{ "for host":
  { "vars": ["ARCH", "HOST_ARCH", "TARGET_ARCH"]
  , "expression":
    { "type": "let*"
    , "bindings":
      [ [ "BUILD_ARCH"
        , { "type": "var"
          , "name": "TARGET_ARCH"
          , "default": {"type": "var", "name": "ARCH"}
          }
        ]
      , [ "TARGET_ARCH"
        , { "type": "var"
          , "name": "HOST_ARCH"
          , "default": {"type": "var", "name": "ARCH"}
          }
        ]
      ]
    , "body": {"type": "env", "vars": ["BUILD_ARCH", "TARGET_ARCH"]}
    }
  }
, "target properties":
  { "vars": ["ARCH", "TARGET_ARCH", "ARCH_DISPATCH"]
  , "expression":
    { "type": "let*"
    , "bindings":
      [ [ "TARGET_ARCH"
        , { "type": "var"
          , "name": "TARGET_ARCH"
          , "default": {"type": "var", "name": "ARCH"}
          }
        ]
      ]
    , "body":
      { "type": "if"
      , "cond":
        { "type": "=="
        , "$1": {"type": "var", "name": "TARGET_ARCH"}
        , "$2": null
        }
      , "then": {"type": "empty_map"}
      , "else":
        { "type": "lookup"
        , "map":
          { "type": "var"
          , "name": "ARCH_DISPATCH"
          , "default": {"type": "empty_map"}
          }
        , "key": {"type": "var", "name": "TARGET_ARCH"}
        , "default": {"type": "empty_map"}
        }
      }
    }
  }
, "maybe for host":
  { "vars": ["ARCH", "HOST_ARCH", "TARGET_ARCH", "ARCH_DISPATCH"]
  , "imports":
    {"target properties": "target properties", "for host": "for host"}
  , "expression":
    { "type": "if"
    , "cond": {"type": "CALL_EXPRESSION", "name": "target properties"}
    , "then": {"type": "empty_map"}
    , "else": {"type": "CALL_EXPRESSION", "name": "for host"}
    }
  }
}