Commonize promotion rules (#207)

This makes the promotion rules for `Fixed` consistent with the rules used within `Normed`:
- `Fixed` and `Integer` are promoted to `floattype`
- `Fixed` and `AbstractFloat` are promoted to `floattype` with sufficient precision

This adds the rule:
- `Fixed` and `Normed` are promoted to `floattype`

This also stops using `@generated` function.

Author: kimikage

src/FixedPointNumbers.jl

@@ -311,6 +311,35 @@ include("normed.jl")
 include("deprecations.jl")
 const UF = (N0f8, N6f10, N4f12, N2f14, N0f16)
 
+# Promotions
+promote_rule(::Type{X}, ::Type{Tf}) where {X <: FixedPoint, Tf <: AbstractFloat} =
+    promote_type(floattype(X), Tf)
+
+# Note that `Tr` does not always have enough domains. 
+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
+    Tp = promote_type(T1, T2)
+    T = (T1 <: Signed || T2 <: Signed) ? signedtype(Tp) : Tp
+    # make sure we have enough integer bits
+    m = max(nbitsint(X1), nbitsint(X2))
+    _widen_rawtype(X{T,f}, m)
+end
+
+function _widen_rawtype(::Type{X}, m) where {T, f, X<:FixedPoint{T,f}}
+    nbitsint(X) >= m && return X
+    Tw = widen1(T)
+    T === Tw && return X
+    _widen_rawtype(wrapper(X){Tw,f}, m)
+end
+
 # Promotions for reductions
 const Treduce = Float64
 Base.add_sum(x::FixedPoint, y::FixedPoint) = Treduce(x) + Treduce(y)

src/fixed.jl

@@ -195,24 +195,5 @@ length(r::AbstractUnitRange{F}) where {F <: Fixed{<:SShorterThanInt,f}} where {f
 length(r::AbstractUnitRange{F}) where {F <: Fixed{T}} where {T <: Signed} =
     checked_add(checked_sub(floor(T, last(r)), floor(T, first(r))), oneunit(T))
 
-promote_rule(ft::Type{Fixed{T,f}}, ::Type{TI}) where {T,f,TI <: Integer} = Fixed{T,f}
-promote_rule(::Type{Fixed{T,f}}, ::Type{TF}) where {T,f,TF <: AbstractFloat} = TF
-promote_rule(::Type{Fixed{T,f}}, ::Type{Rational{TR}}) where {T,f,TR} = Rational{TR}
-
-@generated function promote_rule(::Type{Fixed{T1,f1}}, ::Type{Fixed{T2,f2}}) where {T1,T2,f1,f2}
-    f = max(f1, f2)  # ensure we have enough precision
-    T = promote_type(T1, T2)
-    # make sure we have enough integer bits
-    i1, i2 = bitwidth(T1)-f1, bitwidth(T2)-f2  # number of integer bits for each
-    i = bitwidth(T)-f
-    while i < max(i1, i2)
-        Tw = widen1(T)
-        T == Tw && break
-        T = Tw
-        i = bitwidth(T)-f
-    end
-    :(Fixed{$T,$f})
-end
-
 # TODO: Document and check that it still does the right thing.
 decompose(x::Fixed{T,f}) where {T,f} = x.i, -f, 1

src/normed.jl

@@ -303,24 +303,3 @@ length(r::AbstractUnitRange{N}) where {N <: Normed{<:UShorterThanInt}} =
     floor(Int, last(r)) - floor(Int, first(r)) + 1
 length(r::AbstractUnitRange{N}) where {N <: Normed{T}} where {T<:Unsigned} =
     r.start > r.stop ? T(0) : checked_add(floor(T, last(r)) - floor(T, first(r)), oneunit(T))
-
-# Promotions
-promote_rule(::Type{T}, ::Type{Tf}) where {T <: Normed,Tf <: AbstractFloat} = promote_type(floattype(T), Tf)
-promote_rule(::Type{T}, ::Type{R}) where {T <: Normed,R <: Rational} = R
-function promote_rule(::Type{T}, ::Type{Ti}) where {T <: Normed,Ti <: Union{Signed, Unsigned}}
-    floattype(T)
-end
-@generated function promote_rule(::Type{Normed{T1,f1}}, ::Type{Normed{T2,f2}}) where {T1,T2,f1,f2}
-    f = max(f1, f2)  # ensure we have enough precision
-    T = promote_type(T1, T2)
-    # make sure we have enough integer bits
-    i1, i2 = bitwidth(T1)-f1, bitwidth(T2)-f2  # number of integer bits for each
-    i = bitwidth(T)-f
-    while i < max(i1, i2)
-        Tw = widen1(T)
-        T == Tw && break
-        T = Tw
-        i = bitwidth(T)-f
-    end
-    :(Normed{$T,$f})
-end

src/utilities.jl

@@ -1,6 +1,7 @@
 # utility functions and macros, which are independent of `FixedPoint`
 bitwidth(T::Type) = 8sizeof(T)
 
+widen1(T::Type)         = T # fallback
 widen1(::Type{Int8})    = Int16
 widen1(::Type{UInt8})   = UInt16
 widen1(::Type{Int16})   = Int32
@@ -9,8 +10,6 @@ widen1(::Type{Int32})   = Int64
 widen1(::Type{UInt32})  = UInt64
 widen1(::Type{Int64})   = Int128
 widen1(::Type{UInt64})  = UInt128
-widen1(::Type{Int128})  = Int128
-widen1(::Type{UInt128}) = UInt128
 widen1(x::Integer) = x % widen1(typeof(x))
 
 signedtype(::Type{T}) where {T <: Integer} = typeof(signed(zero(T)))
@@ -48,3 +47,5 @@ if !signbit(signed(unsafe_trunc(UInt, -12.345)))
     # exclude BigFloat (issue #202)
     _unsafe_trunc(::Type{T}, x::BigFloat) where {T <: Integer} = unsafe_trunc(T, x)
 end
+
+wrapper(@nospecialize(T)) = Base.typename(T).wrapper

test/fixed.jl

@@ -455,13 +455,24 @@ end
     @test Fixed{Int16,3}(-1)   == Fixed{Int8,5}(-1)
     @test Fixed{Int16,3}(0.25) == Fixed{Int8,5}(0.25)
 
-    @test promote_type(Q0f7,Float32,Int) == Float32
-    @test promote_type(Q0f7,Int,Float32) == Float32
-    @test promote_type(Int,Q0f7,Float32) == Float32
-    @test promote_type(Int,Float32,Q0f7) == Float32
-    @test promote_type(Float32,Int,Q0f7) == Float32
-    @test promote_type(Float32,Q0f7,Int) == Float32
-    @test promote_type(Q0f7,Q1f6,Q2f5,Q3f4,Q4f3,Q5f2) == Fixed{Int128,7}
+    @test @inferred(promote_type(Q0f7, Float64)) === Float64
+    @test @inferred(promote_type(Float32, Q7f24)) === Float64
+
+    @test @inferred(promote_type(Q0f7, Int8)) === Float32
+    @test @inferred(promote_type(Int128, Q7f24)) === Float64
+
+    @test @inferred(promote_type(Q0f15, Rational{UInt8})) === Rational{UInt8}
+
+    @test @inferred(promote_type(Q0f7, Float32, Int)) === Float32
+    @test @inferred(promote_type(Q0f7, Int, Float32)) === Float32
+    @test @inferred(promote_type(Int, Q0f7, Float32)) === Float32
+    @test @inferred(promote_type(Int, Float32, Q0f7)) === Float32
+    @test @inferred(promote_type(Float32, Int, Q0f7)) === Float32
+    @test @inferred(promote_type(Float32, Q0f7, Int)) === Float32
+
+    @test @inferred(promote_type(Q0f7,Q1f6,Q2f5,Q3f4,Q4f3,Q5f2)) == Fixed{Int128,7}
+
+    @test @inferred(promote_type(Q0f7, N0f32)) === Float64
 end
 
 @testset "show" begin

test/normed.jl

@@ -485,13 +485,24 @@ end
     @test Normed{UInt16,4}(1)   == Normed{UInt8,6}(1)
     @test Normed{UInt16,4}(0.2) == Normed{UInt8,6}(0.2)
 
-    @test promote_type(N0f8,Float32,Int) == Float32
-    @test promote_type(N0f8,Int,Float32) == Float32
-    @test promote_type(Int,N0f8,Float32) == Float32
-    @test promote_type(Int,Float32,N0f8) == Float32
-    @test promote_type(Float32,Int,N0f8) == Float32
-    @test promote_type(Float32,N0f8,Int) == Float32
-    @test promote_type(N0f8,N1f7,N2f6,N3f5,N4f4,N5f3) == Normed{UInt128,8}
+    @test @inferred(promote_type(N0f8, Float64)) === Float64
+    @test @inferred(promote_type(Float32, N8f24)) === Float64
+
+    @test @inferred(promote_type(N0f8, Int8)) === Float32
+    @test @inferred(promote_type(Int128, N8f24)) === Float64
+
+    @test @inferred(promote_type(N0f16, Rational{Int8})) === Rational{Int8}
+
+    @test @inferred(promote_type(N0f8, Float32, Int)) === Float32
+    @test @inferred(promote_type(N0f8, Int, Float32)) === Float32
+    @test @inferred(promote_type(Int, N0f8, Float32)) === Float32
+    @test @inferred(promote_type(Int, Float32, N0f8)) === Float32
+    @test @inferred(promote_type(Float32, Int, N0f8)) === Float32
+    @test @inferred(promote_type(Float32, N0f8, Int)) === Float32
+
+    @test @inferred(promote_type(N0f8,N1f7,N2f6,N3f5,N4f4,N5f3)) === Normed{UInt128,8}
+
+    @test @inferred(promote_type(N0f8, Q0f31)) === Float64
 end
 
 @testset "show" begin