# Backported from upstream vibe: https://github.com/vibe-d/vibe-serialization/pull/27

From ebd472c28f8d98e4488425a52ece07f2eaf9045f Mon Sep 17 00:00:00 2001
From: Andrei Horodniceanu <a.horodniceanu@proton.me>
Date: Wed, 12 Aug 2026 22:12:56 +0300
Subject: [PATCH] source/vibe/data/json.d: Fix initialization of BigInt

Assigning to the `m_bigInt` union member is lowered to an `opAssign`
on the `BigInt` instance, (and its internal `BigUint` member), which
means invariants will be called at the entrance in the function. Now,
the `BigUint` struct has an invariant that checks that its internal
data is non-zero.

This invariant thus fails when a `Json` object is constructed because
the constructor specifically zeros out the memory before assigning the
default value to the `m_bigInt` member.

Replacing the assignment with a call to `core.lifetime.emplace` fixes
the issue by not calling the invariant and directly constructing the
variable with its safe internal state.

This issue can be observed when running the unittests with a stdlib
compiled without `-frelease`. The easiest way to do this is using
`ldc` with `-link-defaultlib-debug`.

Signed-off-by: Andrei Horodniceanu <a.horodniceanu@proton.me>

diff --git i/source/dub/internal/vibecompat/data/json.d w/source/dub/internal/vibecompat/data/json.d
--- i/source/dub/internal/vibecompat/data/json.d
+++ w/source/dub/internal/vibecompat/data/json.d
@@ -1261,7 +1261,7 @@ struct Json {
 	private void initBigInt()
 	nothrow @trusted {
 		// BigInt is a struct, and it has a special BigInt.init value, which differs from null.
-		m_bigInt = BigInt.init;
+		emplace(&m_bigInt);
 	}
 
 	private void runDestructors()