feat(layout): mark various functions as const (#951)

src/layout.rs

@@ -1,3 +1,5 @@
+#![warn(clippy::missing_const_for_fn)]
+
 mod alignment;
 mod constraint;
 mod corner;

src/layout/position.rs

@@ -38,7 +38,7 @@ pub struct Position {
 
 impl Position {
     /// Create a new position
-    pub fn new(x: u16, y: u16) -> Self {
+    pub const fn new(x: u16, y: u16) -> Self {
         Position { x, y }
     }
 }

src/layout/rect.rs

@@ -245,7 +245,7 @@ impl Rect {
     ///     }
     /// }
     /// ```
-    pub fn rows(self) -> Rows {
+    pub const fn rows(self) -> Rows {
         Rows::new(self)
     }
 
@@ -261,7 +261,7 @@ impl Rect {
     ///     }
     /// }
     /// ```
-    pub fn columns(self) -> Columns {
+    pub const fn columns(self) -> Columns {
         Columns::new(self)
     }
 
@@ -279,7 +279,7 @@ impl Rect {
     ///     }
     /// }
     /// ```
-    pub fn positions(self) -> Positions {
+    pub const fn positions(self) -> Positions {
         Positions::new(self)
     }
 
@@ -292,15 +292,15 @@ impl Rect {
     /// let rect = Rect::new(1, 2, 3, 4);
     /// let position = rect.as_position();
     /// ````
-    pub fn as_position(self) -> Position {
+    pub const fn as_position(self) -> Position {
         Position {
             x: self.x,
             y: self.y,
         }
     }
 
     /// Converts the rect into a size struct.
-    pub fn as_size(self) -> Size {
+    pub const fn as_size(self) -> Size {
         Size {
             width: self.width,
             height: self.height,

src/layout/rect/iter.rs

@@ -11,7 +11,7 @@ pub struct Rows {
 
 impl Rows {
     /// Creates a new `Rows` iterator.
-    pub fn new(rect: Rect) -> Self {
+    pub const fn new(rect: Rect) -> Self {
         Self {
             rect,
             current_row: rect.y,
@@ -45,7 +45,7 @@ pub struct Columns {
 
 impl Columns {
     /// Creates a new `Columns` iterator.
-    pub fn new(rect: Rect) -> Self {
+    pub const fn new(rect: Rect) -> Self {
         Self {
             rect,
             current_column: rect.x,
@@ -81,7 +81,7 @@ pub struct Positions {
 
 impl Positions {
     /// Creates a new `Positions` iterator.
-    pub fn new(rect: Rect) -> Self {
+    pub const fn new(rect: Rect) -> Self {
         Self {
             rect,
             current_position: Position::new(rect.x, rect.y),

src/layout/size.rs

@@ -15,7 +15,7 @@ pub struct Size {
 
 impl Size {
     /// Create a new `Size` struct
-    pub fn new(width: u16, height: u16) -> Self {
+    pub const fn new(width: u16, height: u16) -> Self {
         Size { width, height }
     }
 }

src/widgets/canvas/line.rs

@@ -20,7 +20,7 @@ pub struct Line {
 
 impl Line {
     /// Create a new line from `(x1, y1)` to `(x2, y2)` with the given color
-    pub fn new(x1: f64, y1: f64, x2: f64, y2: f64, color: Color) -> Self {
+    pub const fn new(x1: f64, y1: f64, x2: f64, y2: f64, color: Color) -> Self {
         Self {
             x1,
             y1,