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Merged
merged 7 commits into from
Apr 22, 2023
Merged

rustdoc: migrate document_type_layout to askama #109949

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08f204e
rustdoc: migrate `document_type_layout` to askama
notriddle Apr 4, 2023
5f9746b
rustdoc: use a separate template for type layout size
notriddle Apr 18, 2023
3a16db1
rustdoc: create variants list outside of template
notriddle Apr 18, 2023
e26ae95
rustdoc: format type layout template with newline after `<p>`
notriddle Apr 18, 2023
99e1cdb
rustdoc: get rid of redundant, nested `let` lines
notriddle Apr 21, 2023
2b728c1
rustdoc: factor `document_type_layout` into its own module
notriddle Apr 21, 2023
e6664c0
rustdoc: remove unnecessary binding
notriddle Apr 21, 2023
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149 changes: 55 additions & 94 deletions src/librustdoc/html/render/print_item.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@ use rustc_middle::ty::layout::LayoutError;
use rustc_middle::ty::{self, Adt, TyCtxt};
use rustc_span::hygiene::MacroKind;
use rustc_span::symbol::{kw, sym, Symbol};
use rustc_target::abi::{LayoutS, Primitive, TagEncoding, Variants};
use rustc_target::abi::{Primitive, TagEncoding, Variants};
use std::cmp::Ordering;
use std::fmt;
use std::rc::Rc;
Expand Down Expand Up @@ -1936,111 +1936,72 @@ fn document_type_layout<'a, 'cx: 'a>(
cx: &'a Context<'cx>,
ty_def_id: DefId,
) -> impl fmt::Display + 'a + Captures<'cx> {
fn write_size_of_layout(mut w: impl fmt::Write, layout: &LayoutS, tag_size: u64) {
if layout.abi.is_unsized() {
write!(w, "(unsized)").unwrap();
} else {
let size = layout.size.bytes() - tag_size;
write!(w, "{size} byte{pl}", pl = if size == 1 { "" } else { "s" }).unwrap();
if layout.abi.is_uninhabited() {
write!(
w,
" (<a href=\"https://doc.rust-lang.org/stable/reference/glossary.html#uninhabited\">uninhabited</a>)"
).unwrap();
}
}
#[derive(Template)]
#[template(path = "type_layout.html")]
struct TypeLayout<'cx> {
variants: Vec<(Symbol, TypeLayoutSize)>,
type_layout_size: Result<TypeLayoutSize, LayoutError<'cx>>,
}

display_fn(move |mut f| {
#[derive(Template)]
#[template(path = "type_layout_size.html")]
struct TypeLayoutSize {
is_unsized: bool,
is_uninhabited: bool,
size: u64,
}

display_fn(move |f| {
if !cx.shared.show_type_layout {
return Ok(());
}

writeln!(
f,
"<h2 id=\"layout\" class=\"small-section-header\"> \
Layout<a href=\"#layout\" class=\"anchor\">§</a></h2>"
)?;
writeln!(f, "<div class=\"docblock\">")?;

let tcx = cx.tcx();
let param_env = tcx.param_env(ty_def_id);
let ty = tcx.type_of(ty_def_id).subst_identity();
match tcx.layout_of(param_env.and(ty)) {
Ok(ty_layout) => {
writeln!(
f,
"<div class=\"warning\"><p><strong>Note:</strong> Most layout information is \
<strong>completely unstable</strong> and may even differ between compilations. \
The only exception is types with certain <code>repr(...)</code> attributes. \
Please see the Rust Reference’s \
<a href=\"https://doc.rust-lang.org/reference/type-layout.html\">“Type Layout”</a> \
chapter for details on type layout guarantees.</p></div>"
)?;
f.write_str("<p><strong>Size:</strong> ")?;
write_size_of_layout(&mut f, &ty_layout.layout.0, 0);
writeln!(f, "</p>")?;
if let Variants::Multiple { variants, tag, tag_encoding, .. } =
&ty_layout.layout.variants()
{
if !variants.is_empty() {
f.write_str(
"<p><strong>Size for each variant:</strong></p>\
<ul>",
)?;

let Adt(adt, _) = ty_layout.ty.kind() else {
span_bug!(tcx.def_span(ty_def_id), "not an adt")
};

let tag_size = if let TagEncoding::Niche { .. } = tag_encoding {
0
} else if let Primitive::Int(i, _) = tag.primitive() {
i.size().bytes()
} else {
span_bug!(tcx.def_span(ty_def_id), "tag is neither niche nor int")
let type_layout = tcx.layout_of(param_env.and(ty));

let variants =
if let Ok(type_layout) = type_layout &&
let Variants::Multiple { variants, tag, tag_encoding, .. } =
type_layout.layout.variants() &&
!variants.is_empty()
{
let tag_size =
if let TagEncoding::Niche { .. } = tag_encoding {
0
} else if let Primitive::Int(i, _) = tag.primitive() {
i.size().bytes()
} else {
span_bug!(cx.tcx().def_span(ty_def_id), "tag is neither niche nor int")
};
let variants = variants
.iter_enumerated()
.map(|(variant_idx, variant_layout)| {
let Adt(adt, _) = type_layout.ty.kind() else {
span_bug!(cx.tcx().def_span(ty_def_id), "not an adt")
};

for (index, layout) in variants.iter_enumerated() {
let name = adt.variant(index).name;
write!(&mut f, "<li><code>{name}</code>: ")?;
write_size_of_layout(&mut f, layout, tag_size);
writeln!(&mut f, "</li>")?;
}
f.write_str("</ul>")?;
}
}
}
// This kind of layout error can occur with valid code, e.g. if you try to
// get the layout of a generic type such as `Vec<T>`.
Err(LayoutError::Unknown(_)) => {
writeln!(
f,
"<p><strong>Note:</strong> Unable to compute type layout, \
possibly due to this type having generic parameters. \
Layout can only be computed for concrete, fully-instantiated types.</p>"
)?;
}
// This kind of error probably can't happen with valid code, but we don't
// want to panic and prevent the docs from building, so we just let the
// user know that we couldn't compute the layout.
Err(LayoutError::SizeOverflow(_)) => {
writeln!(
f,
"<p><strong>Note:</strong> Encountered an error during type layout; \
the type was too big.</p>"
)?;
}
Err(LayoutError::NormalizationFailure(_, _)) => {
writeln!(
f,
"<p><strong>Note:</strong> Encountered an error during type layout; \
the type failed to be normalized.</p>"
)?;
let name = adt.variant(variant_idx).name;
let is_unsized = variant_layout.abi.is_unsized();
let is_uninhabited = variant_layout.abi.is_uninhabited();
let size = variant_layout.size.bytes() - tag_size;
let type_layout_size = TypeLayoutSize { is_unsized, is_uninhabited, size };
(name, type_layout_size)
}).collect();
variants
} else {
Vec::new()
}
}
;

let type_layout_size = tcx.layout_of(param_env.and(ty)).map(|layout| {
let is_unsized = layout.abi.is_unsized();
let is_uninhabited = layout.abi.is_uninhabited();
let size = layout.size.bytes();
TypeLayoutSize { is_unsized, is_uninhabited, size }
});

writeln!(f, "</div>")
Ok(TypeLayout { variants, type_layout_size }.render_into(f).unwrap())
})
}

Expand Down
53 changes: 53 additions & 0 deletions src/librustdoc/html/templates/type_layout.html
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Original file line number Diff line number Diff line change
@@ -0,0 +1,53 @@
<h2 id="layout" class="small-section-header"> {# #}
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What's the meaning of the {# #} here and below? According to Askama's docs, it's a block comment?

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It's a block comment, yes.

The point of it is to eat the whitespace between the end of this tag and the start of the one on the next line (it would normally be preserved).

Layout<a href="#layout" class="anchor">§</a> {# #}
</h2> {# #}
<div class="docblock"> {# #}
{% match type_layout_size %}
{% when Ok(type_layout_size) %}
<div class="warning"> {# #}
<p> {# #}
<strong>Note:</strong> Most layout information is <strong>completely {#+ #}
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According to Askama's docs, the {#+ #} keeps whitespace, but don't we want to suppress it to reduce page size?

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@notriddle notriddle Apr 5, 2023 •
edited
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If it was {# #}, I'd wind up with <strong>completelyunstable</strong>. If it was completely absent, I'd wind up with the newline and several spaces in a row between the two words.

unstable</strong> and may even differ between compilations. {#+ #}
The only exception is types with certain <code>repr(...)</code> {#+ #}
attributes. Please see the Rust Reference’s {#+ #}
<a href="https://doc.rust-lang.org/reference/type-layout.html">“Type Layout”</a> {#+ #}
chapter for details on type layout guarantees. {# #}
</p> {# #}
</div> {# #}
<p><strong>Size:</strong> {{ type_layout_size|safe }}</p> {# #}
{% if !variants.is_empty() %}
<p> {# #}
<strong>Size for each variant:</strong> {# #}
</p> {# #}
<ul> {# #}
{% for (name, layout_size) in variants %}
<li> {# #}
<code>{{ name }}</code>: {#+ #}
{{ layout_size|safe }}
</li> {# #}
{% endfor %}
</ul> {# #}
{% endif %}
{# This kind of layout error can occur with valid code, e.g. if you try to
get the layout of a generic type such as `Vec<T>`. #}
{% when Err(LayoutError::Unknown(_)) %}
<p> {# #}
<strong>Note:</strong> Unable to compute type layout, {#+ #}
possibly due to this type having generic parameters. {#+ #}
Layout can only be computed for concrete, fully-instantiated types. {# #}
</p> {# #}
{# This kind of error probably can't happen with valid code, but we don't
want to panic and prevent the docs from building, so we just let the
user know that we couldn't compute the layout. #}
{% when Err(LayoutError::SizeOverflow(_)) %}
<p> {# #}
<strong>Note:</strong> Encountered an error during type layout; {#+ #}
the type was too big. {# #}
</p> {# #}
{% when Err(LayoutError::NormalizationFailure(_, _)) %}
<p> {# #}
<strong>Note:</strong> Encountered an error during type layout; {#+ #}
the type failed to be normalized. {# #}
</p> {# #}
{% endmatch %}
</div> {# #}
12 changes: 12 additions & 0 deletions src/librustdoc/html/templates/type_layout_size.html
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Original file line number Diff line number Diff line change
@@ -0,0 +1,12 @@
{% if is_unsized %}
(unsized)
{% else %}
{% if size == 1 %}
1 byte
{% else %}
{{ size +}} bytes
{% endif %}
{% if is_uninhabited %}
{# +#} (<a href="https://doc.rust-lang.org/stable/reference/glossary.html#uninhabited">uninhabited</a>)
{% endif %}
{% endif %}