[QoL][Relax] Infer StructInfo for relax::Tuple on construction

src/relax/ir/expr.cc

@@ -137,9 +137,25 @@ TVM_REGISTER_GLOBAL("relax.If")
     });
 
 Tuple::Tuple(tvm::Array<relay::Expr> fields, Span span) {
+  Optional<StructInfo> tuple_sinfo = [&]() -> Optional<StructInfo> {
+    Array<StructInfo> field_sinfo;
+    for (const auto& field : fields) {
+      if (field->struct_info_.defined()) {
+        field_sinfo.push_back(GetStructInfo(field));
+      } else {
+        return NullOpt;
+      }
+    }
+    return TupleStructInfo(field_sinfo);
+  }();
+
   ObjectPtr<TupleNode> n = make_object<TupleNode>();
   n->fields = std::move(fields);
   n->span = std::move(span);
+  if (tuple_sinfo) {
+    n->checked_type_ = GetStaticType(tuple_sinfo.value());
+  }
+  n->struct_info_ = tuple_sinfo;
   data_ = std::move(n);
 }
 

tests/python/relax/test_expr.py

@@ -86,6 +86,25 @@ def test_tuple() -> None:
         t[-3]
 
 
+def test_tuple_sinfo_inferred_on_construction():
+    v0 = rx.Var("v0", rx.ObjectStructInfo())
+    v1 = rx.Var("v1", rx.ObjectStructInfo())
+    tup = rx.Tuple((v0, v1))
+
+    assert tup.struct_info_ is not None
+    tvm.ir.assert_structural_equal(
+        tup.struct_info, rx.TupleStructInfo([rx.ObjectStructInfo(), rx.ObjectStructInfo()])
+    )
+
+
+def test_tuple_sinfo_requires_fields_with_known_sinfo():
+    v0 = rx.Var("v0", rx.ObjectStructInfo())
+    v1 = rx.Var("v1")
+    tup = rx.Tuple((v0, v1))
+
+    assert tup.struct_info_ is None
+
+
 def test_match_cast() -> None:
     # match_cast([16, 8], [m, n])
     m = tir.Var("m", dtype="int64")