Make KeyEvent::new a const fn (#606)

src/event.rs

@@ -395,7 +395,7 @@ pub struct KeyEvent {
 }
 
 impl KeyEvent {
-    pub fn new(code: KeyCode, modifiers: KeyModifiers) -> KeyEvent {
+    pub const fn new(code: KeyCode, modifiers: KeyModifiers) -> KeyEvent {
         KeyEvent { code, modifiers }
     }
 

src/style/attributes.rs

@@ -85,7 +85,7 @@ impl Attributes {
 
     /// Returns whether the attribute is set.
     #[inline(always)]
-    pub fn has(self, attribute: Attribute) -> bool {
+    pub const fn has(self, attribute: Attribute) -> bool {
         self.0 & attribute.bytes() != 0
     }
 
@@ -97,7 +97,7 @@ impl Attributes {
 
     /// Returns whether there is no attribute set.
     #[inline(always)]
-    pub fn is_empty(self) -> bool {
+    pub const fn is_empty(self) -> bool {
         self.0 == 0
     }
 }