chore(dev-tools): add some more type hints (#10427)

ibis/expr/types/core.py

@@ -137,7 +137,7 @@ def __reduce__(self):
     def __hash__(self):
         return hash((self.__class__, self._arg))
 
-    def equals(self, other):
+    def equals(self, other) -> bool:
         """Return whether this expression is _structurally_ equivalent to `other`.
 
         If you want to produce an equality expression, use `==` syntax.
@@ -375,7 +375,7 @@ def _find_backend(self, *, use_default: bool = False) -> BaseBackend:
 
         return backends[0]
 
-    def get_backend(self):
+    def get_backend(self) -> BaseBackend:
         """Get the current Ibis backend of the expression.
 
         Returns

ibis/expr/types/generic.py

@@ -1561,7 +1561,7 @@ def _bind_to_parent_table(self, value) -> Value | None:
             return literal(value)
         return value
 
-    def __deferred_repr__(self):
+    def __deferred_repr__(self) -> str:
         return f"<column[{self.type()}]>"
 
     def approx_nunique(self, where: ir.BooleanValue | None = None) -> ir.IntegerScalar:

ibis/expr/types/relations.py

@@ -7,7 +7,7 @@
 from collections import deque
 from collections.abc import Callable, Iterable, Iterator, Mapping, Sequence
 from keyword import iskeyword
-from typing import TYPE_CHECKING, Any, Literal
+from typing import TYPE_CHECKING, Any, Literal, NoReturn, overload
 
 import toolz
 from public import public
@@ -286,7 +286,7 @@ def bind(self, *args: Any, **kwargs: Any) -> tuple[Value, ...]:
             result.append(value)
         return tuple(result)
 
-    def as_scalar(self) -> ir.ScalarExpr:
+    def as_scalar(self) -> ir.Scalar:
         """Inform ibis that the table expression should be treated as a scalar.
 
         Note that the table must have exactly one column and one row for this to
@@ -560,6 +560,12 @@ def preview(
             console_width=console_width,
         )
 
+    @overload
+    def __getitem__(self, what: str | int) -> ir.Column: ...
+
+    @overload
+    def __getitem__(self, what: slice | Sequence[str | int]) -> Table: ...
+
     def __getitem__(self, what: str | int | slice | Sequence[str | int]):
         """Select one or more columns or rows from a table expression.
 
@@ -697,7 +703,7 @@ def __getitem__(self, what: str | int | slice | Sequence[str | int]):
         else:
             return self.select(values)
 
-    def __len__(self):
+    def __len__(self) -> NoReturn:
         raise com.ExpressionError("Use .count() instead")
 
     def __getattr__(self, key: str) -> ir.Column:
@@ -4779,13 +4785,13 @@ def unnest(
 
 @public
 class CachedTable(Table):
-    def __exit__(self, *_):
+    def __exit__(self, *_) -> None:
         self.release()
 
-    def __enter__(self):
+    def __enter__(self) -> CachedTable:
         return self
 
-    def release(self):
+    def release(self) -> None:
         """Release the underlying expression from the cache."""
         current_backend = self._find_backend(use_default=True)
         return current_backend._finalize_cached_table(self.op().name)