Fix StoreFastStoreFast to handle NULL from LoadFastAndClear

youknowone · youknowone · commit 289172a2a460 · 2026-03-25T14:20:29.000+09:00
StoreFast uses pop_value_opt() to allow NULL values from
LoadFastAndClear in inlined comprehension cleanup paths.
StoreFastStoreFast must do the same, otherwise the peephole
optimizer's fusion of two StoreFast instructions panics when
restoring unbound locals after an inlined comprehension.
diff --git a/crates/vm/src/frame.rs b/crates/vm/src/frame.rs
@@ -3446,11 +3446,12 @@ impl ExecutingFrame<'_> {
             Instruction::StoreFastStoreFast { var_nums } => {
                 let oparg = var_nums.get(arg);
                 let (idx1, idx2) = oparg.indexes();
-                let value1 = self.pop_value();
-                let value2 = self.pop_value();
+                // pop_value_opt: allows NULL from LoadFastAndClear restore path
+                let value1 = self.pop_value_opt();
+                let value2 = self.pop_value_opt();
                 let fastlocals = self.localsplus.fastlocals_mut();
-                fastlocals[idx1] = Some(value1);
-                fastlocals[idx2] = Some(value2);
+                fastlocals[idx1] = value1;
+                fastlocals[idx2] = value2;
                 Ok(None)
             }
             Instruction::StoreGlobal { namei: idx } => {
