[BridgeJS] Synthesize typed-closure init access from declaration surface

Resolves #709: a public `@JSClass` exposing a
`JSTypedClosure<...>` parameter could not be consumed from another target
because the synthesized `extension JSTypedClosure { init(...) }` was always
internal, leaving downstream callers no way to construct the closure value
without hand-rolling a public wrapper.

Imported skeleton entries now record the source access level
(`public`/`package`/`internal`); the closure-signature collector takes the
maximum across every surface that references a given signature, and
`ClosureCodegen` prefixes the synthesized init with the resulting modifier
(internal stays bare). This matches the pattern `JSClassMacro` already uses
for `init(unsafelyWrapping:)`.

Author: matthewa26

Plugins/BridgeJS/Sources/BridgeJSCore/ClosureCodegen.swift

@@ -21,7 +21,10 @@ public struct ClosureCodegen {
         return "(\(closureParams))\(swiftEffects) -> \(swiftReturnType)"
     }
 
-    func renderClosureHelpers(_ signature: ClosureSignature) throws -> [DeclSyntax] {
+    func renderClosureHelpers(
+        _ signature: ClosureSignature,
+        accessLevel: BridgeJSAccessLevel = .internal
+    ) throws -> [DeclSyntax] {
         let mangledName = signature.mangleName
         let helperName = "_BJS_Closure_\(mangledName)"
         let swiftClosureType = swiftClosureType(for: signature)
@@ -99,9 +102,10 @@ public struct ClosureCodegen {
 
         let helperEnumDecl: DeclSyntax = "\(raw: helperEnumDeclPrinter.lines.joined(separator: "\n"))"
 
+        let initAccessModifier = accessLevel.modifierKeyword.map { "\($0) " } ?? ""
         let typedClosureExtension: DeclSyntax = """
             extension JSTypedClosure where Signature == \(raw: swiftClosureType) {
-                init(fileID: StaticString = #fileID, line: UInt32 = #line, _ body: @escaping \(raw: swiftClosureType)) {
+                \(raw: initAccessModifier)init(fileID: StaticString = #fileID, line: UInt32 = #line, _ body: @escaping \(raw: swiftClosureType)) {
                     self.init(
                         makeClosure: \(raw: externABIName),
                         body: body,
@@ -192,12 +196,13 @@ public struct ClosureCodegen {
         let collector = ClosureSignatureCollectorVisitor(moduleName: skeleton.moduleName)
         var walker = BridgeSkeletonWalker(visitor: collector)
         walker.walk(skeleton)
-        let closureSignatures = walker.visitor.signatures
-        guard !closureSignatures.isEmpty else { return nil }
+        let signatureAccessLevels = walker.visitor.signatureAccessLevels
+        guard !signatureAccessLevels.isEmpty else { return nil }
 
         var decls: [DeclSyntax] = []
-        for signature in closureSignatures.sorted(by: { $0.mangleName < $1.mangleName }) {
-            decls.append(contentsOf: try renderClosureHelpers(signature))
+        for signature in signatureAccessLevels.keys.sorted(by: { $0.mangleName < $1.mangleName }) {
+            let accessLevel = signatureAccessLevels[signature] ?? .internal
+            decls.append(contentsOf: try renderClosureHelpers(signature, accessLevel: accessLevel))
             decls.append(try renderClosureInvokeHandler(signature))
         }
 

Plugins/BridgeJS/Sources/BridgeJSCore/SwiftToSkeleton.swift

@@ -2056,6 +2056,7 @@ private final class ImportSwiftMacrosAPICollector: SyntaxAnyVisitor {
         let name: String
         let jsName: String?
         let from: JSImportFrom?
+        let accessLevel: BridgeJSAccessLevel
         var constructor: ImportedConstructorSkeleton?
         var methods: [ImportedFunctionSkeleton]
         var staticMethods: [ImportedFunctionSkeleton]
@@ -2271,6 +2272,7 @@ private final class ImportSwiftMacrosAPICollector: SyntaxAnyVisitor {
             name: typeName,
             jsName: nil,
             from: nil,
+            accessLevel: .internal,
             constructor: nil,
             methods: [],
             staticMethods: [],
@@ -2279,12 +2281,18 @@ private final class ImportSwiftMacrosAPICollector: SyntaxAnyVisitor {
         )
     }
 
-    private func enterJSClass(_ typeName: String, jsName: String?, from: JSImportFrom?) {
+    private func enterJSClass(
+        _ typeName: String,
+        jsName: String?,
+        from: JSImportFrom?,
+        accessLevel: BridgeJSAccessLevel
+    ) {
         stateStack.append(.jsClassBody(name: typeName))
         currentType = CurrentType(
             name: typeName,
             jsName: jsName,
             from: from,
+            accessLevel: accessLevel,
             constructor: nil,
             methods: [],
             staticMethods: [],
@@ -2305,7 +2313,8 @@ private final class ImportSwiftMacrosAPICollector: SyntaxAnyVisitor {
                     staticMethods: type.staticMethods,
                     getters: type.getters,
                     setters: type.setters,
-                    documentation: nil
+                    documentation: nil,
+                    accessLevel: type.accessLevel
                 )
             )
             currentType = nil
@@ -2318,7 +2327,8 @@ private final class ImportSwiftMacrosAPICollector: SyntaxAnyVisitor {
             let attribute = AttributeChecker.firstJSClassAttribute(node.attributes)
             let jsName = attribute.flatMap(AttributeChecker.extractJSName)
             let from = attribute.flatMap(AttributeChecker.extractJSImportFrom)
-            enterJSClass(node.name.text, jsName: jsName, from: from)
+            let accessLevel = Self.bridgeAccessLevel(from: node.modifiers)
+            enterJSClass(node.name.text, jsName: jsName, from: from, accessLevel: accessLevel)
         }
         return .visitChildren
     }
@@ -2334,7 +2344,8 @@ private final class ImportSwiftMacrosAPICollector: SyntaxAnyVisitor {
             let attribute = AttributeChecker.firstJSClassAttribute(node.attributes)
             let jsName = attribute.flatMap(AttributeChecker.extractJSName)
             let from = attribute.flatMap(AttributeChecker.extractJSImportFrom)
-            enterJSClass(node.name.text, jsName: jsName, from: from)
+            let accessLevel = Self.bridgeAccessLevel(from: node.modifiers)
+            enterJSClass(node.name.text, jsName: jsName, from: from, accessLevel: accessLevel)
         }
         return .visitChildren
     }
@@ -2499,8 +2510,14 @@ private final class ImportSwiftMacrosAPICollector: SyntaxAnyVisitor {
         else {
             return nil
         }
+        // Initializers without an explicit modifier inherit access from the
+        // enclosing `@JSClass` (the user's example pattern: `public init(...)`
+        // inside `public struct JSDocument`).
+        let parentLevel = currentType?.accessLevel ?? .internal
+        let accessLevel = Self.bridgeAccessLevel(from: initializer.modifiers, default: parentLevel)
         return ImportedConstructorSkeleton(
-            parameters: parseParameters(from: initializer.signature.parameterClause)
+            parameters: parseParameters(from: initializer.signature.parameterClause),
+            accessLevel: accessLevel
         )
     }
 
@@ -2533,14 +2550,16 @@ private final class ImportSwiftMacrosAPICollector: SyntaxAnyVisitor {
         } else {
             returnType = .void
         }
+        let accessLevel = Self.bridgeAccessLevel(from: node.modifiers)
         return ImportedFunctionSkeleton(
             name: name,
             jsName: jsName,
             from: from,
             parameters: parameters,
             returnType: returnType,
             effects: effects,
-            documentation: nil
+            documentation: nil,
+            accessLevel: accessLevel
         )
     }
 
@@ -2572,13 +2591,15 @@ private final class ImportSwiftMacrosAPICollector: SyntaxAnyVisitor {
         let propertyName = SwiftToSkeleton.normalizeIdentifier(identifier.identifier.text)
         let jsName = AttributeChecker.extractJSName(from: jsGetter)
         let from = AttributeChecker.extractJSImportFrom(from: jsGetter)
+        let accessLevel = Self.bridgeAccessLevel(from: node.modifiers)
         return ImportedGetterSkeleton(
             name: propertyName,
             jsName: jsName,
             from: from,
             type: propertyType,
             documentation: nil,
-            functionName: nil
+            functionName: nil,
+            accessLevel: accessLevel
         )
     }
 
@@ -2601,12 +2622,14 @@ private final class ImportSwiftMacrosAPICollector: SyntaxAnyVisitor {
             return nil
         }
 
+        let accessLevel = Self.bridgeAccessLevel(from: node.modifiers)
         return ImportedSetterSkeleton(
             name: propertyName,
             jsName: validation.jsName,
             type: validation.valueType,
             documentation: nil,
-            functionName: "\(functionBaseName)_set"
+            functionName: "\(functionBaseName)_set",
+            accessLevel: accessLevel
         )
     }
 
@@ -2652,6 +2675,31 @@ private final class ImportSwiftMacrosAPICollector: SyntaxAnyVisitor {
             modifier.name.tokenKind == .keyword(.static) || modifier.name.tokenKind == .keyword(.class)
         }
     }
+
+    /// Maps Swift's declaration modifiers to a `BridgeJSAccessLevel` for
+    /// recording on imported skeleton entries. Falls back to `default` when no
+    /// access modifier is present (typically `.internal`, but the caller may
+    /// override — e.g. an `init` inheriting from its enclosing `@JSClass`).
+    /// `private`/`fileprivate` are mapped to the fallback because the macros
+    /// already reject those access levels for `@JS*` declarations.
+    fileprivate static func bridgeAccessLevel(
+        from modifiers: DeclModifierListSyntax,
+        default fallback: BridgeJSAccessLevel = .internal
+    ) -> BridgeJSAccessLevel {
+        for modifier in modifiers {
+            switch modifier.name.tokenKind {
+            case .keyword(.public), .keyword(.open):
+                return .public
+            case .keyword(.package):
+                return .package
+            case .keyword(.internal):
+                return .internal
+            default:
+                continue
+            }
+        }
+        return fallback
+    }
 }
 
 extension GenericArgumentListSyntax {