Work around all_symbols_are_used() test limitations

Use clippy symbols as `sym` so that they are caught by the regex.

Author: DanielEScherzer

clippy_lints/src/iter_missing_exact_size.rs

@@ -7,7 +7,7 @@ use rustc_hir::{Body, ExprKind, Impl, ImplItemKind, Item, ItemKind, OwnerId, Own
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::impl_lint_pass;
 use rustc_span::def_id::DefId;
-use rustc_span::sym;
+use rustc_span::sym as rustc_sym;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -108,7 +108,7 @@ fn size_hint_body<'tcx>(cx: &LateContext<'tcx>, owner_id: OwnerId) -> Option<&'t
         .find(|assoc_item| {
             assoc_item.expect_trait_impl().is_ok()
                 && assoc_item.is_method()
-                && assoc_item.name() == clippy_sym::size_hint
+                && assoc_item.name() == sym::size_hint
         })?;
 
     let node = cx.tcx.expect_hir_owner_node(size_hint_fn.def_id.expect_local());
@@ -138,7 +138,7 @@ impl<'tcx> LateLintPass<'tcx> for IterMissingExactSize {
             return;
         };
         // 3) is it the iterator trait?
-        if !cx.tcx.is_diagnostic_item(sym::Iterator, trait_id) {
+        if !cx.tcx.is_diagnostic_item(rustc_sym::Iterator, trait_id) {
             return;
         }
 
@@ -152,7 +152,7 @@ impl<'tcx> LateLintPass<'tcx> for IterMissingExactSize {
             && block.stmts.is_empty()
             && let Some(trailing_expr) = block.expr
             && let ExprKind::MethodCall(method_name, receiver, args, _) = trailing_expr.kind
-            && method_name.ident.name == clippy_sym::size_hint
+            && method_name.ident.name == sym::size_hint
             && let ExprKind::Field(_object, field_name) = receiver.kind
             && args.is_empty()
         {