Bug 1594 – version not honored for invarient declaration

The following program does not compile in 1.022. The error message is "invar.d(6): statement expected to be { }, not int". import std.stdio; version (D_Version2) { string str = "Version 2"; invariant int myint = 2; } else { string str = "Version 1"; const int myint = 1; } void main() { writefln( "str: %s\nmyint: %s", str, myint ); return; } Notice that a version 1 compiler shouldn't be trying to compile the statement where the error occurs: it's in a block designated as being for a different version of the compiler. Change the single occurrence of if "invariant" to "const", and it compiles fine. With this change, the output of the program is str: Version 1 myint: 1 just as you would hope.

I know its not intuitive but the compiler is behaving correctly. All the code inside a version block must be valid code for the compiler you are using. Here is how you need to do what you want to achieve... version(D_Version2) { string str = "Version 2"; mixin("invariant int myint = 2;"); } else { string str = "Version 1"; const int myint = 1; }

[email protected] Wrote: > I know its not intuitive but the compiler is behaving correctly. All the code > inside a version block must be valid code for the compiler you are using. > > Here is how you need to do what you want to achieve... > > version(D_Version2) > { > string str = "Version 2"; > mixin("invariant int myint = 2;"); > } > > else > { > string str = "Version 1"; > const int myint = 1; > } Hmmmm. The following would also work: version (D_Version2) { mixin( "alias invariant int invarInt;" ); invarInt myint = 2; } Unfortunately, this does not work: version (D_Version2) { mixin( "alias invariant int invarInt;" ); } else { alias const int invarInt; } Neither v.1 nor v. 2 likes alias of const. (I can't figure out why neither likes alias of const but v. 2 likes alias of invariant. const is a storage class, not a type modifier; but then, I presume, the same is true for invariant in v. 2.) Could an invariant storage class be added to version 1 that is just equivalent 10 const? We obviously don't want to add a new storage class semantics to version 1--changes to v. 1 at this point should be limited essentially to bug fixes. However, using the word invariant with const semantics might be a small enough change to be a worthwhile. It would be a convenience to those trying to develop for version 1 and version 2 sinultaneously.

Oops, I think I was supposed to close this since I was the one that opened it in the first place.