don't show the type of Union{} in dump

Author: JeffBezanson

base/show.jl

@@ -1663,6 +1663,10 @@ function dump(io::IOContext, x::SimpleVector, n::Int, indent)
 end
 
 function dump(io::IOContext, @nospecialize(x), n::Int, indent)
+    if x === Union{}
+        show(io, x)
+        return
+    end
     T = typeof(x)
     if isa(x, Function)
         print(io, x, " (function of type ", T, ")")

doc/src/devdocs/types.md

@@ -92,12 +92,12 @@ julia> dump(Array)
 UnionAll
   var: TypeVar
     name: Symbol T
-    lb: Core.TypeofBottom Union{}
+    lb: Union{}
     ub: Any
   body: UnionAll
     var: TypeVar
       name: Symbol N
-      lb: Core.TypeofBottom Union{}
+      lb: Union{}
       ub: Any
     body: Array{T,N} <: DenseArray{T,N}
 ```
@@ -178,12 +178,12 @@ TypeName
   wrapper: UnionAll
     var: TypeVar
       name: Symbol T
-      lb: Core.TypeofBottom Union{}
+      lb: Union{}
       ub: Any
     body: UnionAll
       var: TypeVar
         name: Symbol N
-        lb: Core.TypeofBottom Union{}
+        lb: Union{}
         ub: Any
       body: Array{T,N} <: DenseArray{T,N}
   cache: SimpleVector