https://issues.dlang.org/show_bug.cgi?id=24231
Issue ID: 24231
Summary: Can't emplace immutable nested class
Product: D
Version: D2
Hardware: All
OS: All
Status: NEW
Severity: normal
Priority: P1
Component: druntime
Assignee: nob...@puremagic.com
Reporter: snarwin+bugzi...@gmail.com
As of DMD 2.105.3, the following program fails to compile.
---
void main()
{
import core.lifetime;
class O
{
int n = 123;
class I
{
int fun() => n;
}
}
auto buf = new void[](__traits(classInstanceSize, O.I));
emplace!(immutable(O.I))(buf, new immutable(O));
}
---
The error message is:
---
/usr/include/dmd/druntime/import/core/lifetime.d(116): Error: cannot modify
`immutable` expression `chunk.this`
/usr/include/dmd/druntime/import/core/lifetime.d(209): Error: template instance
`core.lifetime.emplace!(immutable(I), immutable(O))` error instantiating
test.d(14): instantiated from here: `emplace!(immutable(I),
immutable(O))`
---
This is caused by emplace attempting to set the .outer field of the emplaced
class instance to the value of its second argument (new immutable(O)). The
assignment fails, because the emplaced instance is immutable, and its fields
cannot be written to.
--
