public boolean isNumberType() {
    TypeKind kind = returnType.getKind();
    return kind.isPrimitive()
        && kind != TypeKind.CHAR
        && kind != TypeKind.BOOLEAN;
  }
Suitable for JavaDocs, intemediate name mangling and for Guava intergration.
@return the raw collection type
value-processor/src/org/immutables/value/processor/meta/ValueAttribute.java