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/P4Compiler/Protocols.swift

@@ -22,12 +22,6 @@ import SwiftTreeSitter
 import TreeSitterExtensions
 import TreeSitterP4
 
-public protocol CompilableStatement {
-  static func Compile(
-    node: Node, withContext context: CompilerContext
-  ) -> Result<(EvaluatableStatement, CompilerContext)>
-}
-
 public protocol CompilableValue {
   static func CompileValue(withValue value: String) -> Result<P4DataValue>
 }
@@ -38,19 +32,27 @@ public protocol CompilableType {
   ) -> Result<P4Type?>
 }
 
-public protocol CompilableDeclaration {
-  /// Info
-  ///
-  /// Extensions should update the context with the newly declared item _unless_
-  /// they are in an extern context (``CompilerContext.extern_context``).
-  static func Compile(
+public protocol CompilableExpression {
+  static func compile(
     node: Node, withContext context: CompilerContext
-  ) -> Result<(Declaration, CompilerContext)?>
+  ) -> Result<P4Expression?>
 }
 
-public protocol Compilable<T> {
-  associatedtype T
+public protocol CompilableLValueExpression {
+  static func compile_as_lvalue(
+    node: Node, withContext context: CompilerContext
+  ) -> Result<P4LValueExpression?>
+}
+
+public protocol Compilable<C> {
+  associatedtype C
   static func Compile(
     node: Node, withContext context: CompilerContext
-  ) -> Result<(T, CompilerContext)>
+  ) -> Result<C>
+}
+
+public protocol CompilableStatement {
+  static func CompileStatement(
+    node: Node, withContext context: CompilerContext
+  ) -> Result<P4Statement>
 }