question: protected TypeMirror binaryPromotedType ( TypeMirror left , TypeMirror right ) { if ( TypesUtils . isBoxedPrimitive ( left ) ) { left = types . unboxedType ( left ) ; } if ( TypesUtils . isBoxedPrimitive ( right ) ) { right = types . unboxedType ( right ) ; } TypeKind promotedTypeKind = TypesUtils . widenedNumericType ( left , right ) ; return types . getPrimitiveType ( promotedTypeKind ) ; }
target:  Compute the type to which two numeric types must be promoted before performing a binary numeric operation on them.  The input types must both be numeric and the output type is primitive.