apache/maven · error · IllegalArgumentException

Key should not contain a type variable: {}

Error message

Key should not contain a type variable: {}

What it means

Error "Key should not contain a type variable: {}" thrown in apache/maven.

Source

Thrown at impl/maven-di/src/main/java/org/apache/maven/di/impl/Types.java:325

        }

        if (original instanceof ParameterizedType parameterizedType) {
            Type[] typeArguments = parameterizedType.getActualTypeArguments();
            Type[] repackedTypeArguments = simplifyTypes(typeArguments);

            if (isAllObjects(repackedTypeArguments)) {
                return parameterizedType.getRawType();
            }

            if (typeArguments != repackedTypeArguments) {
                return parameterizedType(
                        parameterizedType.getOwnerType(), parameterizedType.getRawType(), repackedTypeArguments);
            }
            return original;
        }

        if (original instanceof TypeVariable) {
            throw new IllegalArgumentException("Key should not contain a type variable: " + original);
        }

        if (original instanceof WildcardType wildcardType) {
            Type[] upperBounds = wildcardType.getUpperBounds();
            if (upperBounds.length == 1) {
                Type upperBound = upperBounds[0];
                if (upperBound != Object.class) {
                    return simplifyType(upperBound);
                }
            } else if (upperBounds.length > 1) {
                throw new IllegalArgumentException("Multiple upper bounds not supported: " + original);
            }

            Type[] lowerBounds = wildcardType.getLowerBounds();
            if (lowerBounds.length == 1) {
                return simplifyType(lowerBounds[0]);
            } else if (lowerBounds.length > 1) {
                throw new IllegalArgumentException("Multiple lower bounds not supported: " + original);

View on GitHub (pinned to e4093d4e12)

When it happens

Trigger: Thrown at impl/maven-di/src/main/java/org/apache/maven/di/impl/Types.java:325 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/maven@e4093d4e12 (2026-08-21). Data as JSON: /api/errors/1981ff5aa54881b3. Report an issue: GitHub.