rustdoc/html/render/
type_layout.rs

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1use std::fmt;
2
3use rinja::Template;
4use rustc_abi::{Primitive, TagEncoding, Variants};
5use rustc_hir::def_id::DefId;
6use rustc_middle::span_bug;
7use rustc_middle::ty::layout::LayoutError;
8use rustc_middle::ty::{self};
9use rustc_span::symbol::Symbol;
10
11use crate::html::render::Context;
12
13#[derive(Template)]
14#[template(path = "type_layout.html")]
15struct TypeLayout<'cx> {
16    variants: Vec<(Symbol, TypeLayoutSize)>,
17    type_layout_size: Result<TypeLayoutSize, &'cx LayoutError<'cx>>,
18}
19
20#[derive(Template)]
21#[template(path = "type_layout_size.html")]
22struct TypeLayoutSize {
23    is_unsized: bool,
24    is_uninhabited: bool,
25    size: u64,
26}
27
28pub(crate) fn document_type_layout(cx: &Context<'_>, ty_def_id: DefId) -> impl fmt::Display {
29    fmt::from_fn(move |f| {
30        if !cx.shared.show_type_layout {
31            return Ok(());
32        }
33
34        let tcx = cx.tcx();
35        let typing_env = ty::TypingEnv::post_analysis(tcx, ty_def_id);
36        let ty = tcx.type_of(ty_def_id).instantiate_identity();
37        let type_layout = tcx.layout_of(typing_env.as_query_input(ty));
38
39        let variants = if let Ok(type_layout) = type_layout
40            && let Variants::Multiple { variants, tag, tag_encoding, .. } =
41                type_layout.layout.variants()
42            && !variants.is_empty()
43        {
44            let tag_size = if let TagEncoding::Niche { .. } = tag_encoding {
45                0
46            } else if let Primitive::Int(i, _) = tag.primitive() {
47                i.size().bytes()
48            } else {
49                span_bug!(tcx.def_span(ty_def_id), "tag is neither niche nor int")
50            };
51            variants
52                .iter_enumerated()
53                .map(|(variant_idx, variant_layout)| {
54                    let ty::Adt(adt, _) = type_layout.ty.kind() else {
55                        span_bug!(tcx.def_span(ty_def_id), "not an adt")
56                    };
57                    let name = adt.variant(variant_idx).name;
58                    let is_unsized = variant_layout.is_unsized();
59                    let is_uninhabited = variant_layout.is_uninhabited();
60                    let size = variant_layout.size.bytes() - tag_size;
61                    let type_layout_size = TypeLayoutSize { is_unsized, is_uninhabited, size };
62                    (name, type_layout_size)
63                })
64                .collect()
65        } else {
66            Vec::new()
67        };
68
69        let type_layout_size = tcx.layout_of(typing_env.as_query_input(ty)).map(|layout| {
70            let is_unsized = layout.is_unsized();
71            let is_uninhabited = layout.is_uninhabited();
72            let size = layout.size.bytes();
73            TypeLayoutSize { is_unsized, is_uninhabited, size }
74        });
75
76        TypeLayout { variants, type_layout_size }.render_into(f).unwrap();
77        Ok(())
78    })
79}
rustdoc/html/render/type_layout.rs

rustdoc/html/render/
type_layout.rs
