Use Self everywhere (#3787)

This turns on the clippy lint
[`clippy::use_self`](https://rust-lang.github.io/rust-clippy/v0.0.212/index.html#use_self)
and fixes it everywhere.

crates/epaint/src/shape.rs

@@ -66,9 +66,9 @@ fn shape_impl_send_sync() {
     assert_send_sync::<Shape>();
 }
 
-impl From<Vec<Shape>> for Shape {
+impl From<Vec<Self>> for Shape {
     #[inline(always)]
-    fn from(shapes: Vec<Shape>) -> Self {
+    fn from(shapes: Vec<Self>) -> Self {
         Self::Vec(shapes)
     }
 }
@@ -95,7 +95,7 @@ impl Shape {
     /// A horizontal line.
     pub fn hline(x: impl Into<Rangef>, y: f32, stroke: impl Into<Stroke>) -> Self {
         let x = x.into();
-        Shape::LineSegment {
+        Self::LineSegment {
             points: [pos2(x.min, y), pos2(x.max, y)],
             stroke: stroke.into(),
         }
@@ -104,7 +104,7 @@ impl Shape {
     /// A vertical line.
     pub fn vline(x: f32, y: impl Into<Rangef>, stroke: impl Into<Stroke>) -> Self {
         let y = y.into();
-        Shape::LineSegment {
+        Self::LineSegment {
             points: [pos2(x, y.min), pos2(x, y.max)],
             stroke: stroke.into(),
         }
@@ -182,7 +182,7 @@ impl Shape {
         stroke: impl Into<Stroke>,
         dash_length: f32,
         gap_length: f32,
-        shapes: &mut Vec<Shape>,
+        shapes: &mut Vec<Self>,
     ) {
         dashes_from_line(
             points,
@@ -202,7 +202,7 @@ impl Shape {
         dash_lengths: &[f32],
         gap_lengths: &[f32],
         dash_offset: f32,
-        shapes: &mut Vec<Shape>,
+        shapes: &mut Vec<Self>,
     ) {
         dashes_from_line(
             points,
@@ -309,7 +309,7 @@ impl Shape {
     pub fn image(texture_id: TextureId, rect: Rect, uv: Rect, tint: Color32) -> Self {
         let mut mesh = Mesh::with_texture(texture_id);
         mesh.add_rect_with_uv(rect, uv, tint);
-        Shape::mesh(mesh)
+        Self::mesh(mesh)
     }
 
     /// The visual bounding rectangle (includes stroke widths)
@@ -346,9 +346,9 @@ impl Shape {
 impl Shape {
     #[inline(always)]
     pub fn texture_id(&self) -> super::TextureId {
-        if let Shape::Mesh(mesh) = self {
+        if let Self::Mesh(mesh) = self {
             mesh.texture_id
-        } else if let Shape::Rect(rect_shape) = self {
+        } else if let Self::Rect(rect_shape) = self {
             rect_shape.fill_texture_id
         } else {
             super::TextureId::default()
@@ -358,45 +358,45 @@ impl Shape {
     /// Move the shape by this many points, in-place.
     pub fn translate(&mut self, delta: Vec2) {
         match self {
-            Shape::Noop => {}
-            Shape::Vec(shapes) => {
+            Self::Noop => {}
+            Self::Vec(shapes) => {
                 for shape in shapes {
                     shape.translate(delta);
                 }
             }
-            Shape::Circle(circle_shape) => {
+            Self::Circle(circle_shape) => {
                 circle_shape.center += delta;
             }
-            Shape::LineSegment { points, .. } => {
+            Self::LineSegment { points, .. } => {
                 for p in points {
                     *p += delta;
                 }
             }
-            Shape::Path(path_shape) => {
+            Self::Path(path_shape) => {
                 for p in &mut path_shape.points {
                     *p += delta;
                 }
             }
-            Shape::Rect(rect_shape) => {
+            Self::Rect(rect_shape) => {
                 rect_shape.rect = rect_shape.rect.translate(delta);
             }
-            Shape::Text(text_shape) => {
+            Self::Text(text_shape) => {
                 text_shape.pos += delta;
             }
-            Shape::Mesh(mesh) => {
+            Self::Mesh(mesh) => {
                 mesh.translate(delta);
             }
-            Shape::QuadraticBezier(bezier_shape) => {
+            Self::QuadraticBezier(bezier_shape) => {
                 bezier_shape.points[0] += delta;
                 bezier_shape.points[1] += delta;
                 bezier_shape.points[2] += delta;
             }
-            Shape::CubicBezier(cubic_curve) => {
+            Self::CubicBezier(cubic_curve) => {
                 for p in &mut cubic_curve.points {
                     *p += delta;
                 }
             }
-            Shape::Callback(shape) => {
+            Self::Callback(shape) => {
                 shape.rect = shape.rect.translate(delta);
             }
         }
@@ -484,7 +484,7 @@ impl PathShape {
     /// Use [`Shape::line_segment`] instead if your line only connects two points.
     #[inline]
     pub fn line(points: Vec<Pos2>, stroke: impl Into<Stroke>) -> Self {
-        PathShape {
+        Self {
             points,
             closed: false,
             fill: Default::default(),
@@ -495,7 +495,7 @@ impl PathShape {
     /// A line that closes back to the start point again.
     #[inline]
     pub fn closed_line(points: Vec<Pos2>, stroke: impl Into<Stroke>) -> Self {
-        PathShape {
+        Self {
             points,
             closed: true,
             fill: Default::default(),
@@ -512,7 +512,7 @@ impl PathShape {
         fill: impl Into<Color32>,
         stroke: impl Into<Stroke>,
     ) -> Self {
-        PathShape {
+        Self {
             points,
             closed: true,
             fill: fill.into(),