Issue 4197

module main;
const S S1 = S();
struct S 
{
 static S func( S s_ )
 in{ assert(false,random); }
 out(result){ assert(false,random); }
 body{ return s_; }
 
 const S S2 = func(S());
}
void main(){}
--
main.d(8): Error: __error <---# should be assert failure #
main.d(12): Error: cannot evaluate func((S())) at compile time

(In reply to comment #0)
> module main;
> 
> const S S1 = S();
> 
> struct S 
> {
> static S func( S s_ )
> in{ assert(false,random); }
> out(result){ assert(false,random); }
> body{ return s_; }
> 
> const S S2 = func(S());
> }
> void main(){}
> --
> main.d(8): Error: __error <---# should be assert failure #
> main.d(12): Error: cannot evaluate func((S())) at compile time
The second argument to assert() - if present - is supposed to be a string describing the condition. The error message without the second parameter or with a string there instead is correct.

This can be a simplified version of the same problem:
enum Foo F1 = Foo();
struct Foo {
 const Foo F2 = func();
}
Foo func() {
 assert(false, random);
 return Foo();
}
void main() {}

(In reply to comment #1)
> 
> The second argument to assert() - if present - is supposed to be a string
> describing the condition. The error message without the second parameter or
> with a string there instead is correct.
I was expecting something like :
Error: cannot implicitly cast "random" of type unknown to string
Or 
Error: "random" not defined

Original title was:
"__error iso assert failure in struct function in/out statement"
A reduced test case shows it is a very general ICE.
*Any* error inside an in() or out() contract in a function that is has its semantic run through CTFE, has all errors gagged. This can result in a cryptic error message (as in the original test case), or an ICE. This one is ICE(glue.c), but I've also seen ICE(toir.c). It fails on both D1 and D2.
const Bug4197 s4197 = Bug4197();
int func4197()
in { undefined; }
body { return 0; }
struct Bug4197 {
 static const int S2 = func4197();
}

D2 fix: https://github.com/D-Programming-Language/dmd/commit/0a927f258e89f92f280c0e855a93ceb05e34a260
Partial D1 fix: https://github.com/D-Programming-Language/dmd/commit/31d6751de3a877c72055a2096a9a9c4a9a25ec9b 

D1 fix: https://github.com/D-Programming-Language/dmd/commit/23846aca52ebd21efab36ff32924c5a6cc17c4c0