Resolve enum values

This patch makes it so that the compiler can automatically
increment/decrement values in order for enums while parsing.

Signed-off-by: Slendi <slendi@socopon.com>

src/parser.odin

@@ -159,6 +159,41 @@ parser_parse_struct_definition :: proc(parser: ^Parser) -> ^Node {
 	return n
 }
 
+@(private = "file")
+enum_resolve_value_items :: proc(values: ^[dynamic]EnumValueItem) {
+	// IMPORTANT: Although this should be obvious, THIS DOES NOT DO ANY TYPE
+	//            CHECKING! The `type_check` procedure is for that!
+
+	// What this algorithm basically does is find the first resolved item, then
+	// it resolved backwards, afterwards, it goes and resolves stuff forwards.
+	// This resolves everything as signed integers which may be an issue but i
+	// frankly don't care, if you have an enum which has more 2^63 negative
+	// values that's on you.
+
+	// 1. Find the first element that is resolved, default to the beginning if
+	//    none is found
+	idx_first_resolved := 0
+	for &value, idx in values {
+		if value.resolved {
+			idx_first_resolved = idx
+		}
+	}
+
+	// 2. Resolve backwards from first resolved element
+	for i := idx_first_resolved; i >= 1; i -= 1 {
+		values[i - 1].value = values[i].value - 1
+		values[i].resolved = true
+		values[i - 1].resolved = true
+	}
+
+	// 3. Resolve forwards until the end of the values vector
+	for i in idx_first_resolved ..< len(values) - 1 {
+		values[i + 1].value = values[i].value + 1
+		values[i].resolved = true
+		values[i + 1].resolved = true
+	}
+}
+
 @(private = "file")
 parser_parse_enum_definition :: proc(parser: ^Parser) -> ^Node {
 	range := parser.tok.range
@@ -238,7 +273,7 @@ parser_parse_enum_definition :: proc(parser: ^Parser) -> ^Node {
 	range.range.end = parser.tok.range.range.end
 	parser_next(parser)
 
-	// FIXME: Resolve items
+	enum_resolve_value_items(&enum_value.values)
 
 	enum_value.type = type_node