Hi,

I am little bit confused. I am copied the switch example from lex.html
and expected that case 6 will lead to a syntax error due to the missing
break statement. But the example compiles without error (C:>dmd app)

I tried 3 different dmd version, also the newest beta.

Kind regards
André

import std.stdio: writeln;

void main()
{

int number;
string message;

switch (number)
{
  default:    // valid
	throw new Exception("unknown number");

  case 3:     // valid
	message ~= "three ";
	break;

  case 5:     // valid
	message ~= "five ";
	goto case;

  case 6:     // ERROR: implicit fall-through
	message ~= "six ";

  case 1:     // valid
  case 2:     // valid
	message = "one or two";
}

}

On 03/02/2015 10:58 PM, Andre wrote:
> Hi,
>
> I am little bit confused. I am copied the switch example from lex.html
> and expected that case 6 will lead to a syntax error due to the missing
> break statement. But the example compiles without error (C:>dmd app)
>
> I tried 3 different dmd version, also the newest beta.
>
> Kind regards
> André
>
> import std.stdio: writeln;
>
> void main()
> {
>
> int number;
> string message;
>
> switch (number)
> {
>    default:    // valid
>      throw new Exception("unknown number");
>
>    case 3:     // valid
>      message ~= "three ";
>      break;
>
>    case 5:     // valid
>      message ~= "five ";
>      goto case;
>
>    case 6:     // ERROR: implicit fall-through
>      message ~= "six ";
>
>    case 1:     // valid
>    case 2:     // valid
>      message = "one or two";
> }
>
> }

Compile with -w command line switch. :)

Ali

On Tue, 03 Mar 2015 06:58:14 +0000, Andre wrote:

> Hi,
> 
> I am little bit confused. I am copied the switch example from lex.html and expected that case 6 will lead to a syntax error due to the missing break statement. But the example compiles without error (C:>dmd app)

implicit fallthru is not a fatal bug (but i believe it should be), it generates only warning.

On Tuesday, 3 March 2015 at 07:27:33 UTC, ketmar wrote:
>
> implicit fallthru is not a fatal bug (but i believe it should be), it
> generates only warning.

I am also not really happy with the actual behavor (w / wi switch needed) because the documentation is clear about that it is an error:

-- from language reference:
A ScopeStatementList must either be empty, or be ended with a ContinueStatement, BreakStatement, ReturnStatement, GotoStatement, ThrowStatement or assert(0) expression unless this is the last case. This is to set apart with C's error-prone implicit fall-through behavior. goto case; could be used for explicit fall-through
--

Fortunately dub is using the correct switches by default

Kind regards
André

Andre:

> I am also not really happy with the actual behavor (w / wi switch needed)

You shall always compile your D code with warnings active, unless you need them disabled for some real reason.

Eventually the fall through warning will become a deprecation and then an error. It's meant to be an error, but in D we introduce errors slowly.

Bye,
bearophile