just a patch for bool tensor indexing with shape -1 (#51046)

python/paddle/fluid/variable_index.py

@@ -320,14 +320,19 @@ def get_value_for_bool_tensor(var, item):
             "the dims of bool index except to be equal or less "
             "than {}, but received {}.".format(len(var.shape), len(item.shape))
         )
-    for i, dim_len in enumerate(item.shape):
-        if dim_len != var.shape[i]:
+    i = 0
+    item_shape = item.shape
+    while i < len(item.shape):
+        dim_len = item_shape[i]
+        if dim_len != -1 and var.shape[i] != -1 and dim_len != var.shape[i]:
             raise IndexError(
                 "The dimension of bool index doesn't match indexed array along "
                 "dimension {}, the target dimension is {}, but received {}.".format(
                     i, var.shape[i], dim_len
                 )
             )
+        i += 1
+    empty_shape = [0] + list(var.shape[i:])
 
     def idx_not_empty(var, item):
         from ..tensor import gather_nd
@@ -335,15 +340,12 @@ def get_value_for_bool_tensor(var, item):
         bool_2_idx = paddle.nonzero(item == True)
         return gather_nd(var, bool_2_idx)
 
-    def idx_empty(var):
-        var_shape = list(var.shape)
-        var_shape[0] = 0
-        return paddle.empty(var_shape, dtype=var.dtype)
-
     from paddle.static.nn import cond
 
     return cond(
-        item.any(), lambda: idx_not_empty(var, item), lambda: idx_empty(var)
+        item.any(),
+        lambda: idx_not_empty(var, item),
+        lambda: paddle.empty(empty_shape, var.dtype),
     )
 
 
@@ -848,7 +850,7 @@ def set_value_for_bool_tensor(var, item, value):
             "than {}, but received {}.".format(len(var.shape), len(item.shape))
         )
     for i, dim_len in enumerate(item.shape):
-        if dim_len != var.shape[i]:
+        if dim_len != -1 and var.shape[i] != -1 and dim_len != var.shape[i]:
             raise IndexError(
                 "The dimension of bool index doesn't match indexed array along "
                 "dimension {}, the target dimension is {}, but received {}.".format(