Avoid copying from candidate. (#7527)

Author: ilyalesokhin-starkware

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

@@ -169,12 +169,12 @@ pub fn optimize_matches(lowered: &mut FlatLowered) {
 fn statement_can_be_optimized_out(
     stmt: &Statement,
     info: &mut AnalysisInfo<'_>,
+    mut candidate: OptimizationCandidate<'_>,
     statement_location: (BlockId, usize),
 ) -> Option<FixInfo> {
     let Statement::EnumConstruct(StatementEnumConstruct { variant, input, output }) = stmt else {
         return None;
     };
-    let candidate = info.candidate.as_mut()?;
     if *output != candidate.match_variable {
         return None;
     }
@@ -198,7 +198,7 @@ fn statement_can_be_optimized_out(
     // Compute the demand based on the demand of the specific arm, rather than the current demand
     // (which contains the union of the demands from all the arms).
     // Apply the remapping of the input variable and the additional remappings if exist.
-    let mut demand = candidate.arm_demands[arm_idx].clone();
+    let mut demand = std::mem::take(&mut candidate.arm_demands[arm_idx]);
     demand
         .apply_remapping(&mut EmptyDemandReporter {}, [(var_id, (&input.var_id, ()))].into_iter());
 
@@ -218,8 +218,8 @@ fn statement_can_be_optimized_out(
         arm_idx,
         target_block: arm.block_id,
         remapping,
-        reachable_blocks: candidate.arm_reachable_blocks[arm_idx].clone(),
-        additional_remapping: candidate.additional_remappings.clone().unwrap_or_default(),
+        reachable_blocks: std::mem::take(&mut candidate.arm_reachable_blocks[arm_idx]),
+        additional_remapping: candidate.additional_remappings.unwrap_or_default(),
     })
 }
 
@@ -288,17 +288,20 @@ impl<'a> Analyzer<'a> for MatchOptimizerContext {
         statement_location: StatementLocation,
         stmt: &Statement,
     ) {
-        if let Some(fix_info) = statement_can_be_optimized_out(stmt, info, statement_location) {
-            self.fixes.push(fix_info);
-        } else {
-            info.demand.variables_introduced(&mut EmptyDemandReporter {}, stmt.outputs(), ());
-            info.demand.variables_used(
-                &mut EmptyDemandReporter {},
-                stmt.inputs().iter().map(|VarUsage { var_id, .. }| (var_id, ())),
-            );
+        if let Some(candidate) = std::mem::take(&mut info.candidate) {
+            if let Some(fix_info) =
+                statement_can_be_optimized_out(stmt, info, candidate, statement_location)
+            {
+                self.fixes.push(fix_info);
+                return;
+            }
         }
 
-        info.candidate = None;
+        info.demand.variables_introduced(&mut EmptyDemandReporter {}, stmt.outputs(), ());
+        info.demand.variables_used(
+            &mut EmptyDemandReporter {},
+            stmt.inputs().iter().map(|VarUsage { var_id, .. }| (var_id, ())),
+        );
     }
 
     fn visit_goto(