Bug 1118 – weird switch statement behaviour

The documentation for the switch statement says: SwitchStatement: switch ( Expression ) ScopeStatement So there must not be 'case', 'default' or scoping brackets after the switch. Hence this would be valid code (and actually compiles, throwing a 'Switch Default' error for the first example): switch (1) for (int i=0; i<5; i++) writefln(i); // another, yet acceptable but ugly looking example example switch (true) case true: writefln("foo"); switch (5) { // do anything but no switch/case writefln("foo"); } But beside a ScopeStatement, even a normal Statement gets accepted by the compiler (at least I could not figure out a transition from a ScopeStatement to an ExpressionStatement): switch(2) writefln("foo"); _________________________________________________________________ Examples were tested on Ubuntu Linux with * dmd 1.010 * gdc 0.23 _________________________________________________________________ PS: I think a definition like this would do the job: SwitchStatement: switch ( Expression ) { SwitchItemList } SwitchItemList: SwitchItem SwitchItem SwitchItemList SwitchItem: CaseStatement DefaultStatement

What about cases like this: switch(i) { while(i) { foo(); case 0: bar(); case 1: baz(); case 3: i--; } }

> What about cases like this: > > switch(i) > { > while(i) > { > foo(); > case 0: bar(); > case 1: baz(); > case 3: i--; > } > } > > Nice idea, never had to use it that way. Think this issue should be tagged as INVALID... But looking at the examples given before, it would be nice if the compiler would give at least a warning about missing switch labels.

Not having a case might not be a problem: tuples can be foreached to generate cases and a zero length tuple might be valid. You would however expect their to be a default in that case. int Foo(A...)(int i) { switch(i) { default: // code break; foreach(a;A) { case a: // code // break; } } }

> ------- Comment #3 from [email protected] 2007-04-09 18:41 ------- > Not having a case might not be a problem: tuples can be foreached to generate > cases and a zero length tuple might be valid. You would however expect their to > be a default in that case. > > int Foo(A...)(int i) > { > switch(i) > { > default: > // code > break; > foreach(a;A) > { > case a: > // code > // break; > } > } > } > > Wow, again I'm amazed by D's features! But I could not compile your code (yet a real bug :P ). But I could find a workaround: import std.stdio; // your version (should work, but it doesn't) void Foo1(A...)(int i) { switch (i) { foreach(a; A) { case a: // line 9 writefln(a); } } } // workaround (does exactly the same thing, but with more clumsy code) void Foo2(A...)(int i) { switch (i) { foreach(j, a; A) { case A[j]: writefln(a); } } } void main() { //Foo1!(1,2,3,4,5)(1); // line 29 Foo2!(1,2,3,4,5)(1); } The output is 1 2 3 4 5 just as expected. But uncommenting Foo1 gives an error. Error log from Code::Blocks: hello.d:9: Error: case must be a string or an integral constant, not a hello.d:9: Error: case must be a string or an integral constant, not a hello.d:9: Error: duplicate case 0 in switch statement hello.d:9: Error: case must be a string or an integral constant, not a hello.d:9: Error: duplicate case 0 in switch statement hello.d:9: Error: case must be a string or an integral constant, not a hello.d:9: Error: duplicate case 0 in switch statement hello.d:9: Error: case must be a string or an integral constant, not a hello.d:9: Error: duplicate case 0 in switch statement hello.d:29: template instance hello.Foo1!(1,2,3,4,5) error instantiating :: === Build finished: 10 errors, 0 warnings === I think that's worth a bug report.

Fixed DMD 1.018 and DMD 2.002