Make Error and GameType enums non-exhaustive

So that it's not a breaking change to add more variants in the future.

ffi/src/constants.rs

@@ -37,6 +37,10 @@ pub static LCI_ERROR_POISONED_THREAD_LOCK: c_int = -6;
 #[no_mangle]
 pub static LCI_ERROR_TEXT_ENCODE_FAIL: c_int = -7;
 
+/// The library encountered an error that should not have been possible to encounter.
+#[no_mangle]
+pub static LCI_ERROR_INTERNAL_LOGIC_ERROR: c_int = -8;
+
 /// Game code for The Elder Scrolls III: Morrowind.
 #[no_mangle]
 pub static LCI_GAME_MORROWIND: c_int = 8;

ffi/src/helpers.rs

@@ -28,6 +28,7 @@ fn map_error(err: &Error) -> c_int {
         Error::ParsingError(_, _) => LCI_ERROR_PARSING_ERROR,
         Error::PeParsingError(_, _) => LCI_ERROR_PE_PARSING_ERROR,
         Error::IoError(_, _) => LCI_ERROR_IO_ERROR,
+        _ => LCI_ERROR_INTERNAL_LOGIC_ERROR,
     }
 }
 

src/error.rs

@@ -9,6 +9,7 @@ use nom::error::ErrorKind;
 use nom::Err;
 
 #[derive(Debug)]
+#[non_exhaustive]
 pub enum Error {
     ParsingIncomplete(MoreDataNeeded),
     // The string is the input that was not parsed.

src/lib.rs

@@ -22,9 +22,8 @@ use function::Function;
 
 type ParsingResult<'a, T> = IResult<&'a str, T, ParsingError<&'a str>>;
 
-// GameType variants must not change order, as their integer values are used as
-// constants in the C API.
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+#[non_exhaustive]
 pub enum GameType {
     Oblivion,
     Skyrim,