Clean up code by using Iterator::collect() when constructing instance tables (#2918)

* instances: `Iterator::collect()` instances

* instances: adjust nodes to use iterators

* fix warnings on master

* Bump MSRV

* Port the remaining usages

---------

Co-authored-by: Keavon Chambers <keavon@keavon.com>

node-graph/gcore/src/instances.rs

@@ -27,6 +27,24 @@ impl<T> Instances<T> {
 		}
 	}
 
+	pub fn new_instance(instance: Instance<T>) -> Self {
+		Self {
+			instance: vec![instance.instance],
+			transform: vec![instance.transform],
+			alpha_blending: vec![instance.alpha_blending],
+			source_node_id: vec![instance.source_node_id],
+		}
+	}
+
+	pub fn with_capacity(capacity: usize) -> Self {
+		Self {
+			instance: Vec::with_capacity(capacity),
+			transform: Vec::with_capacity(capacity),
+			alpha_blending: Vec::with_capacity(capacity),
+			source_node_id: Vec::with_capacity(capacity),
+		}
+	}
+
 	pub fn push(&mut self, instance: Instance<T>) {
 		self.instance.push(instance.instance);
 		self.transform.push(instance.transform);
@@ -161,6 +179,18 @@ unsafe impl<T: StaticType + 'static> StaticType for Instances<T> {
 	type Static = Instances<T>;
 }
 
+impl<T> FromIterator<Instance<T>> for Instances<T> {
+	fn from_iter<I: IntoIterator<Item = Instance<T>>>(iter: I) -> Self {
+		let iter = iter.into_iter();
+		let (lower, _) = iter.size_hint();
+		let mut instances = Self::with_capacity(lower);
+		for instance in iter {
+			instances.push(instance);
+		}
+		instances
+	}
+}
+
 fn one_daffine2_default() -> Vec<DAffine2> {
 	vec![DAffine2::IDENTITY]
 }

node-graph/gcore/src/vector/algorithms/poisson_disk.rs

@@ -182,7 +182,7 @@ where
 	A::Item: Clone,
 	B::Item: Clone,
 {
-	a.flat_map(move |i| (b.clone().map(move |j| (i.clone(), j))))
+	a.flat_map(move |i| b.clone().map(move |j| (i.clone(), j)))
 }
 
 /// A square (represented by its top left corner position and width/height of `square_size`) that is currently a candidate for targetting by the dart throwing process.

node-graph/gcore/src/vector/vector_data.rs

@@ -337,7 +337,7 @@ impl VectorData {
 	/// Returns the number of linear segments connected to the given point.
 	pub fn connected_linear_segments(&self, point_id: PointId) -> usize {
 		self.segment_bezier_iter()
-			.filter(|(_, bez, start, end)| ((*start == point_id || *end == point_id) && matches!(bez.handles, BezierHandles::Linear)))
+			.filter(|(_, bez, start, end)| (*start == point_id || *end == point_id) && matches!(bez.handles, BezierHandles::Linear))
 			.count()
 	}