src/etc/natvis/libstd.natvis

<?xml version="1.0" encoding="utf-8"?>
<AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
  <!--
    std::collection::Hash* container visualizers

    Current std impls:
      std::collections::hash::set::HashSet<K, S>      is implemented in terms of...
      std::collections::hash::map::HashMap<K, V, S>   is implemented in terms of...
      hashbrown::map::HashMap<K, V, S>                is implemented in terms of...
      hashbrown::raw::RawTable<(K, V)>

    Ideally, we'd teach rustc to scan dependencies/crates for .natvis files so
    the bulk of this could live alongside the hashbrown crate implementation,
    and std would just forward using e.g. <ExpandedItem>base</ExpandedItem>.

    However, Given that std...Hash*Set* is currently implemented in terms of
    hashbrown...Hash*Map*, which would visualize poorly, we want to customize the
    look/feel at the std type level *anyways*...

    References:
      https://github.com/rust-lang/rust/blob/master/src/libstd/collections/hash/map.rs
      https://github.com/rust-lang/rust/blob/master/src/libstd/collections/hash/set.rs
      https://github.com/rust-lang/hashbrown/blob/master/src/map.rs
      https://github.com/rust-lang/hashbrown/blob/master/src/set.rs
      https://github.com/rust-lang/hashbrown/blob/master/src/raw/mod.rs
  -->

  <Type Name="std::collections::hash::map::HashMap&lt;*,*,*&gt;">
    <DisplayString>{{ size={base.table.items} }}</DisplayString>
    <Expand>
      <Item Name="[size]">base.table.items</Item>
      <Item Name="[capacity]">base.table.items + base.table.growth_left</Item>

      <CustomListItems>
        <Variable Name="i" InitialValue="0" />
        <Variable Name="n" InitialValue="base.table.items" />
        <Size>base.table.items</Size>
        <Loop>
          <Break Condition="n == 0" />
          <If Condition="(base.table.ctrl.pointer[i] &amp; 0x80) == 0">
            <!-- Bucket is populated -->
            <Exec>n--</Exec>
            <Item Name="{base.table.data.pointer[i].__0}">base.table.data.pointer[i].__1</Item>
          </If>
          <Exec>i++</Exec>
        </Loop>
      </CustomListItems>
    </Expand>
  </Type>

  <Type Name="std::collections::hash::set::HashSet&lt;*,*&gt;">
    <DisplayString>{{ size={map.base.table.items} }}</DisplayString>
    <Expand>
      <Item Name="[size]">map.base.table.items</Item>
      <Item Name="[capacity]">map.base.table.items + map.base.table.growth_left</Item>

      <CustomListItems>
        <Variable Name="i" InitialValue="0" />
        <Variable Name="n" InitialValue="map.base.table.items" />
        <Size>map.base.table.items</Size>
        <Loop>
          <Break Condition="n == 0" />
          <If Condition="(map.base.table.ctrl.pointer[i] &amp; 0x80) == 0">
            <!-- Bucket is populated -->
            <Exec>n--</Exec>
            <Item>map.base.table.data.pointer[i].__0</Item>
          </If>
          <Exec>i++</Exec>
        </Loop>
      </CustomListItems>
    </Expand>
  </Type>

  <Type Name="hashbrown::raw::RawTable&lt;*&gt;">
    <!-- RawTable has a nice and simple layout.
      items                     Number of *populated* values in the RawTable (less than the size of ctrl.pointer / data.pointer)
      growth_left               Remaining capacity before growth
      ctrl.pointer[i] & 0x80    Indicates the bucket is empty / should be skipped / doesn't count towards items.
      data.pointer[i]           The (K,V) tuple, if not empty.
    -->
    <DisplayString>{{ size={items} }}</DisplayString>
    <Expand>
      <Item Name="[size]">items</Item>
      <Item Name="[capacity]">items + growth_left</Item>

      <CustomListItems>
        <Variable Name="i" InitialValue="0" />
        <Variable Name="n" InitialValue="items" />
        <Size>items</Size>
        <Loop>
          <Break Condition="n == 0" />
          <If Condition="(ctrl.pointer[i] &amp; 0x80) == 0">
            <!-- Bucket is populated -->
            <Exec>n--</Exec>
            <Item>data.pointer[i]</Item>
          </If>
          <Exec>i++</Exec>
        </Loop>
      </CustomListItems>
    </Expand>
  </Type>
</AutoVisualizer>