init

.venv/lib/python3.8/site-packages/mypy/mro.py

@@ -0,0 +1,61 @@
+from typing import Optional, Callable, List
+
+from mypy.nodes import TypeInfo
+from mypy.types import Instance
+from mypy.typestate import TypeState
+
+
+def calculate_mro(info: TypeInfo, obj_type: Optional[Callable[[], Instance]] = None) -> None:
+    """Calculate and set mro (method resolution order).
+
+    Raise MroError if cannot determine mro.
+    """
+    mro = linearize_hierarchy(info, obj_type)
+    assert mro, "Could not produce a MRO at all for %s" % (info,)
+    info.mro = mro
+    # The property of falling back to Any is inherited.
+    info.fallback_to_any = any(baseinfo.fallback_to_any for baseinfo in info.mro)
+    TypeState.reset_all_subtype_caches_for(info)
+
+
+class MroError(Exception):
+    """Raised if a consistent mro cannot be determined for a class."""
+
+
+def linearize_hierarchy(info: TypeInfo,
+                        obj_type: Optional[Callable[[], Instance]] = None) -> List[TypeInfo]:
+    # TODO describe
+    if info.mro:
+        return info.mro
+    bases = info.direct_base_classes()
+    if (not bases and info.fullname != 'builtins.object' and
+            obj_type is not None):
+        # Second pass in import cycle, add a dummy `object` base class,
+        # otherwise MRO calculation may spuriously fail.
+        # MRO will be re-calculated for real in the third pass.
+        bases = [obj_type().type]
+    lin_bases = []
+    for base in bases:
+        assert base is not None, "Cannot linearize bases for %s %s" % (info.fullname, bases)
+        lin_bases.append(linearize_hierarchy(base, obj_type))
+    lin_bases.append(bases)
+    return [info] + merge(lin_bases)
+
+
+def merge(seqs: List[List[TypeInfo]]) -> List[TypeInfo]:
+    seqs = [s[:] for s in seqs]
+    result: List[TypeInfo] = []
+    while True:
+        seqs = [s for s in seqs if s]
+        if not seqs:
+            return result
+        for seq in seqs:
+            head = seq[0]
+            if not [s for s in seqs if head in s[1:]]:
+                break
+        else:
+            raise MroError()
+        result.append(head)
+        for s in seqs:
+            if s[0] is head:
+                del s[0]