compiler, runtime: Begin Runtime Refactor

Ultimately, the goal is to completely separate the compilation from
the runtime to make it possible to have the interpreter/evaluator
be "just another" entity that can perform meaningful work when
given a parsed GP4 program.

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

Sources/P4Lang/Expressions.swift

@@ -18,9 +18,9 @@
 import Common
 
 public struct KeysetExpression {
-  public let key: EvaluatableExpression
+  public let key: P4Expression
 
-  public init(_ key: EvaluatableExpression) {
+  public init(_ key: P4Expression) {
     self.key = key
   }
 
@@ -65,11 +65,11 @@ public struct SelectCaseExpression {
 }
 
 public struct SelectExpression {
-  public let selector: EvaluatableExpression
+  public let selector: P4Expression
   public let case_expressions: [SelectCaseExpression]
 
   public init(
-    withSelector selector: EvaluatableExpression,
+    withSelector selector: P4Expression,
     withSelectCaseExpressions sces: [SelectCaseExpression]
   ) {
     self.selector = selector
@@ -105,13 +105,13 @@ public struct BinaryOperatorExpression {
 }
 
 public struct ArrayAccessExpression {
-  public let indexor: EvaluatableExpression
-  public let name: EvaluatableExpression
+  public let indexor: P4Expression
+  public let name: P4Expression
   public let type: P4Array
 
   public init(
-    withName name: EvaluatableExpression, withType type: P4Array,
-    withIndexor indexor: EvaluatableExpression
+    withName name: P4Expression, withType type: P4Array,
+    withIndexor indexor: P4Expression
   ) {
     self.name = name
     self.type = type
@@ -121,9 +121,9 @@ public struct ArrayAccessExpression {
 
 public struct FieldAccessExpression {
   public let field: P4StructFieldIdentifier
-  public let strct: EvaluatableExpression
+  public let strct: P4Expression
 
-  public init(withStruct strct: EvaluatableExpression, withField field: P4StructFieldIdentifier) {
+  public init(withStruct strct: P4Expression, withField field: P4StructFieldIdentifier) {
     self.strct = strct
     self.field = field
   }