move show code to Common area

Author: oxinabox

src/tangent_types/structural_tangent.jl

@@ -140,6 +140,33 @@ function Base.map(f, tangent::StructuralTangent{P}) where {P}
     end
 end
 
+
+function Base.show(io::IO, tangent::StructuralTangent{P}) where {P}
+    if tangent isa MutableTangent
+        print(io, "Mutable")
+    end
+    print(io, "Tangent{")
+    str = sprint(show, P, context = io)
+    i = findfirst('{', str)
+    if isnothing(i)
+        print(io, str)
+    else  # for Tangent{T{A,B,C}}(stuff), print {A,B,C} in grey, and trim this part if longer than a line:
+        print(io, str[1:prevind(str, i)])
+        if length(str) < 80
+            printstyled(io, str[i:end], color=:light_black)
+        else
+           printstyled(io, str[i:prevind(str, 80)], "...", color=:light_black) 
+        end
+    end
+    print(io, "}")
+    if isempty(backing(tangent))
+        print(io, "()")  # so it doesn't show `NamedTuple()`
+    else
+        # allow Tuple or NamedTuple `show` to do the rendering of brackets etc
+        show(io, backing(tangent))
+    end
+end
+
 """
     backing(x)
 
@@ -334,32 +361,6 @@ Base.:(==)(a::Tangent{P}, b::Tangent{Q}) where {P,Q} = false
 
 Base.hash(a::Tangent, h::UInt) = Base.hash(backing(canonicalize(a)), h)
 
-function Base.show(io::IO, tangent::StructuralTangent{P}) where {P}
-    if tangent isa MutableTangent
-        print(io, "Mutable")
-    end
-    print(io, "Tangent{")
-    str = sprint(show, P, context = io)
-    i = findfirst('{', str)
-    if isnothing(i)
-        print(io, str)
-    else  # for Tangent{T{A,B,C}}(stuff), print {A,B,C} in grey, and trim this part if longer than a line:
-        print(io, str[1:prevind(str, i)])
-        if length(str) < 80
-            printstyled(io, str[i:end], color=:light_black)
-        else
-           printstyled(io, str[i:prevind(str, 80)], "...", color=:light_black) 
-        end
-    end
-    print(io, "}")
-    if isempty(backing(tangent))
-        print(io, "()")  # so it doesn't show `NamedTuple()`
-    else
-        # allow Tuple or NamedTuple `show` to do the rendering of brackets etc
-        show(io, backing(tangent))
-    end
-end
-
 Base.iszero(::Tangent{<:,NamedTuple{}}) = true
 Base.iszero(::Tangent{<:,Tuple{}}) = true