RocStr roc_panic for wasm gen

crates/compiler/gen_wasm/src/backend.rs

@@ -988,17 +988,27 @@ impl<'a> WasmBackend<'a> {
     }
 
     pub fn stmt_runtime_error(&mut self, msg: &'a str) {
-        // Create a zero-terminated version of the message string
-        let mut bytes = Vec::with_capacity_in(msg.len() + 1, self.env.arena);
-        bytes.extend_from_slice(msg.as_bytes());
-        bytes.push(0);
+        let msg_sym = self.create_symbol("panic_str");
+        let msg_storage = self.storage.allocate_var(
+            self.env.layout_interner,
+            Layout::Builtin(Builtin::Str),
+            msg_sym,
+            StoredVarKind::Variable,
+        );
 
-        // Store it in the app's data section
-        let elements_addr = self.store_bytes_in_data_section(&bytes);
+        // Store the message as a RocStr on the stack
+        let (local_id, offset) = match msg_storage {
+            StoredValue::StackMemory { location, .. } => {
+                location.local_and_offset(self.storage.stack_frame_pointer)
+            }
+            _ => internal_error!("String must always have stack memory"),
+        };
+        self.expr_string_literal(msg, local_id, offset);
 
-        // Pass its address to roc_panic
         let tag_id = 0;
-        self.code_builder.i32_const(elements_addr as i32);
+        // load the pointer
+        self.storage
+            .load_symbols(&mut self.code_builder, &[msg_sym]);
         self.code_builder.i32_const(tag_id);
         self.call_host_fn_after_loading_args("roc_panic", 2, false);