Make v and hcat with numbers work. (#514)

* Make v and hcat with numbers work.

* change RArray to Union{AnyConcrerteRArray, AnyTracedRArray}; add a unit test for this change

* update unit tests

* update unit tests: confirming vcat and hcat are working as expected

* update test: improve reproducibility of test

* update test: w/ deterministic values

Author: jaeminoh

src/Reactant.jl

@@ -202,6 +202,7 @@ end
 # StdLib Overloads
 include("stdlibs/LinearAlgebra.jl")
 include("stdlibs/Random.jl")
+include("stdlibs/Base.jl")
 
 # Other Integrations
 include("Enzyme.jl")

src/stdlibs/Base.jl

@@ -0,0 +1,4 @@
+@inline Base.vcat(a::Number, b::Union{AnyConcreteRArray, AnyTracedRArray}) =
+    @allowscalar(vcat(fill!(similar(b, typeof(a), (1, size(b)[2:end]...)), a), b))
+@inline Base.hcat(a::Number, b::Union{AnyConcreteRArray, AnyTracedRArray}) =
+    @allowscalar(hcat(fill!(similar(b, typeof(a), (size(b)[1:end-1]..., 1)), a), b))

test/basic.jl

@@ -368,6 +368,34 @@ end
         @test y == test_typed_hvncat(x)
         @test eltype(y) === Int
     end
+
+    @testset "Number and RArray" for a in [1.0f0, 1.0e0]
+        typeof_a = typeof(a)
+        _b = [2.0, 3.0, 4.0] .|> typeof_a
+        _c = [2.0 3.0 4.0] .|> typeof_a
+        b = Reactant.to_rarray(_b)
+        c = Reactant.to_rarray(_c)
+    
+        # vcat test        
+        y = @jit vcat(a, b)
+        @test y == vcat(a, _b)
+        @test y isa ConcreteRArray{typeof_a,1}
+    
+        ## vcat test - adjoint
+        y1 = @jit vcat(a, c')
+        @test y1 == vcat(a, _c')
+        @test y1 isa ConcreteRArray{typeof_a,2}
+    
+        # hcat test
+        z = @jit hcat(a, c)
+        @test z == hcat(a, _c)
+        @test z isa ConcreteRArray{typeof_a,2}
+    
+        ## hcat test - adjoint
+        z1 = @jit hcat(a, b')
+        @test z1 == hcat(a, _b')
+        @test z1 isa ConcreteRArray{typeof_a,2}
+    end
 end
 
 @testset "repeat" begin