On 17/02/2013 20:07, Jonathan M Davis wrote:
<snip>
Implicit fall through shouldn't have been allowed from the beginning. It
would appear that this has finally been banned.
Implicit fallthrough is a warning when a case stament is non-empty, but if
it's empty (as in the example), then there is no warning.
What version of DMD are you using?
I'm getting stranger than this (2.061):
----- switch_fallthrough_a.d -----
void main() {
char c = 'x';
switch(c) {
case 'U', 'u' :
case 'L', 'l' :
// code . . .
default:
}
}
----- switch_fallthrough_b.d -----
void main() {
char c = 'x';
switch(c) {
case 'U', 'u' :
c = 'q';
case 'L', 'l' :
c = 'r';
// code . . .
default:
}
}
----------
C:\Users\Stewart\Documents\Programming\D\Tests>dmd switch_fallthrough_a.d
C:\Users\Stewart\Documents\Programming\D\Tests>dmd -w switch_fallthrough_a.d
switch_fallthrough_a.d(5): Error: switch case fallthrough - use 'goto case;' if
intended
switch_fallthrough_a.d(7): Error: switch case fallthrough - use 'goto default;'
if intended
C:\Users\Stewart\Documents\Programming\D\Tests>dmd switch_fallthrough_b.d
C:\Users\Stewart\Documents\Programming\D\Tests>dmd -w switch_fallthrough_b.d
switch_fallthrough_b.d(6): Error: switch case fallthrough - use 'goto case;' if
intended
switch_fallthrough_b.d(9): Error: switch case fallthrough - use 'goto default;'
if intended
----------
You see, it's independent of whether there are any statements between the two case
markers, and there's a further anomaly in that it's an _error_ that's emitted only if
_warnings_ are enabled.
If the compiler is warning about falling through an empty case statement, it's
a bug.
There's no such thing as an "empty case statement", unless you mean the case where the
ScopeStatementList is ";" or "{}" by itself. Look at the grammar carefully.
So by the current spec, the first example is a syntax error, since a CaseStatement
explicitly forbids another CaseStatement as its body.
Stewart.
