fixImmutableConv: incompatible types for (foo) - (bar): both operands are of type const(SysTime)

[zorael]

EndeavourOS/Arch x86_64, ldc v1.40.0 installed with the install.sh script.

LDC - the LLVM D compiler (1.40.0):
based on DMD v2.110.0 and LLVM 18.1.8
built with LDC - the LLVM D compiler (1.39.0)
Default target: x86_64-pc-linux-gnu
Host CPU: alderlake

I'm trying out the preview switches and came across some code that, with -preview=fixImmutableConv, compiles with dmd (v2.109.1) but not with ldc.

Reduced;

import std.datetime.systime;

void main()
{
    const foo = Clock.currTime;
    const bar = Clock.currTime;
    const baz = foo - bar;
}

$ ~/dlang/ldc-1.40.0/bin/ldc2 -preview=fixImmutableConv test.d
test.d(7): Error: incompatible types for `(foo) - (bar)`: both operands are of type `const(SysTime)`

The same happens if I make them immutable, and I'm using immutable SysTimes everywhere in my project. While reducing I encountered similar errors with non-mutable JSONValues.

Should this not work?

[kinke]

This isn't LDC-specific, DMD v2.110.0-beta.1 behaves identically: https://d.godbolt.org/z/azse4j14f