Disallow array * Tangent (#501)

* disallow array * Tangent

* tests

Author: mcabbott

src/tangent_arithmetic.jl

@@ -147,7 +147,7 @@ Base.:+(a::Tangent{P}, b::P) where {P} = b + a
 # We intentionally do not define, `Base.*(::Tangent, ::Tangent)` as that is not meaningful
 # In general one doesn't have to represent multiplications of 2 differentials
 # Only of a differential and a scaling factor (generally `Real`)
-for T in (:Any,)
+for T in (:Number,)
     @eval Base.:*(s::$T, tangent::Tangent) = map(x -> s * x, tangent)
     @eval Base.:*(tangent::Tangent, s::$T) = map(x -> x * s, tangent)
 end

test/tangent_types/tangent.jl

@@ -91,7 +91,11 @@ end
         @test getproperty(Tangent{NT}(; b=(@thunk 2.0^2)), 2) == 4.0
 
         # TODO: uncomment this once https://github.com/JuliaLang/julia/issues/35516
-        @test_broken haskey(Tangent{Tuple{Float64}}(2.0), 1) == true
+        if VERSION >= v"1.8-"
+            @test haskey(Tangent{Tuple{Float64}}(2.0), 1) == true
+        else
+            @test_broken haskey(Tangent{Tuple{Float64}}(2.0), 1) == true
+        end
         @test_broken hasproperty(Tangent{Tuple{Float64}}(2.0), 2) == false
 
         @test length(Tangent{Foo}(; x=2.5)) == 1
@@ -331,6 +335,10 @@ end
         d = Tangent{Dict}(Dict(4 => 3.0))
         two_d = Tangent{Dict}(Dict(4 => 2 * 3.0))
         @test 2 * d == two_d == d * 2
+
+        @test_throws MethodError [1, 2] * Tangent{Foo}(; y=1.5, x=2.5)
+        @test_throws MethodError [1, 2] * d
+        @test_throws MethodError Tangent{Foo}(; y=1.5, x=2.5) * @thunk [1 2; 3 4]
     end
 
     @testset "show" begin