Refactor Parsing/Runtime

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

Sources/Common/Execution.swift

@@ -16,7 +16,7 @@
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
 open class ProgramExecution: CustomStringConvertible {
-    public var scopes: Scopes = Scopes()
+    public var scopes: ValueScopes = ValueScopes()
     var error: Error?
     var debug: DebugLevel = DebugLevel.Error
 
@@ -75,130 +75,5 @@ open class ProgramExecution: CustomStringConvertible {
 
 }
 
-
-public struct Scope: CustomStringConvertible, Equatable {
-    var variables: [Variable] = Array()
-    public init() {}
-
-    public var description: String {
-        var result = String()
-        for v in variables {
-            result += "\(v)\n"
-        }
-        return result
-    }
-
-    public var count: Int {
-        get {
-            variables.count
-        }
-    }
-
-    public func set(identifier: Identifier, value: P4Value) -> Scope? {
-        var updated = false
-        var updated_scope: [Variable] = Array()
-        for v in variables {
-            if v == identifier && v.value_type.type().eq(rhs: value.type()) {
-                updated = true
-                updated_scope.append(Variable(name: v.name, withValue: value, isConstant: false))
-            } else {
-                updated_scope.append(v)
-            }
-        }
-        var new_scope = Scope()
-        new_scope.variables = updated_scope
-        return if updated {
-            new_scope
-        } else {
-            .none
-        }
-    }
-
-    public func lookup(identifier: Identifier) -> Variable? {
-        for v in variables {
-            if v == identifier {
-                return v
-            }
-        }
-        return .none
-    }
-
-    public mutating func declare(variable: Variable) -> Scope {
-        var s = self
-        s.variables.append(variable)
-        return s
-    }
-}
-
-public struct Scopes: CustomStringConvertible, Equatable {
-    var scopes: [Scope] = Array()
-
-    public init() {}
-
-    init(withScopes scopes: [Scope]) {
-        self.scopes = scopes
-    }
-
-    public func enter() -> Scopes {
-        var new_scopes = scopes
-        new_scopes.append(Scope())
-
-        return Scopes(withScopes: new_scopes)
-    }
-
-    public func exit() -> Scopes {
-        var old_scopes = scopes
-        _ = old_scopes.popLast()
-        return Scopes(withScopes: old_scopes)
-    }
-
-    public var description: String {
-        var result = String()
-        for s in scopes {
-            result += "Scope:\n\(s)\n"
-        }
-
-        return result
-    }
-
-    public var current: Scope? {
-        get {
-            scopes.last
-        }
-    }
-
-    public func declare(variable: Variable) -> Scopes {
-        var s = self
-        if var scope = s.scopes.popLast() {
-            s.scopes.append(scope.declare(variable: variable))
-        }
-        return s
-    }
-
-    public func evaluate(identifier: Identifier) -> Result<P4Value> {
-        for scope in scopes {
-            if let vari = scope.lookup(identifier: identifier) {
-                return .Ok(vari.value)
-            }
-        }
-        return .Error(Error(withMessage: "Cannot find \(identifier) in scope."))
-    }
-
-    public var count: Int {
-        get {
-            scopes.count
-        }
-    }
-
-    public func set(identifier: Identifier, value: P4Value) -> Scopes {
-        var new_scopes: [Scope] = Array()
-        for scope in self.scopes {
-            if let updated_scope = scope.set(identifier: identifier, value: value) {
-                new_scopes.append(updated_scope)
-            } else {
-                new_scopes.append(scope)
-            }
-        }
-        return Scopes(withScopes: new_scopes)
-    }
-}
+public typealias ValueScope = Scope<P4Value>
+public typealias ValueScopes = Scopes<P4Value>

Sources/Common/ProgramTypes.swift

@@ -16,7 +16,11 @@
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
 /// A P4 identifier
-public class Identifier: CustomStringConvertible, Equatable {
+public class Identifier: CustomStringConvertible, Equatable, Hashable {
+  public func hash(into hasher: inout Hasher) {
+    hasher.combine(self.name)
+  }
+
   var name: String
 
   public init(name: String) {
@@ -32,22 +36,38 @@ public class Identifier: CustomStringConvertible, Equatable {
   }
 }
 
-/// A P4 variable
-public class Variable: Identifier {
-  var constant: Bool
-  var value: P4Value
+/// A P4 identifier
+public class TypedIdentifier: Identifier {
+  public var parsed_type: P4Type
 
-  public init(name: String, withValue value: P4Value, isConstant constant: Bool) {
+  public init(name: String, withType type: P4Type) {
+    self.parsed_type = type
+    super.init(name: name)
+  }
+
+  public override var description: String {
+    return "\(name)"
+  }
+}
+
+/// A P4 variable
+public class Variable: TypedIdentifier {
+  var constant: Bool
+  var value: P4Value?
+
+  public init(
+    name: String, withType type: P4Type, withValue value: P4Value?, isConstant constant: Bool
+  ) {
     self.constant = constant
     self.value = value
-    super.init(name: name)
+    super.init(name: name, withType: type)
   }
 
   public override var description: String {
     return "\(super.description) = \(value) \(constant ? "(constant)" : "")"
   }
 
-  public var value_type: P4Value {
+  public var value_type: P4Value? {
     value
   }
 }
@@ -78,6 +98,7 @@ extension P4ValueBase: EvaluatableExpression {
 
 /// The type for a P4 struct
 public struct P4Struct: P4Type {
+
   public let name: String
   // The type of the struct created is always anonymous.
   public static func create() -> any P4Type {
@@ -105,10 +126,10 @@ public struct P4Struct: P4Type {
 
 /// The field of a P4 struct
 public struct P4StructField {
-  public let name: Identifier
+  public let name: TypedIdentifier
   public let type: P4Type
 
-  public init(withName name: Identifier, withType type: P4Type) {
+  public init(withName name: TypedIdentifier, withType type: P4Type) {
     self.name = name
     self.type = type
   }
@@ -124,6 +145,7 @@ public class P4StructValue: P4ValueBase<P4Struct> {
 
 /// A P4 boolean type
 public struct P4Boolean: P4Type {
+
   public static func create() -> any P4Type {
     return P4Boolean()
   }
@@ -132,8 +154,8 @@ public struct P4Boolean: P4Type {
   }
   public func eq(rhs: P4Type) -> Bool {
     return switch rhs {
-      case is P4Boolean: true
-      default: false
+    case is P4Boolean: true
+    default: false
     }
   }
 }
@@ -167,8 +189,8 @@ public struct P4Int: P4Type {
   }
   public func eq(rhs: P4Type) -> Bool {
     return switch rhs {
-      case is P4Int: true
-      default: false
+    case is P4Int: true
+    default: false
     }
   }
 }
@@ -192,16 +214,17 @@ public class P4IntValue: P4ValueBase<P4Int> {
 
 /// A P4 string type
 public struct P4String: P4Type {
+
   public static func create() -> any P4Type {
     return P4String()
   }
   public var description: String {
     return "String"
   }
-  public func eq(rhs: P4Type) -> Bool {
+  public func eq(rhs: any P4Type) -> Bool {
     return switch rhs {
-      case is P4String: true
-      default: false
+    case is P4String: true
+    default: false
     }
   }
 }

Sources/Common/Protocols.swift

@@ -21,9 +21,10 @@ public protocol EvaluatableExpression {
     ///  - execution: The execution context in which to evaluate the expression
     /// - Returns: The value of expression
     func evaluate(execution: ProgramExecution) -> Result<P4Value>
+    func type() -> any P4Type
 }
 
-public protocol EvaluatableParserStatement {
+public protocol EvaluatableStatement {
     /// Evaluate a statement for a given execution
     /// - Parameters
     ///  - execution: The execution context in which to evaluate the parser statement
@@ -32,11 +33,11 @@ public protocol EvaluatableParserStatement {
 }
 
 public protocol P4Type: CustomStringConvertible {
-    static func create() -> P4Type
-    func eq(rhs: P4Type) -> Bool
+    static func create() -> any P4Type
+    func eq(rhs: any P4Type) -> Bool
 }
 
 public protocol P4Value: CustomStringConvertible {
-    func type() -> P4Type
+    func type() -> any P4Type
     func eq(rhs: P4Value) -> Bool
 }

Sources/Common/Support.swift

@@ -16,123 +16,126 @@
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
 public enum DebugLevel {
-    case Trace
-    case Verbose
-    case Debug
-    case Error
+  case Trace
+  case Verbose
+  case Debug
+  case Error
 
-    func value() -> UInt8 {
-        return switch self {
-            case DebugLevel.Trace: 3
-            case DebugLevel.Verbose: 2
-            case DebugLevel.Debug: 1
-            case DebugLevel.Error: 0
-        }
-        }
-    public func isTrace() -> Bool {
-        if self.value() >= DebugLevel.Trace.value() {
-            return true
-        }
-        return false
+  func value() -> UInt8 {
+    return switch self {
+    case DebugLevel.Trace: 3
+    case DebugLevel.Verbose: 2
+    case DebugLevel.Debug: 1
+    case DebugLevel.Error: 0
     }
-    public func isVerbose() -> Bool {
-        if self.value() >= DebugLevel.Verbose.value() {
-            return true
-        }
-        return false
+  }
+  public func isTrace() -> Bool {
+    if self.value() >= DebugLevel.Trace.value() {
+      return true
     }
-    public func isDebug() -> Bool {
-        if self.value() >= DebugLevel.Debug.value() {
-            return true
-        }
-        return false
+    return false
+  }
+  public func isVerbose() -> Bool {
+    if self.value() >= DebugLevel.Verbose.value() {
+      return true
     }
-    public func isError() -> Bool {
-        return true
+    return false
+  }
+  public func isDebug() -> Bool {
+    if self.value() >= DebugLevel.Debug.value() {
+      return true
     }
+    return false
+  }
+  public func isError() -> Bool {
+    return true
+  }
 
-    public var description: String {
-        return switch self {
-            case DebugLevel.Trace: "Trace"
-            case DebugLevel.Verbose: "Verbose"
-            case DebugLevel.Debug: "Debug"
-            case DebugLevel.Error: "Error"
-        }
+  public var description: String {
+    return switch self {
+    case DebugLevel.Trace: "Trace"
+    case DebugLevel.Verbose: "Verbose"
+    case DebugLevel.Debug: "Debug"
+    case DebugLevel.Error: "Error"
     }
+  }
 }
 
-public struct Error: Equatable {
-    public private(set) var msg: String
+public struct Error: Equatable, CustomStringConvertible {
+  public private(set) var msg: String
 
-    public init(withMessage msg: String) {
-        self.msg = msg
-    }
+  public init(withMessage msg: String) {
+    self.msg = msg
+  }
+
+  public var description: String {
+    return self.msg
+  }
 }
 
 public struct Nothing: CustomStringConvertible {
-    public var description: String {
-        return "Nothing"
-    }
+  public var description: String {
+    return "Nothing"
+  }
 
-    public init() {}
+  public init() {}
 }
 
-
 public enum Result<OKT>: Equatable {
-    case Ok(OKT)
-    case Error(Error)
+  case Ok(OKT)
+  case Error(Error)
 
-    public static func == (lhs: Result, rhs: Result) -> Bool {
-        switch (lhs, rhs) {
-        case (Ok, Ok):
-            return true
-        case (Error(let le), Error(let re)):
-            return le.msg == re.msg
-        default:
-            return false
-        }
+  public static func == (lhs: Result, rhs: Result) -> Bool {
+    switch (lhs, rhs) {
+    case (Ok, Ok):
+      return true
+    case (Error(let le), Error(let re)):
+      return le.msg == re.msg
+    default:
+      return false
     }
+  }
 
-    public func error() -> Error? {
-        if case Result.Error(let e) = self {
-            return e
-        }
-        return nil
+  public func error() -> Error? {
+    if case Result.Error(let e) = self {
+      return e
     }
+    return nil
+  }
 
-    public func map<T>(block: (OKT) -> Result<T>) -> Result<T> {
-        switch self {
-            case .Ok(let ok): return block(ok)
-            case .Error(let e): return .Error(e)
-        } 
+  public func map<T>(block: (OKT) -> Result<T>) -> Result<T> {
+    switch self {
+    case .Ok(let ok): return block(ok)
+    case .Error(let e): return .Error(e)
     }
+  }
 }
 
 extension Result where OKT: CustomStringConvertible {
-    public var description: String {
-        switch self {
-            case Result.Error(let e):
-                return e.msg
-            case Result.Ok(let o):
-                return "\(o)"
-        }
+  public var description: String {
+    switch self {
+    case Result.Error(let e):
+      return e.msg
+    case Result.Ok(let o):
+      return "\(o)"
     }
+  }
 }
 
-extension Result {
-    public var description: String {
-        switch self {
-            case Result.Error(let e):
-                return e.msg
-            case Result.Ok(_):
-                return "Ok"
-        }
+extension Result: CustomStringConvertible {
+  public var description: String {
+    switch self {
+    case Result.Error(let e):
+      return e.msg
+    case Result.Ok(_):
+      return "Ok"
     }
+  }
 }
 
 @freestanding(expression) public macro RequireOkResult<T>(_: Result<T>) -> Bool =
-    #externalMacro(module: "Macros", type: "RequireResult")
+  #externalMacro(module: "Macros", type: "RequireResult")
 @freestanding(expression) public macro RequireErrorResult<T>(_: Error, _: Result<T>) -> Bool =
-    #externalMacro(module: "Macros", type: "RequireErrorResult")
+  #externalMacro(module: "Macros", type: "RequireErrorResult")
 @freestanding(expression) public macro UseOkResult<T>(_: Result<T>) -> T =
-    #externalMacro(module: "Macros", type: "UseOkResult")
+  #externalMacro(module: "Macros", type: "UseOkResult")

Sources/Macros/Macros.swift

@@ -62,7 +62,7 @@ public struct RequireResult: ExpressionMacro {
         return """
             {
                 switch \(argument) {
-                    case Result.Ok(let _): return true
+                    case Result.Ok(_): return true
                     case Result.Error(let __error):
                         print("Unexpected result: \\(__error)")
                         return false
@@ -79,18 +79,21 @@ public struct RequireErrorResult: ExpressionMacro {
     ) throws -> ExprSyntax {
 
         let arguments = node.argumentList.indices
-        let expected_error = node.argumentList[arguments.startIndex]
-        let error_producer = node.argumentList[arguments.index(after: arguments.startIndex)]
+        let expected_error = node.argumentList[arguments.startIndex].expression
+        let error_producer = node.argumentList[arguments.index(after: arguments.startIndex)].expression
 
-        return """
+        return ExprSyntax("""
             {
-                if case Result.Error(\(expected_error)) = \(error_producer) {
-                    true
+                let __expected_error = \(expected_error)
+                let __actual_error = \(error_producer)
+                if case Result.Error(__expected_error) = __actual_error {
+                    return true
                 } else {
-                    false
+                    print("Expected Error: \\(__expected_error) but got Error: \\(__actual_error)")
+                    return false
                 }
             }()
-            """
+            """)
     }
 }
 

Sources/P4Lang/Parser.swift

@@ -26,10 +26,10 @@ public struct LocalElement {
 }
 
 public struct ParserAssignmentStatement {
-  public let lvalue: Identifier
-  public let value: P4Value
+  public let lvalue: TypedIdentifier
+  public let value: EvaluatableExpression
 
-  public init(withLValue lvalue: Identifier, withValue value: P4Value) {
+  public init(withLValue lvalue: TypedIdentifier, withValue value: EvaluatableExpression) {
     self.lvalue = lvalue
     self.value = value
   }
@@ -96,17 +96,19 @@ public struct ParserTransitionStatement {
 }
 
 public struct VariableDeclarationStatement {
-  public var variable: Variable
-  public init(withVariable variable: Variable) {
-    self.variable = variable
+  public var initializer: EvaluatableExpression
+  public var identifier: Identifier
+  public init(identifier: Identifier, withInitializer initializer: EvaluatableExpression) {
+    self.identifier = identifier
+    self.initializer = initializer
   }
 }
 
 public class ParserState: Equatable, CustomStringConvertible, Comparable {
 
   public private(set) var state_name: String
-  public private(set) var local_elements: [EvaluatableParserStatement]
-  public private(set) var statements: [EvaluatableParserStatement]
+  public private(set) var local_elements: [EvaluatableStatement]
+  public private(set) var statements: [EvaluatableStatement]
   public private(set) var transition: ParserTransitionStatement?
   public private(set) var next_state: ParserState?
 
@@ -127,8 +129,8 @@ public class ParserState: Equatable, CustomStringConvertible, Comparable {
 
   /// Construct a ParserState
   public init(
-    name: String, withLocalElements localElements: [EvaluatableParserStatement]?,
-    withStatements stmts: [EvaluatableParserStatement]?,
+    name: String, withLocalElements localElements: [EvaluatableStatement]?,
+    withStatements stmts: [EvaluatableStatement]?,
     withTransition transitionStatement: ParserTransitionStatement
   ) {
     state_name = name

Sources/P4Parser/Expression.swift

@@ -0,0 +1,205 @@
+// 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 P4Lang
+import SwiftTreeSitter
+import TreeSitterP4
+
+protocol ParseableEvaluatableExpression {
+  static func parse(
+    node: Node, inTree tree: MutableTree, withScopes scopes: LexicalScopes
+  ) -> Result<EvaluatableExpression?>
+}
+
+extension TypedIdentifier: ParseableEvaluatableExpression {
+  static func parse(
+    node: SwiftTreeSitter.Node, inTree tree: SwiftTreeSitter.MutableTree, withScopes scopes: LexicalScopes
+  ) -> Result<EvaluatableExpression?> {
+
+    guard
+      let parser_statement_query = try? SwiftTreeSitter.Query(
+        language: p4lang,
+        data: String(
+          "(expression (identifier) @identifier)"
+        ).data(using: String.Encoding.utf8)!)
+    else {
+      return Result.Error(Error(withMessage: "Could not compile the tree sitter query"))
+    }
+
+    let qr = parser_statement_query.execute(node: node, in: tree)
+
+    guard let result = qr.next() else {
+      return .Ok(.none)
+    }
+
+    let value_capture = result.captures(named: "identifier")
+    guard
+      case Result.Ok(let type) = scopes.lookup(
+        identifier: Identifier(name: value_capture[0].node.text!))
+    else {
+      return .Error(Error(withMessage: "Cannot find \(result.captures[0].node.text!) in scope"))
+    }
+
+    return .Ok(TypedIdentifier(name: result.captures[0].node.text!, withType: type))
+  }
+}
+
+extension P4BooleanValue: ParseableEvaluatableExpression {
+  static func parse(
+    node: SwiftTreeSitter.Node, inTree tree: SwiftTreeSitter.MutableTree, withScopes scopes: LexicalScopes
+  ) -> Result<EvaluatableExpression?> {
+
+    guard
+      let true_query = try? SwiftTreeSitter.Query(
+        language: p4lang,
+        data: String(
+          "(expression (true))"
+        ).data(using: String.Encoding.utf8)!)
+    else {
+      return Result.Error(Error(withMessage: "Could not compile the tree sitter query"))
+    }
+
+    let true_qr = true_query.execute(node: node, in: tree)
+
+    if true_qr.next() != nil {
+      return .Ok(P4BooleanValue(withValue: true))
+    }
+
+    guard
+      let false_query = try? SwiftTreeSitter.Query(
+        language: p4lang,
+        data: String(
+          "(expression (false))"
+        ).data(using: String.Encoding.utf8)!)
+    else {
+      return Result.Error(Error(withMessage: "Could not compile the tree sitter query"))
+    }
+
+    let false_qr = false_query.execute(node: node, in: tree)
+
+    if false_qr.next() != nil {
+      return .Ok(P4BooleanValue(withValue: false))
+    }
+    return .Ok(.none)
+  }
+}
+
+extension P4IntValue: ParseableEvaluatableExpression {
+  static func parse(
+    node: SwiftTreeSitter.Node, inTree tree: SwiftTreeSitter.MutableTree, withScopes scopes: LexicalScopes
+  ) -> Result<EvaluatableExpression?> {
+
+    guard
+      let integer_query = try? SwiftTreeSitter.Query(
+        language: p4lang,
+        data: String(
+          "(expression (integer) @value)"
+        ).data(using: String.Encoding.utf8)!)
+    else {
+      return Result.Error(Error(withMessage: "Could not compile the tree sitter query"))
+    }
+
+    let integer_qr = integer_query.execute(node: node, in: tree)
+
+    guard let result = integer_qr.next() else {
+      return .Ok(.none)
+    }
+
+    let value_capture = result.captures(named: "value")
+    if let parsed_int = Int(value_capture[0].node.text!) {
+      return .Ok(P4IntValue(withValue: parsed_int))
+    } else {
+      print("HERE!!")
+      return .Error(Error(withMessage: "Failed to parse integer: \(result.captures[0].node.text!)"))
+    }
+  }
+}
+
+extension P4StringValue: ParseableEvaluatableExpression {
+  static func parse(
+    node: SwiftTreeSitter.Node, inTree tree: SwiftTreeSitter.MutableTree, withScopes scopes: LexicalScopes
+  ) -> Result<EvaluatableExpression?> {
+
+    guard
+      let string_query = try? SwiftTreeSitter.Query(
+        language: p4lang,
+        data: String(
+          "(expression (string_literal) @value)"
+        ).data(using: String.Encoding.utf8)!)
+    else {
+      return Result.Error(Error(withMessage: "Could not compile the tree sitter query"))
+    }
+
+    let string_qr = string_query.execute(node: node, in: tree)
+
+    guard let result = string_qr.next() else {
+      return .Ok(.none)
+    }
+
+    return .Ok(P4StringValue(withValue: result.captures[0].node.text!))
+  }
+}
+
+struct Expression {
+  public static func Parse(
+    node: Node, inTree: MutableTree, withScopes scopes: LexicalScopes
+  ) -> Result<EvaluatableExpression> {
+    let localElementsParsers: [ParseableEvaluatableExpression.Type] = [
+      P4BooleanValue.self, P4StringValue.self, P4IntValue.self, TypedIdentifier.self,
+    ]
+
+    for le_parser in localElementsParsers {
+      if case Result.Ok(.some(let parsed)) = le_parser.parse(
+        node: node, inTree: inTree, withScopes: scopes)
+      {
+        return .Ok(parsed)
+      }
+    }
+
+    return Result.Error(Error(withMessage: "Could not parse into expression."))
+  }
+}
+
+extension ExpressionStatement: ParseableStatement {
+  public static func Parse(
+    node: Node, inTree tree: MutableTree, withScopes scopes: LexicalScopes
+  ) -> Result<(EvaluatableStatement?, LexicalScopes)> {
+    guard
+      let expression_statement_query = try? SwiftTreeSitter.Query(
+        language: p4lang,
+        data: String(
+          "(expressionStatement (expression) @expression)"
+        ).data(using: String.Encoding.utf8)!)
+    else {
+      return Result.Ok((.none, scopes))
+    }
+
+    let qr = expression_statement_query.execute(node: node, in: tree)
+    guard let query_result = qr.next() else {
+      return Result.Ok((.none, scopes))
+    }
+
+    let expression_capture = query_result.captures(named: "expression")
+    if !expression_capture.isEmpty {
+      // TODO: Actually create an ExpressionStatement
+      return Result.Ok((ExpressionStatement(), scopes))
+    }
+    return Result.Ok((.none, scopes))
+  }
+}
+

Sources/P4Parser/Parser.swift

@@ -0,0 +1,387 @@
+// 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 P4Lang
+import P4Runtime
+import SwiftTreeSitter
+import TreeSitterExtensions
+import TreeSitterP4
+
+let p4lang = Language(tree_sitter_p4())
+
+extension ParserAssignmentStatement: ParseableStatement {
+  public static func Parse(
+    node: Node, inTree tree: MutableTree, withScopes scopes: LexicalScopes
+  ) -> Result<(EvaluatableStatement?, LexicalScopes)> {
+
+    guard
+      let parser_assignment_statement_query = try? SwiftTreeSitter.Query(
+        language: p4lang,
+        data: String(
+          "(assignmentStatement (expression) @lvalue (assignment) (expression) @value)"
+        ).data(using: String.Encoding.utf8)!)
+    else {
+      return Result.Ok((.none, scopes))
+    }
+
+    let qr = parser_assignment_statement_query.execute(node: node, in: tree)
+    guard let parser_assignment_statement = qr.next() else {
+      return Result.Ok((.none, scopes))
+    }
+
+    let lvalue_capture = parser_assignment_statement.captures(named: "lvalue")
+    let rvalue_capture = parser_assignment_statement.captures(named: "value")
+
+    // There must be a type name and a variable name
+    guard !lvalue_capture.isEmpty,
+      !rvalue_capture.isEmpty,
+      let lvalue_expression_raw = lvalue_capture[0].node.text
+    else {
+      return Result.Error(
+        Error(withMessage: "Could not parse a parser assignment statement"))
+    }
+
+    let rvalue_raw = rvalue_capture[0].node
+    let maybe_parsed_rvalue = Expression.Parse(node: rvalue_raw, inTree: tree, withScopes: scopes)
+    guard case Result.Ok(let rvalue) = maybe_parsed_rvalue else {
+      return Result.Error(maybe_parsed_rvalue.error()!)
+    }
+
+    let lvalue_identifier = Identifier(name: lvalue_expression_raw)
+    guard case Result.Ok(let lvalue_type) = scopes.lookup(identifier: lvalue_identifier) else {
+      return Result.Error(
+        Error(withMessage: "Cannot assign to variable \(lvalue_identifier) not in scope"))
+    }
+
+    if rvalue.type().eq(rhs: lvalue_type) {
+      return Result.Ok(
+        (
+          ParserAssignmentStatement(
+            withLValue: TypedIdentifier(name: lvalue_expression_raw, withType: lvalue_type),
+            withValue: rvalue
+          ), scopes
+        ))
+
+    } else {
+      return Result.Error(
+        Error(
+          withMessage:
+            "Cannot assign value of type \(rvalue.type()) to \(lvalue_identifier) (with type \(lvalue_type))"
+        ))
+
+    }
+  }
+}
+
+public struct Parser {
+  public struct LocalElements {
+    static func Parse(
+      node: Node, inTree tree: MutableTree, withScope scopes: LexicalScopes
+    ) -> Result<(EvaluatableStatement, LexicalScopes)> {
+      let localElementsParsers: [ParseableStatement.Type] = [
+        VariableDeclarationStatement.self
+      ]
+
+      for local_element_parser in localElementsParsers {
+        switch local_element_parser.Parse(node: node, inTree: tree, withScopes: scopes) {
+        case Result.Ok((.some(let parsed), let parsed_updated_scopes)):
+          return Result.Ok((parsed, parsed_updated_scopes))
+        case Result.Error(let e):
+          return Result.Error(Error(withMessage: "Failed to parse local element: \(e)"))
+        default: continue
+        }
+      }
+
+      return Result.Error(
+        Error(
+          withMessage:
+            "Failed to parse any local elements from specified local elements: \(node.text!)")
+      )
+    }
+  }
+
+  public struct Statements {
+    static func Parse(
+      node: Node, inTree tree: MutableTree, withScope scopes: LexicalScopes
+    ) -> Result<(EvaluatableStatement, LexicalScopes)> {
+      let statementParsers: [ParseableStatement.Type] = [
+        ParserAssignmentStatement.self, ExpressionStatement.self,
+        VariableDeclarationStatement.self,
+      ]
+
+      // Iterate through statement parsers and give each one a chance.
+      for parser in statementParsers {
+        switch parser.Parse(node: node, inTree: tree, withScopes: scopes) {
+        case Result.Ok((.some(let parsed), let updatedLexicalScopes)):
+          return .Ok((parsed, updatedLexicalScopes))
+        case Result.Error(let e):
+          return .Error(Error(withMessage: "Failed to parse a statement element: \(e)"))
+        default: continue
+        }
+      }
+      return Result.Error(
+        Error(withMessage: "Failed to parse a statement element: \(node.text!)"))
+    }
+  }
+
+  public struct TransitionSelectExpressionCaseStatement {
+    static func Parse(
+      node: Node, inTree tree: MutableTree, withLexicalScopes scopes: LexicalScopes
+    ) -> Result<([KeysetExpression], LexicalScopes)> {
+      guard
+        let transition_selection_expression_query = try? SwiftTreeSitter.Query(
+          language: p4lang,
+          data: String(
+            "((keysetExpression (expression) @ks) (colon) (identifier) @next-state)"
+          ).data(using: String.Encoding.utf8)!)
+      else {
+        return Result.Error(Error(withMessage: "Could not compile the tree sitter query"))
+      }
+
+      let qr = transition_selection_expression_query.execute(node: node, in: tree)
+
+      var kses: [KeysetExpression] = Array()
+
+      for expression in qr {
+        let next_state_name = expression.captures[1].node.text!
+        if case .Error(let e) = Expression.Parse(
+          node: expression.captures[0].node, inTree: tree, withScopes: scopes
+        )
+        .map(block: { expression in
+          kses.append(
+            KeysetExpression(
+              withKey: expression, withNextStateName: next_state_name))
+          return .Ok(expression)
+        }) {
+          return .Error(e)
+        }
+      }
+
+      return .Ok((kses, scopes))
+    }
+  }
+
+  public struct TransitionSelectExpression {
+    static func Parse(
+      node: Node, inTree tree: MutableTree, withScope scopes: LexicalScopes
+    ) -> Result<(ParserTransitionStatement?, LexicalScopes)> {
+      guard
+        let transition_selection_expression_query = try? SwiftTreeSitter.Query(
+          language: p4lang,
+          data: String(
+            "(parserTransitionStatement (transition) (transitionSelectionExpression (selectExpression (select) (expression) @selector (selectBody) @body)))"
+          ).data(using: String.Encoding.utf8)!)
+      else {
+        return Result.Error(Error(withMessage: "Could not compile the tree sitter query"))
+      }
+
+      let qr = transition_selection_expression_query.execute(node: node, in: tree)
+
+      guard let query_result = qr.next() else {
+        return .Error(Error(withMessage: "Could not find transition select expression"))
+      }
+
+      let selector = query_result.captures(named: "selector")
+      let body = query_result.captures(named: "body")
+
+      return Expression.Parse(node: selector[0].node, inTree: tree, withScopes: scopes).map {
+        expression in
+        return
+          switch TransitionSelectExpressionCaseStatement.Parse(
+            node: body[0].node, inTree: tree, withLexicalScopes: scopes)
+        {
+        case .Ok((let kse, let newLexicalScopes)):
+          Result<(ParserTransitionStatement?, LexicalScopes)>.Ok(
+            (
+              ParserTransitionStatement(
+                withTransitionExpression: ParserTransitionSelectExpression(
+                  withSelector: expression, withKeysetExpressions: kse)), newLexicalScopes
+            ))
+        case .Error(let e): Result.Error(e)
+        }
+      }
+    }
+  }
+
+  public struct TransitionStatement {
+    static func Parse(
+      node: Node, inTree tree: MutableTree, withScope scopes: LexicalScopes
+    ) -> Result<(ParserTransitionStatement?, LexicalScopes)> {
+      guard
+        let next_state_query = try? SwiftTreeSitter.Query(
+          language: p4lang,
+          data: String(
+            "(parserTransitionStatement (transition) (transitionSelectionExpression (identifier) @next-state))"
+          ).data(using: String.Encoding.utf8)!)
+      else {
+        return Result.Error(Error(withMessage: "Could not compile the tree sitter query"))
+      }
+
+      let qr = next_state_query.execute(node: node, in: tree)
+
+      if let next_state_result = qr.next() {
+        let transition_capture = next_state_result.captures(named: "next-state")
+        return .Ok(
+          (ParserTransitionStatement(withNextState: transition_capture[0].node.text!), scopes))
+      }
+
+      return TransitionSelectExpression.Parse(node: node, inTree: tree, withScope: scopes)
+    }
+  }
+
+  public struct State {
+    static func Parse(
+      node: Node, inTree tree: MutableTree, withLexicalScopes scopes: LexicalScopes
+    ) -> Result<(ParserState, LexicalScopes)> {
+      guard
+        let parser_state_query = try? SwiftTreeSitter.Query(
+          language: p4lang,
+          data: String(
+            "(parserState (state) (identifier) @state-name (parserLocalElements ((parserLocalElement) @state-local-element (semicolon))*)* (parserStatements ((parserStatement) @state-statement (semicolon))*)* (parserTransitionStatement) @transition)"
+          ).data(using: String.Encoding.utf8)!)
+      else {
+        return Result.Error(Error(withMessage: "Could not compile the tree sitter query"))
+      }
+
+      let qr = parser_state_query.execute(node: node, in: tree)
+
+      let parser_declaration = qr.next()!
+
+      let transition_capture = parser_declaration.captures(named: "transition")
+      let state_name_capture = parser_declaration.captures(named: "state-name")
+      let state_le_capture = parser_declaration.captures(named: "state-local-element")
+      let statements_capture = parser_declaration.captures(named: "state-statement")
+
+      var parsed_les: [EvaluatableStatement] = Array()
+      var parse_err: Error? = .none
+      var current_scopes = scopes.enter()
+
+      defer {
+        current_scopes = current_scopes.exit()
+      }
+
+      for state_le in state_le_capture {
+        state_le.node.enumerateChildren { node in
+          switch LocalElements.Parse(
+            node: node, inTree: tree, withScope: current_scopes)
+          {
+          case .Ok((let le, let le_parsed_scopes)):
+            current_scopes = le_parsed_scopes
+            parsed_les.append(le)
+          case .Error(let e):
+            parse_err = e
+          }
+        }
+      }
+
+      if let parse_err = parse_err {
+        return Result.Error(parse_err)
+      }
+
+      var parsed_s: [EvaluatableStatement] = Array()
+
+      if !statements_capture.isEmpty {
+        for statement in statements_capture {
+          statement.node.enumerateChildren { node in
+            switch Statements.Parse(
+              node: node, inTree: tree, withScope: current_scopes)
+            {
+            case .Ok((let le, let le_parsed_scopes)):
+              current_scopes = le_parsed_scopes
+              parsed_s.append(le)
+            case .Error(let e):
+              parse_err = e
+            }
+          }
+        }
+      }
+
+      if let parse_err = parse_err {
+        return Result.Error(parse_err)
+      }
+
+      print("current_scopes: \(current_scopes)")
+      // TODO: Now that scopes are involved, doing this out of order will not work!
+      guard !state_name_capture.isEmpty,
+        !transition_capture.isEmpty,
+        let parsed_state_name = state_name_capture[0].node.text
+      else {
+        return Result.Error(Error(withMessage: "Could not parse a parser declaration"))
+      }
+
+      switch TransitionStatement.Parse(
+        node: transition_capture[0].node, inTree: tree, withScope: current_scopes)
+      {
+      case .Ok((.some(let transition_statement), let current_scopes)):
+        return Result.Ok(
+          (
+            ParserState(
+              name: parsed_state_name, withLocalElements: parsed_les,
+              withStatements: parsed_s,
+              withTransition: transition_statement), current_scopes
+          ))
+      case .Error(let e): return .Error(e)
+      case .Ok((.none, _)): return .Error(Error(withMessage: "Missing transition statement"))
+      }
+
+    }
+  }
+
+  static func Parse(
+    withName name: Identifier, node: Node, inTree tree: MutableTree,
+    withLexicalScopes scopes: LexicalScopes
+  ) -> Result<(P4Lang.Parser, LexicalScopes)> {
+    guard
+      let parser_state_query = try? SwiftTreeSitter.Query(
+        language: p4lang,
+        data: String(
+          "(parserStates) @parser-states"
+        ).data(using: String.Encoding.utf8)!)
+    else {
+      return Result.Error(
+        Error(withMessage: "Could not compile the parser state tree sitter query"))
+    }
+
+    var parser = P4Lang.Parser(withName: name)
+
+    // Build a state from each one listed.
+    let qr = parser_state_query.execute(node: node, in: tree)
+    let qr_value = qr.next()!
+    let captures = qr_value.captures(named: "parser-states")
+
+    var error: Error? = .none
+
+    var parser_scopes = scopes
+
+    // TODO: Assert that there is only one.
+    captures[0].node.enumerateChildren { parser_state in
+      switch Parser.State.Parse(node: parser_state, inTree: tree, withLexicalScopes: scopes) {
+      case Result.Ok(let (state, new_parser_scopes)):
+        parser.states = parser.states.append(state: state)
+        parser_scopes = new_parser_scopes
+      case Result.Error(let e): error = e
+      }
+    }
+
+    if let error = error {
+      return .Error(error)
+    }
+
+    return Result.Ok((parser, parser_scopes))
+  }
+}

Sources/P4Parser/Program.swift

@@ -0,0 +1,75 @@
+// 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 P4Lang
+import P4Runtime
+import SwiftTreeSitter
+import TreeSitterExtensions
+import TreeSitterP4
+
+public struct Program {
+  public static func Parse(_ source: String) -> Result<P4Lang.Program> {
+    let p = SwiftTreeSitter.Parser.init()
+
+    do {
+      try p.setLanguage(p4lang)
+    } catch {
+      return Result.Error(Error(withMessage: "Could not configure the P4 parser"))
+    }
+
+    let result = p.parse(source)
+    guard let tree = result,
+      !tree.isError(lang: p4lang),
+      !tree.containsMissing(lang: p4lang)
+    else {
+      return Result.Error(Error(withMessage: "Could not compile the P4 program"))
+    }
+
+    guard
+      let parser_declaration_query = try? SwiftTreeSitter.Query(
+        language: p4lang,
+        data: String(
+          "(parserDeclaration (parserType parser_name: (identifier) @parser-name) (parserStates) @parser-states)"
+        ).data(using: String.Encoding.utf8)!)
+    else {
+      return Result.Error(
+        Error(withMessage: "Could not compile the parser declaration tree sitter query"))
+    }
+
+    var program = P4Lang.Program()
+
+    // Set up a lexical scope for parsing.
+    var program_scope = LexicalScopes().enter()
+
+    let parser_qc = parser_declaration_query.execute(in: tree)
+
+    for parser_declaration in parser_qc {
+      switch Parser.Parse(
+        withName: Identifier(name: parser_declaration.nodes[0].text!),
+        node: parser_declaration.nodes[1], inTree: tree, withLexicalScopes: program_scope)
+      {
+      case Result.Ok((let parser, let new_program_scope)):
+        program.types.append(parser)
+        program_scope = new_program_scope
+      case Result.Error(let error): return Result.Error(error)
+      }
+    }
+
+    return Result.Ok(program)
+  }
+}

Sources/P4Parser/Protocols.swift

@@ -0,0 +1,37 @@
+// 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 P4Lang
+import P4Runtime
+import SwiftTreeSitter
+import TreeSitterExtensions
+import TreeSitterP4
+
+public protocol ParseableStatement {
+  static func Parse(
+    node: Node, inTree tree: MutableTree, withScopes scopes: LexicalScopes
+  ) -> Result<(EvaluatableStatement?, LexicalScopes)>
+}
+
+public protocol ParseableValue {
+  static func ParseValue(withValue value: String) -> Result<P4Value>
+}
+
+public protocol ParseableType {
+  static func ParseType(type: String) -> Result<P4Type?>
+}

Sources/P4Parser/Statement.swift

@@ -0,0 +1,86 @@
+// 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 P4Lang
+import P4Runtime
+import SwiftTreeSitter
+import TreeSitterExtensions
+import TreeSitterP4
+
+extension VariableDeclarationStatement: ParseableStatement {
+  public static func Parse(
+    node: Node, inTree tree: MutableTree, withScopes scopes: LexicalScopes
+  ) -> Result<(EvaluatableStatement?, LexicalScopes)> {
+    guard
+      let variable_declaration_query = try? SwiftTreeSitter.Query(
+        language: p4lang,
+        data: String(
+          "(variableDeclaration (annotations)? (typeRef) @type-name variable_name: (identifier) @identifier ((assignment) (expression) @value)?)"
+        ).data(using: String.Encoding.utf8)!)
+    else {
+      return Result.Ok((.none, scopes))
+    }
+
+    let qr = variable_declaration_query.execute(node: node, in: tree)
+    guard let variable_declaration = qr.next() else {
+      return .Ok((.none, scopes))
+    }
+
+    let type_name_capture = variable_declaration.captures(named: "type-name")
+    let variable_name_capture = variable_declaration.captures(named: "identifier")
+    let value_capture = variable_declaration.captures(named: "value")
+
+    // There must be a type name and a variable name
+    guard !type_name_capture.isEmpty,
+      !variable_name_capture.isEmpty,
+      !value_capture.isEmpty,
+      let variable_name = variable_name_capture[0].node.text,
+      let type_name = type_name_capture[0].node.text
+    else {
+      return Result.Error(
+        Error(withMessage: "Could not parse a parser variable declaration statement"))
+    }
+
+    guard case .Ok(let declaration_p4_type) = Types.ParseBasicType(type: type_name) else {
+      return Result.Error(
+        Error(withMessage: "Could not parse a P4 type from \(type_name)"))
+    }
+
+    let rvalue_raw = value_capture[0].node
+    let maybe_parsed_rvalue = Expression.Parse(node: rvalue_raw, inTree: tree, withScopes: scopes)
+    guard case Result.Ok(let rvalue) = maybe_parsed_rvalue else {
+      return Result.Error(maybe_parsed_rvalue.error()!)
+    }
+
+    if rvalue.type().eq(rhs: declaration_p4_type) {
+      return Result.Ok(
+        (
+          VariableDeclarationStatement(identifier: Identifier(name: variable_name), withInitializer: rvalue),
+          scopes.declare(identifier: Identifier(name: variable_name), withValue: declaration_p4_type)
+        ))
+
+    } else {
+      return Result.Error(
+        Error(
+          withMessage:
+            "Cannot initialize \(variable_name) (with type \(declaration_p4_type)) from rvalue with type \(rvalue.type())"
+        ))
+
+    }
+  }
+}

Sources/P4Parser/Types.swift

@@ -0,0 +1,54 @@
+// 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 P4Lang
+import P4Runtime
+import SwiftTreeSitter
+import TreeSitterExtensions
+import TreeSitterP4
+
+extension P4Boolean: ParseableType {
+  public static func ParseType(type: String) -> Common.Result<(any Common.P4Type)?> {
+    return type == "bool" ? .Ok(P4Boolean.create()) : .Ok(.none)
+  }
+}
+
+extension P4Int: ParseableType {
+  public static func ParseType(type: String) -> Common.Result<(any Common.P4Type)?> {
+    return type == "int" ? .Ok(P4Int.create()) : .Ok(.none)
+  }
+}
+
+extension P4String: ParseableType {
+  public static func ParseType(type: String) -> Common.Result<(any Common.P4Type)?> {
+    return type == "string" ? .Ok(P4String.create()) : .Ok(.none)
+  }
+}
+public struct Types {
+  static func ParseBasicType(type: String) -> Result<P4Type> {
+    let type_parsers: [ParseableType.Type] = [P4Boolean.self, P4Int.self, P4String.self]
+    for type_parser in type_parsers {
+      switch type_parser.ParseType(type: type) {
+      case .Ok(.some(let type)): return .Ok(type)
+      case .Ok(.none): continue
+      case .Error(let e): return .Error(e)
+      }
+    }
+    return Result.Error(Error(withMessage: "Type name not recognized"))
+  }
+}

Sources/P4Runtime/Parser.swift

@@ -16,11 +16,14 @@
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
 import Common
-import Lang
+import P4Lang
 
-extension ParserAssignmentStatement: EvaluatableParserStatement {
+extension ParserAssignmentStatement: EvaluatableStatement {
   public func evaluate(execution: ProgramExecution) -> ProgramExecution {
-    let updated_scopes = execution.scopes.set(identifier: self.lvalue, value: self.value)
+    guard case Result.Ok(let value) = self.value.evaluate(execution: execution) else {
+      return execution.setError(error: Error(withMessage: "AHHHHH"))
+    }
+    let updated_scopes = execution.scopes.set(identifier: self.lvalue, withValue: value)
 
     execution.scopes = updated_scopes
 
@@ -53,7 +56,7 @@ public struct ParserStateDirectTransition: ParserStateInstance {
     return false
   }
 
-  public func current() -> Lang.ParserState {
+  public func current() -> P4Lang.ParserState {
     return currrent_state
   }
 
@@ -72,7 +75,7 @@ public struct ParserStateNoTransition: ParserStateInstance {
     return true
   }
 
-  public func current() -> Lang.ParserState {
+  public func current() -> P4Lang.ParserState {
     return currrent_state
   }
 }
@@ -116,7 +119,7 @@ public struct ParserStateSelectTransition: ParserStateInstance {
     return false
   }
 
-  public func current() -> Lang.ParserState {
+  public func current() -> P4Lang.ParserState {
     return currrent_state
   }
 

Sources/P4Runtime/Program.swift

@@ -15,26 +15,33 @@
 // 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 Lang
+import P4Lang
 import Common
 
-extension VariableDeclarationStatement: EvaluatableParserStatement {
+extension VariableDeclarationStatement: EvaluatableStatement {
   public func evaluate(execution: ProgramExecution) -> ProgramExecution {
-    let new_scopes = execution.scopes.declare(variable: self.variable)
+    guard case .Ok(let initial_value) = self.initializer.evaluate(execution: execution) else {
+      return execution.setError(error: Error(withMessage: "Could not evaluate \(self.initializer)"))
+    }
+    let new_scopes = execution.scopes.declare(identifier: self.identifier, withValue: initial_value)
     execution.scopes = new_scopes
     return execution
   }
 }
 
-extension ExpressionStatement: EvaluatableParserStatement {
+extension ExpressionStatement: EvaluatableStatement {
   public func evaluate(execution: ProgramExecution) -> ProgramExecution {
     return execution
   }
 }
 
 // Variables are evaluatable because they can be looked up by identifiers.
-extension Identifier: EvaluatableExpression {
+extension TypedIdentifier: EvaluatableExpression {
+    public func type() -> any Common.P4Type {
+      return self.parsed_type
+    }
+
     public func evaluate(execution: Common.ProgramExecution) -> Result<P4Value> {
-      return execution.scopes.evaluate(identifier: self)
+      return execution.scopes.lookup(identifier: self)
     }
 }

Sources/P4Runtime/Protocols.swift

@@ -16,7 +16,7 @@
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
 import Common
-import Lang
+import P4Lang
 
 protocol EvaluatableParserTransition {
   func program(execution: ProgramExecution) -> (ParserState, ProgramExecution)

Sources/P4Runtime/Runtime.swift

@@ -16,7 +16,7 @@
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
 import Common
-import Lang
+import P4Lang
 
 /// The runtime for a parser
 public class ParserRuntime: CustomStringConvertible {
@@ -27,12 +27,12 @@ public class ParserRuntime: CustomStringConvertible {
   }
 
   /// Create a parser runtime from a P4 program
-  public static func create(program: Lang.Program) -> Result<ParserRuntime> {
+  public static func create(program: P4Lang.Program) -> Result<ParserRuntime> {
 
     return switch program.starting_parser() {
     case .Ok(let parser):
       switch ParserInstance.compile(parser) {
-      case .Ok(let execution): .Ok(Runtime.ParserRuntime(execution: execution))
+      case .Ok(let execution): .Ok(P4Runtime.ParserRuntime(execution: execution))
       case .Error(let error): .Error(error)
       }
     case .Error(let error): .Error(error)

Sources/Parser/Expression.swift

@@ -1,107 +0,0 @@
-// 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 SwiftTreeSitter
-import TreeSitterP4
-
-protocol ParseableEvaluatableExpression {
-  static func parse(node: Node, inTree tree: MutableTree, withScopes scopes: Scopes) -> Result<EvaluatableExpression?>
-}
-
-extension Identifier: ParseableEvaluatableExpression {
-  static func parse(
-    node: SwiftTreeSitter.Node, inTree tree: SwiftTreeSitter.MutableTree, withScopes scopes: Scopes
-  ) -> Result<EvaluatableExpression?> {
-
-    guard
-      let parser_statement_query = try? SwiftTreeSitter.Query(
-        language: p4lang,
-        data: String(
-          "(expression (identifier) @identifier)"
-        ).data(using: String.Encoding.utf8)!)
-    else {
-      return Result.Error(Error(withMessage: "Could not compile the tree sitter query"))
-    }
-
-    let qr = parser_statement_query.execute(node: node, in: tree)
-
-    guard let result = qr.next() else {
-      return .Ok(.none)
-    }
-
-    return .Ok(Identifier(name: result.captures[0].node.text!))
-  }
-}
-
-extension P4BooleanValue: ParseableEvaluatableExpression {
-  static func parse(
-    node: SwiftTreeSitter.Node, inTree tree: SwiftTreeSitter.MutableTree, withScopes scopes: Scopes
-  ) -> Result<EvaluatableExpression?> {
-
-    guard
-      let true_query = try? SwiftTreeSitter.Query(
-        language: p4lang,
-        data: String(
-          "(expression (true))"
-        ).data(using: String.Encoding.utf8)!)
-    else {
-      return Result.Error(Error(withMessage: "Could not compile the tree sitter query"))
-    }
-
-    let true_qr = true_query.execute(node: node, in: tree)
-
-    if true_qr.next() != nil {
-      return .Ok(P4BooleanValue(withValue: true))
-    }
-
-    guard
-      let false_query = try? SwiftTreeSitter.Query(
-        language: p4lang,
-        data: String(
-          "(expression (false))"
-        ).data(using: String.Encoding.utf8)!)
-    else {
-      return Result.Error(Error(withMessage: "Could not compile the tree sitter query"))
-    }
-
-    let false_qr = false_query.execute(node: node, in: tree)
-
-    if false_qr.next() != nil {
-      return .Ok(P4BooleanValue(withValue: false))
-    }
-    return .Ok(.none)
-  }
-}
-
-struct Expression {
-  public static func Parse(node: Node, inTree: MutableTree, withScopes scopes: Scopes) -> Result<EvaluatableExpression> {
-    let localElementsParsers: [ParseableEvaluatableExpression.Type] = [
-      P4BooleanValue.self, Identifier.self,
-    ]
-
-    for le_parser in localElementsParsers {
-      if case Result.Ok(.some(let parsed)) = le_parser.parse(
-        node: node, inTree: inTree, withScopes: scopes)
-      {
-        return .Ok(parsed)
-      }
-    }
-
-    return Result.Error(Error(withMessage: "Could not parse into expression."))
-  }
-}

Sources/Parser/Parser.swift

@@ -1,541 +0,0 @@
-// 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 Lang
-import Runtime
-import SwiftTreeSitter
-import TreeSitterExtensions
-import TreeSitterP4
-
-let p4lang = Language(tree_sitter_p4())
-
-public protocol ParseableParserStatement {
-  static func Parse(
-    node: Node, inTree tree: MutableTree, withScope scopes: Scopes
-  ) -> Result<(EvaluatableParserStatement?, Scopes)>
-}
-
-extension ExpressionStatement: ParseableParserStatement {
-  public static func Parse(
-    node: Node, inTree tree: MutableTree, withScope scopes: Scopes
-  ) -> Result<(EvaluatableParserStatement?, Scopes)> {
-    guard
-      let parser_state_query = try? SwiftTreeSitter.Query(
-        language: p4lang,
-        data: String(
-          "(expressionStatement (expression) @expression)"
-        ).data(using: String.Encoding.utf8)!)
-    else {
-      return Result.Ok((.none, scopes))
-    }
-
-    let qr = parser_state_query.execute(node: node, in: tree)
-    guard let query_result = qr.next() else {
-      return Result.Ok((.none, scopes))
-    }
-
-    let expression_capture = query_result.captures(named: "expression")
-    if !expression_capture.isEmpty {
-      // TODO: Actually create an ExpressionStatement
-      return Result.Ok((ExpressionStatement(), scopes))
-    }
-    return Result.Ok((.none, scopes))
-  }
-}
-
-extension ParserAssignmentStatement: ParseableParserStatement {
-  public static func Parse(
-    node: Node, inTree tree: MutableTree, withScope scopes: Scopes
-  ) -> Result<(EvaluatableParserStatement?, Scopes)> {
-
-    guard
-      let parser_state_query = try? SwiftTreeSitter.Query(
-        language: p4lang,
-        data: String(
-          "(assignmentStatement (expression) @lvalue (assignment) (expression) @value)"
-        ).data(using: String.Encoding.utf8)!)
-    else {
-      return Result.Ok((.none, scopes))
-    }
-
-    let qr = parser_state_query.execute(node: node, in: tree)
-    let parser_declaration = qr.next()!
-
-    let lvalue_capture = parser_declaration.captures(named: "lvalue")
-    let value_capture = parser_declaration.captures(named: "value")
-
-    // There must be a type name and a variable name
-    guard !lvalue_capture.isEmpty,
-      !value_capture.isEmpty,
-      let lvalue_expression_raw = lvalue_capture[0].node.text,
-      let value_capture_raw = value_capture[0].node.text
-    else {
-      return Result.Error(
-        Error(withMessage: "Could not parse a parser assignment statement"))
-    }
-
-    let lvalue_identifier = Identifier(name: lvalue_expression_raw)
-
-    let value =
-      if !value_capture_raw.isEmpty {
-        value_capture_raw
-      } else {
-        ""
-      }
-
-    guard case Result.Ok(let declared_value) = scopes.evaluate(identifier: lvalue_identifier) else {
-      return Result.Error(
-        Error(withMessage: "Cannot assign to variable not in scope"))
-    }
-
-    return switch Parser.ParseValueType(type: declared_value.type(), withValue: value) {
-    case Result.Ok(let value_type):
-      Result.Ok(
-        (ParserAssignmentStatement(withLValue: lvalue_identifier, withValue: value_type), scopes))
-    case Result.Error(let e):
-      Result.Error(
-        Error(
-          withMessage:
-            "\(declared_value) has type \(declared_value.type()) but rvalue has mismatched type (\(e))"))
-    }
-  }
-}
-
-extension VariableDeclarationStatement: ParseableParserStatement {
-  public static func Parse(
-    node: Node, inTree tree: MutableTree, withScope scopes: Scopes
-  ) -> Result<(EvaluatableParserStatement?, Scopes)> {
-    guard
-      let parser_state_query = try? SwiftTreeSitter.Query(
-        language: p4lang,
-        data: String(
-          "(variableDeclaration (annotations)? (typeRef) @type-name variable_name: (identifier) @identifier ((assignment) (expression) @value)?)"
-        ).data(using: String.Encoding.utf8)!)
-    else {
-      return Result.Ok((.none, scopes))
-    }
-
-    let qr = parser_state_query.execute(node: node, in: tree)
-    guard let parser_declaration = qr.next() else {
-      return .Ok((.none, scopes))
-    }
-
-    let type_name_capture = parser_declaration.captures(named: "type-name")
-    let variable_name_capture = parser_declaration.captures(named: "identifier")
-    let value_capture = parser_declaration.captures(named: "value")
-
-    // There must be a type name and a variable name
-    guard !type_name_capture.isEmpty,
-      !variable_name_capture.isEmpty,
-      let variable_name = variable_name_capture[0].node.text,
-      let type_name = type_name_capture[0].node.text
-    else {
-      return Result.Error(
-        Error(withMessage: "Could not parse a parser variable declaration statement"))
-    }
-
-    let value =
-      if !value_capture.isEmpty {
-        value_capture[0].node.text!
-      } else {
-        ""
-      }
-
-    guard case .Ok(let p4_type) = Parser.ParseBasicType(type: type_name) else {
-      return Result.Error(
-        Error(withMessage: "Could not parse a P4 type from \(type_name)"))
-    }
-
-    return switch Parser.ParseValueType(type: p4_type, withValue: value) {
-    case Result.Ok(let value_type):
-      // This scope should have an additional variable in scope.
-      Result.Ok(
-        (
-          VariableDeclarationStatement(
-            withVariable: Variable(name: variable_name, withValue: value_type, isConstant: false)),
-          scopes.declare(
-            variable: Variable(name: variable_name, withValue: value_type, isConstant: false))
-        ))
-    case Result.Error(let e):
-      Result.Error(e)
-    }
-  }
-}
-
-public struct Parser {
-  static func ParseBasicType(type: String) -> Result<P4Type> {
-    if type == "bool" {
-      return .Ok(P4Boolean.create())
-    } else if type == "string" {
-      return .Ok(P4String.create())
-    } else if type == "int" {
-      return .Ok(P4Int.create())
-    }
-    return Result.Error(Error(withMessage: "Type name not recognized"))
-  }
-
-  static func ParseValueType(type: P4Type, withValue value: String) -> Result<P4Value> {
-    if type.eq(rhs: P4Boolean.create()) {
-      // Default
-      if value == "" {
-        return .Ok(P4BooleanValue(withValue: false))
-      }
-      if value == "true" {
-        return .Ok(P4BooleanValue(withValue: true))
-      } else if value == "false" {
-        return .Ok(P4BooleanValue(withValue: false))
-      }
-      return .Error(Error(withMessage: "Cannot convert \(value) into boolean value"))
-
-    } else if type.eq(rhs: P4String.create()) {
-      return .Ok(P4StringValue.init(withValue: value))
-
-    } else if type.eq(rhs: P4Int.create()) {
-      // Default
-      if value == "" {
-        return .Ok(P4IntValue.init(withValue: 0))
-      }
-
-      guard let parsed_value = Swift.Int(value) else {
-        return .Error(Error(withMessage: "Cannot convert \(value) into integer value"))
-      }
-      return .Ok(P4IntValue.init(withValue: parsed_value))
-    }
-
-    return .Error(Error(withMessage: "Invalid type"))
-  }
-
-  public struct P4Parser {
-
-    static func LocalElements(
-      node: Node, inTree tree: MutableTree, withScope scopes: Scopes
-    ) -> Result<(EvaluatableParserStatement, Scopes)> {
-      let localElementsParsers: [ParseableParserStatement.Type] = [
-        VariableDeclarationStatement.self
-      ]
-
-      for local_element_parser in localElementsParsers {
-        if case Result.Ok((.some(let parsed), let parsed_updated_scopes)) =
-          local_element_parser.Parse(
-            node: node, inTree: tree, withScope: scopes)
-        {
-          return Result.Ok((parsed, parsed_updated_scopes))
-        }
-      }
-
-      return Result.Error(
-        Error(
-          withMessage:
-            "Failed to parse any local elements from specified local elements: \(node.text!)")
-      )
-    }
-
-    static func Statements(
-      node: Node, inTree tree: MutableTree, withScope scopes: Scopes
-    ) -> Result<(EvaluatableParserStatement, Scopes)> {
-      let statementParsers: [ParseableParserStatement.Type] = [
-        ExpressionStatement.self, VariableDeclarationStatement.self, ParserAssignmentStatement.self
-      ]
-
-      // Iterate through statement parsers and give each one a chance.
-      for parser in statementParsers {
-        if case Result.Ok((.some(let parsed), let updatedScopes)) = parser.Parse(
-          node: node, inTree: tree, withScope: scopes)
-        {
-          return .Ok((parsed, updatedScopes))
-        }
-
-      }
-      return Result.Error(
-        Error(withMessage: "Failed to parse a statement element: \(node.text!)"))
-    }
-
-    static func TransitionKeysetExpression(
-      node: Node, inTree tree: MutableTree, withScopes scopes: Scopes
-    ) -> Result<([KeysetExpression], Scopes)> {
-      guard
-        let transition_selection_expression_query = try? SwiftTreeSitter.Query(
-          language: p4lang,
-          data: String(
-            "((keysetExpression (expression) @ks) (colon) (identifier) @next-state)"
-          ).data(using: String.Encoding.utf8)!)
-      else {
-        return Result.Error(Error(withMessage: "Could not compile the tree sitter query"))
-      }
-
-      let qr = transition_selection_expression_query.execute(node: node, in: tree)
-
-      var kses: [KeysetExpression] = Array()
-
-      for expression in qr {
-        let next_state_name = expression.captures[1].node.text!
-        if case .Error(let e) = Expression.Parse(
-          node: expression.captures[0].node, inTree: tree, withScopes: scopes
-        )
-        .map(block: { expression in
-          kses.append(
-            KeysetExpression(
-              withKey: expression, withNextStateName: next_state_name))
-          return .Ok(expression)
-        }) {
-          return .Error(e)
-        }
-      }
-
-      return .Ok((kses, scopes))
-    }
-
-    static func TransitionSelectExpression(
-      node: Node, inTree tree: MutableTree, withScope scopes: Scopes
-    ) -> Result<(ParserTransitionStatement?, Scopes)> {
-      guard
-        let transition_selection_expression_query = try? SwiftTreeSitter.Query(
-          language: p4lang,
-          data: String(
-            "(parserTransitionStatement (transition) (transitionSelectionExpression (selectExpression (select) (expression) @selector (selectBody) @body)))"
-          ).data(using: String.Encoding.utf8)!)
-      else {
-        return Result.Error(Error(withMessage: "Could not compile the tree sitter query"))
-      }
-
-      let qr = transition_selection_expression_query.execute(node: node, in: tree)
-
-      guard let query_result = qr.next() else {
-        return .Error(Error(withMessage: "Could not find transition select expression"))
-      }
-
-      let selector = query_result.captures(named: "selector")
-      let body = query_result.captures(named: "body")
-
-      return Expression.Parse(node: selector[0].node, inTree: tree, withScopes: scopes).map {
-        expression in
-        return
-          switch TransitionKeysetExpression(node: body[0].node, inTree: tree, withScopes: scopes)
-        {
-        case .Ok((let kse, let newScopes)):
-          Result<(ParserTransitionStatement?, Scopes)>.Ok(
-            (
-              ParserTransitionStatement(
-                withTransitionExpression: ParserTransitionSelectExpression(
-                  withSelector: expression, withKeysetExpressions: kse)), newScopes
-            ))
-        case .Error(let e): Result.Error(e)
-        }
-      }
-    }
-
-    static func TransitionStatement(
-      node: Node, inTree tree: MutableTree, withScope scopes: Scopes
-    ) -> Result<(ParserTransitionStatement?, Scopes)> {
-      guard
-        let next_state_query = try? SwiftTreeSitter.Query(
-          language: p4lang,
-          data: String(
-            "(parserTransitionStatement (transition) (transitionSelectionExpression (identifier) @next-state))"
-          ).data(using: String.Encoding.utf8)!)
-      else {
-        return Result.Error(Error(withMessage: "Could not compile the tree sitter query"))
-      }
-
-      let qr = next_state_query.execute(node: node, in: tree)
-
-      if let next_state_result = qr.next() {
-        let transition_capture = next_state_result.captures(named: "next-state")
-        return .Ok(
-          (ParserTransitionStatement(withNextState: transition_capture[0].node.text!), scopes))
-      }
-
-      return TransitionSelectExpression(node: node, inTree: tree, withScope: scopes)
-    }
-
-    static func State(
-      node: Node, inTree tree: MutableTree, withScopes scopes: Scopes
-    ) -> Result<(ParserState, Scopes)> {
-      guard
-        let parser_state_query = try? SwiftTreeSitter.Query(
-          language: p4lang,
-          data: String(
-            "(parserState (state) (identifier) @state-name (parserLocalElements ((parserLocalElement) @state-local-element (semicolon))*)* (parserStatements ((parserStatement) @state-statement (semicolon))*)* (parserTransitionStatement) @transition)"
-          ).data(using: String.Encoding.utf8)!)
-      else {
-        return Result.Error(Error(withMessage: "Could not compile the tree sitter query"))
-      }
-
-      let qr = parser_state_query.execute(node: node, in: tree)
-
-      let parser_declaration = qr.next()!
-
-      let transition_capture = parser_declaration.captures(named: "transition")
-      let state_name_capture = parser_declaration.captures(named: "state-name")
-      let state_le_capture = parser_declaration.captures(named: "state-local-element")
-      let statements_capture = parser_declaration.captures(named: "state-statement")
-
-      // TODO: Now that scopes are involved, doing this out of order will not work!
-      guard !state_name_capture.isEmpty,
-        !transition_capture.isEmpty,
-        let parsed_state_name = state_name_capture[0].node.text,
-        case .Ok((let transition_statement, (var newStateScopes))) = TransitionStatement(
-          node: transition_capture[0].node, inTree: tree, withScope: scopes)
-      else {
-        return Result.Error(Error(withMessage: "Could not parse a parser declaration"))
-      }
-
-      var parsed_les: [EvaluatableParserStatement] = Array()
-      var parse_err: Error? = .none
-
-      for state_le in state_le_capture {
-        state_le.node.enumerateChildren { node in
-          switch LocalElements(
-            node: node, inTree: tree, withScope: newStateScopes)
-          {
-          case .Ok((let le, let le_parsed_scopes)):
-            newStateScopes = le_parsed_scopes
-            parsed_les.append(le)
-          case .Error(let e):
-            parse_err = e
-          }
-        }
-      }
-
-      if let parse_err = parse_err {
-        return Result.Error(parse_err)
-      }
-
-      var parsed_s: [EvaluatableParserStatement] = Array()
-
-      if !statements_capture.isEmpty {
-        for statement in statements_capture {
-          statement.node.enumerateChildren { node in
-            switch Statements(
-              node: node, inTree: tree, withScope: newStateScopes)
-            {
-            case .Ok((let le, let le_parsed_scopes)):
-              newStateScopes = le_parsed_scopes
-              parsed_s.append(le)
-            case .Error(let e):
-              parse_err = e
-            }
-          }
-        }
-      }
-
-      if let parse_err = parse_err {
-        return Result.Error(parse_err)
-      }
-
-      return Result.Ok(
-        (
-          ParserState(
-            name: parsed_state_name, withLocalElements: parsed_les,
-            withStatements: parsed_s,
-            withTransition: transition_statement!), newStateScopes
-        ))
-    }
-  }
-  static func Parser(
-    withName name: Identifier, node: Node, inTree tree: MutableTree, withScopes scopes: Scopes
-  ) -> Result<(Lang.Parser, Scopes)> {
-    guard
-      let parser_state_query = try? SwiftTreeSitter.Query(
-        language: p4lang,
-        data: String(
-          "(parserStates) @parser-states"
-        ).data(using: String.Encoding.utf8)!)
-    else {
-      return Result.Error(
-        Error(withMessage: "Could not compile the parser state tree sitter query"))
-    }
-
-    var parser = Lang.Parser(withName: name)
-
-    // Build a state from each one listed.
-    let qr = parser_state_query.execute(node: node, in: tree)
-    let qr_value = qr.next()!
-    let captures = qr_value.captures(named: "parser-states")
-
-    var error: Error? = .none
-
-    var parser_scopes = scopes
-
-    // TODO: Assert that there is only one.
-    captures[0].node.enumerateChildren { parser_state in
-      switch P4Parser.State(node: parser_state, inTree: tree, withScopes: scopes) {
-      case Result.Ok(let (state, new_parser_scopes)):
-        parser.states = parser.states.append(state: state)
-        parser_scopes = new_parser_scopes
-      case Result.Error(let e): error = e
-      }
-    }
-
-    if let error = error {
-      return .Error(error)
-    }
-
-    return Result.Ok((parser, parser_scopes))
-  }
-
-  public static func Program(_ source: String) -> Result<Program> {
-    let p = SwiftTreeSitter.Parser.init()
-
-    do {
-      try p.setLanguage(p4lang)
-    } catch {
-      return Result.Error(Error(withMessage: "Could not configure the P4 parser"))
-    }
-
-    let result = p.parse(source)
-    guard let tree = result,
-      !tree.isError(lang: p4lang),
-      !tree.containsMissing(lang: p4lang)
-    else {
-      return Result.Error(Error(withMessage: "Could not compile the P4 program"))
-    }
-
-    guard
-      let parser_declaration_query = try? SwiftTreeSitter.Query(
-        language: p4lang,
-        data: String(
-          "(parserDeclaration (parserType parser_name: (identifier) @parser-name) (parserStates) @parser-states)"
-        ).data(using: String.Encoding.utf8)!)
-    else {
-      return Result.Error(
-        Error(withMessage: "Could not compile the parser declaration tree sitter query"))
-    }
-
-    var program = Lang.Program()
-
-    // Set up a lexical scope for parsing.
-    var program_scope = Scopes().enter()
-
-    let parser_qc = parser_declaration_query.execute(in: tree)
-
-    for parser_declaration in parser_qc {
-      switch Parser(
-        withName: Identifier(name: parser_declaration.nodes[0].text!),
-        node: parser_declaration.nodes[1], inTree: tree, withScopes: program_scope)
-      {
-      case Result.Ok((let parser, let new_program_scope)):
-        program.types.append(parser)
-        program_scope = new_program_scope
-      case Result.Error(let error): return Result.Error(error)
-      }
-    }
-
-    return Result.Ok(program)
-  }
-}