Refactor Parsing/Runtime

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

Tests/p4rseTests/ScopeTests.swift

@@ -0,0 +1,66 @@
+// p4rse, Copyright 2026, Will Hawkins
+//
+// This file is part of p4rse.
+//
+// This file is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+import Common
+import Foundation
+import Macros
+import P4Runtime
+import SwiftTreeSitter
+import Testing
+import TreeSitter
+import TreeSitterP4
+
+@testable import P4Parser
+
+@Test func test_scope() async throws {
+  let s = LexicalScope()
+  let s2 = s.declare(identifier: Identifier(name: "first"), withValue: P4Int.create())
+  let found_first = try! #require(s2.lookup(identifier: Identifier(name: "first")))
+
+  #expect(found_first.eq(rhs: P4Int.create()))
+  #expect(s2.count == 1)
+}
+
+@Test func test_scope_no_set() async throws {
+  var ss = LexicalScopes().enter()
+  ss = ss.declare(identifier: Identifier(name: "first"), withValue: P4Int.create())
+  ss = ss.enter()
+  ss = ss.declare(identifier: Identifier(name: "second"), withValue: P4Boolean.create())
+
+  let found_first = try! #UseOkResult(ss.lookup(identifier: Identifier(name: "first")))
+  let found_second = try! #UseOkResult(ss.lookup(identifier: Identifier(name: "second")))
+
+  #expect(found_first.eq(rhs: P4Int.create()))
+  #expect(found_second.eq(rhs: P4Boolean.create()))
+}
+
+@Test func test_scope_set() async throws {
+  var ss = LexicalScopes().enter()
+  let id = Identifier(name: "first")
+  let id_type = P4Int.create()
+
+  ss = ss.declare(identifier: id, withValue: id_type)
+  ss = ss.enter()
+  ss = ss.declare(identifier: Identifier(name: "second"), withValue: P4Boolean.create())
+  // Change the value of `first`.
+  ss = ss.set(identifier: id, withValue: P4String.create())
+
+  // Verify the change!
+  let found = try! #UseOkResult(ss.lookup(identifier: id))
+
+  #expect(found.eq(rhs: P4String.create()))
+}