Allow renaming a variable twice as it might happen in some cases.

crates/cairo-lang-lowering/src/optimizations/cancel_ops.rs

@@ -34,11 +34,16 @@ pub fn cancel_ops(lowered: &mut FlatLowered) {
         BackAnalysis { lowered: &*lowered, block_info: Default::default(), analyzer: ctx };
     analysis.get_root_info();
 
-    let CancelOpsContext { mut var_remapper, mut stmts_to_remove, .. } = analysis.analyzer;
+    let CancelOpsContext { mut var_remapper, stmts_to_remove, .. } = analysis.analyzer;
 
     // Remove no-longer needed statements.
-    stmts_to_remove.sort_by_key(|(block_id, stmt_id)| (block_id.0, *stmt_id));
-    for (block_id, stmt_id) in stmts_to_remove.into_iter().rev() {
+    // Note that dedup() is used since a statement might be marked for removal more then once.
+    for (block_id, stmt_id) in stmts_to_remove
+        .into_iter()
+        .sorted_by_key(|(block_id, stmt_id)| (block_id.0, *stmt_id))
+        .rev()
+        .dedup()
+    {
         lowered.blocks[block_id].statements.remove(stmt_id);
     }
 
@@ -77,12 +82,7 @@ fn get_use_sites<'a>(
 
 impl<'a> CancelOpsContext<'a> {
     fn rename_var(&mut self, from: VariableId, to: VariableId) {
-        assert!(
-            self.var_remapper.renamed_vars.insert(from, to).is_none(),
-            "Variable {:?} was already renamed",
-            from
-        );
-
+        self.var_remapper.renamed_vars.insert(from, to);
         // Move `from` used sites to `to` to allow the optimization to be applied to them.
         if let Some(from_use_sites) = self.use_sites.remove(&from) {
             self.use_sites.entry(to).or_default().extend(from_use_sites);

crates/cairo-lang-lowering/src/optimizations/test_data/cancel_ops

@@ -497,3 +497,52 @@ blk3:
 Statements:
 End:
   Return(v5)
+
+//! > ==========================================================================
+
+//! > Test variable renamed twice.
+
+//! > test_runner_name
+test_cancel_ops
+
+//! > function
+fn foo(a: (felt252, felt252)) -> (felt252, felt252) {
+  let (b, c) = a;
+  let a = (b, c);
+  let (d, e) = a;
+  use_tuple((d, e));
+  (e, d)
+}
+
+//! > function_name
+foo
+
+//! > module_code
+extern fn use_tuple(a: (felt252, felt252)) nopanic;
+
+//! > semantic_diagnostics
+
+//! > lowering_diagnostics
+
+//! > before
+Parameters: v0: (core::felt252, core::felt252)
+blk0 (root):
+Statements:
+  (v1: core::felt252, v2: core::felt252) <- struct_destructure(v0)
+  (v3: (core::felt252, core::felt252)) <- struct_construct(v1, v2)
+  (v4: core::felt252, v5: core::felt252) <- struct_destructure(v3)
+  (v6: (core::felt252, core::felt252)) <- struct_construct(v4, v5)
+  () <- test::use_tuple(v6)
+  (v7: (core::felt252, core::felt252)) <- struct_construct(v5, v4)
+End:
+  Return(v7)
+
+//! > after
+Parameters: v0: (core::felt252, core::felt252)
+blk0 (root):
+Statements:
+  (v1: core::felt252, v2: core::felt252) <- struct_destructure(v0)
+  () <- test::use_tuple(v0)
+  (v7: (core::felt252, core::felt252)) <- struct_construct(v2, v1)
+End:
+  Return(v7)