def var_subtractive_cancellation(self, x_name, y_name, output_type):
    if x_name in self.known_offsets:
      for (prev_var_name, offset) in self.known_offsets[x_name]:
        if prev_var_name == y_name:
          return self.cast(const(offset), output_type)
Expand specials like $!PRODUCT_DIR in |path|.
dataset/ETHPy150Open iskandr/parakeet/parakeet/transforms/offset_propagation.py/OffsetPropagation.var_subtractive_cancellation--crossover with--dataset/ETHPy150Open adblockplus/gyp/pylib/gyp/generator/ninja.py/NinjaWriter.ExpandSpecial