ARROW-11040: [Rust] Simplified builders

rust/arrow/src/array/array_binary.rs

@@ -25,8 +25,7 @@ use std::{
 
 use super::{
     array::print_long_array, raw_pointer::RawPtrBox, Array, ArrayData, ArrayDataRef,
-    FixedSizeListArray, GenericBinaryIter, GenericListArray, LargeListArray, ListArray,
-    OffsetSizeTrait,
+    FixedSizeListArray, GenericBinaryIter, GenericListArray, OffsetSizeTrait,
 };
 use crate::util::bit_util;
 use crate::{buffer::Buffer, datatypes::ToByteSlice};
@@ -105,7 +104,7 @@ impl<OffsetSize: BinaryOffsetSizeTrait> GenericBinaryArray<OffsetSize> {
         let mut length_so_far: OffsetSize = OffsetSize::zero();
         offsets.push(length_so_far);
         for s in &v {
-            length_so_far = length_so_far + OffsetSize::from_usize(s.len()).unwrap();
+            length_so_far += OffsetSize::from_usize(s.len()).unwrap();
             offsets.push(length_so_far);
             values.extend_from_slice(s);
         }
@@ -236,8 +235,7 @@ where
                 if let Some(s) = s {
                     let s = s.as_ref();
                     bit_util::set_bit(null_slice, i);
-                    length_so_far =
-                        length_so_far + OffsetSize::from_usize(s.len()).unwrap();
+                    length_so_far += OffsetSize::from_usize(s.len()).unwrap();
                     values.extend_from_slice(s);
                 }
                 // always add an element in offsets
@@ -294,15 +292,9 @@ impl From<Vec<Option<&[u8]>>> for LargeBinaryArray {
     }
 }
 
-impl From<ListArray> for BinaryArray {
-    fn from(v: ListArray) -> Self {
-        BinaryArray::from_list(v)
-    }
-}
-
-impl From<LargeListArray> for LargeBinaryArray {
-    fn from(v: LargeListArray) -> Self {
-        LargeBinaryArray::from_list(v)
+impl<T: BinaryOffsetSizeTrait> From<GenericListArray<T>> for GenericBinaryArray<T> {
+    fn from(v: GenericListArray<T>) -> Self {
+        GenericBinaryArray::<T>::from_list(v)
     }
 }
 
@@ -633,7 +625,10 @@ impl Array for DecimalArray {
 
 #[cfg(test)]
 mod tests {
-    use crate::datatypes::Field;
+    use crate::{
+        array::{LargeListArray, ListArray},
+        datatypes::Field,
+    };
 
     use super::*;
 

rust/arrow/src/array/array_list.rs

@@ -30,7 +30,7 @@ use crate::datatypes::ArrowNativeType;
 use crate::datatypes::DataType;
 
 /// trait declaring an offset size, relevant for i32 vs i64 array types.
-pub trait OffsetSizeTrait: ArrowNativeType + Num + Ord {
+pub trait OffsetSizeTrait: ArrowNativeType + Num + Ord + std::ops::AddAssign {
     fn prefix() -> &'static str;
 
     fn to_isize(&self) -> isize;

rust/arrow/src/array/array_string.rs

@@ -22,7 +22,7 @@ use std::{any::Any, iter::FromIterator};
 
 use super::{
     array::print_long_array, raw_pointer::RawPtrBox, Array, ArrayData, ArrayDataRef,
-    GenericListArray, GenericStringIter, LargeListArray, ListArray, OffsetSizeTrait,
+    GenericListArray, GenericStringIter, OffsetSizeTrait,
 };
 use crate::util::bit_util;
 use crate::{buffer::Buffer, datatypes::ToByteSlice};
@@ -128,7 +128,7 @@ impl<OffsetSize: StringOffsetSizeTrait> GenericStringArray<OffsetSize> {
         let mut length_so_far = OffsetSize::zero();
         offsets.push(length_so_far);
         for s in &v {
-            length_so_far = length_so_far + OffsetSize::from_usize(s.len()).unwrap();
+            length_so_far += OffsetSize::from_usize(s.len()).unwrap();
             offsets.push(length_so_far);
             values.extend_from_slice(s.as_bytes());
         }
@@ -168,7 +168,7 @@ where
                 let null_slice = null_buf.as_slice_mut();
                 bit_util::set_bit(null_slice, i);
 
-                length_so_far = length_so_far + OffsetSize::from_usize(s.len()).unwrap();
+                length_so_far += OffsetSize::from_usize(s.len()).unwrap();
                 offsets.push(length_so_far);
                 values.extend_from_slice(s.as_bytes());
             } else {
@@ -269,15 +269,9 @@ pub type StringArray = GenericStringArray<i32>;
 /// whose maximum length (in bytes) is represented by a i64.
 pub type LargeStringArray = GenericStringArray<i64>;
 
-impl From<ListArray> for StringArray {
-    fn from(v: ListArray) -> Self {
-        StringArray::from_list(v)
-    }
-}
-
-impl From<LargeListArray> for LargeStringArray {
-    fn from(v: LargeListArray) -> Self {
-        LargeStringArray::from_list(v)
+impl<T: StringOffsetSizeTrait> From<GenericListArray<T>> for GenericStringArray<T> {
+    fn from(v: GenericListArray<T>) -> Self {
+        GenericStringArray::<T>::from_list(v)
     }
 }