compiler, language, runtime: Separate Parser Type From Instances

In P4, parsers are considered types. Those parsers are instantiated.
The instantiated parsers are values. Previously, gp4 treated a parser
type and a parser value as identical. This PR makes that difference
clear _and_ sets the stage for the future.

TODO: Make the same distinction between control and action types and
values.

Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Sources/P4Runtime/CodeGen.swift

@@ -72,14 +72,16 @@ public struct CodeGenerator: LanguageVisitor {
       }
     }
 
+    /// TODO: Handle instances.
+    /*
     result = Fold(
       input: v.instances, initial: result
     ) { (current, acc) in
       return switch acc {
-      case .Ok(let acc): acc.getVisitorDriver().visit(current.baseType(), context: acc)
+      case .Ok(let acc): acc.getVisitorDriver().visit(current, context: acc)
       case .Error(let e): .Error(e)
       }
-    }
+    }*/
 
     result = result.map {
       .Ok($0.next(uc: $0.getUserContext().append("]")))
@@ -115,7 +117,7 @@ public struct CodeGenerator: LanguageVisitor {
   }
 
   public func visit(
-    _ v: InstantiatedParserState, _ c: VisitorContext<Generated>
+    _ v: ParserState, _ c: VisitorContext<Generated>
   ) -> Result<VisitorContext<Generated>> {
     let direct_transition_codegen = {
       (
@@ -135,14 +137,14 @@ public struct CodeGenerator: LanguageVisitor {
       (
         state: ParserStateSelectTransition, c: VisitorContext<Generated>
       ) -> Result<VisitorContext<Generated>> in
-      return switch self.visit(state.selectExpression, c.next(uc: c.getUserContext().append("["))) {
+      return switch self.visit(state.te, c.next(uc: c.getUserContext().append("["))) {
       case .Ok(let res): .Ok(res.next(uc: res.getUserContext().append("]")))
       case .Error(let e): .Error(e)
       }
     }
 
     var initial = "{"
-    initial += "name: \"\(v.state)\","
+    initial += "name: \"\(v.getName())\","
     initial += "transitions: "
 
     let result: Result<VisitorContext<Generated>> =
@@ -281,4 +283,9 @@ public struct CodeGenerator: LanguageVisitor {
   ) -> Result<VisitorContext<Generated>> {
     return .Ok(c)
   }
+  public func visit(
+    _ parser_state: P4Lang.InstantiatedParserState, _ c: P4Lang.VisitorContext<Generated>
+  ) -> Common.Result<P4Lang.VisitorContext<Generated>> {
+    return .Ok(c)
+  }
 }