lint: fix condition in diagnostic lints

Unfortunately, the diagnostic lints are very broken and trigger much
more often than they should. Correct the conditional which checks if the
function call being made is to a diagnostic function so that it returns
in every intended case.

Signed-off-by: David Wood <[email protected]>

Author: davidtwco

compiler/rustc_lint/src/internal.rs

@@ -406,9 +406,12 @@ impl LateLintPass<'_> for Diagnostics {
     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
         let Some((span, def_id, substs)) = typeck_results_of_method_fn(cx, expr) else { return };
         debug!(?span, ?def_id, ?substs);
-        if let Ok(Some(instance)) = ty::Instance::resolve(cx.tcx, cx.param_env, def_id, substs) &&
-            !cx.tcx.has_attr(instance.def_id(), sym::rustc_lint_diagnostics)
-        {
+        let has_attr = ty::Instance::resolve(cx.tcx, cx.param_env, def_id, substs)
+            .ok()
+            .and_then(|inst| inst)
+            .map(|inst| cx.tcx.has_attr(inst.def_id(), sym::rustc_lint_diagnostics))
+            .unwrap_or(false);
+        if !has_attr {
             return;
         }