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<h1>Source code for typing</h1><div class="highlight"><pre>
<span></span><span class="sd">"""</span>
<span class="sd">The typing module: Support for gradual typing as defined by PEP 484.</span>
<span class="sd">At large scale, the structure of the module is following:</span>
<span class="sd">* Imports and exports, all public names should be explicitly added to __all__.</span>
<span class="sd">* Internal helper functions: these should never be used in code outside this module.</span>
<span class="sd">* _SpecialForm and its instances (special forms): Any, NoReturn, ClassVar, Union, Optional</span>
<span class="sd">* Two classes whose instances can be type arguments in addition to types: ForwardRef and TypeVar</span>
<span class="sd">* The core of internal generics API: _GenericAlias and _VariadicGenericAlias, the latter is</span>
<span class="sd"> currently only used by Tuple and Callable. All subscripted types like X[int], Union[int, str],</span>
<span class="sd"> etc., are instances of either of these classes.</span>
<span class="sd">* The public counterpart of the generics API consists of two classes: Generic and Protocol.</span>
<span class="sd">* Public helper functions: get_type_hints, overload, cast, no_type_check,</span>
<span class="sd"> no_type_check_decorator.</span>
<span class="sd">* Generic aliases for collections.abc ABCs and few additional protocols.</span>
<span class="sd">* Special types: NewType, NamedTuple, TypedDict.</span>
<span class="sd">* Wrapper submodules for re and io related types.</span>
<span class="sd">"""</span>
<span class="kn">from</span> <span class="nn">abc</span> <span class="kn">import</span> <span class="n">abstractmethod</span><span class="p">,</span> <span class="n">ABCMeta</span>
<span class="kn">import</span> <span class="nn">collections</span>
<span class="kn">import</span> <span class="nn">collections.abc</span>
<span class="kn">import</span> <span class="nn">contextlib</span>
<span class="kn">import</span> <span class="nn">functools</span>
<span class="kn">import</span> <span class="nn">operator</span>
<span class="kn">import</span> <span class="nn">re</span> <span class="k">as</span> <span class="nn">stdlib_re</span> <span class="c1"># Avoid confusion with the re we export.</span>
<span class="kn">import</span> <span class="nn">sys</span>
<span class="kn">import</span> <span class="nn">types</span>
<span class="kn">from</span> <span class="nn">types</span> <span class="kn">import</span> <span class="n">WrapperDescriptorType</span><span class="p">,</span> <span class="n">MethodWrapperType</span><span class="p">,</span> <span class="n">MethodDescriptorType</span>
<span class="c1"># Please keep __all__ alphabetized within each category.</span>
<span class="n">__all__</span> <span class="o">=</span> <span class="p">[</span>
<span class="c1"># Super-special typing primitives.</span>
<span class="s1">'Any'</span><span class="p">,</span>
<span class="s1">'Callable'</span><span class="p">,</span>
<span class="s1">'ClassVar'</span><span class="p">,</span>
<span class="s1">'Final'</span><span class="p">,</span>
<span class="s1">'ForwardRef'</span><span class="p">,</span>
<span class="s1">'Generic'</span><span class="p">,</span>
<span class="s1">'Literal'</span><span class="p">,</span>
<span class="s1">'Optional'</span><span class="p">,</span>
<span class="s1">'Protocol'</span><span class="p">,</span>
<span class="s1">'Tuple'</span><span class="p">,</span>
<span class="s1">'Type'</span><span class="p">,</span>
<span class="s1">'TypeVar'</span><span class="p">,</span>
<span class="s1">'Union'</span><span class="p">,</span>
<span class="c1"># ABCs (from collections.abc).</span>
<span class="s1">'AbstractSet'</span><span class="p">,</span> <span class="c1"># collections.abc.Set.</span>
<span class="s1">'ByteString'</span><span class="p">,</span>
<span class="s1">'Container'</span><span class="p">,</span>
<span class="s1">'ContextManager'</span><span class="p">,</span>
<span class="s1">'Hashable'</span><span class="p">,</span>
<span class="s1">'ItemsView'</span><span class="p">,</span>
<span class="s1">'Iterable'</span><span class="p">,</span>
<span class="s1">'Iterator'</span><span class="p">,</span>
<span class="s1">'KeysView'</span><span class="p">,</span>
<span class="s1">'Mapping'</span><span class="p">,</span>
<span class="s1">'MappingView'</span><span class="p">,</span>
<span class="s1">'MutableMapping'</span><span class="p">,</span>
<span class="s1">'MutableSequence'</span><span class="p">,</span>
<span class="s1">'MutableSet'</span><span class="p">,</span>
<span class="s1">'Sequence'</span><span class="p">,</span>
<span class="s1">'Sized'</span><span class="p">,</span>
<span class="s1">'ValuesView'</span><span class="p">,</span>
<span class="s1">'Awaitable'</span><span class="p">,</span>
<span class="s1">'AsyncIterator'</span><span class="p">,</span>
<span class="s1">'AsyncIterable'</span><span class="p">,</span>
<span class="s1">'Coroutine'</span><span class="p">,</span>
<span class="s1">'Collection'</span><span class="p">,</span>
<span class="s1">'AsyncGenerator'</span><span class="p">,</span>
<span class="s1">'AsyncContextManager'</span><span class="p">,</span>
<span class="c1"># Structural checks, a.k.a. protocols.</span>
<span class="s1">'Reversible'</span><span class="p">,</span>
<span class="s1">'SupportsAbs'</span><span class="p">,</span>
<span class="s1">'SupportsBytes'</span><span class="p">,</span>
<span class="s1">'SupportsComplex'</span><span class="p">,</span>
<span class="s1">'SupportsFloat'</span><span class="p">,</span>
<span class="s1">'SupportsIndex'</span><span class="p">,</span>
<span class="s1">'SupportsInt'</span><span class="p">,</span>
<span class="s1">'SupportsRound'</span><span class="p">,</span>
<span class="c1"># Concrete collection types.</span>
<span class="s1">'ChainMap'</span><span class="p">,</span>
<span class="s1">'Counter'</span><span class="p">,</span>
<span class="s1">'Deque'</span><span class="p">,</span>
<span class="s1">'Dict'</span><span class="p">,</span>
<span class="s1">'DefaultDict'</span><span class="p">,</span>
<span class="s1">'List'</span><span class="p">,</span>
<span class="s1">'OrderedDict'</span><span class="p">,</span>
<span class="s1">'Set'</span><span class="p">,</span>
<span class="s1">'FrozenSet'</span><span class="p">,</span>
<span class="s1">'NamedTuple'</span><span class="p">,</span> <span class="c1"># Not really a type.</span>
<span class="s1">'TypedDict'</span><span class="p">,</span> <span class="c1"># Not really a type.</span>
<span class="s1">'Generator'</span><span class="p">,</span>
<span class="c1"># One-off things.</span>
<span class="s1">'AnyStr'</span><span class="p">,</span>
<span class="s1">'cast'</span><span class="p">,</span>
<span class="s1">'final'</span><span class="p">,</span>
<span class="s1">'get_args'</span><span class="p">,</span>
<span class="s1">'get_origin'</span><span class="p">,</span>
<span class="s1">'get_type_hints'</span><span class="p">,</span>
<span class="s1">'NewType'</span><span class="p">,</span>
<span class="s1">'no_type_check'</span><span class="p">,</span>
<span class="s1">'no_type_check_decorator'</span><span class="p">,</span>
<span class="s1">'NoReturn'</span><span class="p">,</span>
<span class="s1">'overload'</span><span class="p">,</span>
<span class="s1">'runtime_checkable'</span><span class="p">,</span>
<span class="s1">'Text'</span><span class="p">,</span>
<span class="s1">'TYPE_CHECKING'</span><span class="p">,</span>
<span class="p">]</span>
<span class="c1"># The pseudo-submodules 're' and 'io' are part of the public</span>
<span class="c1"># namespace, but excluded from __all__ because they might stomp on</span>
<span class="c1"># legitimate imports of those modules.</span>
<span class="k">def</span> <span class="nf">_type_check</span><span class="p">(</span><span class="n">arg</span><span class="p">,</span> <span class="n">msg</span><span class="p">,</span> <span class="n">is_argument</span><span class="o">=</span><span class="kc">True</span><span class="p">):</span>
<span class="w"> </span><span class="sd">"""Check that the argument is a type, and return it (internal helper).</span>
<span class="sd"> As a special case, accept None and return type(None) instead. Also wrap strings</span>
<span class="sd"> into ForwardRef instances. Consider several corner cases, for example plain</span>
<span class="sd"> special forms like Union are not valid, while Union[int, str] is OK, etc.</span>
<span class="sd"> The msg argument is a human-readable error message, e.g::</span>
<span class="sd"> "Union[arg, ...]: arg should be a type."</span>
<span class="sd"> We append the repr() of the actual value (truncated to 100 chars).</span>
<span class="sd"> """</span>
<span class="n">invalid_generic_forms</span> <span class="o">=</span> <span class="p">(</span><span class="n">Generic</span><span class="p">,</span> <span class="n">Protocol</span><span class="p">)</span>
<span class="k">if</span> <span class="n">is_argument</span><span class="p">:</span>
<span class="n">invalid_generic_forms</span> <span class="o">=</span> <span class="n">invalid_generic_forms</span> <span class="o">+</span> <span class="p">(</span><span class="n">ClassVar</span><span class="p">,</span> <span class="n">Final</span><span class="p">)</span>
<span class="k">if</span> <span class="n">arg</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
<span class="k">return</span> <span class="nb">type</span><span class="p">(</span><span class="kc">None</span><span class="p">)</span>
<span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">arg</span><span class="p">,</span> <span class="nb">str</span><span class="p">):</span>
<span class="k">return</span> <span class="n">ForwardRef</span><span class="p">(</span><span class="n">arg</span><span class="p">)</span>
<span class="k">if</span> <span class="p">(</span><span class="nb">isinstance</span><span class="p">(</span><span class="n">arg</span><span class="p">,</span> <span class="n">_GenericAlias</span><span class="p">)</span> <span class="ow">and</span>
<span class="n">arg</span><span class="o">.</span><span class="n">__origin__</span> <span class="ow">in</span> <span class="n">invalid_generic_forms</span><span class="p">):</span>
<span class="k">raise</span> <span class="ne">TypeError</span><span class="p">(</span><span class="sa">f</span><span class="s2">"</span><span class="si">{</span><span class="n">arg</span><span class="si">}</span><span class="s2"> is not valid as type argument"</span><span class="p">)</span>
<span class="k">if</span> <span class="p">(</span><span class="nb">isinstance</span><span class="p">(</span><span class="n">arg</span><span class="p">,</span> <span class="n">_SpecialForm</span><span class="p">)</span> <span class="ow">and</span> <span class="n">arg</span> <span class="ow">not</span> <span class="ow">in</span> <span class="p">(</span><span class="n">Any</span><span class="p">,</span> <span class="n">NoReturn</span><span class="p">)</span> <span class="ow">or</span>
<span class="n">arg</span> <span class="ow">in</span> <span class="p">(</span><span class="n">Generic</span><span class="p">,</span> <span class="n">Protocol</span><span class="p">)):</span>
<span class="k">raise</span> <span class="ne">TypeError</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Plain </span><span class="si">{</span><span class="n">arg</span><span class="si">}</span><span class="s2"> is not valid as type argument"</span><span class="p">)</span>
<span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">arg</span><span class="p">,</span> <span class="p">(</span><span class="nb">type</span><span class="p">,</span> <span class="n">TypeVar</span><span class="p">,</span> <span class="n">ForwardRef</span><span class="p">)):</span>
<span class="k">return</span> <span class="n">arg</span>
<span class="k">if</span> <span class="ow">not</span> <span class="nb">callable</span><span class="p">(</span><span class="n">arg</span><span class="p">):</span>
<span class="k">raise</span> <span class="ne">TypeError</span><span class="p">(</span><span class="sa">f</span><span class="s2">"</span><span class="si">{</span><span class="n">msg</span><span class="si">}</span><span class="s2"> Got </span><span class="si">{</span><span class="n">arg</span><span class="si">!r:</span><span class="s2">.100</span><span class="si">}</span><span class="s2">."</span><span class="p">)</span>
<span class="k">return</span> <span class="n">arg</span>
<span class="k">def</span> <span class="nf">_type_repr</span><span class="p">(</span><span class="n">obj</span><span class="p">):</span>
<span class="w"> </span><span class="sd">"""Return the repr() of an object, special-casing types (internal helper).</span>
<span class="sd"> If obj is a type, we return a shorter version than the default</span>
<span class="sd"> type.__repr__, based on the module and qualified name, which is</span>
<span class="sd"> typically enough to uniquely identify a type. For everything</span>
<span class="sd"> else, we fall back on repr(obj).</span>
<span class="sd"> """</span>
<span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="nb">type</span><span class="p">):</span>
<span class="k">if</span> <span class="n">obj</span><span class="o">.</span><span class="vm">__module__</span> <span class="o">==</span> <span class="s1">'builtins'</span><span class="p">:</span>
<span class="k">return</span> <span class="n">obj</span><span class="o">.</span><span class="vm">__qualname__</span>
<span class="k">return</span> <span class="sa">f</span><span class="s1">'</span><span class="si">{</span><span class="n">obj</span><span class="o">.</span><span class="vm">__module__</span><span class="si">}</span><span class="s1">.</span><span class="si">{</span><span class="n">obj</span><span class="o">.</span><span class="vm">__qualname__</span><span class="si">}</span><span class="s1">'</span>
<span class="k">if</span> <span class="n">obj</span> <span class="ow">is</span> <span class="o">...</span><span class="p">:</span>
<span class="k">return</span><span class="p">(</span><span class="s1">'...'</span><span class="p">)</span>
<span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="n">types</span><span class="o">.</span><span class="n">FunctionType</span><span class="p">):</span>
<span class="k">return</span> <span class="n">obj</span><span class="o">.</span><span class="vm">__name__</span>
<span class="k">return</span> <span class="nb">repr</span><span class="p">(</span><span class="n">obj</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">_collect_type_vars</span><span class="p">(</span><span class="n">types</span><span class="p">):</span>
<span class="w"> </span><span class="sd">"""Collect all type variable contained in types in order of</span>
<span class="sd"> first appearance (lexicographic order). For example::</span>
<span class="sd"> _collect_type_vars((T, List[S, T])) == (T, S)</span>
<span class="sd"> """</span>
<span class="n">tvars</span> <span class="o">=</span> <span class="p">[]</span>
<span class="k">for</span> <span class="n">t</span> <span class="ow">in</span> <span class="n">types</span><span class="p">:</span>
<span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">t</span><span class="p">,</span> <span class="n">TypeVar</span><span class="p">)</span> <span class="ow">and</span> <span class="n">t</span> <span class="ow">not</span> <span class="ow">in</span> <span class="n">tvars</span><span class="p">:</span>
<span class="n">tvars</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">t</span><span class="p">)</span>
<span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">t</span><span class="p">,</span> <span class="n">_GenericAlias</span><span class="p">)</span> <span class="ow">and</span> <span class="ow">not</span> <span class="n">t</span><span class="o">.</span><span class="n">_special</span><span class="p">:</span>
<span class="n">tvars</span><span class="o">.</span><span class="n">extend</span><span class="p">([</span><span class="n">t</span> <span class="k">for</span> <span class="n">t</span> <span class="ow">in</span> <span class="n">t</span><span class="o">.</span><span class="n">__parameters__</span> <span class="k">if</span> <span class="n">t</span> <span class="ow">not</span> <span class="ow">in</span> <span class="n">tvars</span><span class="p">])</span>
<span class="k">return</span> <span class="nb">tuple</span><span class="p">(</span><span class="n">tvars</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">_subs_tvars</span><span class="p">(</span><span class="n">tp</span><span class="p">,</span> <span class="n">tvars</span><span class="p">,</span> <span class="n">subs</span><span class="p">):</span>
<span class="w"> </span><span class="sd">"""Substitute type variables 'tvars' with substitutions 'subs'.</span>
<span class="sd"> These two must have the same length.</span>
<span class="sd"> """</span>
<span class="k">if</span> <span class="ow">not</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">tp</span><span class="p">,</span> <span class="n">_GenericAlias</span><span class="p">):</span>
<span class="k">return</span> <span class="n">tp</span>
<span class="n">new_args</span> <span class="o">=</span> <span class="nb">list</span><span class="p">(</span><span class="n">tp</span><span class="o">.</span><span class="n">__args__</span><span class="p">)</span>
<span class="k">for</span> <span class="n">a</span><span class="p">,</span> <span class="n">arg</span> <span class="ow">in</span> <span class="nb">enumerate</span><span class="p">(</span><span class="n">tp</span><span class="o">.</span><span class="n">__args__</span><span class="p">):</span>
<span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">arg</span><span class="p">,</span> <span class="n">TypeVar</span><span class="p">):</span>
<span class="k">for</span> <span class="n">i</span><span class="p">,</span> <span class="n">tvar</span> <span class="ow">in</span> <span class="nb">enumerate</span><span class="p">(</span><span class="n">tvars</span><span class="p">):</span>
<span class="k">if</span> <span class="n">arg</span> <span class="o">==</span> <span class="n">tvar</span><span class="p">:</span>
<span class="n">new_args</span><span class="p">[</span><span class="n">a</span><span class="p">]</span> <span class="o">=</span> <span class="n">subs</span><span class="p">[</span><span class="n">i</span><span class="p">]</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">new_args</span><span class="p">[</span><span class="n">a</span><span class="p">]</span> <span class="o">=</span> <span class="n">_subs_tvars</span><span class="p">(</span><span class="n">arg</span><span class="p">,</span> <span class="n">tvars</span><span class="p">,</span> <span class="n">subs</span><span class="p">)</span>
<span class="k">if</span> <span class="n">tp</span><span class="o">.</span><span class="n">__origin__</span> <span class="ow">is</span> <span class="n">Union</span><span class="p">:</span>
<span class="k">return</span> <span class="n">Union</span><span class="p">[</span><span class="nb">tuple</span><span class="p">(</span><span class="n">new_args</span><span class="p">)]</span>
<span class="k">return</span> <span class="n">tp</span><span class="o">.</span><span class="n">copy_with</span><span class="p">(</span><span class="nb">tuple</span><span class="p">(</span><span class="n">new_args</span><span class="p">))</span>
<span class="k">def</span> <span class="nf">_check_generic</span><span class="p">(</span><span class="bp">cls</span><span class="p">,</span> <span class="n">parameters</span><span class="p">):</span>
<span class="w"> </span><span class="sd">"""Check correct count for parameters of a generic cls (internal helper).</span>
<span class="sd"> This gives a nice error message in case of count mismatch.</span>
<span class="sd"> """</span>
<span class="k">if</span> <span class="ow">not</span> <span class="bp">cls</span><span class="o">.</span><span class="n">__parameters__</span><span class="p">:</span>
<span class="k">raise</span> <span class="ne">TypeError</span><span class="p">(</span><span class="sa">f</span><span class="s2">"</span><span class="si">{</span><span class="bp">cls</span><span class="si">}</span><span class="s2"> is not a generic class"</span><span class="p">)</span>
<span class="n">alen</span> <span class="o">=</span> <span class="nb">len</span><span class="p">(</span><span class="n">parameters</span><span class="p">)</span>
<span class="n">elen</span> <span class="o">=</span> <span class="nb">len</span><span class="p">(</span><span class="bp">cls</span><span class="o">.</span><span class="n">__parameters__</span><span class="p">)</span>
<span class="k">if</span> <span class="n">alen</span> <span class="o">!=</span> <span class="n">elen</span><span class="p">:</span>
<span class="k">raise</span> <span class="ne">TypeError</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Too </span><span class="si">{</span><span class="s1">'many'</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">alen</span><span class="w"> </span><span class="o">></span><span class="w"> </span><span class="n">elen</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="s1">'few'</span><span class="si">}</span><span class="s2"> parameters for </span><span class="si">{</span><span class="bp">cls</span><span class="si">}</span><span class="s2">;"</span>
<span class="sa">f</span><span class="s2">" actual </span><span class="si">{</span><span class="n">alen</span><span class="si">}</span><span class="s2">, expected </span><span class="si">{</span><span class="n">elen</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">_remove_dups_flatten</span><span class="p">(</span><span class="n">parameters</span><span class="p">):</span>
<span class="w"> </span><span class="sd">"""An internal helper for Union creation and substitution: flatten Unions</span>
<span class="sd"> among parameters, then remove duplicates.</span>
<span class="sd"> """</span>
<span class="c1"># Flatten out Union[Union[...], ...].</span>
<span class="n">params</span> <span class="o">=</span> <span class="p">[]</span>
<span class="k">for</span> <span class="n">p</span> <span class="ow">in</span> <span class="n">parameters</span><span class="p">:</span>
<span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">p</span><span class="p">,</span> <span class="n">_GenericAlias</span><span class="p">)</span> <span class="ow">and</span> <span class="n">p</span><span class="o">.</span><span class="n">__origin__</span> <span class="ow">is</span> <span class="n">Union</span><span class="p">:</span>
<span class="n">params</span><span class="o">.</span><span class="n">extend</span><span class="p">(</span><span class="n">p</span><span class="o">.</span><span class="n">__args__</span><span class="p">)</span>
<span class="k">elif</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">p</span><span class="p">,</span> <span class="nb">tuple</span><span class="p">)</span> <span class="ow">and</span> <span class="nb">len</span><span class="p">(</span><span class="n">p</span><span class="p">)</span> <span class="o">></span> <span class="mi">0</span> <span class="ow">and</span> <span class="n">p</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="ow">is</span> <span class="n">Union</span><span class="p">:</span>
<span class="n">params</span><span class="o">.</span><span class="n">extend</span><span class="p">(</span><span class="n">p</span><span class="p">[</span><span class="mi">1</span><span class="p">:])</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">params</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">p</span><span class="p">)</span>
<span class="c1"># Weed out strict duplicates, preserving the first of each occurrence.</span>
<span class="n">all_params</span> <span class="o">=</span> <span class="nb">set</span><span class="p">(</span><span class="n">params</span><span class="p">)</span>
<span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="n">all_params</span><span class="p">)</span> <span class="o"><</span> <span class="nb">len</span><span class="p">(</span><span class="n">params</span><span class="p">):</span>
<span class="n">new_params</span> <span class="o">=</span> <span class="p">[]</span>
<span class="k">for</span> <span class="n">t</span> <span class="ow">in</span> <span class="n">params</span><span class="p">:</span>
<span class="k">if</span> <span class="n">t</span> <span class="ow">in</span> <span class="n">all_params</span><span class="p">:</span>
<span class="n">new_params</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">t</span><span class="p">)</span>
<span class="n">all_params</span><span class="o">.</span><span class="n">remove</span><span class="p">(</span><span class="n">t</span><span class="p">)</span>
<span class="n">params</span> <span class="o">=</span> <span class="n">new_params</span>
<span class="k">assert</span> <span class="ow">not</span> <span class="n">all_params</span><span class="p">,</span> <span class="n">all_params</span>
<span class="k">return</span> <span class="nb">tuple</span><span class="p">(</span><span class="n">params</span><span class="p">)</span>
<span class="n">_cleanups</span> <span class="o">=</span> <span class="p">[]</span>
<span class="k">def</span> <span class="nf">_tp_cache</span><span class="p">(</span><span class="n">func</span><span class="p">):</span>
<span class="w"> </span><span class="sd">"""Internal wrapper caching __getitem__ of generic types with a fallback to</span>
<span class="sd"> original function for non-hashable arguments.</span>
<span class="sd"> """</span>
<span class="n">cached</span> <span class="o">=</span> <span class="n">functools</span><span class="o">.</span><span class="n">lru_cache</span><span class="p">()(</span><span class="n">func</span><span class="p">)</span>
<span class="n">_cleanups</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">cached</span><span class="o">.</span><span class="n">cache_clear</span><span class="p">)</span>
<span class="nd">@functools</span><span class="o">.</span><span class="n">wraps</span><span class="p">(</span><span class="n">func</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">inner</span><span class="p">(</span><span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwds</span><span class="p">):</span>
<span class="k">try</span><span class="p">:</span>
<span class="k">return</span> <span class="n">cached</span><span class="p">(</span><span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwds</span><span class="p">)</span>
<span class="k">except</span> <span class="ne">TypeError</span><span class="p">:</span>
<span class="k">pass</span> <span class="c1"># All real errors (not unhashable args) are raised below.</span>
<span class="k">return</span> <span class="n">func</span><span class="p">(</span><span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwds</span><span class="p">)</span>
<span class="k">return</span> <span class="n">inner</span>
<span class="k">def</span> <span class="nf">_eval_type</span><span class="p">(</span><span class="n">t</span><span class="p">,</span> <span class="n">globalns</span><span class="p">,</span> <span class="n">localns</span><span class="p">):</span>
<span class="w"> </span><span class="sd">"""Evaluate all forward references in the given type t.</span>
<span class="sd"> For use of globalns and localns see the docstring for get_type_hints().</span>
<span class="sd"> """</span>
<span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">t</span><span class="p">,</span> <span class="n">ForwardRef</span><span class="p">):</span>
<span class="k">return</span> <span class="n">t</span><span class="o">.</span><span class="n">_evaluate</span><span class="p">(</span><span class="n">globalns</span><span class="p">,</span> <span class="n">localns</span><span class="p">)</span>
<span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">t</span><span class="p">,</span> <span class="n">_GenericAlias</span><span class="p">):</span>
<span class="n">ev_args</span> <span class="o">=</span> <span class="nb">tuple</span><span class="p">(</span><span class="n">_eval_type</span><span class="p">(</span><span class="n">a</span><span class="p">,</span> <span class="n">globalns</span><span class="p">,</span> <span class="n">localns</span><span class="p">)</span> <span class="k">for</span> <span class="n">a</span> <span class="ow">in</span> <span class="n">t</span><span class="o">.</span><span class="n">__args__</span><span class="p">)</span>
<span class="k">if</span> <span class="n">ev_args</span> <span class="o">==</span> <span class="n">t</span><span class="o">.</span><span class="n">__args__</span><span class="p">:</span>
<span class="k">return</span> <span class="n">t</span>
<span class="n">res</span> <span class="o">=</span> <span class="n">t</span><span class="o">.</span><span class="n">copy_with</span><span class="p">(</span><span class="n">ev_args</span><span class="p">)</span>
<span class="n">res</span><span class="o">.</span><span class="n">_special</span> <span class="o">=</span> <span class="n">t</span><span class="o">.</span><span class="n">_special</span>
<span class="k">return</span> <span class="n">res</span>
<span class="k">return</span> <span class="n">t</span>
<span class="k">class</span> <span class="nc">_Final</span><span class="p">:</span>
<span class="w"> </span><span class="sd">"""Mixin to prohibit subclassing"""</span>
<span class="vm">__slots__</span> <span class="o">=</span> <span class="p">(</span><span class="s1">'__weakref__'</span><span class="p">,)</span>
<span class="k">def</span> <span class="nf">__init_subclass__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="o">/</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwds</span><span class="p">):</span>
<span class="k">if</span> <span class="s1">'_root'</span> <span class="ow">not</span> <span class="ow">in</span> <span class="n">kwds</span><span class="p">:</span>
<span class="k">raise</span> <span class="ne">TypeError</span><span class="p">(</span><span class="s2">"Cannot subclass special typing classes"</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">_Immutable</span><span class="p">:</span>
<span class="w"> </span><span class="sd">"""Mixin to indicate that object should not be copied."""</span>
<span class="k">def</span> <span class="nf">__copy__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="bp">self</span>
<span class="k">def</span> <span class="nf">__deepcopy__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">memo</span><span class="p">):</span>
<span class="k">return</span> <span class="bp">self</span>
<span class="k">class</span> <span class="nc">_SpecialForm</span><span class="p">(</span><span class="n">_Final</span><span class="p">,</span> <span class="n">_Immutable</span><span class="p">,</span> <span class="n">_root</span><span class="o">=</span><span class="kc">True</span><span class="p">):</span>
<span class="w"> </span><span class="sd">"""Internal indicator of special typing constructs.</span>
<span class="sd"> See _doc instance attribute for specific docs.</span>
<span class="sd"> """</span>
<span class="vm">__slots__</span> <span class="o">=</span> <span class="p">(</span><span class="s1">'_name'</span><span class="p">,</span> <span class="s1">'_doc'</span><span class="p">)</span>
<span class="k">def</span> <span class="fm">__new__</span><span class="p">(</span><span class="bp">cls</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwds</span><span class="p">):</span>
<span class="w"> </span><span class="sd">"""Constructor.</span>
<span class="sd"> This only exists to give a better error message in case</span>
<span class="sd"> someone tries to subclass a special typing object (not a good idea).</span>
<span class="sd"> """</span>
<span class="k">if</span> <span class="p">(</span><span class="nb">len</span><span class="p">(</span><span class="n">args</span><span class="p">)</span> <span class="o">==</span> <span class="mi">3</span> <span class="ow">and</span>
<span class="nb">isinstance</span><span class="p">(</span><span class="n">args</span><span class="p">[</span><span class="mi">0</span><span class="p">],</span> <span class="nb">str</span><span class="p">)</span> <span class="ow">and</span>
<span class="nb">isinstance</span><span class="p">(</span><span class="n">args</span><span class="p">[</span><span class="mi">1</span><span class="p">],</span> <span class="nb">tuple</span><span class="p">)):</span>
<span class="c1"># Close enough.</span>
<span class="k">raise</span> <span class="ne">TypeError</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Cannot subclass </span><span class="si">{</span><span class="bp">cls</span><span class="si">!r}</span><span class="s2">"</span><span class="p">)</span>
<span class="k">return</span> <span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="fm">__new__</span><span class="p">(</span><span class="bp">cls</span><span class="p">)</span>
<span class="k">def</span> <span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">name</span><span class="p">,</span> <span class="n">doc</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">_name</span> <span class="o">=</span> <span class="n">name</span>
<span class="bp">self</span><span class="o">.</span><span class="n">_doc</span> <span class="o">=</span> <span class="n">doc</span>
<span class="k">def</span> <span class="fm">__eq__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">other</span><span class="p">):</span>
<span class="k">if</span> <span class="ow">not</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">other</span><span class="p">,</span> <span class="n">_SpecialForm</span><span class="p">):</span>
<span class="k">return</span> <span class="bp">NotImplemented</span>
<span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">_name</span> <span class="o">==</span> <span class="n">other</span><span class="o">.</span><span class="n">_name</span>
<span class="k">def</span> <span class="fm">__hash__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="nb">hash</span><span class="p">((</span><span class="bp">self</span><span class="o">.</span><span class="n">_name</span><span class="p">,))</span>
<span class="k">def</span> <span class="fm">__repr__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="s1">'typing.'</span> <span class="o">+</span> <span class="bp">self</span><span class="o">.</span><span class="n">_name</span>
<span class="k">def</span> <span class="nf">__reduce__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">_name</span>
<span class="k">def</span> <span class="fm">__call__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwds</span><span class="p">):</span>
<span class="k">raise</span> <span class="ne">TypeError</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Cannot instantiate </span><span class="si">{</span><span class="bp">self</span><span class="si">!r}</span><span class="s2">"</span><span class="p">)</span>
<span class="k">def</span> <span class="fm">__instancecheck__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">obj</span><span class="p">):</span>
<span class="k">raise</span> <span class="ne">TypeError</span><span class="p">(</span><span class="sa">f</span><span class="s2">"</span><span class="si">{</span><span class="bp">self</span><span class="si">}</span><span class="s2"> cannot be used with isinstance()"</span><span class="p">)</span>
<span class="k">def</span> <span class="fm">__subclasscheck__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="bp">cls</span><span class="p">):</span>
<span class="k">raise</span> <span class="ne">TypeError</span><span class="p">(</span><span class="sa">f</span><span class="s2">"</span><span class="si">{</span><span class="bp">self</span><span class="si">}</span><span class="s2"> cannot be used with issubclass()"</span><span class="p">)</span>
<span class="nd">@_tp_cache</span>
<span class="k">def</span> <span class="fm">__getitem__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">parameters</span><span class="p">):</span>
<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">_name</span> <span class="ow">in</span> <span class="p">(</span><span class="s1">'ClassVar'</span><span class="p">,</span> <span class="s1">'Final'</span><span class="p">):</span>
<span class="n">item</span> <span class="o">=</span> <span class="n">_type_check</span><span class="p">(</span><span class="n">parameters</span><span class="p">,</span> <span class="sa">f</span><span class="s1">'</span><span class="si">{</span><span class="bp">self</span><span class="o">.</span><span class="n">_name</span><span class="si">}</span><span class="s1"> accepts only single type.'</span><span class="p">)</span>
<span class="k">return</span> <span class="n">_GenericAlias</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="p">(</span><span class="n">item</span><span class="p">,))</span>
<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">_name</span> <span class="o">==</span> <span class="s1">'Union'</span><span class="p">:</span>
<span class="k">if</span> <span class="n">parameters</span> <span class="o">==</span> <span class="p">():</span>
<span class="k">raise</span> <span class="ne">TypeError</span><span class="p">(</span><span class="s2">"Cannot take a Union of no types."</span><span class="p">)</span>
<span class="k">if</span> <span class="ow">not</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">parameters</span><span class="p">,</span> <span class="nb">tuple</span><span class="p">):</span>
<span class="n">parameters</span> <span class="o">=</span> <span class="p">(</span><span class="n">parameters</span><span class="p">,)</span>
<span class="n">msg</span> <span class="o">=</span> <span class="s2">"Union[arg, ...]: each arg must be a type."</span>
<span class="n">parameters</span> <span class="o">=</span> <span class="nb">tuple</span><span class="p">(</span><span class="n">_type_check</span><span class="p">(</span><span class="n">p</span><span class="p">,</span> <span class="n">msg</span><span class="p">)</span> <span class="k">for</span> <span class="n">p</span> <span class="ow">in</span> <span class="n">parameters</span><span class="p">)</span>
<span class="n">parameters</span> <span class="o">=</span> <span class="n">_remove_dups_flatten</span><span class="p">(</span><span class="n">parameters</span><span class="p">)</span>
<span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="n">parameters</span><span class="p">)</span> <span class="o">==</span> <span class="mi">1</span><span class="p">:</span>
<span class="k">return</span> <span class="n">parameters</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
<span class="k">return</span> <span class="n">_GenericAlias</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">parameters</span><span class="p">)</span>
<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">_name</span> <span class="o">==</span> <span class="s1">'Optional'</span><span class="p">:</span>
<span class="n">arg</span> <span class="o">=</span> <span class="n">_type_check</span><span class="p">(</span><span class="n">parameters</span><span class="p">,</span> <span class="s2">"Optional[t] requires a single type."</span><span class="p">)</span>
<span class="k">return</span> <span class="n">Union</span><span class="p">[</span><span class="n">arg</span><span class="p">,</span> <span class="nb">type</span><span class="p">(</span><span class="kc">None</span><span class="p">)]</span>
<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">_name</span> <span class="o">==</span> <span class="s1">'Literal'</span><span class="p">:</span>
<span class="c1"># There is no '_type_check' call because arguments to Literal[...] are</span>
<span class="c1"># values, not types.</span>
<span class="k">return</span> <span class="n">_GenericAlias</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">parameters</span><span class="p">)</span>
<span class="k">raise</span> <span class="ne">TypeError</span><span class="p">(</span><span class="sa">f</span><span class="s2">"</span><span class="si">{</span><span class="bp">self</span><span class="si">}</span><span class="s2"> is not subscriptable"</span><span class="p">)</span>
<span class="n">Any</span> <span class="o">=</span> <span class="n">_SpecialForm</span><span class="p">(</span><span class="s1">'Any'</span><span class="p">,</span> <span class="n">doc</span><span class="o">=</span>
<span class="w"> </span><span class="sd">"""Special type indicating an unconstrained type.</span>
<span class="sd"> - Any is compatible with every type.</span>
<span class="sd"> - Any assumed to have all methods.</span>
<span class="sd"> - All values assumed to be instances of Any.</span>
<span class="sd"> Note that all the above statements are true from the point of view of</span>
<span class="sd"> static type checkers. At runtime, Any should not be used with instance</span>
<span class="sd"> or class checks.</span>
<span class="sd"> """</span><span class="p">)</span>
<span class="n">NoReturn</span> <span class="o">=</span> <span class="n">_SpecialForm</span><span class="p">(</span><span class="s1">'NoReturn'</span><span class="p">,</span> <span class="n">doc</span><span class="o">=</span>
<span class="w"> </span><span class="sd">"""Special type indicating functions that never return.</span>
<span class="sd"> Example::</span>
<span class="sd"> from typing import NoReturn</span>
<span class="sd"> def stop() -> NoReturn:</span>
<span class="sd"> raise Exception('no way')</span>
<span class="sd"> This type is invalid in other positions, e.g., ``List[NoReturn]``</span>
<span class="sd"> will fail in static type checkers.</span>
<span class="sd"> """</span><span class="p">)</span>
<span class="n">ClassVar</span> <span class="o">=</span> <span class="n">_SpecialForm</span><span class="p">(</span><span class="s1">'ClassVar'</span><span class="p">,</span> <span class="n">doc</span><span class="o">=</span>
<span class="w"> </span><span class="sd">"""Special type construct to mark class variables.</span>
<span class="sd"> An annotation wrapped in ClassVar indicates that a given</span>
<span class="sd"> attribute is intended to be used as a class variable and</span>
<span class="sd"> should not be set on instances of that class. Usage::</span>
<span class="sd"> class Starship:</span>
<span class="sd"> stats: ClassVar[Dict[str, int]] = {} # class variable</span>
<span class="sd"> damage: int = 10 # instance variable</span>
<span class="sd"> ClassVar accepts only types and cannot be further subscribed.</span>
<span class="sd"> Note that ClassVar is not a class itself, and should not</span>
<span class="sd"> be used with isinstance() or issubclass().</span>
<span class="sd"> """</span><span class="p">)</span>
<span class="n">Final</span> <span class="o">=</span> <span class="n">_SpecialForm</span><span class="p">(</span><span class="s1">'Final'</span><span class="p">,</span> <span class="n">doc</span><span class="o">=</span>
<span class="w"> </span><span class="sd">"""Special typing construct to indicate final names to type checkers.</span>
<span class="sd"> A final name cannot be re-assigned or overridden in a subclass.</span>
<span class="sd"> For example:</span>
<span class="sd"> MAX_SIZE: Final = 9000</span>
<span class="sd"> MAX_SIZE += 1 # Error reported by type checker</span>
<span class="sd"> class Connection:</span>
<span class="sd"> TIMEOUT: Final[int] = 10</span>
<span class="sd"> class FastConnector(Connection):</span>
<span class="sd"> TIMEOUT = 1 # Error reported by type checker</span>
<span class="sd"> There is no runtime checking of these properties.</span>
<span class="sd"> """</span><span class="p">)</span>
<span class="n">Union</span> <span class="o">=</span> <span class="n">_SpecialForm</span><span class="p">(</span><span class="s1">'Union'</span><span class="p">,</span> <span class="n">doc</span><span class="o">=</span>
<span class="w"> </span><span class="sd">"""Union type; Union[X, Y] means either X or Y.</span>
<span class="sd"> To define a union, use e.g. Union[int, str]. Details:</span>
<span class="sd"> - The arguments must be types and there must be at least one.</span>
<span class="sd"> - None as an argument is a special case and is replaced by</span>
<span class="sd"> type(None).</span>
<span class="sd"> - Unions of unions are flattened, e.g.::</span>
<span class="sd"> Union[Union[int, str], float] == Union[int, str, float]</span>
<span class="sd"> - Unions of a single argument vanish, e.g.::</span>
<span class="sd"> Union[int] == int # The constructor actually returns int</span>
<span class="sd"> - Redundant arguments are skipped, e.g.::</span>
<span class="sd"> Union[int, str, int] == Union[int, str]</span>
<span class="sd"> - When comparing unions, the argument order is ignored, e.g.::</span>
<span class="sd"> Union[int, str] == Union[str, int]</span>
<span class="sd"> - You cannot subclass or instantiate a union.</span>
<span class="sd"> - You can use Optional[X] as a shorthand for Union[X, None].</span>
<span class="sd"> """</span><span class="p">)</span>
<span class="n">Optional</span> <span class="o">=</span> <span class="n">_SpecialForm</span><span class="p">(</span><span class="s1">'Optional'</span><span class="p">,</span> <span class="n">doc</span><span class="o">=</span>
<span class="w"> </span><span class="sd">"""Optional type.</span>
<span class="sd"> Optional[X] is equivalent to Union[X, None].</span>
<span class="sd"> """</span><span class="p">)</span>
<span class="n">Literal</span> <span class="o">=</span> <span class="n">_SpecialForm</span><span class="p">(</span><span class="s1">'Literal'</span><span class="p">,</span> <span class="n">doc</span><span class="o">=</span>
<span class="w"> </span><span class="sd">"""Special typing form to define literal types (a.k.a. value types).</span>
<span class="sd"> This form can be used to indicate to type checkers that the corresponding</span>
<span class="sd"> variable or function parameter has a value equivalent to the provided</span>
<span class="sd"> literal (or one of several literals):</span>
<span class="sd"> def validate_simple(data: Any) -> Literal[True]: # always returns True</span>
<span class="sd"> ...</span>
<span class="sd"> MODE = Literal['r', 'rb', 'w', 'wb']</span>
<span class="sd"> def open_helper(file: str, mode: MODE) -> str:</span>
<span class="sd"> ...</span>
<span class="sd"> open_helper('/some/path', 'r') # Passes type check</span>
<span class="sd"> open_helper('/other/path', 'typo') # Error in type checker</span>
<span class="sd"> Literal[...] cannot be subclassed. At runtime, an arbitrary value</span>
<span class="sd"> is allowed as type argument to Literal[...], but type checkers may</span>
<span class="sd"> impose restrictions.</span>
<span class="sd"> """</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">ForwardRef</span><span class="p">(</span><span class="n">_Final</span><span class="p">,</span> <span class="n">_root</span><span class="o">=</span><span class="kc">True</span><span class="p">):</span>
<span class="w"> </span><span class="sd">"""Internal wrapper to hold a forward reference."""</span>
<span class="vm">__slots__</span> <span class="o">=</span> <span class="p">(</span><span class="s1">'__forward_arg__'</span><span class="p">,</span> <span class="s1">'__forward_code__'</span><span class="p">,</span>
<span class="s1">'__forward_evaluated__'</span><span class="p">,</span> <span class="s1">'__forward_value__'</span><span class="p">,</span>
<span class="s1">'__forward_is_argument__'</span><span class="p">)</span>
<span class="k">def</span> <span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">arg</span><span class="p">,</span> <span class="n">is_argument</span><span class="o">=</span><span class="kc">True</span><span class="p">):</span>
<span class="k">if</span> <span class="ow">not</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">arg</span><span class="p">,</span> <span class="nb">str</span><span class="p">):</span>
<span class="k">raise</span> <span class="ne">TypeError</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Forward reference must be a string -- got </span><span class="si">{</span><span class="n">arg</span><span class="si">!r}</span><span class="s2">"</span><span class="p">)</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">code</span> <span class="o">=</span> <span class="nb">compile</span><span class="p">(</span><span class="n">arg</span><span class="p">,</span> <span class="s1">'<string>'</span><span class="p">,</span> <span class="s1">'eval'</span><span class="p">)</span>
<span class="k">except</span> <span class="ne">SyntaxError</span><span class="p">:</span>
<span class="k">raise</span> <span class="ne">SyntaxError</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Forward reference must be an expression -- got </span><span class="si">{</span><span class="n">arg</span><span class="si">!r}</span><span class="s2">"</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">__forward_arg__</span> <span class="o">=</span> <span class="n">arg</span>
<span class="bp">self</span><span class="o">.</span><span class="n">__forward_code__</span> <span class="o">=</span> <span class="n">code</span>
<span class="bp">self</span><span class="o">.</span><span class="n">__forward_evaluated__</span> <span class="o">=</span> <span class="kc">False</span>
<span class="bp">self</span><span class="o">.</span><span class="n">__forward_value__</span> <span class="o">=</span> <span class="kc">None</span>
<span class="bp">self</span><span class="o">.</span><span class="n">__forward_is_argument__</span> <span class="o">=</span> <span class="n">is_argument</span>
<span class="k">def</span> <span class="nf">_evaluate</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">globalns</span><span class="p">,</span> <span class="n">localns</span><span class="p">):</span>
<span class="k">if</span> <span class="ow">not</span> <span class="bp">self</span><span class="o">.</span><span class="n">__forward_evaluated__</span> <span class="ow">or</span> <span class="n">localns</span> <span class="ow">is</span> <span class="ow">not</span> <span class="n">globalns</span><span class="p">:</span>
<span class="k">if</span> <span class="n">globalns</span> <span class="ow">is</span> <span class="kc">None</span> <span class="ow">and</span> <span class="n">localns</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
<span class="n">globalns</span> <span class="o">=</span> <span class="n">localns</span> <span class="o">=</span> <span class="p">{}</span>
<span class="k">elif</span> <span class="n">globalns</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
<span class="n">globalns</span> <span class="o">=</span> <span class="n">localns</span>
<span class="k">elif</span> <span class="n">localns</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
<span class="n">localns</span> <span class="o">=</span> <span class="n">globalns</span>
<span class="bp">self</span><span class="o">.</span><span class="n">__forward_value__</span> <span class="o">=</span> <span class="n">_type_check</span><span class="p">(</span>
<span class="nb">eval</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">__forward_code__</span><span class="p">,</span> <span class="n">globalns</span><span class="p">,</span> <span class="n">localns</span><span class="p">),</span>
<span class="s2">"Forward references must evaluate to types."</span><span class="p">,</span>
<span class="n">is_argument</span><span class="o">=</span><span class="bp">self</span><span class="o">.</span><span class="n">__forward_is_argument__</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">__forward_evaluated__</span> <span class="o">=</span> <span class="kc">True</span>
<span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">__forward_value__</span>
<span class="k">def</span> <span class="fm">__eq__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">other</span><span class="p">):</span>
<span class="k">if</span> <span class="ow">not</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">other</span><span class="p">,</span> <span class="n">ForwardRef</span><span class="p">):</span>
<span class="k">return</span> <span class="bp">NotImplemented</span>
<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">__forward_evaluated__</span> <span class="ow">and</span> <span class="n">other</span><span class="o">.</span><span class="n">__forward_evaluated__</span><span class="p">:</span>
<span class="k">return</span> <span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">__forward_arg__</span> <span class="o">==</span> <span class="n">other</span><span class="o">.</span><span class="n">__forward_arg__</span> <span class="ow">and</span>
<span class="bp">self</span><span class="o">.</span><span class="n">__forward_value__</span> <span class="o">==</span> <span class="n">other</span><span class="o">.</span><span class="n">__forward_value__</span><span class="p">)</span>
<span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">__forward_arg__</span> <span class="o">==</span> <span class="n">other</span><span class="o">.</span><span class="n">__forward_arg__</span>
<span class="k">def</span> <span class="fm">__hash__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="nb">hash</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">__forward_arg__</span><span class="p">)</span>