Add test merging VarInfos with different dimensions for a variable

Author: mhauru

test/varinfo.jl

@@ -869,6 +869,17 @@ end
             @test DynamicPPL.getgid(varinfo_merged, @varname(x)) == gidset_left
             @test DynamicPPL.getgid(varinfo_merged, @varname(y)) == gidset_right
         end
+
+        # The below used to error, testing to avoid regression.
+        @testset "merge different dimensions" begin
+            vn = @varname(x)
+            vi_single = VarInfo()
+            vi_single = push!!(vi_single, vn, 1.0, Normal())
+            vi_double = VarInfo()
+            vi_double = push!!(vi_double, vn, [2.0, 3.0], Normal())
+            @test merge(vi_single, vi_double)[vn] == 1.0
+            @test merge(vi_double, vi_single)[vn] == [2.0, 3.0]
+        end
     end
 
     @testset "VarInfo with selectors" begin