fixup! refactor: split handle validation into early pass in `Validato…

…r::validate`

Resolves <gfx-rs#2090 (comment)>.

src/valid/analyzer.rs

@@ -288,12 +288,6 @@ impl ops::Index<Handle<crate::Expression>> for FunctionInfo {
     }
 }
 
-impl ops::IndexMut<Handle<crate::Expression>> for FunctionInfo {
-    fn index_mut(&mut self, handle: Handle<crate::Expression>) -> &mut ExpressionInfo {
-        &mut self.expressions[handle.index()]
-    }
-}
-
 /// Disruptor of the uniform control flow.
 #[derive(Clone, Copy, Debug, thiserror::Error)]
 #[cfg_attr(test, derive(PartialEq))]
@@ -713,7 +707,7 @@ impl FunctionInfo {
         };
 
         let ty = resolve_context.resolve(expression, |h| Ok(&self[h].ty))?;
-        self[handle] = ExpressionInfo {
+        self.expressions[handle.index()] = ExpressionInfo {
             uniformity,
             ref_count: 0,
             assignable_global,