From 2d314e88335639fe4e25f886fced13c3a5eef890 Mon Sep 17 00:00:00 2001
From: kimikage <kimikage.ceo@gmail.com>
Date: Sun, 27 Sep 2026 23:06:12 +0900
Subject: [PATCH] Relax the type constraints for
 `promote_rule(::Type{<:FixedPoint}, ::Type{<:FixedPoint})`

---
 src/FixedPointNumbers.jl | 21 ++++++++++++++-------
 test/traits.jl           | 12 +++++++++++-
 2 files changed, 25 insertions(+), 8 deletions(-)

diff --git a/src/FixedPointNumbers.jl b/src/FixedPointNumbers.jl
index 0e394c0..37193fd 100644
--- a/src/FixedPointNumbers.jl
+++ b/src/FixedPointNumbers.jl
@@ -49,7 +49,8 @@ reinterpret(::Type{X}, x::T) where {T <: Integer, X <: FixedPoint{T}} = X(x, 0)
 
 # static parameters
 nbitsfrac(::Type{X}) where {T, f, X <: FixedPoint{T,f}} = f
-rawtype(::Type{X}) where {T, X <: FixedPoint{T}} = T
+rawtype(::Type{X}) where {T <: Integer, X <: FixedPoint{T}} = T
+rawtype(::Type{<:FixedPoint}) = Union{} # Don't care the constraints for `T`
 
 # traits based on static parameters
 signbits(::Type{X}) where {T, X <: FixedPoint{T}} = T <: Unsigned ? 0 : 1
@@ -531,12 +532,18 @@ promote_rule(::Type{X}, ::Type{Tr}) where {X <: FixedPoint, Tr <: Rational} = Tr
 
 promote_rule(::Type{X}, ::Type{Ti}) where {X <: FixedPoint, Ti <: Integer} = floattype(X)
 
-function promote_rule(::Type{X1}, ::Type{X2}) where {T1, f1, X1 <: FixedPoint{T1,f1},
-                                                     T2, f2, X2 <: FixedPoint{T2,f2}}
-    X = wrapper(X1)
-    X !== wrapper(X2) && return promote_type(floattype(X1), floattype(X2))
-
-    f = max(f1, f2)  # ensure we have enough precision
+function promote_rule(::Type{X1}, ::Type{X2}) where {X1 <: FixedPoint, X2 <: FixedPoint}
+    X1w, X2w = wrapper.((X1, X2))
+    if X1w !== X2w
+        X1w <: X2w && return X2w
+        X2w <: X1w && return X1w
+        return promote_type(floattype(X1), floattype(X2))
+    end
+    X = X1w
+    T1, T2 = rawtype.((X1, X2))
+    isconcretetype(T1) && isconcretetype(T2) || return X{promote_type(T1, T2)}
+    f1, f2 = nbitsfrac.((X1, X2))
+    f = max(f1, f2) # ensure we have enough precision
     Tp = promote_type(T1, T2)
     T = (T1 <: Signed || T2 <: Signed) ? signedtype(Tp) : Tp
     # make sure we have enough integer bits
diff --git a/test/traits.jl b/test/traits.jl
index 0987051..4dadccd 100644
--- a/test/traits.jl
+++ b/test/traits.jl
@@ -1,5 +1,5 @@
 using FixedPointNumbers, Test
-using FixedPointNumbers: bitwidth
+using FixedPointNumbers: bitwidth, rawtype
 
 struct MyReal <: Real end
 struct MyInteger <: Integer end
@@ -32,3 +32,13 @@ struct MyInteger <: Integer end
     @test_throws MethodError floattype(MyReal) # See #177.
     @test floattype(MyInteger) === Float64
 end
+
+@testset "rawtype" begin
+    @test rawtype(FixedPoint) === Union{}
+    @test rawtype(Normed) === Union{}
+    @test rawtype(Fixed) === Union{}
+    @test rawtype(Normed{<:Unsigned}) === Union{}
+    @test rawtype(Fixed{Union{Int8, Int16}}) === Union{Int8, Int16}
+    @test rawtype(N0f8) === UInt8
+    @test rawtype(Q0f7) === Int8
+end