[fine] Assignments!

And new error capabilities!

fine/build.rs

@@ -1,8 +1,25 @@
-use quote::{format_ident, quote};
+use proc_macro2::{Delimiter, Group, Ident, Literal, Punct, Spacing, Span, TokenStream};
+use quote::{format_ident, quote, TokenStreamExt};
 use std::env;
 use std::fs;
 use std::path::{Path, PathBuf};
 
+struct ExpectedErrors(Vec<String>);
+
+impl quote::ToTokens for ExpectedErrors {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let mut inner = TokenStream::new();
+        for err in self.0.iter() {
+            inner.append(Literal::string(err));
+            inner.append(Punct::new(',', Spacing::Alone));
+        }
+
+        tokens.append(Ident::new("vec", Span::call_site()));
+        tokens.append(Punct::new('!', Spacing::Joint));
+        tokens.append(Group::new(Delimiter::Parenthesis, inner))
+    }
+}
+
 fn generate_test_for_file(path: PathBuf) -> String {
     let contents = fs::read_to_string(&path)
         .expect("Unable to read input")
@@ -92,6 +109,21 @@ fn generate_test_for_file(path: PathBuf) -> String {
             assertions.push(quote! {
                 crate::assert_check_error(&_tree, &_lines, #expected);
             });
+        } else if line == "@expect-errors:" {
+            let mut errors = Vec::new();
+            while let Some(line) = lines.next() {
+                let line = match line.strip_prefix("// | ") {
+                    Some(line) => line,
+                    None => break,
+                };
+
+                errors.push(line.to_string());
+            }
+
+            let errors = ExpectedErrors(errors);
+            assertions.push(quote! {
+                crate::assert_errors(&_tree, &_lines, #errors);
+            });
         } else if line.starts_with("@") {
             panic!("Test file {display_path} has unknown directive: {line}");
         }