chore: add vendor dependencies for kauma build

vendor/syn/tests/test_grouping.rs

@@ -0,0 +1,53 @@
+#![allow(clippy::uninlined_format_args)]
+
+#[macro_use]
+mod macros;
+
+use proc_macro2::{Delimiter, Group, Literal, Punct, Spacing, TokenStream, TokenTree};
+use syn::Expr;
+
+#[test]
+fn test_grouping() {
+    let tokens: TokenStream = TokenStream::from_iter([
+        TokenTree::Literal(Literal::i32_suffixed(1)),
+        TokenTree::Punct(Punct::new('+', Spacing::Alone)),
+        TokenTree::Group(Group::new(
+            Delimiter::None,
+            TokenStream::from_iter([
+                TokenTree::Literal(Literal::i32_suffixed(2)),
+                TokenTree::Punct(Punct::new('+', Spacing::Alone)),
+                TokenTree::Literal(Literal::i32_suffixed(3)),
+            ]),
+        )),
+        TokenTree::Punct(Punct::new('*', Spacing::Alone)),
+        TokenTree::Literal(Literal::i32_suffixed(4)),
+    ]);
+
+    assert_eq!(tokens.to_string(), "1i32 + 2i32 + 3i32 * 4i32");
+
+    snapshot!(tokens as Expr, @r###"
+    Expr::Binary {
+        left: Expr::Lit {
+            lit: 1i32,
+        },
+        op: BinOp::Add,
+        right: Expr::Binary {
+            left: Expr::Group {
+                expr: Expr::Binary {
+                    left: Expr::Lit {
+                        lit: 2i32,
+                    },
+                    op: BinOp::Add,
+                    right: Expr::Lit {
+                        lit: 3i32,
+                    },
+                },
+            },
+            op: BinOp::Mul,
+            right: Expr::Lit {
+                lit: 4i32,
+            },
+        },
+    }
+    "###);
+}