Show members of DeclContexts (i.e., class members) in Visual Studio native visualizers

[mspertus]

Summary

This change shows members of DeclContext objects in the Visual Studio debugger. It will also cast a TagType like a class or a struct to a DeclContext, so its methods and fields are visualized. For example, suppose we have a class

struct A {
  int foo();
};

With this change, the CXXRecordDecl * representing A will be displayed in the Visual Studio debugger as

D                 0x0067ab48 struct A
|- DeclKind       CXXRecord
|- [0]            struct A
|- [1]            Method {foo}
|- [Raw View]     //Remaining fields//

[aaron.ballman]

Mostly LGTM with one question about a comment.

clang.natvis

77

The only hard-wiring I see uses 3 bits, so is this comment still accurate?

[mspertus]

I think the code is correct as written, see response in comment

clang.natvis

77

I think the code is correct.

llvm::PointerIntPair<Decl *, 2, unsigned> NextInContextAndBits;

so NextInContextAndBits uses 2 bits for the int part. Just to be sure, I also double checked in the debugger (an IntMask of 3 represents two bits :) ),

		((((clang::DeclContext *)(clang::CXXRecordDecl *)D)->FirstDecl)->NextInContextAndBits).IntMask	IntMask (3)	llvm::PointerIntPair<clang::Decl *,2,unsigned int,llvm::PointerLikeTypeTraits<clang::Decl *> >::<unnamed-enum-PointerBitMask>

[aaron.ballman]

LGTM!

clang.natvis

77

Oh yeah, that's right, an IntMask of 3 does represent 2 bits. Sorry for the confusion!

[mspertus]

Thanks, Aaron. Committed as revision 263794

clang.natvis

<Type Name="clang::RValueReferenceType">
     <Expand>
       <ExpandedItem>*(clang::Type *)this, view(cmn)</ExpandedItem>
       <Item Name="PointeeType">PointeeType</Item>
     </Expand>
   </Type>
   <Type Name="clang::AttributedType">
     <DisplayString>{ModifiedType} Attribute={(clang::AttributedType::Kind)AttributedTypeBits.AttrKind}</DisplayString>
   </Type>
+  
+  <!-- Unfortunately, Visual Studio has trouble seeing the PointerBitMask member PointerIntUnion, so I hardwire it to 2 bits-->
+  <Type Name="clang::DeclContext">
+    <DisplayString>{(clang::Decl::Kind)DeclKind,en}Decl</DisplayString>
+    <Expand>
+      <Item Name="DeclKind">(clang::Decl::Kind)DeclKind,en</Item>
+      <LinkedListItems>
+        <HeadPointer>FirstDecl</HeadPointer>
+        <NextPointer>(clang::Decl *)(NextInContextAndBits.Value &amp; ~3)</NextPointer>
+        <ValueNode>*this</ValueNode>
+      </LinkedListItems>
+    </Expand>
+  </Type>
+  <Type Name="clang::FieldDecl">
+    <DisplayString>Field {{{*(clang::NamedDecl *)this,view(cpp)nd}}}</DisplayString>
+  </Type>
+  <Type Name="clang::CXXMethodDecl">
+    <DisplayString>Method {{{*(clang::NamedDecl *)this,view(cpp)nd}}}</DisplayString>
+  </Type>
+  <Type Name="clang::CXXConstructorDecl">
+    <DisplayString>Constructor {{{*(clang::NamedDecl *)this,view(cpp)nd}}}</DisplayString>
+  </Type>
+  <Type Name="clang::CXXDestructorDecl">
+    <DisplayString>Destructor {{{*(clang::NamedDecl *)this,view(cpp)nd}}}</DisplayString>
+  </Type>
   <Type Name="clang::NamedDecl" >
     <DisplayString IncludeView="cpp">{Name,view(cpp)}</DisplayString>
     <DisplayString>{Name}</DisplayString>
   </Type>
   <Type Name="clang::TagDecl">
     <DisplayString Condition="TagDeclKind==clang::TagTypeKind::TTK_Struct">struct {Name,view(cpp)}</DisplayString>
     <DisplayString Condition="TagDeclKind==clang::TagTypeKind::TTK_Interface">interface {Name,view(cpp)}</DisplayString>
     <DisplayString Condition="TagDeclKind==clang::TagTypeKind::TTK_Union">union {Name,view(cpp)}</DisplayString>
     <DisplayString Condition="TagDeclKind==clang::TagTypeKind::TTK_Class">class {Name,view(cpp)}</DisplayString>
     <DisplayString Condition="TagDeclKind==clang::TagTypeKind::TTK_Enum">enum {Name,view(cpp)}</DisplayString>
+    <Expand>
+      <ExpandedItem>(clang::DeclContext *)this</ExpandedItem>
+    </Expand>
   </Type>
   <Type Name="clang::TagType">
     <DisplayString>{*decl}</DisplayString>
     <Expand>
       <ExpandedItem>*(clang::Type *)this, view(cmn)</ExpandedItem>
       <Item Name="decl">decl</Item>
     </Expand>
   </Type>
   <Type Name="clang::RecordType">
     <DisplayString>{*(clang::TagType *)this}</DisplayString>
     <Expand>
       <Item Name="TagType">*(clang::TagType *)this</Item>
     </Expand>
   </Type>
-
   <Type Name="clang::SubstTemplateTypeParmType">
     <DisplayString>{*Replaced,view(cpp)} &lt;= {CanonicalType,view(cpp)}</DisplayString>
     <Expand>
       <ExpandedItem>*(clang::Type *)this, view(cmn)</ExpandedItem>
       <Item Name="Replaced">*Replaced</Item>
     </Expand>
   </Type>
   <Type Name="clang::TemplateTypeParmType">