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_data_structures::captures::Captures;
6use rustc_hir::def_id::DefId;
7use rustc_middle::span_bug;
8use rustc_middle::ty::layout::LayoutError;
9use rustc_middle::ty::{self};
10use rustc_span::symbol::Symbol;
11
12use crate::html::render::Context;
13
14#[derive(Template)]
15#[template(path = "type_layout.html")]
16struct TypeLayout<'cx> {
17    variants: Vec<(Symbol, TypeLayoutSize)>,
18    type_layout_size: Result<TypeLayoutSize, &'cx LayoutError<'cx>>,
19}
20
21#[derive(Template)]
22#[template(path = "type_layout_size.html")]
23struct TypeLayoutSize {
24    is_unsized: bool,
25    is_uninhabited: bool,
26    size: u64,
27}
28
29pub(crate) fn document_type_layout<'a, 'cx: 'a>(
30    cx: &'a Context<'cx>,
31    ty_def_id: DefId,
32) -> impl fmt::Display + 'a + Captures<'cx> {
33    fmt::from_fn(move |f| {
34        if !cx.shared.show_type_layout {
35            return Ok(());
36        }
37
38        let tcx = cx.tcx();
39        let typing_env = ty::TypingEnv::post_analysis(tcx, ty_def_id);
40        let ty = tcx.type_of(ty_def_id).instantiate_identity();
41        let type_layout = tcx.layout_of(typing_env.as_query_input(ty));
42
43        let variants = if let Ok(type_layout) = type_layout
44            && let Variants::Multiple { variants, tag, tag_encoding, .. } =
45                type_layout.layout.variants()
46            && !variants.is_empty()
47        {
48            let tag_size = if let TagEncoding::Niche { .. } = tag_encoding {
49                0
50            } else if let Primitive::Int(i, _) = tag.primitive() {
51                i.size().bytes()
52            } else {
53                span_bug!(tcx.def_span(ty_def_id), "tag is neither niche nor int")
54            };
55            variants
56                .iter_enumerated()
57                .map(|(variant_idx, variant_layout)| {
58                    let ty::Adt(adt, _) = type_layout.ty.kind() else {
59                        span_bug!(tcx.def_span(ty_def_id), "not an adt")
60                    };
61                    let name = adt.variant(variant_idx).name;
62                    let is_unsized = variant_layout.is_unsized();
63                    let is_uninhabited = variant_layout.is_uninhabited();
64                    let size = variant_layout.size.bytes() - tag_size;
65                    let type_layout_size = TypeLayoutSize { is_unsized, is_uninhabited, size };
66                    (name, type_layout_size)
67                })
68                .collect()
69        } else {
70            Vec::new()
71        };
72
73        let type_layout_size = tcx.layout_of(typing_env.as_query_input(ty)).map(|layout| {
74            let is_unsized = layout.is_unsized();
75            let is_uninhabited = layout.is_uninhabited();
76            let size = layout.size.bytes();
77            TypeLayoutSize { is_unsized, is_uninhabited, size }
78        });
79
80        TypeLayout { variants, type_layout_size }.render_into(f).unwrap();
81        Ok(())
82    })
83}
rustdoc/html/render/type_layout.rs

rustdoc/html/render/
type_layout.rs
