Merge pull request swiftlang#200 from ahoppen/base-not-optional-initialiser

For base nodes, add an initializer that takes an optional parameter

Author: ahoppen

Sources/SwiftSyntax/SyntaxBaseNodes.swift.gyb

@@ -51,13 +51,20 @@ public extension Syntax {
 public struct ${node.name}: ${node.name}Protocol, SyntaxHashable {
   public let _syntaxNode: Syntax
 
+  /// Create a `${node.name}` node from a specialized syntax node.
   public init<S: ${node.name}Protocol>(_ syntax: S) {
     // We know this cast is going to succeed. Go through init(_: SyntaxData)
     // to do a sanity check and verify the kind matches in debug builds and get
     // maximum performance in release builds.
     self.init(syntax._syntaxNode.data)
   }
 
+  /// Create a `${node.name}` node from a specialized optional syntax node.
+  public init?<S: ${node.name}Protocol>(_ syntax: S?) {
+    guard let syntax = syntax else { return nil }
+    self.init(syntax)
+  }
+
   /// Converts the given `Syntax` node to a `${node.name}` if possible. Returns
   /// `nil` if the conversion is not possible.
   public init?(_ syntax: Syntax) {

Sources/SwiftSyntax/gyb_generated/SyntaxBaseNodes.swift

@@ -38,13 +38,20 @@ public extension Syntax {
 public struct DeclSyntax: DeclSyntaxProtocol, SyntaxHashable {
   public let _syntaxNode: Syntax
 
+  /// Create a `DeclSyntax` node from a specialized syntax node.
   public init<S: DeclSyntaxProtocol>(_ syntax: S) {
     // We know this cast is going to succeed. Go through init(_: SyntaxData)
     // to do a sanity check and verify the kind matches in debug builds and get
     // maximum performance in release builds.
     self.init(syntax._syntaxNode.data)
   }
 
+  /// Create a `DeclSyntax` node from a specialized optional syntax node.
+  public init?<S: DeclSyntaxProtocol>(_ syntax: S?) {
+    guard let syntax = syntax else { return nil }
+    self.init(syntax)
+  }
+
   /// Converts the given `Syntax` node to a `DeclSyntax` if possible. Returns
   /// `nil` if the conversion is not possible.
   public init?(_ syntax: Syntax) {
@@ -135,13 +142,20 @@ public extension Syntax {
 public struct ExprSyntax: ExprSyntaxProtocol, SyntaxHashable {
   public let _syntaxNode: Syntax
 
+  /// Create a `ExprSyntax` node from a specialized syntax node.
   public init<S: ExprSyntaxProtocol>(_ syntax: S) {
     // We know this cast is going to succeed. Go through init(_: SyntaxData)
     // to do a sanity check and verify the kind matches in debug builds and get
     // maximum performance in release builds.
     self.init(syntax._syntaxNode.data)
   }
 
+  /// Create a `ExprSyntax` node from a specialized optional syntax node.
+  public init?<S: ExprSyntaxProtocol>(_ syntax: S?) {
+    guard let syntax = syntax else { return nil }
+    self.init(syntax)
+  }
+
   /// Converts the given `Syntax` node to a `ExprSyntax` if possible. Returns
   /// `nil` if the conversion is not possible.
   public init?(_ syntax: Syntax) {
@@ -232,13 +246,20 @@ public extension Syntax {
 public struct StmtSyntax: StmtSyntaxProtocol, SyntaxHashable {
   public let _syntaxNode: Syntax
 
+  /// Create a `StmtSyntax` node from a specialized syntax node.
   public init<S: StmtSyntaxProtocol>(_ syntax: S) {
     // We know this cast is going to succeed. Go through init(_: SyntaxData)
     // to do a sanity check and verify the kind matches in debug builds and get
     // maximum performance in release builds.
     self.init(syntax._syntaxNode.data)
   }
 
+  /// Create a `StmtSyntax` node from a specialized optional syntax node.
+  public init?<S: StmtSyntaxProtocol>(_ syntax: S?) {
+    guard let syntax = syntax else { return nil }
+    self.init(syntax)
+  }
+
   /// Converts the given `Syntax` node to a `StmtSyntax` if possible. Returns
   /// `nil` if the conversion is not possible.
   public init?(_ syntax: Syntax) {
@@ -329,13 +350,20 @@ public extension Syntax {
 public struct TypeSyntax: TypeSyntaxProtocol, SyntaxHashable {
   public let _syntaxNode: Syntax
 
+  /// Create a `TypeSyntax` node from a specialized syntax node.
   public init<S: TypeSyntaxProtocol>(_ syntax: S) {
     // We know this cast is going to succeed. Go through init(_: SyntaxData)
     // to do a sanity check and verify the kind matches in debug builds and get
     // maximum performance in release builds.
     self.init(syntax._syntaxNode.data)
   }
 
+  /// Create a `TypeSyntax` node from a specialized optional syntax node.
+  public init?<S: TypeSyntaxProtocol>(_ syntax: S?) {
+    guard let syntax = syntax else { return nil }
+    self.init(syntax)
+  }
+
   /// Converts the given `Syntax` node to a `TypeSyntax` if possible. Returns
   /// `nil` if the conversion is not possible.
   public init?(_ syntax: Syntax) {
@@ -426,13 +454,20 @@ public extension Syntax {
 public struct PatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
   public let _syntaxNode: Syntax
 
+  /// Create a `PatternSyntax` node from a specialized syntax node.
   public init<S: PatternSyntaxProtocol>(_ syntax: S) {
     // We know this cast is going to succeed. Go through init(_: SyntaxData)
     // to do a sanity check and verify the kind matches in debug builds and get
     // maximum performance in release builds.
     self.init(syntax._syntaxNode.data)
   }
 
+  /// Create a `PatternSyntax` node from a specialized optional syntax node.
+  public init?<S: PatternSyntaxProtocol>(_ syntax: S?) {
+    guard let syntax = syntax else { return nil }
+    self.init(syntax)
+  }
+
   /// Converts the given `Syntax` node to a `PatternSyntax` if possible. Returns
   /// `nil` if the conversion is not possible.
   public init?(_ syntax: Syntax) {

Tests/SwiftSyntaxTest/SyntaxTests.swift

@@ -119,5 +119,8 @@ public class SyntaxTests: XCTestCase {
     case .integerLiteralExpr: break
     default: XCTFail("failed to convert to SyntaxEnum")
     }
+
+    XCTAssertNil(ExprSyntax(nil as IntegerLiteralExprSyntax?))
+    XCTAssertEqual(ExprSyntax(integerExpr).as(IntegerLiteralExprSyntax.self)!, integerExpr)
   }
 }