[REG 2.104] inout error with -profile=gc

[dlangBugzillaToGithub]

Tim reported this on 2024-02-08T22:10:50Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=24378

Description

```
inout(char)[] foo(inout(char)[] s) pure @safe
{
    s = s[0..1] ~ '%';
    return s;
}
```

The above code compiled with and without -profile=gc until DMD version 2.103. Since DMD 2.104 it only compiles without -profile=gc and produces the following error with -profile=gc:

/path/to/dmd.linux/dmd2/linux/bin64/../../src/druntime/import/core/lifetime.d(1573): Error: `inout` on `return` means `inout` must be on a parameter as well for `pure nothrow @nogc @property @safe inout(char)[]()`
/path/to/dmd.linux/dmd2/linux/bin64/../../src/druntime/import/core/internal/array/concatenation.d(174): Error: template instance `core.internal.array.concatenation._d_arraycatnTXTrace!(inout(char)[], inout(char)[], inout(char))._d_arraycatnTXTrace.forward!(__param_3, __param_4)` error instantiating
onlineapp.d(3):        instantiated from here: `_d_arraycatnTXTrace!(inout(char)[], inout(char)[], inout(char))`

As a result of this issue, compiling DMD itself with -profile=gc does not work any more.

[dlangBugzillaToGithub]

tim.dlang commented on 2024-02-09T17:13:06Z

It seems to fail since this PR: https://github.com/dlang/dmd/pull/14550