From 7367922a57cf8fc3e3b7a20157281b6f313d82da Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Patrick=20H=C3=A4cker?= <patrick.haecker@bosch.com>
Date: Thu, 10 Sep 2026 04:59:46 +0200
Subject: [PATCH] Create BitIntegers package extension for cross-conversions
 between types

---
 Project.toml          |  7 +++++++
 README.md             |  9 +++++++++
 ext/BitIntegersExt.jl |  8 ++++++++
 test/bitintegers.jl   | 24 ++++++++++++++++++++++++
 test/runtests.jl      |  1 +
 5 files changed, 49 insertions(+)
 create mode 100644 ext/BitIntegersExt.jl
 create mode 100644 test/bitintegers.jl

diff --git a/Project.toml b/Project.toml
index bf6397c..4264028 100644
--- a/Project.toml
+++ b/Project.toml
@@ -10,7 +10,14 @@ projects = ["test"]
 PrecompileTools = "aea7be01-6a6a-4083-8856-8a6e6704d82a"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 
+[weakdeps]
+BitIntegers = "c3b6d118-76ef-56ca-8cc7-ebb389d030a1"
+
+[extensions]
+BitIntegersExt = "BitIntegers"
+
 [compat]
+BitIntegers = "0.3"
 PrecompileTools = "1"
 Random = "1"
 julia = "1.10"
diff --git a/README.md b/README.md
index acabfd4..028c2db 100644
--- a/README.md
+++ b/README.md
@@ -128,6 +128,15 @@ const Int7_8 = Int7
 
 The signedness of data and storage types are always identical.
 
+When both packages are loaded, a package extension enables checked conversion
+from emulated integers to BitIntegers types, including user-defined types from
+`@define_integers`.
+
+```jldoctest usage
+julia> Int256(UInt3(7))
+7
+```
+
 If you want to `@emulate` multiple types, you can simply provide multiple arguments to the macro with regular macro syntax:
 
 ```jldoctest usage
diff --git a/ext/BitIntegersExt.jl b/ext/BitIntegersExt.jl
new file mode 100644
index 0000000..cc01cf1
--- /dev/null
+++ b/ext/BitIntegersExt.jl
@@ -0,0 +1,8 @@
+module BitIntegersExt
+
+using EmulatedBitIntegers: EmulatedInteger
+using BitIntegers: AbstractBitSigned, AbstractBitUnsigned
+
+(::Type{Target})(value::EmulatedInteger) where {Target<:Union{AbstractBitSigned, AbstractBitUnsigned}} = Target(value[])
+
+end
\ No newline at end of file
diff --git a/test/bitintegers.jl b/test/bitintegers.jl
new file mode 100644
index 0000000..86c64f6
--- /dev/null
+++ b/test/bitintegers.jl
@@ -0,0 +1,24 @@
+@define_integers 24 ConversionInt24 ConversionUInt24
+
+@testset "BitIntegers conversion" begin
+    @emulate Int3 UInt3 Int3_128 UInt3_128 Int129 UInt129
+
+    for Source in (Int3, UInt3, Int3_128, UInt3_128, Int129, UInt129)
+        for Target in (Int256, UInt256, Int512, UInt512, Int1024, UInt1024, ConversionInt24, ConversionUInt24)
+            for value in (typemin(Source), zero(Source), one(Source), typemax(Source))
+                if typemin(Target) <= BigInt(value[]) <= typemax(Target)
+                    expected = Target(value[])
+                    @test (@inferred Target(value)) === expected
+                    @test (@inferred convert(Target, value)) === expected
+                else
+                    @test_throws InexactError Target(value)
+                    @test_throws InexactError convert(Target, value)
+                end
+            end
+        end
+    end
+
+    @test Int256(Int3(1)) === Int256(1)
+    extension = Base.get_extension(EmulatedBitIntegers, :BitIntegersExt)
+    @test isempty(Test.detect_ambiguities(EmulatedBitIntegers, BitIntegers, extension))
+end
\ No newline at end of file
diff --git a/test/runtests.jl b/test/runtests.jl
index e81fac2..edeffaa 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -18,6 +18,7 @@ values(x) = x |> fieldvalues |> collect
 include("comparisons.jl")
 include("sums.jl")
 include("broadcasting.jl")
+include("bitintegers.jl")
 
 # ============================================================================
 # Static analysis