Use #[must_use] more.

src/blend.rs

@@ -102,6 +102,7 @@ pub struct BlendMode {
 impl BlendMode {
     /// Creates a new blend mode from color mixing and layer composition
     /// functions.
+    #[must_use]
     pub fn new(mix: Mix, compose: Compose) -> Self {
         Self { mix, compose }
     }

src/blob.rs

@@ -73,31 +73,37 @@ impl<T> Blob<T> {
     }
 
     /// Consumes self and returns the inner components of the blob.
+    #[must_use]
     pub fn into_raw_parts(self) -> (Arc<dyn AsRef<[T]> + Send + Sync>, u64) {
         (self.data, self.id)
     }
 
     /// Returns the length of the data.
+    #[must_use]
     pub fn len(&self) -> usize {
         self.data().len()
     }
 
     /// Returns true if the blob is empty.
+    #[must_use]
     pub fn is_empty(&self) -> bool {
         self.len() == 0
     }
 
     /// Returns a reference to the underlying data.
+    #[must_use]
     pub fn data(&self) -> &[T] {
         self.data.as_ref().as_ref()
     }
 
     /// Returns the unique identifier associated with the data.
+    #[must_use]
     pub fn id(&self) -> u64 {
         self.id
     }
 
     /// Downgrades the shared blob to a weak reference.
+    #[must_use]
     pub fn downgrade(&self) -> WeakBlob<T> {
         WeakBlob {
             data: Arc::downgrade(&self.data),
@@ -123,12 +129,14 @@ impl<T> Clone for WeakBlob<T> {
 
 impl<T> WeakBlob<T> {
     /// Returns the unique identifier associated with the data.
+    #[must_use]
     pub fn id(&self) -> u64 {
         self.id
     }
 
     /// Upgrades the weak reference. Returns `None` if the inner value has been
     /// dropped.
+    #[must_use]
     pub fn upgrade(&self) -> Option<Blob<T>> {
         Some(Blob {
             data: self.data.upgrade()?,

src/brush.rs

@@ -45,6 +45,7 @@ pub enum BrushRef<'a> {
 
 impl<'a> BrushRef<'a> {
     /// Converts the reference to an owned brush.
+    #[must_use]
     pub fn to_owned(&self) -> Brush {
         match self {
             Self::Solid(color) => Brush::Solid(*color),

src/color.rs

@@ -19,11 +19,13 @@ pub struct Color {
 
 impl Color {
     /// Creates a new RGB color with 255 alpha.
+    #[must_use]
     pub const fn rgb8(r: u8, g: u8, b: u8) -> Self {
         Self { r, g, b, a: 255 }
     }
 
     /// Creates a new RGBA color.
+    #[must_use]
     pub const fn rgba8(r: u8, g: u8, b: u8, a: u8) -> Self {
         Self { r, g, b, a }
     }
@@ -32,6 +34,7 @@ impl Color {
     ///
     /// The interpretation is the same as rgb8, and no greater precision is
     /// (currently) assumed.
+    #[must_use]
     pub fn rgb(r: f64, g: f64, b: f64) -> Self {
         Self::rgba(r, g, b, 1.0)
     }
@@ -40,6 +43,7 @@ impl Color {
     ///
     /// The interpretation is the same as rgba32, and no greater precision is
     /// (currently) assumed.
+    #[must_use]
     pub fn rgba(r: f64, g: f64, b: f64, a: f64) -> Self {
         let r = (r.clamp(0.0, 1.0) * 255.0).round() as u8;
         let g = (g.clamp(0.0, 1.0) * 255.0).round() as u8;
@@ -65,6 +69,7 @@ impl Color {
     /// Currently out-of-gamut values are clipped to the nearest sRGB color,
     /// which is perhaps not ideal (the clipping might change the hue). See
     /// <https://github.com/d3/d3-color/issues/33> for discussion.
+    #[must_use]
     pub fn hlc(h: f64, l: f64, c: f64) -> Self {
         Self::hlca(h, l, c, 1.0)
     }
@@ -75,6 +80,7 @@ impl Color {
     #[allow(non_snake_case)]
     #[allow(clippy::many_single_char_names)]
     #[allow(clippy::unreadable_literal)]
+    #[must_use]
     pub fn hlca(h: f64, l: f64, c: f64, a: f64) -> Color {
         let alpha = a;
         // The reverse transformation from Lab to XYZ, see
@@ -125,19 +131,22 @@ impl Color {
     ///
     /// Currently accepts CSS style hexadecimal colors of the forms #RGB, #RGBA,
     /// #RRGGBB, #RRGGBBAA or the name of an SVG color such as "aliceblue".
+    #[must_use]
     pub fn parse(s: &str) -> Option<Self> {
         parse_color(s)
     }
 
     /// Returns the color with the alpha component multiplied by the specified
     /// factor.
+    #[must_use]
     pub fn with_alpha_factor(self, alpha: f32) -> Self {
         let mut result = self;
         result.a = ((result.a as f32) * alpha).round() as u8;
         result
     }
 
     /// Returns the color as a packed premultiplied value.
+    #[must_use]
     pub fn to_premul_u32(self) -> u32 {
         let a = self.a as f64 * (1.0 / 255.0);
         let r = (self.r as f64 * a).round() as u32;

src/font.rs

@@ -14,6 +14,7 @@ pub struct Font {
 
 impl Font {
     /// Creates a new font with the given data and collection index.
+    #[must_use]
     pub fn new(data: Blob<u8>, index: u32) -> Self {
         Self { data, index }
     }

src/gradient.rs

@@ -39,6 +39,7 @@ impl cmp::Eq for ColorStop {}
 impl ColorStop {
     /// Returns the color stop with the alpha component multiplied by the specified
     /// factor.
+    #[must_use]
     pub fn with_alpha_factor(self, alpha: f32) -> Self {
         Self {
             offset: self.offset,
@@ -178,12 +179,14 @@ impl Gradient {
     }
 
     /// Builder method for setting the gradient extend mode.
+    #[must_use]
     pub fn with_extend(mut self, mode: Extend) -> Self {
         self.extend = mode;
         self
     }
 
     /// Builder method for setting the color stop collection.
+    #[must_use]
     pub fn with_stops(mut self, stops: impl ColorStopsSource) -> Self {
         self.stops.clear();
         stops.collect_stops(&mut self.stops);

src/image.rs

@@ -15,6 +15,7 @@ impl Format {
     /// of the given dimensions.
     ///
     /// A result of `None` indicates an overflow in the size calculation.
+    #[must_use]
     pub fn size_in_bytes(self, width: u32, height: u32) -> Option<usize> {
         match self {
             Self::Rgba8 => 4usize
@@ -41,6 +42,7 @@ pub struct Image {
 
 impl Image {
     /// Creates a new image with the given data, [format](Format) and dimensions.
+    #[must_use]
     pub fn new(data: Blob<u8>, format: Format, width: u32, height: u32) -> Self {
         Self {
             data,
@@ -52,6 +54,7 @@ impl Image {
     }
 
     /// Builder method for setting the image [extend mode](Extend).
+    #[must_use]
     pub fn with_extend(mut self, mode: Extend) -> Self {
         self.extend = mode;
         self

src/style.rs

@@ -74,6 +74,7 @@ impl Default for Stroke {
 
 impl Stroke {
     /// Creates a new stroke with the specified width.
+    #[must_use]
     pub fn new(width: f32) -> Self {
         Self {
             width,
@@ -82,37 +83,43 @@ impl Stroke {
     }
 
     /// Builder method for setting the join style.
+    #[must_use]
     pub fn with_join(mut self, join: Join) -> Self {
         self.join = join;
         self
     }
 
     /// Builder method for setting the limit for miter joins.
+    #[must_use]
     pub fn with_miter_limit(mut self, limit: f32) -> Self {
         self.miter_limit = limit;
         self
     }
 
     /// Builder method for setting the cap style for the start of the stroke.
+    #[must_use]
     pub fn with_start_cap(mut self, cap: Cap) -> Self {
         self.start_cap = cap;
         self
     }
 
     /// Builder method for setting the cap style for the end of the stroke.
+    #[must_use]
     pub fn with_end_cap(mut self, cap: Cap) -> Self {
         self.end_cap = cap;
         self
     }
 
     /// Builder method for setting the cap style.
+    #[must_use]
     pub fn with_caps(mut self, cap: Cap) -> Self {
         self.start_cap = cap;
         self.end_cap = cap;
         self
     }
 
     /// Builder method for setting the dashing parameters.
+    #[must_use]
     pub fn with_dashes<P>(mut self, offset: f32, pattern: P) -> Self
     where
         P: IntoIterator,
@@ -127,6 +134,7 @@ impl Stroke {
 
     /// Builder method for setting whether or not the stroke should be affected
     /// by the scale of any applied transform.
+    #[must_use]
     pub fn with_scale(mut self, yes: bool) -> Self {
         self.scale = yes;
         self
@@ -173,6 +181,7 @@ pub enum StyleRef<'a> {
 
 impl<'a> StyleRef<'a> {
     /// Converts the reference to an owned draw.
+    #[must_use]
     pub fn to_owned(&self) -> Style {
         match self {
             Self::Fill(fill) => Style::Fill(*fill),