types: better error message for invalid fallthrough case

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Now matches the gc compiler.

Fixes #15594.

Change-Id: I9f3942367bc0acf883c6216b8ca44820832f5fe3
Reviewed-on: https://go-review.googlesource.com/27241
TryBot-Result: Gobot Gobot <gobot@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This commit is contained in:
Robert Griesemer 2016-08-17 14:05:47 -07:00
parent 0c819b654f
commit d1272a8b5c
2 changed files with 25 additions and 5 deletions
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18
src/go/types/stmt.go
View File

@ -68,13 +68,19 @@ func (check *Checker) usage(scope *Scope) {
}
// stmtContext is a bitset describing which
// control-flow statements are permissible.
// control-flow statements are permissible,
// and provides additional context information
// for better error messages.
type stmtContext uint
const (
// permissible control-flow statements
breakOk stmtContext = 1 << iota
continueOk
fallthroughOk
// additional context information
finalSwitchCase
)
func (check *Checker) simpleStmt(s ast.Stmt) {
@ -292,7 +298,7 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
}(check.scope)
}
inner := ctxt &^ fallthroughOk
inner := ctxt &^ (fallthroughOk | finalSwitchCase)
switch s := s.(type) {
case *ast.BadStmt, *ast.EmptyStmt:
// ignore
@ -454,7 +460,11 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
}
case token.FALLTHROUGH:
if ctxt&fallthroughOk == 0 {
check.error(s.Pos(), "fallthrough statement out of place")
msg := "fallthrough statement out of place"
if ctxt&finalSwitchCase != 0 {
msg = "cannot fallthrough final case in switch"
}
check.error(s.Pos(), msg)
}
default:
check.invalidAST(s.Pos(), "branch statement: %s", s.Tok)
@ -523,6 +533,8 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
inner := inner
if i+1 < len(s.Body.List) {
inner |= fallthroughOk
} else {
inner |= finalSwitchCase
}
check.stmtList(inner, clause.Body)
check.closeScope()

12
src/go/types/testdata/stmt0.src vendored
View File

@ -536,7 +536,7 @@ func switches1() {
default:
fallthrough; ;
case 4:
fallthrough /* ERROR "fallthrough statement out of place" */
fallthrough /* ERROR "cannot fallthrough final case in switch" */
}
var y interface{}
@ -573,7 +573,7 @@ func switches1() {
goto L6
goto L7
goto L8
L6: L7: L8: fallthrough /* ERROR "fallthrough statement out of place" */
L6: L7: L8: fallthrough /* ERROR "cannot fallthrough final case in switch" */
}
switch x {
@ -589,6 +589,14 @@ func switches1() {
fallthrough /* ERROR "fallthrough statement out of place" */
{ /* empty block is not an empty statement */ }; ;
default:
fallthrough /* ERROR "cannot fallthrough final case in switch" */
}
switch x {
case 0:
{
fallthrough /* ERROR "fallthrough statement out of place" */
}
}
}