Merge pull request #2739 from ahoppen/accessor-decl-header-initializer

Fix issue that caused `AccessorDeclSyntax` initializer with header + body to be misparsed

Author: ahoppen

Sources/SwiftSyntaxBuilder/SyntaxNodeWithBody.swift

@@ -12,8 +12,10 @@
 
 #if swift(>=6)
 public import SwiftSyntax
+internal import SwiftParser
 #else
 import SwiftSyntax
+import SwiftParser
 #endif
 
 // MARK: - PartialSyntaxNode
@@ -124,7 +126,22 @@ extension WithOptionalCodeBlockSyntax where Self: DeclSyntaxProtocol {
     _ header: SyntaxNodeString,
     @CodeBlockItemListBuilder bodyBuilder: () throws -> CodeBlockItemListSyntax
   ) throws {
-    let decl = DeclSyntax("\(header) {}")
+    // If the type provides a custom `SyntaxParseable` implementation, use that. Otherwise construct it as a
+    // `DeclSyntax`.
+    // We cannot use normal string interpolation here because the conformance to `ExpressibleByStringInterpolation` is
+    // not implied by `SyntaxParsable` but generated for each type by
+    // `SyntaxExpressibleByStringInterpolationConformances.swift`. And we can’t use that protocol in the `as?` check
+    // because then the compiler complains that `parsableType` is not instantiable. So, manually do the same work that
+    // a string literal with interpolation segments would do.
+    let decl: DeclSyntax
+    var stringInterpolation = SyntaxStringInterpolation(literalCapacity: 1, interpolationCount: 1)
+    stringInterpolation.appendInterpolation(header)
+    stringInterpolation.appendLiteral(" {}")
+    if let parsableType = Self.self as? SyntaxParseable.Type {
+      decl = parsableType.init(stringInterpolation: stringInterpolation).cast(DeclSyntax.self)
+    } else {
+      decl = DeclSyntax(stringInterpolation: stringInterpolation)
+    }
     guard let castedDecl = decl.as(Self.self) else {
       throw SyntaxStringInterpolationInvalidNodeTypeError(expectedType: Self.self, actualNode: decl)
     }
@@ -170,7 +187,17 @@ extension HasTrailingMemberDeclBlock where Self: DeclSyntaxProtocol {
     _ header: SyntaxNodeString,
     @MemberBlockItemListBuilder membersBuilder: () throws -> MemberBlockItemListSyntax
   ) throws {
-    let decl = DeclSyntax("\(header) {}")
+    // If the type provides a custom `SyntaxParseable` implementation, use that. Otherwise construct it as a
+    // `DeclSyntax`.
+    let decl: DeclSyntax
+    var stringInterpolation = SyntaxStringInterpolation(literalCapacity: 1, interpolationCount: 1)
+    stringInterpolation.appendInterpolation(header)
+    stringInterpolation.appendLiteral(" {}")
+    if let parsableType = Self.self as? SyntaxParseable.Type {
+      decl = parsableType.init(stringInterpolation: stringInterpolation).cast(DeclSyntax.self)
+    } else {
+      decl = DeclSyntax(stringInterpolation: stringInterpolation)
+    }
     guard let castedDecl = decl.as(Self.self) else {
       throw SyntaxStringInterpolationInvalidNodeTypeError(expectedType: Self.self, actualNode: decl)
     }

Tests/SwiftSyntaxBuilderTest/AccessorDeclTests.swift

@@ -0,0 +1,24 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import SwiftSyntax
+import SwiftSyntaxBuilder
+import XCTest
+
+final class AccessorDeclTests: XCTestCase {
+  func testCreateAccessorWithHeaderAndBody() throws {
+    let accessor = try AccessorDeclSyntax("get") {
+      ExprSyntax("1")
+    }
+    XCTAssertEqual(accessor.body?.statements.count, 1)
+  }
+}