Bug 3748 – inout does not work properly

Created attachment 558 file to test whether inout is properly implemented inout as defined by DIP2 is not implemented properly on dmd 2.039. Attached is a testing program that should be used to determine if inout is properly implemented. I tried to include every subtle detail that I could on inout, but I'm not sure that I got them all. If the compiler passes this test, inout should be ready for most uses. Since half of the definition of inout is what *doesn't* compile, I have included multiple errors in the file. Because of the nature of compiler errors, each error can be individually enabled or disabled using version statements, a la error1, error2, etc. When no error statements are enabled, the program should compile correctly. There is no need to run the program, since all asserts are static.

Created attachment 950 Fixed some minor syntax error. Fixed the position of ';' on line 22. Added back the missing is() on lines 48 and 50. (Just a note: as of commit 48950d4ce371316184e2 (2.052) DMD still cannot compile this file successfully.)

*** Issue 4968 has been marked as a duplicate of this issue. ***

My patch doesn't forbid to declare inout variable outside inout function. It is treated same as const variable, even with my patch. I think it is debatable thing.

it is not debateable. The issue is, when inside an inout-enabled function, all inout variables are *assignable* from other inout variables. So for example, if you have: inout(int) * globalvar; inout(int)* foo(inout(int)* x) { return globalvar; } void main() { int x; auto y = foo(&x); } what type is y? inout(T) is changed to just T in this scenario, since the constancy factor is mutable, so essentially, you now have a mutable pointer to what is treated as const as you say. The type system *must* prevent non-local variables (i.e. variables not on the stack) from being inout. Otherwise, you cannot make guarantees about inout.

Created attachment 1035 Corrected some errors that were previously hard to detect because inout didn't work uploaded a fixed version of testinout.d error8 and error11 still compile, so this isn't completely resolved, but inout is definitely is usable. I will open a new bug for that, as this is a single problem with inout (allowing inout variables anywhere, not just as auto variables of inout functions). Note that Kenji stated those holes were still present. But this is definitely a huge step forward.

See new bug 6770

For fixing error8 and error11. https://github.com/D-Programming-Language/dmd/pull/433

*** Issue 6519 has been marked as a duplicate of this issue. ***