@nogc: yields a wrong error where @nogc on each definition does not

[dlangBugzillaToGithub]

Eyal reported this on 2017-12-20T09:53:08Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=18106

CC List

• Ketmar Dark

Description

This compiles correctly:

  auto ignoreDlg(void function() dlg) {}
  @nogc void foo() { ignoreDlg({ new int(5); }); }

But this gives an incorrect error about the "new" violating @nogc:

  auto ignoreDlg(void function() dlg) {}
  @nogc: void foo() { ignoreDlg({ new int(5); }); }

[dlangBugzillaToGithub]

ketmar commented on 2017-12-20T13:34:43Z

it's not *technically* incorrect: `@nogc:` affects *all* followind definitions, including lambdas. thus, in the second case, we actually have `auto __lambda () @nogc { new int(5); }`, and compiler complains.

[dlangBugzillaToGithub]

ketmar commented on 2017-12-20T13:35:28Z

`return new int(5);`, of course, sorry.

[dlangBugzillaToGithub]

eyal commented on 2017-12-20T15:39:07Z

It does not affect other kinds of nested scopes.

For example, this does compile:

auto ignoreDlg(void function() dlg) {}
@nogc: struct S { void foo() { ignoreDlg(() { new int(5); }); } }

[dlangBugzillaToGithub]

ketmar commented on 2017-12-20T15:47:27Z

yes, `struct` (and `class`, i believe) isn't affected. outer @nogc for *struct* (and class) doesn't change member attrs, only inner @nogc does. this is the logic compiler applies. ;-)

i'm still not sure if `@nogc` should do the same thing as `@nogc:` or not, tho. it prolly should, but let's wait for some compiler dev to clarify the things.

[dlangBugzillaToGithub]

eyal commented on 2017-12-20T16:31:09Z

It makes no sense at all for "@nogc" to apply to statements within a statement block of a function.

It would only make sense if it applied recursively to *all* nested scopes.

[dlangBugzillaToGithub]

timon.gehr commented on 2019-06-05T22:40:52Z

This is a more general problem, applying to other function attributes as well as @nogc.

The pull request below should be reverted as soon as this issue is fixed (it is an ugly hack fixing the problem only for the `static foreach` lowering and only for @nogc):
https://github.com/dlang/dmd/pull/9922/commits/0a65ef981578e263a380f6df4668572dce0a52d6