Adding Concurrency and Error Throws (#77)

Author: leogdion

.swiftlint.yml

@@ -111,6 +111,10 @@ identifier_name:
   excluded:
     - id
     - no
+type_name:
+  excluded:
+    - If
+    - Do
 excluded:
   - DerivedData
   - .build

Examples/Completed/concurrency/code.swift

@@ -0,0 +1,42 @@
+enum VendingMachineError: Error {
+    case invalidSelection
+    case insufficientFunds(coinsNeeded: Int)
+    case outOfStock
+}
+
+class VendingMachine {
+    var inventory = [
+        "Candy Bar": Item(price: 12, count: 7),
+        "Chips": Item(price: 10, count: 4),
+        "Pretzels": Item(price: 7, count: 11)
+    ]
+    var coinsDeposited = 0
+
+
+    func vend(itemNamed name: String) throws {
+        guard let item = inventory[name] else {
+            throw VendingMachineError.invalidSelection
+        }
+
+
+        guard item.count > 0 else {
+            throw VendingMachineError.outOfStock
+        }
+
+
+        guard item.price <= coinsDeposited else {
+            throw VendingMachineError.insufficientFunds(coinsNeeded: item.price - coinsDeposited)
+        }
+
+
+        coinsDeposited -= item.price
+
+
+        var newItem = item
+        newItem.count -= 1
+        inventory[name] = newItem
+
+
+        print("Dispensing \(name)")
+    }
+}

Examples/Completed/concurrency/dsl.swift

@@ -0,0 +1,48 @@
+Enum("VendingMachineError") {
+    Case("invalidSelection")
+    Case("insufficientFunds").associatedValue("coinsNeeded", type: "Int")
+    Case("outOfStock")
+}
+
+Class("VendingMachine") {
+    Variable(.var, name: "inventory", equals: Literal.dictionary(Dictionary(uniqueKeysWithValues: [
+        ("Candy Bar", Item(price: 12, count: 7)),
+        ("Chips", Item(price: 10, count: 4)),
+        ("Pretzels", Item(price: 7, count: 11))
+    ])))
+    Variable(.var, name: "coinsDeposited", equals: 0)
+
+    Function("vend"){
+        Parameter("name", labeled: "itemNamed", type: "String")
+    } _: {
+        Guard("let item = inventory[itemNamed]") else: {
+            Throw(
+                EnumValue("VendingMachineError", case: "invalidSelection")
+            )
+        }
+        Guard("item.count > 0") else: {
+            Throw(
+                EnumValue("VendingMachineError", case: "outOfStock")
+            )
+        }
+        Guard("item.price <= coinsDeposited") else: {
+            Throw(
+                EnumValue("VendingMachineError", case: "insufficientFunds"){
+                    ParameterExp("coinsNeeded", value: Infix("-"){
+                        VariableExp("item").property("price")
+                        VariableExp("coinsDeposited")
+                    })
+                }
+            )
+        }
+        Infix("-=", "coinsDeposited", VariableExp("item").property("price"))
+        Variable("newItem", equals: VariableExp("item"))
+        Infix("-=", "newItem.count", 1)
+        Assignment("inventory[itemNamed]", .ref("newItem"))
+        Call("print", "Dispensing \\(itemNamed)")
+    }
+}
+
+
+
+

Examples/Completed/concurrency/syntax.json

@@ -0,0 +1,23 @@
+
+var vendingMachine = VendingMachine()
+vendingMachine.coinsDeposited = 8
+do {
+    try buyFavoriteSnack(person: "Alice", vendingMachine: vendingMachine)
+    print("Success! Yum.")
+} catch VendingMachineError.invalidSelection {
+    print("Invalid Selection.")
+} catch VendingMachineError.outOfStock {
+    print("Out of Stock.")
+} catch VendingMachineError.insufficientFunds(let coinsNeeded) {
+    print("Insufficient funds. Please insert an additional \(coinsNeeded) coins.")
+} catch {
+    print("Unexpected error: \(error).")
+}
+
+func summarize(_ ratings: [Int]) throws(StatisticsError) {
+    guard !ratings.isEmpty else { throw .noRatings }
+}
+
+async let data = fetchUserData(id: 1)
+async let posts = fetchUserPosts(id: 1)
+let (fetchedData, fetchedPosts) = try await (data, posts)

Examples/Completed/errors_async/code.swift

@@ -0,0 +1,74 @@
+Variable(.var, name: "vendingMachine", equals: Init("VendingMachine"))
+Assignment("vendingMachine.coinsDeposited", Literal.integer(8))
+Do {
+    Call("buyFavoriteSnack") {
+        ParameterExp(name: "person", value: Literal.string("Alice"))
+        ParameterExp(name: "vendingMachine", value: Literal.ref("vendingMachine"))
+    }.throwing()
+    Call("print") {
+        ParameterExp(unlabeled: Literal.string("Success! Yum."))
+    }
+} catch: {
+    Catch(EnumCase("invalidSelection")) {
+        Call("print") {
+        ParameterExp(unlabeled: Literal.string("Invalid Selection."))
+        }
+    }
+    Catch(EnumCase("outOfStock")) {
+        Call("print") {
+        ParameterExp(unlabeled: Literal.string("Out of Stock."))
+        }
+    }
+    Catch(
+        EnumCase("insufficientFunds").associatedValue(
+        "coinsNeeded", type: "Int")
+    ) {
+        Call("print") {
+        ParameterExp(
+            unlabeled: Literal.string(
+            "Insufficient funds. Please insert an additional \\(coinsNeeded) coins."))
+        }
+    }
+    Catch {
+        Call("print") {
+        ParameterExp(unlabeled: Literal.string("Unexpected error: \\(error)."))
+        }
+    }
+}
+
+Function("summarize") {
+    Parameter(name: "ratings", type: "[Int]")
+} _: {
+    Guard{
+        VariableExp("ratings").property("isEmpty").not()
+    } else: {
+        Throw(EnumCase("noRatings"))
+    }
+}.throws("StatisticsError")
+
+Do {
+    Variable(.let, name: "data") {
+        Call("fetchUserData") {
+            ParameterExp(name: "id", value: Literal.integer(1))
+        }
+    }.async()
+    Variable(.let, name: "posts") {
+        Call("fetchUserPosts") {
+            ParameterExp(name: "id", value: Literal.integer(1))
+        }
+    }.async()
+    TupleAssignment(["fetchedData", "fetchedPosts"], equals: Tuple {
+        VariableExp("data")
+        VariableExp("posts")
+    }).async().throwing()
+} catch: {
+    Catch(EnumCase("fetchError")) {
+        // Example catch for async/await
+    }
+}
+
+
+
+
+
+

Examples/Completed/errors_async/dsl.swift

@@ -0,0 +1,58 @@
+
+var vendingMachine = VendingMachine()
+vendingMachine.coinsDeposited = 8
+do {
+    try buyFavoriteSnack(person: "Alice", vendingMachine: vendingMachine)
+    print("Success! Yum.")
+} catch VendingMachineError.invalidSelection {
+    print("Invalid Selection.")
+} catch VendingMachineError.outOfStock {
+    print("Out of Stock.")
+} catch VendingMachineError.insufficientFunds(let coinsNeeded) {
+    print("Insufficient funds. Please insert an additional \(coinsNeeded) coins.")
+} catch {
+    print("Unexpected error: \(error).")
+}
+
+func summarize(_ ratings: [Int]) throws(StatisticsError) {
+    guard !ratings.isEmpty else { throw .noRatings }
+}
+
+// MARK: - Task Groups
+func fetchMultipleUsers(ids: [Int]) async throws -> [String] {
+    try await withThrowingTaskGroup(of: String.self) { group in
+        for id in ids {
+            group.addTask {
+                try await fetchUserData(id: id)
+            }
+        }
+
+        var results: [String] = []
+        for try await result in group {
+            results.append(result)
+        }
+        return results
+    }
+}
+
+// Demonstrate concurrent tasks
+print("\nFetching user data and posts concurrently...")
+async let data = fetchUserData(id: 1)
+async let posts = fetchUserPosts(id: 1)
+let (fetchedData, fetchedPosts) = try await (data, posts)
+print("Data: \(fetchedData)")
+print("Posts: \(fetchedPosts)")
+
+
+Task {
+    _ = try await fetchUserData(id: 1)
+}
+
+Task { @MainActor [unowned self] in
+    _ = try await fetchUserData(id: 1)
+}
+
+
+func nonThrowingFunction() throws(Never) {
+    
+}

Examples/Completed/errors_async/syntax.json

@@ -5,7 +5,8 @@
 //  Created by Leo Dion on 6/16/25.
 //
 
-/// Represents a single comment line that can be attached to a syntax node when using `.comment { ... }` in the DSL.
+/// Represents a single comment line that can be attached to a syntax node when using 
+/// `.comment { ... }` in the DSL.
 public struct Line {
   public enum Kind {
     /// Regular line comment that starts with `//`.