stream: Fix Chunk adapters size hints (#2611)

Author: jefftt

futures-util/src/stream/stream/chunks.rs

@@ -79,7 +79,7 @@ impl<St: Stream> Stream for Chunks<St> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         let chunk_len = if self.items.is_empty() { 0 } else { 1 };
         let (lower, upper) = self.stream.size_hint();
-        let lower = lower.saturating_add(chunk_len);
+        let lower = (lower / self.cap).saturating_add(chunk_len);
         let upper = match upper {
             Some(x) => x.checked_add(chunk_len),
             None => None,

futures-util/src/stream/stream/ready_chunks.rs

@@ -87,7 +87,7 @@ impl<St: Stream> Stream for ReadyChunks<St> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         let chunk_len = if self.items.is_empty() { 0 } else { 1 };
         let (lower, upper) = self.stream.size_hint();
-        let lower = lower.saturating_add(chunk_len);
+        let lower = (lower / self.cap).saturating_add(chunk_len);
         let upper = match upper {
             Some(x) => x.checked_add(chunk_len),
             None => None,

futures-util/src/stream/try_stream/try_chunks.rs

@@ -83,7 +83,7 @@ impl<St: TryStream> Stream for TryChunks<St> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         let chunk_len = if self.items.is_empty() { 0 } else { 1 };
         let (lower, upper) = self.stream.size_hint();
-        let lower = lower.saturating_add(chunk_len);
+        let lower = (lower / self.cap).saturating_add(chunk_len);
         let upper = match upper {
             Some(x) => x.checked_add(chunk_len),
             None => None,