[Lang] Type check assignments between tensors (taichi-dev#7480)

Issue: fix taichi-dev#7453

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

taichi/transforms/frontend_type_check.cpp

@@ -48,7 +48,20 @@ class FrontendTypeCheck : public IRVisitor {
   }
 
   void visit(FrontendAssignStmt *stmt) override {
+    auto lhs_type = stmt->lhs->ret_type;
+    auto rhs_type = stmt->rhs->ret_type;
+
+    auto error = [&]() {
+      throw TaichiTypeError(fmt::format("{}cannot assign '{}' to '{}'",
+                                        stmt->tb, rhs_type->to_string(),
+                                        lhs_type->to_string()));
+    };
+
     // No implicit cast at frontend for now
+    if (is_tensor(lhs_type) && is_tensor(rhs_type) &&
+        lhs_type.get_shape() != rhs_type.get_shape()) {
+      error();
+    }
   }
 
   void visit(FrontendIfStmt *stmt) override {

tests/python/test_type_check.py

@@ -80,3 +80,18 @@ def foo():
             "Only 0-dimensional numpy array can be used to initialize a scalar expression"
     ):
         foo()
+
+
+@test_utils.test(arch=ti.cpu)
+def test_assign():
+    f = ti.Vector.field(4, dtype=ti.i32, shape=())
+
+    @ti.kernel
+    def floor():
+        f[None] = ti.Vector([1, 2, 3])
+
+    with pytest.raises(
+            ti.TaichiTypeError,
+            match=
+            r"cannot assign '\[Tensor \(3\) i32\]' to '\[Tensor \(4\) i32\]'"):
+        floor()