This allows testing optnum, optenum, errnum and resnum as alternatives to errtype.

resources/lib/std/libc.c3

@@ -216,7 +216,7 @@ extern fn int strcoll(char* str1, char* str2);
 extern fn char* strcpy(char* dst, char* src);
 extern fn char* strncpy(char* dst, char* src, usize n);
 extern fn usize strcspn(char* str1, char* str2);
-extern fn char* strerror(int errnum);
+extern fn char* strerror(int errn);
 extern fn usize strlen(char* str);
 extern fn char* strpbrk(char* str1, char* str2);
 extern fn usize strspn(char* str1, char* str2);

src/compiler/enums.h

@@ -464,6 +464,11 @@ typedef enum
 	TOKEN_VAR,
 	TOKEN_WHILE,
 
+	TOKEN_ERRNUM,
+	TOKEN_OPTNUM,
+	TOKEN_OPTENUM,
+	TOKEN_RESNUM,
+
 	TOKEN_CT_ALIGNOF,       // $alignof
 	TOKEN_CT_ASSERT,        // $assert
 	TOKEN_CT_CASE,          // $case

src/compiler/parse_global.c

@@ -79,6 +79,10 @@ void recover_top_level(ParseContext *context)
 			case TOKEN_GENERIC:
 			case TOKEN_DEFINE:
 			case TOKEN_ERRTYPE:
+			case TOKEN_OPTENUM:
+			case TOKEN_OPTNUM:
+			case TOKEN_ERRNUM:
+			case TOKEN_RESNUM:
 				return;
 			case TOKEN_IDENT: // Incr arrays only
 			case TOKEN_CONST:
@@ -1774,7 +1778,8 @@ static inline Decl *parse_macro_declaration(ParseContext *context, Visibility vi
  */
 static inline Decl *parse_error_declaration(ParseContext *context, Visibility visibility)
 {
-	advance_and_verify(context, TOKEN_ERRTYPE);
+	advance(context);
+	// advance_and_verify(context, TOKEN_ERRTYPE);
 
 	Decl *decl = decl_new_with_type(context->tok.id, DECL_ERRTYPE, visibility);
 
@@ -2317,6 +2322,10 @@ Decl *parse_top_level_statement(ParseContext *context)
 			ASSIGN_DECL_ELSE(decl, parse_enum_declaration(context, visibility), poisoned_decl);
 			break;
 		}
+		case TOKEN_OPTENUM:
+		case TOKEN_OPTNUM:
+		case TOKEN_ERRNUM:
+		case TOKEN_RESNUM:
 		case TOKEN_ERRTYPE:
 		{
 			ASSIGN_DECL_ELSE(decl, parse_error_declaration(context, visibility), poisoned_decl);

src/compiler/parse_stmt.c

@@ -947,6 +947,10 @@ Ast *parse_stmt(ParseContext *context)
 		case TOKEN_EXTERN:
 		case TOKEN_STRUCT:
 		case TOKEN_ERRTYPE:
+		case TOKEN_OPTENUM:
+		case TOKEN_OPTNUM:
+		case TOKEN_ERRNUM:
+		case TOKEN_RESNUM:
 		case TOKEN_UNION:
 		case TOKEN_DEFINE:
 		case TOKEN_DOCS_START:

src/compiler/tokens.c

@@ -270,6 +270,16 @@ const char *token_type_to_string(TokenType type)
 			return "var";
 		case TOKEN_WHILE:
 			return "while";
+		// Aliases to test out
+		case TOKEN_OPTENUM:
+			return "optenum";
+		case TOKEN_OPTNUM:
+			return "optnum";
+		case TOKEN_ERRNUM:
+			return "errnum";
+		case TOKEN_RESNUM:
+			return "resnum";
+
 
 		// Named types
 		case TOKEN_VOID: