refactor: make Swift forward-declaration collection polymorphic (#1846)

packages/nitrogen/src/autolinking/ios/createSwiftCxxBridge.ts

@@ -8,11 +8,8 @@ import {
 import type { SourceFile } from '../../syntax/SourceFile.js'
 import { getReferencedTypes } from '../../syntax/getReferencedTypes.js'
 import { SwiftCxxBridgedType } from '../../syntax/swift/SwiftCxxBridgedType.js'
+import type { SwiftCxxHelper } from '../../syntax/swift/SwiftCxxTypeHelper.js'
 import { filterDuplicateHelperBridges, indent } from '../../utils.js'
-import { getTypeAs } from '../../syntax/types/getTypeAs.js'
-import { HybridObjectType } from '../../syntax/types/HybridObjectType.js'
-import { getForwardDeclaration } from '../../syntax/c++/getForwardDeclaration.js'
-import { getHybridObjectName } from '../../syntax/getHybridObjectName.js'
 
 export function createSwiftCxxBridge(): SourceFile[] {
   const bridgeName = NitroConfig.current.getSwiftBridgeHeaderName()
@@ -28,8 +25,8 @@ export function createSwiftCxxBridge(): SourceFile[] {
         return bridge.getRequiredBridge()
       })
     })
-    .filter((b) => b != null)
-    .flatMap((b) => [b, ...b?.dependencies])
+    .filter((b): b is SwiftCxxHelper => b != null)
+    .flatMap((b) => [b, ...b.dependencies])
     .filter(filterDuplicateHelperBridges)
   const headerHelperFunctions = bridges
     .map((b) => `// pragma MARK: ${b.cxxType}\n${b.cxxHeader.code}`)
@@ -62,20 +59,7 @@ export function createSwiftCxxBridge(): SourceFile[] {
     .filter(isNotDuplicate)
 
   const forwardDeclaredSwiftTypes = types
-    .filter((t) => t.type.kind === 'hybrid-object')
-    .map((t) => {
-      const hybridObject = getTypeAs(t.type, HybridObjectType)
-      const hybridObjectModuleName =
-        hybridObject.sourceConfig.getIosModuleName()
-      const { HybridTSpecCxx } = getHybridObjectName(
-        hybridObject.hybridObjectName
-      )
-      return getForwardDeclaration(
-        'class',
-        HybridTSpecCxx,
-        hybridObjectModuleName
-      )
-    })
+    .flatMap((t) => t.type.getForwardDeclarations?.() ?? [])
     .filter(isNotDuplicate)
 
   const header = `

packages/nitrogen/src/autolinking/ios/createSwiftUmbrellaHeader.ts

@@ -1,15 +1,11 @@
 import { NitroConfig } from '../../config/NitroConfig.js'
-import { getForwardDeclaration } from '../../syntax/c++/getForwardDeclaration.js'
 import { includeHeader } from '../../syntax/c++/includeNitroHeader.js'
 import { getAllKnownTypes } from '../../syntax/createType.js'
-import { getHybridObjectName } from '../../syntax/getHybridObjectName.js'
 import {
   createFileMetadataString,
   isNotDuplicate,
 } from '../../syntax/helpers.js'
 import type { SourceFile } from '../../syntax/SourceFile.js'
-import { getTypeAs } from '../../syntax/types/getTypeAs.js'
-import { HybridObjectType } from '../../syntax/types/HybridObjectType.js'
 
 export function getUmbrellaHeaderName(): string {
   const moduleName = NitroConfig.current.getIosModuleName()
@@ -23,18 +19,7 @@ export function createSwiftUmbrellaHeader(): SourceFile {
   const types = getAllKnownTypes('swift')
 
   const swiftForwardDeclares = types
-    .filter((t) => t.kind === 'hybrid-object')
-    .map((t) => {
-      const hybridObjectType = getTypeAs(t, HybridObjectType)
-      const hybridObjectModuleName =
-        hybridObjectType.sourceConfig.getIosModuleName()
-      const name = getHybridObjectName(hybridObjectType.hybridObjectName)
-      return getForwardDeclaration(
-        'class',
-        name.HybridTSpecCxx,
-        hybridObjectModuleName
-      )
-    })
+    .flatMap((t) => t.getForwardDeclarations?.() ?? [])
     .filter(isNotDuplicate)
 
   const imports = types.flatMap((t) => t.getRequiredImports('c++'))

packages/nitrogen/src/syntax/types/HybridObjectType.ts

@@ -198,4 +198,10 @@ export class HybridObjectType implements Type {
 
     return imports
   }
+
+  getForwardDeclarations(): string[] {
+    const name = getHybridObjectName(this.hybridObjectName)
+    const moduleName = this.sourceConfig.getIosModuleName()
+    return [getForwardDeclaration('class', name.HybridTSpecCxx, moduleName)]
+  }
 }

packages/nitrogen/src/syntax/types/Type.ts

@@ -69,6 +69,17 @@ export interface Type {
    * Get all required extra imports that need to be **imported** for this type to properly work.
    */
   getRequiredImports(language: Language): SourceImport[]
+  /**
+   * Get any C++ forward declarations this type needs beyond those already
+   * carried by {@linkcode getRequiredImports | getRequiredImports()}.
+   *
+   * This is an optional capability: only some types declare any (currently
+   * `HybridObjectType`, to forward-declare its Swift-generated `*Cxx` wrapper
+   * class). Letting the type own this keeps dependency collection polymorphic
+   * instead of callers hardcoding `kind`-checks and reaching into concrete
+   * type classes.
+   */
+  getForwardDeclarations?(): string[]
 }
 
 export interface NamedType extends Type {