Backport partially JuliaMath#207

Author: kimikage

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)))

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)) === Float32 # Float64 on v0.9 (#207)
+
+    @test @inferred(promote_type(Q0f7, Int8)) === Q0f7 # Float32 on v0.9 (#207)
+    @test @inferred(promote_type(Int128, Q7f24)) === Q7f24 # Float64 on v0.9 (#207)
+
+    @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)) === FixedPoint # Float64 on v0.9 (#207)
 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)) === FixedPoint # Float64 on v0.9 (#207)
 end
 
 @testset "show" begin