feat(pyarrow): support conversion to pyarrow map and struct types

ibis/backends/pyarrow/datatypes.py

@@ -30,28 +30,36 @@
 
 
 @functools.singledispatch
-def to_pyarrow_type(dtype):
+def to_pyarrow_type(dtype: dt.DataType):
     return _to_pyarrow_types[dtype.__class__]
 
 
 @to_pyarrow_type.register(dt.Array)
-def from_ibis_array(dtype):
-    return pa.list_(to_pyarrow_type(dtype.value_type))
-
-
 @to_pyarrow_type.register(dt.Set)
-def from_ibis_set(dtype):
+def from_ibis_collection(dtype: dt.Array | dt.Set):
     return pa.list_(to_pyarrow_type(dtype.value_type))
 
 
-@to_pyarrow_type.register(dt.Interval)
-def from_ibis_interval(dtype):
+@to_pyarrow_type.register
+def from_ibis_interval(dtype: dt.Interval):
     try:
         return pa.duration(dtype.unit)
     except ValueError:
         raise com.IbisTypeError(f"Unsupported interval unit: {dtype.unit}")
 
 
+@to_pyarrow_type.register
+def from_ibis_struct(dtype: dt.Struct):
+    return pa.struct(
+        pa.field(name, to_pyarrow_type(typ)) for name, typ in dtype.pairs.items()
+    )
+
+
+@to_pyarrow_type.register
+def from_ibis_map(dtype: dt.Map):
+    return pa.map_(to_pyarrow_type(dtype.key_type), to_pyarrow_type(dtype.value_type))
+
+
 _to_ibis_dtypes = {
     pa.int8(): dt.Int8,
     pa.int16(): dt.Int16,