rustdoc: create variants list outside of template

Author: notriddle

src/librustdoc/html/render/print_item.rs

@@ -5,15 +5,13 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_hir as hir;
 use rustc_hir::def::CtorKind;
 use rustc_hir::def_id::DefId;
-use rustc_index::vec::IndexVec;
 use rustc_middle::middle::stability;
 use rustc_middle::span_bug;
-use rustc_middle::ty::layout::{LayoutError, TyAndLayout};
+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, VariantIdx, Variants};
-use std::borrow::Borrow;
+use rustc_target::abi::{Primitive, TagEncoding, Variants};
 use std::cmp::Ordering;
 use std::fmt;
 use std::rc::Rc;
@@ -1940,9 +1938,9 @@ fn document_type_layout<'a, 'cx: 'a>(
 ) -> impl fmt::Display + 'a + Captures<'cx> {
     #[derive(Template)]
     #[template(path = "type_layout.html")]
-    struct TypeLayout<'a, 'cx> {
-        cx: &'a Context<'cx>,
-        ty_def_id: DefId,
+    struct TypeLayout<'cx> {
+        variants: Vec<(Symbol, TypeLayoutSize)>,
+        type_layout_size: Result<TypeLayoutSize, LayoutError<'cx>>,
     }
 
     #[derive(Template)]
@@ -1953,62 +1951,61 @@ fn document_type_layout<'a, 'cx: 'a>(
         size: u64,
     }
 
-    impl<'a, 'cx: 'a> TypeLayout<'a, 'cx> {
-        fn variants<'b: 'a>(&'b self) -> Option<&'b IndexVec<VariantIdx, LayoutS>> {
-            if let Variants::Multiple { variants, .. } =
-                    self.type_layout().unwrap().layout.variants() && !variants.is_empty() {
-                Some(&variants)
-            } else {
-                None
-            }
-        }
-        fn type_layout<'b: 'a>(&'b self) -> Result<TyAndLayout<'cx>, LayoutError<'cx>> {
-            let tcx = self.cx.tcx();
-            let param_env = tcx.param_env(self.ty_def_id);
-            let ty = tcx.type_of(self.ty_def_id).subst_identity();
-            tcx.layout_of(param_env.and(ty))
+    display_fn(move |f| {
+        if !cx.shared.show_type_layout {
+            return Ok(());
         }
-        fn variant_name<'b: 'a>(&'b self, index: VariantIdx) -> Symbol {
-            let Adt(adt, _) = self.type_layout().unwrap().ty.kind() else {
-                span_bug!(self.cx.tcx().def_span(self.ty_def_id), "not an adt")
-            };
-            adt.variant(index).name
-        }
-        fn tag_size<'b: 'a>(&'b self) -> u64 {
-            if let Variants::Multiple { variants, tag, tag_encoding, .. } =
-                    self.type_layout().unwrap().layout.variants() && !variants.is_empty() {
-                if let TagEncoding::Niche { .. } = tag_encoding {
-                    0
-                } else if let Primitive::Int(i, _) = tag.primitive() {
-                    i.size().bytes()
-                } else {
-                    span_bug!(self.cx.tcx().def_span(self.ty_def_id), "tag is neither niche nor int")
-                }
+
+        let variants = {
+            let tcx = cx.tcx();
+            let param_env = tcx.param_env(ty_def_id);
+            let ty = tcx.type_of(ty_def_id).subst_identity();
+            let type_layout = tcx.layout_of(param_env.and(ty));
+            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")
+                        };
+                        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 {
-                0
+                Vec::new()
             }
-        }
-        fn write_size<'b: 'a>(
-            &'b self,
-            layout: &'b LayoutS,
-            tag_size: u64,
-        ) -> impl fmt::Display + Captures<'cx> + Captures<'b> {
-            display_fn(move |f| {
+        };
+
+        let type_layout_size = {
+            let tcx = cx.tcx();
+            let param_env = tcx.param_env(ty_def_id);
+            let ty = tcx.type_of(ty_def_id).subst_identity();
+            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() - tag_size;
-                TypeLayoutSize { is_unsized, is_uninhabited, size }.render_into(f).unwrap();
-                Ok(())
+                let size = layout.size.bytes();
+                TypeLayoutSize { is_unsized, is_uninhabited, size }
             })
-        }
-    }
-
-    display_fn(move |f| {
-        if !cx.shared.show_type_layout {
-            return Ok(());
-        }
+        };
 
-        Ok(TypeLayout { cx, ty_def_id }.render_into(f).unwrap())
+        Ok(TypeLayout { variants, type_layout_size }.render_into(f).unwrap())
     })
 }
 

src/librustdoc/html/templates/type_layout.html

@@ -2,8 +2,8 @@ <h2 id="layout" class="small-section-header">  {# #}
     Layout<a href="#layout" class="anchor">§</a> {# #}
 </h2> {# #}
 <div class="docblock"> {# #}
-    {% match self.type_layout() %}
-        {% when Ok(ty_layout) %}
+    {% match type_layout_size %}
+        {% when Ok(type_layout_size) %}
             <div class="warning"> {# #}
                 <p> {# #}
                     <strong>Note:</strong> Most layout information is <strong>completely {#+ #}
@@ -14,14 +14,14 @@ <h2 id="layout" class="small-section-header">  {# #}
                     chapter for details on type layout guarantees. {# #}
                 </p> {# #}
             </div> {# #}
-            <p><strong>Size:</strong> {{ self.write_size(ty_layout.layout.0.borrow(), 0) | safe }}</p> {# #}
-            {% if let Some(variants) = self.variants() %}
+            <p><strong>Size:</strong> {{ type_layout_size|safe }}</p> {# #}
+            {% if !variants.is_empty() %}
                 <p><strong>Size for each variant:</strong></p> {# #}
                 <ul> {# #}
-                    {% for (index, layout) in variants.iter_enumerated() %}
+                    {% for (name, layout_size) in variants %}
                         <li> {# #}
-                            <code>{{ self.variant_name(index.clone()) }}</code>: {#+ #}
-                            {{ self.write_size(layout, self.tag_size()) | safe }}
+                            <code>{{ name }}</code>: {#+ #}
+                            {{ layout_size|safe }}
                         </li> {# #}
                     {% endfor %}
                 </ul> {# #}