treewide: enforce strict clippy check

fix-runtime/src/machine.rs

@@ -3,11 +3,11 @@ use std::path::{Path, PathBuf};
 
 use fix_error::Error;
 use fix_lang::{self, StringId};
-use gc_arena::Mutation;
+use gc_arena::{Gc, Mutation};
 
 use crate::{
-    Break, BytecodeReader, CallFrame, ForceMode, Forced, GcEnv, NixType, PendingLoad, Step,
-    StrictValue, Value, VmError,
+    AttrSet, Break, BytecodeReader, CallFrame, ForceMode, Forced, GcEnv, NixType, PendingLoad,
+    Step, StrictValue, Value, VmError,
 };
 
 /// Abstract VM-side operations consumed by instruction handlers and primops.
@@ -65,6 +65,10 @@ pub trait Machine<'gc> {
     ) -> Step;
 
     #[inline(always)]
+    #[expect(
+        clippy::unreachable,
+        reason = "a primop only returns via `return_from_primop` while its call frame is still on the stack, so `pop_call_frame` is always `Some`"
+    )]
     fn return_from_primop(&mut self, val: Value<'gc>, reader: &mut BytecodeReader<'_>) -> Step {
         self.push(val);
         let Some(CallFrame {
@@ -91,6 +95,10 @@ pub trait Machine<'gc> {
     fn set_env(&mut self, env: GcEnv<'gc>);
 
     #[inline(always)]
+    #[expect(
+        clippy::indexing_slicing,
+        reason = "codegen guarantees the local index is within the resolved frame's `locals`"
+    )]
     fn local(&self, layer: u8, idx: u32) -> Value<'gc> {
         let mut cur = self.env();
         for _ in 0..layer {
@@ -109,7 +117,7 @@ pub trait Machine<'gc> {
         self.finish_err(err.into_error())
     }
 
-    fn builtins(&self) -> Value<'gc>;
+    fn builtins(&self) -> Gc<'gc, AttrSet<'gc>>;
     fn functor_sym(&self) -> StringId;
     fn empty_list(&self) -> Value<'gc>;
     fn empty_attrs(&self) -> Value<'gc>;