Wrap code in SubfieldCode

Signed-off-by: Nico Wagner <[email protected]>

crates/pica-format/src/lib.rs

@@ -2,7 +2,7 @@ use std::ops::RangeTo;
 use std::str::FromStr;
 
 use pica_matcher::{OccurrenceMatcher, SubfieldMatcher, TagMatcher};
-use pica_record::{FieldRef, RecordRef, SubfieldRef};
+use pica_record::{FieldRef, RecordRef, SubfieldCode, SubfieldRef};
 use thiserror::Error;
 use winnow::prelude::*;
 
@@ -123,7 +123,7 @@ impl Formatter for Fragments {
 
 #[derive(Debug, Clone, PartialEq)]
 struct Value {
-    codes: Vec<char>,
+    codes: Vec<SubfieldCode>,
     prefix: Option<String>,
     suffix: Option<String>,
     bounds: RangeTo<usize>,

crates/pica-format/src/parse.rs

@@ -5,6 +5,7 @@ use bstr::ByteSlice;
 use pica_matcher::parser::{
     parse_occurrence_matcher, parse_subfield_matcher, parse_tag_matcher,
 };
+use pica_record::SubfieldCode;
 use winnow::ascii::{digit1, multispace0, multispace1};
 use winnow::combinator::{
     alt, delimited, empty, opt, preceded, repeat, separated, terminated,
@@ -180,14 +181,14 @@ fn parse_list_and_then(i: &mut &[u8]) -> PResult<List> {
 }
 
 /// Parses a subfield code (a single alpha-numeric character)
-fn parse_code(i: &mut &[u8]) -> PResult<char> {
+fn parse_code(i: &mut &[u8]) -> PResult<SubfieldCode> {
     one_of(('0'..='9', 'a'..='z', 'A'..='Z'))
-        .map(char::from)
+        .map(SubfieldCode::from_unchecked)
         .parse_next(i)
 }
 
 /// Parses a sequence of subfield codes.
-fn parse_codes(i: &mut &[u8]) -> PResult<Vec<char>> {
+fn parse_codes(i: &mut &[u8]) -> PResult<Vec<SubfieldCode>> {
     alt((
         parse_code.map(|code| vec![code]),
         delimited(ws('['), repeat(2.., parse_code), ws(']')),