rustdoc: properly indent fn signatures in traits

Author: QuietMisdreavus

src/librustdoc/html/format.rs

@@ -41,8 +41,6 @@ pub struct UnsafetySpace(pub hir::Unsafety);
 /// with a space after it.
 #[derive(Copy, Clone)]
 pub struct ConstnessSpace(pub hir::Constness);
-/// Wrapper struct for properly emitting a method declaration.
-pub struct Method<'a>(pub &'a clean::FnDecl, pub usize);
 /// Similar to VisSpace, but used for mutability
 #[derive(Copy, Clone)]
 pub struct MutableSpace(pub clean::Mutability);
@@ -55,10 +53,23 @@ pub struct TyParamBounds<'a>(pub &'a [clean::TyParamBound]);
 pub struct CommaSep<'a, T: 'a>(pub &'a [T]);
 pub struct AbiSpace(pub Abi);
 
+/// Wrapper struct for properly emitting a method declaration.
+pub struct Method<'a> {
+    /// The declaration to emit.
+    pub decl: &'a clean::FnDecl,
+    /// The length of the function's "name", used to determine line-wrapping.
+    pub name_len: usize,
+    /// The number of spaces to indent each successive line with, if line-wrapping is necessary.
+    pub indent: usize,
+}
+
 /// Wrapper struct for emitting a where clause from Generics.
 pub struct WhereClause<'a>{
+    /// The Generics from which to emit a where clause.
     pub gens: &'a clean::Generics,
+    /// The number of spaces to indent each line with.
     pub indent: usize,
+    /// Whether the where clause needs to add a comma and newline after the last bound.
     pub end_newline: bool,
 }
 
@@ -936,8 +947,7 @@ impl fmt::Display for clean::FnDecl {
 
 impl<'a> fmt::Display for Method<'a> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        let decl = self.0;
-        let indent = self.1;
+        let &Method { decl, name_len, indent } = self;
         let amp = if f.alternate() { "&" } else { "&amp;" };
         let mut args = String::new();
         let mut args_plain = String::new();
@@ -1004,15 +1014,19 @@ impl<'a> fmt::Display for Method<'a> {
             format!("{}", decl.output)
         };
 
-        let pad = repeat(" ").take(indent).collect::<String>();
+        let pad = repeat(" ").take(name_len).collect::<String>();
         let plain = format!("{pad}({args}){arrow}",
                         pad = pad,
                         args = args_plain,
                         arrow = arrow_plain);
 
         let output = if plain.len() > 80 {
-            let pad = "<br>&nbsp;&nbsp;&nbsp;&nbsp;";
-            format!("({args}<br>){arrow}", args = args.replace("<br>", pad), arrow = arrow)
+            let full_pad = format!("<br>{}", repeat("&nbsp;").take(indent + 4).collect::<String>());
+            let close_pad = format!("<br>{}", repeat("&nbsp;").take(indent).collect::<String>());
+            format!("({args}{close}){arrow}",
+                    args = args.replace("<br>", &full_pad),
+                    close = close_pad,
+                    arrow = arrow)
         } else {
             format!("({args}){arrow}", args = args.replace("<br>", ""), arrow = arrow)
         };

src/librustdoc/html/render.rs

@@ -1995,13 +1995,13 @@ fn item_function(w: &mut fmt::Formatter, cx: &Context, it: &clean::Item,
         UnstableFeatures::Allow => f.constness,
         _ => hir::Constness::NotConst
     };
-    let indent = format!("{}{}{}{:#}fn {}{:#}",
-                         VisSpace(&it.visibility),
-                         ConstnessSpace(vis_constness),
-                         UnsafetySpace(f.unsafety),
-                         AbiSpace(f.abi),
-                         it.name.as_ref().unwrap(),
-                         f.generics).len();
+    let name_len = format!("{}{}{}{:#}fn {}{:#}",
+                           VisSpace(&it.visibility),
+                           ConstnessSpace(vis_constness),
+                           UnsafetySpace(f.unsafety),
+                           AbiSpace(f.abi),
+                           it.name.as_ref().unwrap(),
+                           f.generics).len();
     write!(w, "<pre class='rust fn'>")?;
     render_attributes(w, it)?;
     write!(w, "{vis}{constness}{unsafety}{abi}fn \
@@ -2013,7 +2013,11 @@ fn item_function(w: &mut fmt::Formatter, cx: &Context, it: &clean::Item,
            name = it.name.as_ref().unwrap(),
            generics = f.generics,
            where_clause = WhereClause { gens: &f.generics, indent: 0, end_newline: true },
-           decl = Method(&f.decl, indent))?;
+           decl = Method {
+               decl: &f.decl,
+               name_len: name_len,
+               indent: 0,
+           })?;
     document(w, cx, it)
 }
 
@@ -2326,21 +2330,17 @@ fn render_assoc_item(w: &mut fmt::Formatter,
             UnstableFeatures::Allow => constness,
             _ => hir::Constness::NotConst
         };
-        let prefix = format!("{}{}{:#}fn {}{:#}",
-                             ConstnessSpace(vis_constness),
-                             UnsafetySpace(unsafety),
-                             AbiSpace(abi),
-                             name,
-                             *g);
-        let mut indent = prefix.len();
-        let (where_indent, end_newline) = if parent == ItemType::Trait {
-            indent += 4;
+        let mut head_len = format!("{}{}{:#}fn {}{:#}",
+                                   ConstnessSpace(vis_constness),
+                                   UnsafetySpace(unsafety),
+                                   AbiSpace(abi),
+                                   name,
+                                   *g).len();
+        let (indent, end_newline) = if parent == ItemType::Trait {
+            head_len += 4;
             (4, false)
-        } else if parent == ItemType::Impl {
-            (0, true)
         } else {
-            let prefix = prefix + &format!("{:#}", Method(d, indent));
-            (prefix.lines().last().unwrap().len() + 1, true)
+            (0, true)
         };
         write!(w, "{}{}{}fn <a href='{href}' class='fnname'>{name}</a>\
                    {generics}{decl}{where_clause}",
@@ -2350,10 +2350,14 @@ fn render_assoc_item(w: &mut fmt::Formatter,
                href = href,
                name = name,
                generics = *g,
-               decl = Method(d, indent),
+               decl = Method {
+                   decl: d,
+                   name_len: head_len,
+                   indent: indent,
+               },
                where_clause = WhereClause {
                    gens: g,
-                   indent: where_indent,
+                   indent: indent,
                    end_newline: end_newline,
                })
     }