apple/pkl · error · VmTypeMismatchException.Simple

VmTypeMismatchException.Simple (value is not an Int16 in…

Error message

VmTypeMismatchException.Simple (value is not an Int16 in range)

What it means

Int16TypeAliasTypeNode checks the `Int16` typealias: the value must be an Int within the 16-bit signed range (-32768..32767). Non-Int values are rejected via VmTypeMismatchException.Simple using the typealias's base type section; out-of-range but integer values hit the constraint check instead.

Solutions

  1. Bring the value into -32768..32767 or convert strings with `.toInt()`.
  2. Widen the annotation to `Int32`, `Int`, or `Number` if larger values are valid.
  3. Add an `isBetween(-32768, 32767)` guard upstream to fail with a clearer message.

Example fix

// before
size: Int16 = 100000
// after
size: Int32 = 100000
Defensive patterns

Strategy: validation

Validate before calling

// Pkl: range-check before assigning to Int16
function toInt16(v: Int): Int16 =
  if (v.isBetween(-32768, 32767)) v else throw("Int16 out of range: \(v)")

Type guard

value is Int && value >= -32768 && value <= 32767

Prevention

When it happens

Trigger: A property typed `Int16` receives a non-Int value or an Int outside -32768..32767 (e.g. `medium: Int16 = 100000`).

Common situations: IDs, sizes, or thresholds that exceed 16-bit range; values computed at evaluation time overflowing the range; string inputs from external data.

Understand the failure class

Background: "value must be between 0 and 1" / "out of range" / "must not be negative" errors: fixing range-validation failures across open-source libraries — this error's family across 42 libraries.

Related errors

AI-assisted analysis of apple/pkl@f3efcbfc9b (2026-09-08). Data as JSON: /api/errors/6138219aa8361933. Report an issue: GitHub.

Appendix: source

Thrown at pkl-core/src/main/java/org/pkl/core/ast/type/TypeNode.java:2660

    }
  }

  public static final class Int16TypeAliasTypeNode extends IntSlotTypeNode {
    public Int16TypeAliasTypeNode() {
      super(VmUtils.unavailableSourceSection());
    }

    @Override
    protected Object executeLazily(VirtualFrame frame, Object value) {
      if (value instanceof Long l) {
        if (l == l.shortValue()) return value;

        CompilerDirectives.transferToInterpreterAndInvalidate();
        var sourceSection = BaseModule.getInt16TypeAlias().getConstraintSection();
        throw constraintException(value, sourceSection);
      }

      throw new VmTypeMismatchException.Simple(
          BaseModule.getInt16TypeAlias().getBaseTypeSection(), value, BaseModule.getIntClass());
    }

    @Override
    public VmClass getVmClass() {
      return BaseModule.getIntClass();
    }

    @Override
    public VmTypeAlias getVmTypeAlias() {
      return BaseModule.getInt16TypeAlias();
    }

    @Override
    public VmTyped getMirror() {
      return MirrorFactories.typeAliasTypeFactory.create(this);
    }

View on GitHub (pinned to f3efcbfc9b)