test: harden performance batch regressions

crates/perry-runtime/src/closure/alloc.rs

@@ -488,6 +488,10 @@ pub(crate) fn test_captured_singleton_closure_cache_entries(
 /// covers the per-batch fan-out shape (50 promises) found in
 /// `benchmarks/app-patterns/kernels/promise_all_chains.ts`.
 const MAX_CAPTURED_CLOSURE_SLOTS: usize = 64;
+const _: () = assert!(
+    MAX_CAPTURED_CLOSURE_SLOTS <= u8::MAX as usize,
+    "hint_indices_plus_one stores an entry index plus one in a u8"
+);
 
 /// Per-`func_ptr` cache miss-streak counter for the adaptive bypass.
 /// Closures whose captures change every call (per-call boxes for
@@ -581,9 +585,8 @@ pub extern "C" fn js_closure_alloc_with_captures_singleton(
     }
     crate::promise::bump(&CLOSURE_CAP_SINGLETON_MISS);
 
-    // Slow path: allocate, populate captures, insert into cache as
-    // the most-recent entry. If the slot list is full, drop the
-    // least-recent (back of the Vec).
+    // Slow path: allocate, populate captures, and insert with a fresh usage
+    // timestamp. If the entry list is full, replace its oldest timestamp.
     let capture_scope = crate::gc::RuntimeHandleScope::new();
     let capture_handles: Vec<_> = captures_slice
         .iter()

crates/perry/tests/static_method_object_literal.rs

@@ -8,6 +8,29 @@ use std::path::{Path, PathBuf};
 use std::process::{Command, Output};
 use std::sync::Once;
 
+/// Keep the forced-moving arm independent of ambient developer/CI settings.
+/// Some inputs affect code generation, so normalize the runtime build,
+/// fixture compile, and child process alike.
+const GC_ENV_OVERRIDES: &[&str] = &[
+    "PERRY_GEN_GC",
+    "PERRY_GC_SCAVENGE",
+    "PERRY_GC_SCAVENGE_NURSERY_MB",
+    "PERRY_GC_MOVING_SAFEPOINT",
+    "PERRY_GC_MOVING_LOOP_POLLS",
+    "PERRY_GC_FORCE_EVACUATE",
+    "PERRY_GC_VERIFY_EVACUATION",
+    "PERRY_CONSERVATIVE_STACK_SCAN",
+    "PERRY_WRITE_BARRIERS",
+    "PERRY_GC_INCREMENTAL",
+    "PERRY_GC_HEAP_LIMIT",
+];
+
+fn remove_gc_env_overrides(command: &mut Command) {
+    for key in GC_ENV_OVERRIDES {
+        command.env_remove(key);
+    }
+}
+
 fn perry_bin() -> PathBuf {
     PathBuf::from(env!("CARGO_BIN_EXE_perry"))
 }
@@ -25,6 +48,7 @@ fn runtime_dir() -> PathBuf {
         let cargo = std::env::var_os("CARGO").unwrap_or_else(|| "cargo".into());
         let mut command = Command::new(cargo);
         command.current_dir(workspace_root()).arg("build");
+        remove_gc_env_overrides(&mut command);
         if !cfg!(debug_assertions) {
             command.arg("--release");
         }
@@ -48,14 +72,11 @@ fn runtime_dir() -> PathBuf {
 
 fn run_fixture(binary: &Path, force_evacuation: bool) -> Output {
     let mut command = Command::new(binary);
+    remove_gc_env_overrides(&mut command);
     if force_evacuation {
         command
             .env("PERRY_GC_FORCE_EVACUATE", "1")
             .env("PERRY_GC_VERIFY_EVACUATION", "1");
-    } else {
-        command
-            .env_remove("PERRY_GC_FORCE_EVACUATE")
-            .env_remove("PERRY_GC_VERIFY_EVACUATION");
     }
     command.output().expect("run method-literal fixture")
 }
@@ -108,15 +129,18 @@ console.log(
     )
     .expect("write method-literal fixture");
 
-    let compile = Command::new(perry_bin())
+    let mut compile_command = Command::new(perry_bin());
+    compile_command
         .current_dir(dir.path())
         .arg("compile")
         .arg(&entry)
         .arg("-o")
         .arg(&binary)
         .arg("--no-cache")
         .arg("--no-auto-optimize")
-        .env("PERRY_RUNTIME_DIR", runtime_dir())
+        .env("PERRY_RUNTIME_DIR", runtime_dir());
+    remove_gc_env_overrides(&mut compile_command);
+    let compile = compile_command
         .output()
         .expect("compile method-literal fixture");
     assert!(