syntax: parse const fn for free functions and inherent methods.

src/librustdoc/html/format.rs

@@ -35,6 +35,10 @@ pub struct VisSpace(pub Option<ast::Visibility>);
 /// space after it.
 #[derive(Copy, Clone)]
 pub struct UnsafetySpace(pub ast::Unsafety);
+/// Similarly to VisSpace, this structure is used to render a function constness
+/// with a space after it.
+#[derive(Copy)]
+pub struct ConstnessSpace(pub ast::Constness);
 /// Wrapper struct for properly emitting a method declaration.
 pub struct Method<'a>(pub &'a clean::SelfTy, pub &'a clean::FnDecl);
 /// Similar to VisSpace, but used for mutability
@@ -63,6 +67,12 @@ impl UnsafetySpace {
     }
 }
 
+impl ConstnessSpace {
+    pub fn get(&self) -> ast::Constness {
+        let ConstnessSpace(v) = *self; v
+    }
+}
+
 impl<'a, T: fmt::Display> fmt::Display for CommaSep<'a, T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         for (i, item) in self.0.iter().enumerate() {
@@ -607,6 +617,15 @@ impl fmt::Display for UnsafetySpace {
     }
 }
 
+impl fmt::Display for ConstnessSpace {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self.get() {
+            ast::Constness::Const => write!(f, "const "),
+            ast::Constness::NotConst => Ok(())
+        }
+    }
+}
+
 impl fmt::Display for clean::Import {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match *self {