Add #[must_use] annotation to all iterator structs

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/-/merge_requests/1690>

gstreamer-analytics/src/classification.rs

@@ -133,6 +133,7 @@ impl AnalyticsMtdRef<'_, AnalyticsClassificationMtd> {
     }
 }
 
+#[must_use = "iterators are lazy and do nothing unless consumed"]
 pub struct AnalyticsClassificationIterator<'a> {
     mtd: &'a AnalyticsMtdRef<'a, AnalyticsClassificationMtd>,
     index: usize,

gstreamer-analytics/src/relation_meta.rs

@@ -468,6 +468,7 @@ impl<'a, T: AnalyticsMtd> AsRef<AnalyticsMtdRef<'a, T>> for AnalyticsMtdRefMut<'
 
 macro_rules! define_mtd_iter {
     ($name:ident, $metaref:ty, $itemref:ty, $copy_meta:expr) => {
+        #[must_use = "iterators are lazy and do nothing unless consumed"]
         pub struct $name<'a, T: AnalyticsMtd> {
             meta: $metaref,
             state: glib::ffi::gpointer,

gstreamer-audio/src/audio_format.rs

@@ -225,6 +225,7 @@ pub const AUDIO_FORMAT_F32: crate::AudioFormat = crate::AudioFormat::F32le;
 #[cfg(target_endian = "little")]
 pub const AUDIO_FORMAT_F64: crate::AudioFormat = crate::AudioFormat::F64le;
 
+#[must_use = "iterators are lazy and do nothing unless consumed"]
 pub struct AudioFormatIterator {
     idx: usize,
     len: usize,

gstreamer-pbutils/src/discoverer_stream_info.rs

@@ -3,6 +3,7 @@ use std::fmt;
 
 use crate::{prelude::*, DiscovererStreamInfo};
 
+#[must_use = "iterators are lazy and do nothing unless consumed"]
 #[derive(Debug)]
 pub struct Iter {
     stream_info: Option<DiscovererStreamInfo>,

gstreamer-sdp/src/sdp_media.rs

@@ -651,6 +651,7 @@ impl ToOwned for SDPMediaRef {
 
 macro_rules! define_iter(
     ($name:ident, $typ:ty, $get_item:expr, $get_len:expr) => {
+    #[must_use = "iterators are lazy and do nothing unless consumed"]
     #[derive(Debug)]
     pub struct $name<'a> {
         media: &'a SDPMediaRef,

gstreamer-sdp/src/sdp_message.rs

@@ -1007,6 +1007,7 @@ impl glib::value::ToValueOptional for SDPMessageRef {
 
 macro_rules! define_iter(
     ($name:ident, $typ:ty, $get_item:expr, $get_len:expr) => {
+    #[must_use = "iterators are lazy and do nothing unless consumed"]
     #[derive(Debug)]
     pub struct $name<'a> {
         message: &'a SDPMessageRef,
@@ -1103,6 +1104,7 @@ macro_rules! define_iter(
 
 macro_rules! define_iter_mut(
     ($name:ident, $typ:ty, $get_item:expr, $get_len:expr) => {
+    #[must_use = "iterators are lazy and do nothing unless consumed"]
     #[derive(Debug)]
     pub struct $name<'a> {
         message: &'a mut SDPMessageRef,

gstreamer-video/src/video_format.rs

@@ -336,6 +336,7 @@ impl Ord for crate::VideoFormat {
     }
 }
 
+#[must_use = "iterators are lazy and do nothing unless consumed"]
 pub struct VideoFormatIterator {
     idx: usize,
     len: usize,

gstreamer-video/src/video_meta.rs

@@ -415,6 +415,7 @@ impl VideoRegionOfInterestMeta {
     }
 }
 
+#[must_use = "iterators are lazy and do nothing unless consumed"]
 pub struct ParamsIter<'a> {
     _meta: &'a VideoRegionOfInterestMeta,
     list: Option<ptr::NonNull<glib::ffi::GList>>,

gstreamer-video/src/video_overlay_composition.rs

@@ -454,6 +454,7 @@ impl<'a> std::iter::FromIterator<&'a VideoOverlayRectangle> for VideoOverlayComp
     }
 }
 
+#[must_use = "iterators are lazy and do nothing unless consumed"]
 pub struct Iter<'a> {
     composition: &'a VideoOverlayCompositionRef,
     idx: usize,

gstreamer-video/src/video_vbi_parser.rs

@@ -152,6 +152,7 @@ impl<'a> TryFrom<&'a crate::VideoInfo> for VideoVBIParser {
     }
 }
 
+#[must_use = "iterators are lazy and do nothing unless consumed"]
 #[derive(Debug)]
 pub struct AncillaryIter<'a> {
     parser: &'a mut VideoVBIParser,

gstreamer/src/buffer.rs

@@ -873,6 +873,7 @@ impl BufferRef {
 
 macro_rules! define_meta_iter(
     ($name:ident, $typ:ty, $mtyp:ty, $prepare_buffer:expr, $from_ptr:expr) => {
+    #[must_use = "iterators are lazy and do nothing unless consumed"]
     pub struct $name<'a, T: MetaAPI + 'a> {
         buffer: $typ,
         state: glib::ffi::gpointer,
@@ -1331,6 +1332,7 @@ pub struct Dump<'a> {
     end: Bound<usize>,
 }
 
+#[must_use = "iterators are lazy and do nothing unless consumed"]
 struct BufferChunked16Iter<'a> {
     buffer: &'a BufferRef,
     mem_idx: usize,

gstreamer/src/bus.rs

@@ -320,6 +320,7 @@ impl Bus {
     }
 }
 
+#[must_use = "iterators are lazy and do nothing unless consumed"]
 #[derive(Debug)]
 pub struct Iter<'a> {
     bus: &'a Bus,

gstreamer/src/iterator.rs

@@ -694,6 +694,7 @@ impl<T: StaticType> glib::translate::FromGlibPtrFull<*mut ffi::GstIterator> for
     }
 }
 
+#[must_use = "iterators are lazy and do nothing unless consumed"]
 pub struct StdIterator<T> {
     inner: Iterator<T>,
     error: Option<IteratorError>,

gstreamer/src/structure.rs

@@ -1780,6 +1780,7 @@ crate::utils::define_fixed_size_iter!(
     }
 );
 
+#[must_use = "iterators are lazy and do nothing unless consumed"]
 #[derive(Debug)]
 pub struct Iter<'a> {
     iter: FieldIterator<'a>,
@@ -1844,6 +1845,7 @@ impl ExactSizeIterator for Iter<'_> {}
 impl std::iter::FusedIterator for Iter<'_> {}
 
 #[cfg(feature = "v1_26")]
+#[must_use = "iterators are lazy and do nothing unless consumed"]
 #[derive(Debug)]
 pub struct IdIter<'a> {
     iter: FieldIdIterator<'a>,

gstreamer/src/tags.rs

@@ -635,6 +635,7 @@ impl PartialEq for TagListRef {
 
 impl Eq for TagListRef {}
 
+#[must_use = "iterators are lazy and do nothing unless consumed"]
 #[derive(Debug)]
 pub struct TagIter<'a, T: Tag<'a>> {
     taglist: &'a TagListRef,
@@ -743,6 +744,7 @@ where
 {
 }
 
+#[must_use = "iterators are lazy and do nothing unless consumed"]
 #[derive(Debug)]
 pub struct GenericTagIter<'a> {
     taglist: &'a TagListRef,
@@ -837,6 +839,7 @@ impl ExactSizeIterator for GenericTagIter<'_> {}
 
 impl std::iter::FusedIterator for GenericTagIter<'_> {}
 
+#[must_use = "iterators are lazy and do nothing unless consumed"]
 #[derive(Debug)]
 pub struct GenericIter<'a> {
     taglist: &'a TagListRef,
@@ -931,6 +934,7 @@ impl ExactSizeIterator for GenericIter<'_> {}
 
 impl std::iter::FusedIterator for GenericIter<'_> {}
 
+#[must_use = "iterators are lazy and do nothing unless consumed"]
 #[derive(Debug)]
 pub struct Iter<'a> {
     taglist: &'a TagListRef,

gstreamer/src/utils.rs

@@ -81,6 +81,7 @@ where
 
 macro_rules! define_fixed_size_iter(
     ($name:ident, $typ:ty, $ityp:ty, $get_len:expr, $get_item:expr) => {
+        #[must_use = "iterators are lazy and do nothing unless consumed"]
         #[derive(Debug)]
         pub struct $name<'a> {
             pub(crate) collection: $typ,