vm2: Remove `toSymbolName` unnecessary symbol-text-symbol conversion

There's no need for macro `toSymbolName` to convert fork enum values to their
presentation texts (logging etc) then re-parse them back to a fork enum value.
`asFork` is already used in the same function and works without these steps,
so use it consistently.

Same applies to `op.toSymbolName` and `asOp`.

This makes the code simpler, and removes a text pattern-matching requirement.
The patch has been checked to confirm it doesn't change the compiled code.

Motivation: The forks list will be removed from VM because it is used outside
the VM as well.  Doing so highlighted vm2's `toSymbolName`.  It's not needed,
and it's best if the VM doesn't constrain text strings used outside the VM

Signed-off-by: Jamie Lokier <jamie@shareable.org>

nimbus/vm2/interpreter/forks_list.nim

@@ -8,20 +8,11 @@
 # at your option. This file may not be copied, modified, or distributed except
 # according to those terms.
 
-## List of known Etheroum forks
+## List of known Ethereum forks
 ## ============================
 ##
 ## See `here <../../ex/vm/interpreter/forks_list.html>`_ for an
 ## overview.
-##
-## Assumptions on the naming of the fork list:
-##  * each symbol start with the prefix "Fk"
-##  * the first word of the prettified text representaion is the same
-##    text as the one following the "Fk" in the symbol name (irrespective
-##    of character case.)
-
-import
-  strutils
 
 type
   Fork* = enum
@@ -35,9 +26,4 @@ type
     FkIstanbul = "istanbul"
     FkBerlin = "berlin"
 
-proc toSymbolName*(fork: Fork): string =
-  ## Given a `fork` argument, print the symbol name so that it can be used
-  ## in a macro statement.
-  "Fk" & ($fork).split(' ')[0]
-
 # End

nimbus/vm2/interpreter/op_codes.nim

@@ -208,12 +208,6 @@ type
     SelfDestruct =   0xff  ## Halt execution and register account for later
                            ## deletion.
 
-
-proc toSymbolName*(op: Op): string =
-  ## Given an `op` argument, print the symbol name so that it can be used
-  ## in a macro statement.
-  $op
-
 # ------------------------------------------------------------------------------
 # Verify that Op is contiguous and sym names follow some standards
 # ------------------------------------------------------------------------------

nimbus/vm2/interpreter/op_dispatcher.nim

@@ -74,15 +74,13 @@ proc toCaseStmt(forkArg, opArg, k: NimNode): NimNode =
   let branchOnOp = quote do: `opArg`
   result = nnkCaseStmt.newTree(branchOnOp)
   for op in Op:
+    let asOp = quote do: Op(`op`)
 
     # Inner case/switch => Fork
     let branchOnFork = quote do: `forkArg`
     var forkCaseSubExpr = nnkCaseStmt.newTree(branchOnFork)
     for fork in Fork:
-
-      let
-        asFork = quote do: Fork(`fork`)
-        asOp = quote do: Op(`op`)
+      let asFork = quote do: Fork(`fork`)
 
       let branchStmt = block:
         if op == Stop:
@@ -95,9 +93,7 @@ proc toCaseStmt(forkArg, opArg, k: NimNode): NimNode =
           quote do:
             handleOtherDirective(`asFork`,`asOp`,`k`)
 
-      forkCaseSubExpr.add nnkOfBranch.newTree(
-        newIdentNode(fork.toSymbolName),
-        branchStmt)
+      forkCaseSubExpr.add nnkOfBranch.newTree(asFork, branchStmt)
 
     # Wrap innner case/switch into outer case/switch
     let branchStmt = block:
@@ -115,9 +111,7 @@ proc toCaseStmt(forkArg, opArg, k: NimNode): NimNode =
         quote do:
           `forkCaseSubExpr`
 
-    result.add nnkOfBranch.newTree(
-      newIdentNode(op.toSymbolName),
-      branchStmt)
+    result.add nnkOfBranch.newTree(asOp, branchStmt)
 
   when isChatty:
     echo ">>> ", result.repr