JetBrains/intellij-community · warning · ConfigurationException

type.migration.dialog.message.void.not.applicable

Error message

type.migration.dialog.message.void.not.applicable

What it means

Thrown by TypeMigrationDialog.canRun() (TypeMigrationDialog.java:222) when isIllegalVoidMigration() is true — the user set 'void' as the migration target type. void is not a data type: fields, parameters, and variables cannot be void, so Type Migration refuses the run before touching any usage.

Source

Thrown at java/java-impl-refactorings/src/com/intellij/refactoring/typeMigration/ui/TypeMigrationDialog.java:222

      init();
      validateButtons();
    }

    @Override
    protected void canRun() throws ConfigurationException {
      super.canRun();
      if (isIllegalVarargMigration()) {
        throw new ConfigurationException(JavaBundle.message("type.migration.dialog.message.vararg.type.not.applicable"));
      }
      if (isIllegalDisjunctionTypeMigration()) {
        throw new ConfigurationException(JavaBundle.message("type.migration.dialog.message.disjunction.type.not.applicable"));
      }
      if (isIllegalTypeMigration(getMigrationType())) {
        throw new ConfigurationException(
          JavaBundle.message("type.migration.dialog.message.invalid.type", StringUtil.escapeXmlEntities(myTypeCodeFragment.getText())));
      }
      if (isIllegalVoidMigration()) {
        throw new ConfigurationException(JavaBundle.message("type.migration.dialog.message.void.not.applicable"));
      }
      if (getMigrationType().equals(getRootType())) {
        throw new ConfigurationException(null);
      }
    }

    @Override
    public JComponent getPreferredFocusedComponent() {
      return myToTypeEditor;
    }

    @Override
    protected void appendMigrationTypeEditor(JPanel panel, GridBagConstraints gc) {
      final PsiType type = getRootType();
      final String typeText = type != null ? type.getPresentableText() : "<unknown>";
      panel.add(new JLabel(getTypeMigrationLabelText(myRoots[0], typeText)), gc);
      panel.add(myToTypeEditor, gc);
    }

View on GitHub (pinned to be881553f2)

Solutions

1. Choose a real reference type as the migration target (e.g. java.lang.Void boxed only if genuinely intended and accepted).
2. To change a method's return type, use Change Signature or direct editing instead of Type Migration.
3. Re-open the dialog and clear the To-type field, then pick from completion.

Example fix

// before
// migrate root 'count' (int field) to: void -> blocked

// after
// migrate root 'count' to: java.lang.Integer -> proceeds

String typeText = myTypeCodeFragment.getText().trim();
if (typeText.equals("void") || typeText.equals("java.lang.void")) {
  // block: void cannot be a migration target; ask for a reference type
}

When it happens

Trigger: Refactoring | Type Migration on any field/local/parameter and typing 'void' (or 'java.lang.Void' resolving to a void-like classification in the editor) into the 'migrate to' field.

Common situations: Exploratory clicking in the dialog; intending to migrate a method's return type and selecting the method element whose migration target was set to void; autocomplete inserting 'Void' where the dialog's classifier treats it as void in a value position.

Related errors

• type.migration.dialog.message.invalid.type
• Invalid package name: {0}
• Nothing found to extract
• ''{0}'' is invalid extracted class name
• Extracted class should have unique name. Name ''{0}'' is alr

AI-assisted analysis of JetBrains/intellij-community@be881553f2 (2026-08-14). Data as JSON: /api/errors/f8a86830e1c78c12. Report an issue: GitHub.