Auto merge of #76985 - hbina:clone_check, r=estebank

Prevent stack overflow in deeply nested types.

Related issue #75577 (?)

Unfortunately, I am unable to test whether this actually solves the problem because apparently, 12GB RAM + 2GB swap is not enough to compile the (admittedly toy) source file.

Author: bors

compiler/rustc_ast/src/ast.rs

@@ -27,6 +27,7 @@ use crate::token::{self, CommentKind, DelimToken};
 use crate::tokenstream::{DelimSpan, TokenStream, TokenTree};
 
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
+use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_data_structures::sync::Lrc;
 use rustc_data_structures::thin_vec::ThinVec;
 use rustc_macros::HashStable_Generic;
@@ -1864,14 +1865,25 @@ pub enum AssocTyConstraintKind {
     Bound { bounds: GenericBounds },
 }
 
-#[derive(Clone, Encodable, Decodable, Debug)]
+#[derive(Encodable, Decodable, Debug)]
 pub struct Ty {
     pub id: NodeId,
     pub kind: TyKind,
     pub span: Span,
     pub tokens: Option<TokenStream>,
 }
 
+impl Clone for Ty {
+    fn clone(&self) -> Self {
+        ensure_sufficient_stack(|| Self {
+            id: self.id,
+            kind: self.kind.clone(),
+            span: self.span,
+            tokens: self.tokens.clone(),
+        })
+    }
+}
+
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub struct BareFnTy {
     pub unsafety: Unsafe,