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Transition a few fmt::Display impls to functions 

This introduces a WithFormatter abstraction that permits one-time
fmt::Display on an arbitrary closure, created via `display_fn`. This
allows us to prevent allocation while still using functions instead of
structs, which are a bit unwieldy to thread arguments through as they
can't easily call each other (and are generally a bit opaque).

The eventual goal here is likely to move us off of the formatting
infrastructure entirely in favor of something more structured, but this
is a good step to move us in that direction as it makes, for example,
passing a context describing current state to the formatting impl much
easier.
This commit is contained in:
Mark Rousskov 2019-08-12 14:36:09 -04:00
parent dafdfee33e
commit edfd5556f1
2 changed files with 56 additions and 52 deletions
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102
src/librustdoc/html/format.rs
View File

@ -6,6 +6,7 @@
//! them in the future to instead emit any format desired.
use std::borrow::Cow;
use std::cell::Cell;
use std::fmt;
use rustc::hir::def_id::DefId;
@ -38,8 +39,6 @@ pub struct AsyncSpace(pub hir::IsAsync);
pub struct MutableSpace(pub clean::Mutability);
/// Wrapper struct for emitting type parameter bounds.
pub struct GenericBounds<'a>(pub &'a [clean::GenericBound]);
/// Wrapper struct for emitting a comma-separated list of items
pub struct CommaSep<'a, T>(pub &'a [T]);
pub struct AbiSpace(pub Abi);
pub struct DefaultSpace(pub bool);
@ -68,11 +67,6 @@ pub struct WhereClause<'a>{
pub end_newline: bool,
}
pub struct HRef<'a> {
did: DefId,
text: &'a str,
}
impl<'a> VisSpace<'a> {
pub fn get(self) -> &'a Option<clean::Visibility> {
let VisSpace(v) = self; v
@ -91,14 +85,14 @@ impl ConstnessSpace {
}
}
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() {
fn comma_sep<T: fmt::Display>(items: &[T]) -> impl fmt::Display + '_ {
display_fn(move |f| {
for (i, item) in items.iter().enumerate() {
if i != 0 { write!(f, ", ")?; }
fmt::Display::fmt(item, f)?;
}
Ok(())
}
})
}
impl<'a> fmt::Display for GenericBounds<'a> {
@ -165,9 +159,9 @@ impl fmt::Display for clean::Generics {
return Ok(());
}
if f.alternate() {
write!(f, "<{:#}>", CommaSep(&real_params))
write!(f, "<{:#}>", comma_sep(&real_params))
} else {
write!(f, "&lt;{}&gt;", CommaSep(&real_params))
write!(f, "&lt;{}&gt;", comma_sep(&real_params))
}
}
}
@ -265,9 +259,9 @@ impl fmt::Display for clean::PolyTrait {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
if !self.generic_params.is_empty() {
if f.alternate() {
write!(f, "for<{:#}> ", CommaSep(&self.generic_params))?;
write!(f, "for<{:#}> ", comma_sep(&self.generic_params))?;
} else {
write!(f, "for&lt;{}&gt; ", CommaSep(&self.generic_params))?;
write!(f, "for&lt;{}&gt; ", comma_sep(&self.generic_params))?;
}
}
if f.alternate() {
@ -452,16 +446,15 @@ fn resolved_path(w: &mut fmt::Formatter<'_>, did: DefId, path: &clean::Path,
write!(w, "{}{:#}", &last.name, last.args)?;
} else {
let path = if use_absolute {
match href(did) {
Some((_, _, fqp)) => {
format!("{}::{}",
fqp[..fqp.len() - 1].join("::"),
HRef::new(did, fqp.last().unwrap()))
}
None => HRef::new(did, &last.name).to_string(),
if let Some((_, _, fqp)) = href(did) {
format!("{}::{}",
fqp[..fqp.len() - 1].join("::"),
anchor(did, fqp.last().unwrap()))
} else {
last.name.to_string()
}
} else {
HRef::new(did, &last.name).to_string()
anchor(did, &last.name).to_string()
};
write!(w, "{}{}", path, last.args)?;
}
@ -513,35 +506,30 @@ fn primitive_link(f: &mut fmt::Formatter<'_>,
}
/// Helper to render type parameters
fn tybounds(w: &mut fmt::Formatter<'_>,
param_names: &Option<Vec<clean::GenericBound>>) -> fmt::Result {
match *param_names {
Some(ref params) => {
for param in params {
write!(w, " + ")?;
fmt::Display::fmt(param, w)?;
fn tybounds(param_names: &Option<Vec<clean::GenericBound>>) -> impl fmt::Display + '_ {
display_fn(move |f| {
match *param_names {
Some(ref params) => {
for param in params {
write!(f, " + ")?;
fmt::Display::fmt(param, f)?;
}
Ok(())
}
Ok(())
None => Ok(())
}
None => Ok(())
}
})
}
impl<'a> HRef<'a> {
pub fn new(did: DefId, text: &'a str) -> HRef<'a> {
HRef { did: did, text: text }
}
}
impl<'a> fmt::Display for HRef<'a> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
if let Some((url, short_ty, fqp)) = href(self.did) {
pub fn anchor(did: DefId, text: &str) -> impl fmt::Display + '_ {
display_fn(move |f| {
if let Some((url, short_ty, fqp)) = href(did) {
write!(f, r#"<a class="{}" href="{}" title="{} {}">{}</a>"#,
short_ty, url, short_ty, fqp.join("::"), self.text)
short_ty, url, short_ty, fqp.join("::"), text)
} else {
write!(f, "{}", self.text)
write!(f, "{}", text)
}
}
})
}
fn fmt_type(t: &clean::Type, f: &mut fmt::Formatter<'_>, use_absolute: bool) -> fmt::Result {
@ -555,7 +543,7 @@ fn fmt_type(t: &clean::Type, f: &mut fmt::Formatter<'_>, use_absolute: bool) ->
}
// Paths like `T::Output` and `Self::Output` should be rendered with all segments.
resolved_path(f, did, path, is_generic, use_absolute)?;
tybounds(f, param_names)
fmt::Display::fmt(&tybounds(param_names), f)
}
clean::Infer => write!(f, "_"),
clean::Primitive(prim) => primitive_link(f, prim, prim.as_str()),
@ -564,12 +552,12 @@ fn fmt_type(t: &clean::Type, f: &mut fmt::Formatter<'_>, use_absolute: bool) ->
write!(f, "{}{:#}fn{:#}{:#}",
UnsafetySpace(decl.unsafety),
AbiSpace(decl.abi),
CommaSep(&decl.generic_params),
comma_sep(&decl.generic_params),
decl.decl)
} else {
write!(f, "{}{}", UnsafetySpace(decl.unsafety), AbiSpace(decl.abi))?;
primitive_link(f, PrimitiveType::Fn, "fn")?;
write!(f, "{}{}", CommaSep(&decl.generic_params), decl.decl)
write!(f, "{}{}", comma_sep(&decl.generic_params), decl.decl)
}
}
clean::Tuple(ref typs) => {
@ -583,7 +571,7 @@ fn fmt_type(t: &clean::Type, f: &mut fmt::Formatter<'_>, use_absolute: bool) ->
}
many => {
primitive_link(f, PrimitiveType::Tuple, "(")?;
fmt::Display::fmt(&CommaSep(many), f)?;
fmt::Display::fmt(&comma_sep(many), f)?;
primitive_link(f, PrimitiveType::Tuple, ")")
}
}
@ -1063,3 +1051,19 @@ impl fmt::Display for DefaultSpace {
}
}
}
crate fn display_fn(
f: impl FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result,
) -> impl fmt::Display {
WithFormatter(Cell::new(Some(f)))
}
struct WithFormatter<F>(Cell<Option<F>>);
impl<F> fmt::Display for WithFormatter<F>
where F: FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
(self.0.take()).unwrap()(f)
}
}

6
src/librustdoc/html/render.rs
View File

@ -2644,19 +2644,19 @@ fn item_module(w: &mut fmt::Formatter<'_>, cx: &Context,
match myitem.inner {
clean::ExternCrateItem(ref name, ref src) => {
use crate::html::format::HRef;
use crate::html::format::anchor;
match *src {
Some(ref src) => {
write!(w, "<tr><td><code>{}extern crate {} as {};",
VisSpace(&myitem.visibility),
HRef::new(myitem.def_id, src),
anchor(myitem.def_id, src),
name)?
}
None => {
write!(w, "<tr><td><code>{}extern crate {};",
VisSpace(&myitem.visibility),
HRef::new(myitem.def_id, name))?
anchor(myitem.def_id, name))?
}
}
write!(w, "</code></td></tr>")?;