Use section numbers when resolving local labels

This changes the semantics of local labels. Previously, local labels
were just shorthand for writing out `name.local`, which meant if there
were multiple sections named "name", there could potentially be name
collisions.

This commit adds a unique numeric suffix to each section's ID string.
This guarantees that locals in one section won't interfere with those in
a different section.

src/labels/process.rs

@@ -43,7 +43,8 @@ pub fn process_labels(board: &mut Board) {
 /// Resolve ".local" labels to "name.local" form.
 fn resolve_local_labels(stats: &mut [ParsedStat]) {
     for stat in stats.iter_mut() {
-        let mut section = CompactString::const_new("");
+        let mut section_counter = 0;
+        let mut section = CompactString::const_new("$0");
         for chunk in stat.iter_mut() {
             match chunk {
                 Chunk::Label {
@@ -57,12 +58,13 @@ fn resolve_local_labels(stats: &mut [ParsedStat]) {
                     if label.name.is_empty() {
                         // Expand :.local to :name.local
                         assert!(label.local.is_some());
-                        label.name = section.clone()
+                        label.name = section.clone();
                     } else if label.local.is_none() {
                         // Interpret label :name as start of new section.
                         // Only label definitions do this; label references have no effect.
                         if !*is_ref {
-                            section = label.name.clone();
+                            section_counter += 1;
+                            section = format!("{}${}", &label.name, section_counter).into();
                         }
                     }
                 }

src/labels/snapshots/zasm__labels__process__test__local_labels.snap

@@ -18,3 +18,38 @@ expression: board_to_text(board)
 '
 :stop
 #walk i
+---
+'Using locals before any globals are defined
+:_loop1
+#take gems 1 _break
+#_loop1
+:_break
+---
+'Multiple sections with the same name
+#end
+:touch
+Trying to sell you some ammo...
+#take gems 10 _skip
+#give ammo 10
+:_skip
+#zap touch
+#end
+:touch
+Trying to sell you some torches...
+#take gems 15 _skip0
+#give torches 5
+:_skip0
+#restore touch
+---
+'Multiple locals with the same name
+#end
+:repeat3
+:_z
+:_z
+:_z
+#take gems 1 _skip1
+#give score 1
+:_skip1
+#zap _z
+#_z
+:_z