From f353cbf1a145603e1f69c2aaaef171dd60ca4c65 Mon Sep 17 00:00:00 2001
From: Wesley Wiser <wesleywiser@microsoft.com>
Date: Mon, 26 Apr 2021 14:39:57 -0400
Subject: [PATCH] Generate better debuginfo for directly tagged enums

---
 .../src/debuginfo/metadata.rs                 |  9 +++--
 compiler/rustc_codegen_llvm/src/llvm/ffi.rs   |  2 +-
 .../src/debuginfo/type_names.rs               |  8 ++++
 src/etc/natvis/intrinsic.natvis               | 38 +++++++++++++++++++
 src/etc/natvis/libcore.natvis                 | 17 ---------
 5 files changed, 52 insertions(+), 22 deletions(-)

diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
index 0db6659f8e2..7a44e887c89 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
@@ -1574,7 +1574,7 @@ fn create_member_descriptions(&self, cx: &CodegenCx<'ll, 'tcx>) -> Vec<MemberDes
 
                         MemberDescription {
                             name: if fallback {
-                                String::new()
+                                format!("Variant{}", i.as_u32())
                             } else {
                                 variant_info.variant_name()
                             },
@@ -1886,8 +1886,9 @@ fn describe_enum_variant(
                 // We have the layout of an enum variant, we need the layout of the outer enum
                 let enum_layout = cx.layout_of(layout.ty);
                 let offset = enum_layout.fields.offset(tag_field.as_usize());
+                let tag_name = if cx.tcx.sess.target.is_like_msvc { "variant$" } else { "RUST$ENUM$DISR" };
                 let args =
-                    ("RUST$ENUM$DISR".to_owned(), enum_layout.field(cx, tag_field.as_usize()).ty);
+                    (tag_name.to_owned(), enum_layout.field(cx, tag_field.as_usize()).ty);
                 (Some(offset), Some(args))
             }
             _ => (None, None),
@@ -2062,7 +2063,7 @@ fn prepare_enum_metadata(
             unsafe {
                 llvm::LLVMRustDIBuilderCreateUnionType(
                     DIB(cx),
-                    containing_scope,
+                    None,
                     enum_name.as_ptr().cast(),
                     enum_name.len(),
                     file_metadata,
@@ -2437,7 +2438,7 @@ fn create_union_stub(
 
         llvm::LLVMRustDIBuilderCreateUnionType(
             DIB(cx),
-            containing_scope,
+            Some(containing_scope),
             union_type_name.as_ptr().cast(),
             union_type_name.len(),
             unknown_file_metadata(cx),
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index 8b1dcea3fa2..54ef1a28468 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -2038,7 +2038,7 @@ pub fn LLVMRustDIBuilderCreateEnumerationType(
 
     pub fn LLVMRustDIBuilderCreateUnionType(
         Builder: &DIBuilder<'a>,
-        Scope: &'a DIScope,
+        Scope: Option<&'a DIScope>,
         Name: *const c_char,
         NameLen: size_t,
         File: &'a DIFile,
diff --git a/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs b/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
index d1bbf74307c..626c71abf63 100644
--- a/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
+++ b/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
@@ -45,8 +45,16 @@ pub fn push_debuginfo_type_name<'tcx>(
         ty::Float(float_ty) => output.push_str(float_ty.name_str()),
         ty::Foreign(def_id) => push_item_name(tcx, def_id, qualified, output),
         ty::Adt(def, substs) => {
+            if def.is_enum() && cpp_like_names {
+                output.push_str("_enum<");
+            }
+
             push_item_name(tcx, def.did, qualified, output);
             push_type_params(tcx, substs, output, visited);
+
+            if def.is_enum() && cpp_like_names {
+                output.push('>');
+            }
         }
         ty::Tuple(component_types) => {
             if cpp_like_names {
diff --git a/src/etc/natvis/intrinsic.natvis b/src/etc/natvis/intrinsic.natvis
index 030892a432b..45e36f929b4 100644
--- a/src/etc/natvis/intrinsic.natvis
+++ b/src/etc/natvis/intrinsic.natvis
@@ -149,4 +149,42 @@
       <Synthetic Name="[...]"><DisplayString>...</DisplayString></Synthetic>
     </Expand>
   </Type>
+  <Type Name="_enum&lt;*&gt;">
+    <Intrinsic Name="tag" Expression="Variant0.variant$" />
+    <DisplayString Condition="tag() == 0">{tag(),en}</DisplayString>
+    <DisplayString Condition="tag() == 1" Optional="true">{tag(),en}</DisplayString>
+    <DisplayString Condition="tag() == 2" Optional="true">{tag(),en}</DisplayString>
+    <DisplayString Condition="tag() == 3" Optional="true">{tag(),en}</DisplayString>
+    <DisplayString Condition="tag() == 4" Optional="true">{tag(),en}</DisplayString>
+    <DisplayString Condition="tag() == 5" Optional="true">{tag(),en}</DisplayString>
+    <DisplayString Condition="tag() == 6" Optional="true">{tag(),en}</DisplayString>
+    <DisplayString Condition="tag() == 7" Optional="true">{tag(),en}</DisplayString>
+    <DisplayString Condition="tag() == 8" Optional="true">{tag(),en}</DisplayString>
+    <DisplayString Condition="tag() == 9" Optional="true">{tag(),en}</DisplayString>
+    <DisplayString Condition="tag() == 10" Optional="true">{tag(),en}</DisplayString>
+    <DisplayString Condition="tag() == 11" Optional="true">{tag(),en}</DisplayString>
+    <DisplayString Condition="tag() == 12" Optional="true">{tag(),en}</DisplayString>
+    <DisplayString Condition="tag() == 13" Optional="true">{tag(),en}</DisplayString>
+    <DisplayString Condition="tag() == 14" Optional="true">{tag(),en}</DisplayString>
+    <DisplayString Condition="tag() == 15" Optional="true">{tag(),en}</DisplayString>
+
+    <Expand>
+      <ExpandedItem Condition="tag() == 0">Variant0</ExpandedItem>
+      <ExpandedItem Condition="tag() == 1" Optional="true">Variant1</ExpandedItem>
+      <ExpandedItem Condition="tag() == 2" Optional="true">Variant2</ExpandedItem>
+      <ExpandedItem Condition="tag() == 3" Optional="true">Variant3</ExpandedItem>
+      <ExpandedItem Condition="tag() == 4" Optional="true">Variant4</ExpandedItem>
+      <ExpandedItem Condition="tag() == 5" Optional="true">Variant5</ExpandedItem>
+      <ExpandedItem Condition="tag() == 6" Optional="true">Variant6</ExpandedItem>
+      <ExpandedItem Condition="tag() == 7" Optional="true">Variant7</ExpandedItem>
+      <ExpandedItem Condition="tag() == 8" Optional="true">Variant8</ExpandedItem>
+      <ExpandedItem Condition="tag() == 9" Optional="true">Variant9</ExpandedItem>
+      <ExpandedItem Condition="tag() == 10" Optional="true">Variant10</ExpandedItem>
+      <ExpandedItem Condition="tag() == 11" Optional="true">Variant11</ExpandedItem>
+      <ExpandedItem Condition="tag() == 12" Optional="true">Variant12</ExpandedItem>
+      <ExpandedItem Condition="tag() == 13" Optional="true">Variant13</ExpandedItem>
+      <ExpandedItem Condition="tag() == 14" Optional="true">Variant14</ExpandedItem>
+      <ExpandedItem Condition="tag() == 15" Optional="true">Variant15</ExpandedItem>
+    </Expand>
+  </Type>
 </AutoVisualizer>
diff --git a/src/etc/natvis/libcore.natvis b/src/etc/natvis/libcore.natvis
index 9c3c26f5978..17667770520 100644
--- a/src/etc/natvis/libcore.natvis
+++ b/src/etc/natvis/libcore.natvis
@@ -14,14 +14,6 @@
     </Expand>
   </Type>
 
-  <Type Name="core::option::Option&lt;*&gt;">
-    <DisplayString Condition="RUST$ENUM$DISR == 0x0">None</DisplayString>
-    <DisplayString Condition="RUST$ENUM$DISR == 0x1">Some({__0})</DisplayString>
-    <Expand>
-      <Item Name="[value]" ExcludeView="simple" Condition="RUST$ENUM$DISR == 1">__0</Item>
-    </Expand>
-  </Type>
-
   <Type Name="core::option::Option&lt;*&gt;" Priority="MediumLow">
     <DisplayString Condition="*(void**)this == nullptr">None</DisplayString>
     <DisplayString>Some({($T1 *)this})</DisplayString>
@@ -30,15 +22,6 @@
     </Expand>
   </Type>
 
-  <Type Name="core::result::Result&lt;*&gt;">
-    <DisplayString Condition="RUST$ENUM$DISR == 0x0">Ok({__0})</DisplayString>
-    <DisplayString Condition="RUST$ENUM$DISR == 0x1">Err({(*($T2*) &amp;__0)})</DisplayString>
-    <Expand>
-      <Item Name="[value]" Condition="RUST$ENUM$DISR == 0x0">__0</Item>
-      <Item Name="[value]" Condition="RUST$ENUM$DISR == 0x1">(*($T2*) &amp;__0)</Item>
-    </Expand>
-  </Type>
-
   <Type Name="core::ptr::non_null::NonNull&lt;*&gt;">
     <DisplayString>{(void*) pointer}</DisplayString>
     <Expand>