fixing promote_type for Const and Identity

Author: Stephan Sahm

src/Const.jl

@@ -38,9 +38,9 @@ Base.convert(::Type{Const{T}}, x::Const) where {T} = Const(Base.convert(T, x.val
 # Const is covariate
 # promote_rule only works on concrete types, more general checks Type{<:Const} may overwrite
 # unintentionally more specific promote_rule types
-promote_rule(::Type{Const{T}}, ::Type{Const{S}}) where {T, S<:T} = Const{T}
-promote_rule(::Type{Const{T}}, ::Type{Const}) where T = Const
-promote_rule(::Type{Const}, ::Type{Const}) = Const
+Base.promote_rule(::Type{Const{T}}, ::Type{Const{S}}) where {T, S<:T} = Const{T}
+Base.promote_rule(::Type{Const{T}}, ::Type{Const}) where T = Const
+Base.promote_rule(::Type{Const}, ::Type{Const}) = Const
 
 # we need this for safety, if someone overwrites promote_typejoin for Unions with Const
 Base.promote_typejoin(::Type{Const{T}}, ::Type{Const{T}}) where T = Const{T}

src/Identity.jl

@@ -27,9 +27,9 @@ Base.convert(::Type{Identity{T}}, x::Identity) where {T} = Identity(Base.convert
 # Identity is covariate
 # promote_rule only works on concrete types, more general checks Type{<:Const} may overwrite
 # unintentionally more specific promote_rule types
-promote_rule(::Type{Identity{T}}, ::Type{Identity{S}}) where {T, S<:T} = Identity{T}
-promote_rule(::Type{Identity{T}}, ::Type{Identity}) where T = Identity
-promote_rule(::Type{Identity}, ::Type{Identity}) = Identity
+Base.promote_rule(::Type{Identity{T}}, ::Type{Identity{S}}) where {T, S<:T} = Identity{T}
+Base.promote_rule(::Type{Identity{T}}, ::Type{Identity}) where T = Identity
+Base.promote_rule(::Type{Identity}, ::Type{Identity}) = Identity
 
 # we need this for safety, if someone overwrites typejoin for Unions with Identiy
 Base.promote_typejoin(::Type{Identity{T}}, ::Type{Identity{T}}) where T = Identity{T}

test/promote_type.jl

@@ -5,25 +5,25 @@ using DataTypesBasic
 # =====
 
 @test promote_type(Const{Int}, Const{Number}) == Const{Number}
-@test promote_type(Const{Int}, Const) = Const
-@test promote_type(Const, Const) = Const
+@test promote_type(Const{Int}, Const) == Const
+@test promote_type(Const, Const) == Const
 
 @test Base.promote_typejoin(Const{Number}, Const{Number}) == Const{Number}
 @test Base.promote_typejoin(Const{Int}, Const{Number}) == Const
-@test Base.promote_typejoin(Const{Int}, Const) = Const
-@test Base.promote_typejoin(Const, Const) = Const
+@test Base.promote_typejoin(Const{Int}, Const) == Const
+@test Base.promote_typejoin(Const, Const) == Const
 
 # Identity
 # ========
 
 @test promote_type(Identity{Int}, Identity{Number}) == Identity{Number}
-@test promote_type(Identity{Int}, Identity) = Identity
-@test promote_type(Identity, Identity) = Identity
+@test promote_type(Identity{Int}, Identity) == Identity
+@test promote_type(Identity, Identity) == Identity
 
 @test Base.promote_typejoin(Identity{Number}, Identity{Number}) == Identity{Number}
 @test Base.promote_typejoin(Identity{Int}, Identity{Number}) == Identity
-@test Base.promote_typejoin(Identity{Int}, Identity) = Identity
-@test Base.promote_typejoin(Identity, Identity) = Identity
+@test Base.promote_typejoin(Identity{Int}, Identity) == Identity
+@test Base.promote_typejoin(Identity, Identity) == Identity
 
 
 # Option