isolate memory type definition

how:
  extract from methods implementation source into separate file

nimbus/vm2/memory_defs.nim

@@ -0,0 +1,15 @@
+# Nimbus
+# Copyright (c) 2018 Status Research & Development GmbH
+# Licensed under either of
+#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
+#    http://www.apache.org/licenses/LICENSE-2.0)
+#  * MIT license ([LICENSE-MIT](LICENSE-MIT) or
+#    http://opensource.org/licenses/MIT)
+# at your option. This file may not be copied, modified, or distributed except
+# according to those terms.
+
+type
+  Memory* = ref object
+    bytes*:  seq[byte]
+
+# End

nimbus/vm2/v2computation.nim

@@ -15,7 +15,7 @@ import
   sets, eth/[common, keys],
   ../constants, ../errors,
   ./interpreter/[v2opcode_values, gas_meter, v2gas_costs, v2forks],
-  ./code_stream, ./v2memory, ./v2message, ./stack, ./v2types, ./v2state,
+  ./code_stream, ./memory_defs, ./v2message, ./stack, ./v2types, ./v2state,
   ../db/[accounts_cache, db_chain],
   ../utils/header, ./v2precompiles,
   ./transaction_tracer, ../utils

nimbus/vm2/v2memory.nim

@@ -13,16 +13,15 @@ when defined(evmc_enabled):
 import
   sequtils,
   chronicles, eth/common/eth_types,
-  ../errors, ../validation,
+  ../errors, ../validation, ./memory_defs,
   ./interpreter/utils/v2utils_numeric
 
+export
+  Memory
+
 logScope:
   topics = "vm memory"
 
-type
-  Memory* = ref object
-    bytes*:  seq[byte]
-
 proc newMemory*: Memory =
   new(result)
   result.bytes = @[]

nimbus/vm2/v2types.nim

@@ -16,7 +16,7 @@ when defined(evmc_enabled):
 import
   tables, eth/common,
   options, json, sets,
-  ./v2memory, ./stack_defs, ./code_stream,
+  ./stack_defs,  ./memory_defs, ./code_stream,
   ./interpreter/[v2gas_costs, v2opcode_values, v2forks],
   # TODO - will be hidden at a lower layer
   ../db/[db_chain, accounts_cache]