Avoid passing a full Expr when only the Span is used

Author: oli-obk

compiler/rustc_hir_typeck/src/expr.rs

@@ -835,7 +835,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // We always require that the type provided as the value for
         // a type parameter outlives the moment of instantiation.
         let args = self.typeck_results.borrow().node_args(expr.hir_id);
-        self.add_wf_bounds(args, expr);
+        self.add_wf_bounds(args, expr.span);
 
         ty
     }

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -579,11 +579,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     }
 
     /// Registers obligations that all `args` are well-formed.
-    pub(crate) fn add_wf_bounds(&self, args: GenericArgsRef<'tcx>, expr: &hir::Expr<'_>) {
+    pub(crate) fn add_wf_bounds(&self, args: GenericArgsRef<'tcx>, span: Span) {
         for arg in args.iter().filter(|arg| {
             matches!(arg.unpack(), GenericArgKind::Type(..) | GenericArgKind::Const(..))
         }) {
-            self.register_wf_obligation(arg, expr.span, ObligationCauseCode::WellFormed(None));
+            self.register_wf_obligation(arg, span, ObligationCauseCode::WellFormed(None));
         }
     }
 

compiler/rustc_hir_typeck/src/method/confirm.rs

@@ -611,7 +611,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
 
         // this is a projection from a trait reference, so we have to
         // make sure that the trait reference inputs are well-formed.
-        self.add_wf_bounds(all_args, self.call_expr);
+        self.add_wf_bounds(all_args, self.call_expr.span);
 
         // the function type must also be well-formed (this is not
         // implied by the args being well-formed because of inherent