simplify things by using tcx.fn_trait_kind_from_def_id

compiler/rustc_mir_build/src/check_tail_calls.rs

@@ -91,22 +91,16 @@ impl<'tcx> TailCallCkVisitor<'_, 'tcx> {
  // Closures in thir look something akin to
  // `for<'a> extern "rust-call" fn(&'a [closure@...], ()) -> <[closure@...] as FnOnce<()>>::Output {<[closure@...] as Fn<()>>::call}`
  // So we have to check for them in this weird way...
- if let &ty::FnDef(did, substs) = ty.kind() {
+ if let &ty::FnDef(did, args) = ty.kind() {
  let parent = self.tcx.parent(did);
- let fn_ = self.tcx.require_lang_item(LangItem::Fn, Some(expr.span));
- let fn_once = self.tcx.require_lang_item(LangItem::FnOnce, Some(expr.span));
- let fn_mut = self.tcx.require_lang_item(LangItem::FnMut, Some(expr.span));
- if [fn_, fn_once, fn_mut].contains(&parent) {
- if substs.first().and_then(|arg| arg.as_type()).is_some_and(|t| t.is_closure()) {
- self.report_calling_closure(
- &self.thir[fun],
- substs[1].as_type().unwrap(),
- expr,
- );
-
- // Tail calling is likely to cause unrelated errors (ABI, argument mismatches)
- return;
- }
+ if self.tcx.fn_trait_kind_from_def_id(parent).is_some()
+ && args.first().and_then(|arg| arg.as_type()).is_some_and(Ty::is_closure)
+ {
+ self.report_calling_closure(&self.thir[fun], args[1].as_type().unwrap(), expr);
+
+ // Tail calling is likely to cause unrelated errors (ABI, argument mismatches),
+ // skip them, producing an error about calling a closure is enough.
+ return;
  };
  }