Add EffectfulExprSyntax syntax trait

Introduces the `EffectfulExprSyntax` protocol, designed to provide a common interface for effectful expressions such as `try` and `await`.

Solves #2549

Author: Matejkob

CodeGeneration/Sources/SyntaxSupport/ExprNodes.swift

@@ -152,6 +152,9 @@ public let EXPR_NODES: [Node] = [
     kind: .awaitExpr,
     base: .expr,
     nameForDiagnostics: "'await' expression",
+    traits: [
+      "EffectfulExpr"
+    ],
     children: [
       Child(
         name: "awaitKeyword",
@@ -1914,6 +1917,9 @@ public let EXPR_NODES: [Node] = [
       try! foo()
       ```
       """,
+    traits: [
+      "EffectfulExpr"
+    ],
     children: [
       Child(
         name: "tryKeyword",

CodeGeneration/Sources/SyntaxSupport/Traits.swift

@@ -66,6 +66,18 @@ public let TRAITS: [Trait] = [
       Child(name: "memberBlock", kind: .node(kind: .memberBlock)),
     ]
   ),
+  Trait(
+    traitName: "EffectfulExpr",
+    documentation: "Syntax trait for effectful expressions, such as `try` and `await`.",
+    children: [
+      Child(name: "expression", kind: .node(kind: .expr)),
+      Child(
+        name: "keyword",
+        kind: .token(choices: [.keyword(.try), .keyword(.await)]),
+        documentation: "The token that represents the specific keyword of the effectful expression."
+      ),
+    ]
+  ),
   Trait(
     traitName: "EffectSpecifiers",
     children: [

Release Notes/610.md

@@ -0,0 +1,25 @@
+# Swift Syntax 610 Release Notes
+
+## New APIs
+
+- `EffectfulExprSyntax`
+  - Description: A protocol for unified handling of `try` and `await` expressions, with a `keyword` property to identify the expression's specific keyword.
+  - Issue: https://github.com/apple/swift-syntax/issues/2549
+  - Pull Request: https://github.com/apple/swift-syntax/pull/2572
+
+## API Behavior Changes
+
+## Deprecations
+
+## API-Incompatible Changes
+
+## Template
+
+- *Affected API or two word description*
+  - Description: *A 1-2 sentence description of the new/modified API*
+  - Issue: *If an issue exists for this change, a link to the issue*
+  - Pull Request: *Link to the pull request(s) that introduces this change*
+  - Migration steps: Steps that adopters of swift-syntax should take to move to the new API (required for deprecations and API-incompatible changes).
+  - Notes: *In case of deprecations or API-incompatible changes, the reason why this change was made and the suggested alternative*
+
+*Insert entries in chronological order, with newer entries at the bottom*

Sources/SwiftSyntax/CustomTraits.swift

@@ -21,6 +21,17 @@ extension ActorDeclSyntax {
   }
 }
 
+extension AwaitExprSyntax {
+  public var keyword: TokenSyntax {
+    get {
+      return awaitKeyword
+    }
+    set {
+      awaitKeyword = newValue
+    }
+  }
+}
+
 extension ClassDeclSyntax {
   public var introducer: TokenSyntax {
     get {
@@ -76,6 +87,17 @@ extension StructDeclSyntax {
   }
 }
 
+extension TryExprSyntax {
+  public var keyword: TokenSyntax {
+    get {
+      return tryKeyword
+    }
+    set {
+      tryKeyword = newValue
+    }
+  }
+}
+
 //==========================================================================//
 // IMPORTANT: If you are tempted to add an extension here, please insert    //
 // it in alphabetical order above                                           //

Sources/SwiftSyntax/Documentation.docc/generated/SwiftSyntax.md

@@ -392,6 +392,7 @@ These articles are intended for developers wishing to contribute to SwiftSyntax
 
 - <doc:SwiftSyntax/BracedSyntax>
 - <doc:SwiftSyntax/DeclGroupSyntax>
+- <doc:SwiftSyntax/EffectfulExprSyntax>
 - <doc:SwiftSyntax/EffectSpecifiersSyntax>
 - <doc:SwiftSyntax/FreestandingMacroExpansionSyntax>
 - <doc:SwiftSyntax/NamedDeclSyntax>

Sources/SwiftSyntax/generated/SyntaxTraits.swift

@@ -132,6 +132,55 @@ public extension SyntaxProtocol {
   }
 }
 
+// MARK: - EffectfulExprSyntax
+
+/// Syntax trait for effectful expressions, such as `try` and `await`.
+public protocol EffectfulExprSyntax: SyntaxProtocol {
+  var expression: ExprSyntax {
+    get
+    set
+  }
+  
+  /// The token that represents the specific keyword of the effectful expression.
+  ///
+  /// ### Tokens
+  /// 
+  /// For syntax trees generated by the parser, this is guaranteed to be one of the following kinds:
+  ///  - `try`
+  ///  - `await`
+  var keyword: TokenSyntax {
+    get
+    set
+  }
+}
+
+public extension EffectfulExprSyntax {
+  /// Without this function, the `with` function defined on `SyntaxProtocol`
+  /// does not work on existentials of this protocol type.
+  @_disfavoredOverload
+  func with<T>(_ keyPath: WritableKeyPath<EffectfulExprSyntax, T>, _ newChild: T) -> EffectfulExprSyntax {
+    var copy: EffectfulExprSyntax = self
+    copy[keyPath: keyPath] = newChild
+    return copy
+  }
+}
+
+public extension SyntaxProtocol {
+  /// Check whether the non-type erased version of this syntax node conforms to
+  /// `EffectfulExprSyntax`.
+  /// Note that this will incur an existential conversion.
+  func isProtocol(_: EffectfulExprSyntax.Protocol) -> Bool {
+    return self.asProtocol(EffectfulExprSyntax.self) != nil
+  }
+  
+  /// Return the non-type erased version of this syntax node if it conforms to
+  /// `EffectfulExprSyntax`. Otherwise return `nil`.
+  /// Note that this will incur an existential conversion.
+  func asProtocol(_: EffectfulExprSyntax.Protocol) -> EffectfulExprSyntax? {
+    return Syntax(self).asProtocol(SyntaxProtocol.self) as? EffectfulExprSyntax
+  }
+}
+
 // MARK: - EffectSpecifiersSyntax
 
 public protocol EffectSpecifiersSyntax: SyntaxProtocol {
@@ -689,6 +738,8 @@ extension AttributedTypeSyntax: WithAttributesSyntax {}
 
 extension AvailabilityArgumentSyntax: WithTrailingCommaSyntax {}
 
+extension AwaitExprSyntax: EffectfulExprSyntax {}
+
 extension CatchClauseSyntax: WithCodeBlockSyntax {}
 
 extension CatchItemSyntax: WithTrailingCommaSyntax {}
@@ -831,6 +882,8 @@ extension SwitchCaseSyntax: WithStatementsSyntax {}
 
 extension SwitchExprSyntax: BracedSyntax {}
 
+extension TryExprSyntax: EffectfulExprSyntax {}
+
 extension TupleExprSyntax: ParenthesizedSyntax {}
 
 extension TuplePatternElementSyntax: WithTrailingCommaSyntax {}