add a basic similarterm for matchable types

Author: shashi

src/code.jl

@@ -740,8 +740,9 @@ function cse_block!(assignments, counter, names, name, state, x)
         if isterm(x)
             return term(operation(x), args...)
         else
-            return similarterm(x, operation(x), args, symtype(x),
-                        metadata=metadata(x))
+            return similarterm(x, operation(x),
+                               args, symtype(x),
+                               metadata=metadata(x))
         end
     else
         return x

src/utils.jl

@@ -223,6 +223,7 @@ macro matchable(expr)
         SymbolicUtils.operation(::$name) = $name
         SymbolicUtils.arguments(x::$name) = getfield.((x,), ($(QuoteNode.(fields)...),))
         Base.length(x::$name) = $(length(fields) + 1)
+        SymbolicUtils.similarterm(x::$name, f, args, type; kw...) = f(args...)
     end |> esc
 end