var a: FooNotNil should give CT error, breaks not nil semantics, causing SIGSEGV

[timotheecour]

var a: FooNotNil should give CT error, breaks not nil semantics, causing SIGSEGV

Example

when true:
  type Foo = ref object
    x: int
  type Foo2 = Foo not nil
  proc main2(a: Foo2) =
    echo a.x
  block:
    var x: Foo2 # BUG: should give CT error
    main2(x) # SIGSEGV
  block:
    var x = default(Foo2)  # BUG: should give CT error
    main2(x)  # SIGSEGV

Current Output

SIGSEGV: Illegal storage access

Expected Output

CT error for both var x: Foo2 and var x = default(Foo2)

Additional Information

• devel 19cab9f
• I could not find a similar issue in not nil issues we have
• Stronger enforcement of not nil and requiresInit #13808 could maybe fix and add a test for this? /cc @zah

[zah]

#13808 detects these situations. The original version of the PR was producing errors for them, but Araq and I agreed to settle for warnings for now. This would give the community more time to decide how to deal with some of the trickier issues such as seq.setLen being unsafe for not nil types as well.

[timotheecour]

some of the trickier issues such as seq.setLen being unsafe for not nil types as well.

I've suggested ignoreNotNil here: #13808 (comment) for that and all such cases