BridgeJS: Add compatibility helper for GenericArgumentSyntax

Author: kateinoigakukun

Plugins/BridgeJS/Sources/BridgeJSCore/SwiftToSkeleton.swift

@@ -104,7 +104,8 @@ public final class SwiftToSkeleton {
             identifierType.name.text == "JSTypedClosure",
             let genericArgs = identifierType.genericArgumentClause?.arguments,
             genericArgs.count == 1,
-            let signatureType = lookupType(for: genericArgs.first!.argument, errors: &errors),
+            let argument = genericArgs.firstAsTypeSyntax,
+            let signatureType = lookupType(for: argument, errors: &errors),
             case .closure(let signature) = signatureType
         {
             return .closure(signature)
@@ -2506,3 +2507,18 @@ private final class ImportSwiftMacrosAPICollector: SyntaxAnyVisitor {
         }
     }
 }
+
+extension GenericArgumentListSyntax {
+    /// Compatibility helper for accessing the first argument as a TypeSyntax
+    ///
+    /// Note: SwiftSyntax 601 and later support InlineArrayTypeSyntax and
+    /// ``GenericArgumentSyntax/argument`` is now a ``TypeSyntax`` or ``ExprSyntax``.
+    fileprivate var firstAsTypeSyntax: TypeSyntax? {
+        guard let first = self.first else { return nil }
+        #if canImport(SwiftSyntax601)
+        return first.argument.as(TypeSyntax.self)
+        #else
+        return TypeSyntax(first.argument)
+        #endif
+    }
+}