A backslash at the end of a quoted string has nothing after it to escape.

A recognized bespoke filter keyword (such as classname:) is missing its required value, or a query: expression contains an invalid query string.

An unexpected token was encountered where a name or identifier was expected.

Reserved error code for an incomplete or expression; currently not emitted by the filter engine.

An opening parenthesis ( in the filter expression has no matching closing parenthesis ).

A ** wildcard token directly follows a * wildcard in a dotted name path (for example, A.*.**.X), which is not allowed.

A lone ~ character was found that is not part of the ~= not-equal operator.

A comparison operator other than = or ~= was used with a property type that only supports equality comparisons.

The named property does not exist on any reflected class known to the filter engine.

A sub-field index (such as .W) was used with a vector or color property that does not have a field by that name.

The value string provided for a property comparison cannot be parsed into the expected type for that property (for example, Locked=notabool).

A sub-field index was used with a property type that does not support field access (for example, Locked.X=true).

The named property exists but its type is not supported by the filter engine (for example, complex datatypes such as CFrame or TweenInfo).

A . in a dotted name path is not followed by a valid name, number, or wildcard token.

A token that cannot be a value (such as an operator) appears where a value is expected after a comparison operator.

An and or or binary operator appears with no right-hand operand.

A quoted string was opened but not closed before the end of the filter input.

A name:value token uses a keyword that is not a recognized bespoke filter type (for example, foo:Bar).

A wildcard (* or **) appears in the property portion of a dotted expression where a concrete property name is required.