invalidObjectMemberModifier

invalidObjectMemberModifier

Error message

invalidObjectMemberModifier (dynamic errorMessage key)

What it means

`doVisitModifiers` validates each modifier against a bitmask of modifiers valid in the current context; when a modifier (e.g. `abstract` on a property, or `hidden` on a class) is not allowed, it throws `invalidObjectMemberModifier` with the modifier name interpolated into the message (AstBuilder.java:2998).

Solutions

Read the interpolated modifier name in the message and remove it from that declaration.
Check Pkl docs for modifiers valid for the member kind (properties: `local`, `hidden`, `fixed`, `external`; classes: `open`, `abstract`, `open` etc.).
Move the modifier to the correct declaration site if it belongs elsewhere.

Example fix

// before
abstract foo = 1
// after
foo = 1

Defensive patterns

Strategy: validation

Validate before calling

// valid member modifiers per Pkl grammar: local, hidden, fixed, external, abstract
const VALID = new Set(["local", "hidden", "fixed", "external", "abstract", "open"]);
const mods = [...pklSource.matchAll(/^\s*([a-zA-Z]+)\s+[a-zA-Z_]\w*/gm)].map(m => m[1]);
mods.forEach(m => { if (!VALID.has(m)) throw new Error(`invalid modifier: ${m}`); });

Prevention

Check the Pkl language reference table of valid modifiers per declaration kind.
Add one modifier at a time and re-run `pkl eval`.
Don't copy modifier lists blindly between class and property declarations.

When it happens

Trigger: Using a modifier outside its allowed context, e.g. `open`/`abstract` on a non-class member, `fixed` on an object method, or any member modifier at module level where only a subset is valid.

Common situations: Copy-pasting modifiers between property/class declarations; misunderstanding which modifiers apply to object members vs classes; typos producing unexpected modifier placements.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

AI-assisted analysis of apple/pkl@f3efcbfc9b (2026-09-08). Data as JSON: /api/errors/dfd1106895a7c58a. Report an issue: GitHub.

Appendix: source

Thrown at pkl-core/src/main/java/org/pkl/core/ast/builder/AstBuilder.java:2998

      var previousValue = EconomicMaps.put(members, key, value);
      if (previousValue != null) {
        CompilerDirectives.transferToInterpreter();
        throw exceptionBuilder()
            .evalError("duplicateDefinition", new ProgramValue("", key))
            .withSourceSection(value.getHeaderSection())
            .build();
      }
    }
  }

  private int doVisitModifiers(
      List<? extends Modifier> modifiers, int validModifiers, String errorMessage) {

    var result = VmModifier.NONE;
    for (var ctx : modifiers) {
      int modifier = visitModifier(ctx);
      if ((modifier & validModifiers) == 0) {
        throw exceptionBuilder()
            .evalError(errorMessage, ctx.getValue().name().toLowerCase(Locale.ROOT))
            .withSourceSection(createSourceSection(ctx))
            .build();
      }
      result += modifier;
    }

    // flag modifier combinations that are never valid right away

    if (VmModifier.isExternal(result) && !ModuleKeys.isStdLibModule(moduleKey)) {
      throw exceptionBuilder()
          .evalError("cannotDefineExternalMember")
          .withSourceSection(createSourceSection(modifiers, ModifierValue.EXTERNAL))
          .build();
    }

    if (VmModifier.isLocal(result) && VmModifier.isHidden(result)) {
      throw exceptionBuilder()

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