projectlombok/lombok · error · AnnotationValueDecodeFail

Can't translate to a class object.

Error message

Can't translate ${guess} to a class object.

What it means

guessToType() handles Class-typed annotation members by resolving ClassLiteral guesses via Class.forName(toFQ(...)). If the class literal's name cannot be loaded (ClassNotFoundException), lombok throws AnnotationValueDecodeFail: the annotation references a class that could not be resolved to a class object at annotation-processing time.

Solutions

1. Fix the class name/package in the class literal so it resolves at compile time.
2. Add the missing dependency/jar to the compile (and annotation-processing) classpath.
3. Verify the class still exists — check for renames after dependency upgrades.
4. Use a fully qualified class literal instead of relying on imports/wildcards.

Example fix

// before
@Builder(obvious = true) referencing MyClassyHelper.class // typo
// after
@X(helper = com.example.MyClassyHelper.class) // correct FQN, class on classpath

try { Class.forName(fqn); } catch (ClassNotFoundException e) { throw new IllegalStateException("Class in annotation not on classpath: " + fqn); }

function classExists(fqn) { try { java.lang.Class.forName(fqn); return true; } catch (ClassNotFoundException e) { return false; } }

try { Class<?> c = annotationValues.getValue("target"); } catch (AnnotationValueDecodeFail e) { log.error("Class literal in annotation could not be loaded: " + e.getMessage()); }

When it happens

Trigger: An annotation member of type Class (e.g. Class<?> value()) given a class literal whose toFQ-qualified name is not found on the compile classpath — ClassNotFoundException thrown from Class.forName inside guessToType.

Common situations: Misspelled or wrongly packaged class in an annotation like @Delegate(types = {...}); dependency missing from the annotation processor's classpath; class exists only at runtime (provided scope differences) or was removed in a dependency upgrade.

Related errors

• I can't make sense of this annotation value. Try using a…
• Expected a single value, but
• Can't translate to an enum of type
• You must use constant literals in lombok annotations; they…
• Can't translate a to the expected

AI-assisted analysis of projectlombok/lombok@6d6a3e9fec (2026-09-07). Data as JSON: /api/errors/5a668aa23de82a95. Report an issue: GitHub.

Appendix: source

Thrown at src/core/lombok/core/AnnotationValues.java:357

		
		if (Enum.class.isAssignableFrom(expected) ) {
			if (guess instanceof FieldSelect) {
				String fieldSel = ((FieldSelect) guess).getFinalPart();
				for (Object enumConstant : expected.getEnumConstants()) {
					String target = ((Enum<?>) enumConstant).name();
					if (target.equals(fieldSel)) return enumConstant;
				}
				throw new AnnotationValueDecodeFail(v,
					"Can't translate " + fieldSel + " to an enum of type " + expected, pos);
			}
		}
		
		if (expected == Class.class) {
			if (guess instanceof ClassLiteral) try {
				String classLit = ((ClassLiteral) guess).getClassName();
				return Class.forName(toFQ(classLit));
			} catch (ClassNotFoundException e) {
				throw new AnnotationValueDecodeFail(v,
					"Can't translate " + guess + " to a class object.", pos);
			}
		}
		
		if (guess instanceof AnnotationValues) {
			return ((AnnotationValues<?>) guess).getInstance();
		}
		
		if (guess instanceof FieldSelect) throw new AnnotationValueDecodeFail(v,
			"You must use constant literals in lombok annotations; they cannot be references to (static) fields.", pos);
		
		throw new AnnotationValueDecodeFail(v,
			"Can't translate a " + guess.getClass() + " to the expected " + expected, pos);
	}
	
	/**
	 * Returns the raw expressions used for the provided {@code annotationMethodName}.
	 * 

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