[clangd] show layout info when hovering on a class/field definition.

[sammccall]

Summary

This triggers only on the definition itself, not on references (probably too
noisy). Inspecting the definition seems like a decent hint for being interested
in layout.

[kadircet]

clang-tools-extra/clangd/Hover.cpp

659

QuantityType seems to be an alias for int64_t, not sure how likely it is that someone will have a type that's bigger than 4GB, but still, should we make typeof HoverInfo::Size optional<int64_t> instead of unsigned?

661

nit: either make this else if or put a return above ?

664

similar to size, offset is also of type uint64_t

clang-tools-extra/clangd/unittests/HoverTests.cpp

69

any reason for changing these from int to char ?

1882

maybe also add offset?

[sammccall]

address comments

clang-tools-extra/clangd/unittests/HoverTests.cpp

69

hardcoding sizeof(int) isn't portable unless we want to set the target explicitly

[kadircet]

thanks!

clang-tools-extra/clangd/unittests/HoverTests.cpp

69

right, the test already sets the target though.

I suppose relying less on it is better, so feel free to keep it.

clang-tools-extra/clangd/Hover.h

struct HoverInfo {
   /// Set for functions and lambdas.
   llvm::Optional<std::string> ReturnType;
   /// Set for functions, lambdas and macros with parameters.
   llvm::Optional<std::vector<Param>> Parameters;
   /// Set for all templates(function, class, variable).
   llvm::Optional<std::vector<Param>> TemplateParameters;
   /// Contains the evaluated value of the symbol if available.
   llvm::Optional<std::string> Value;
+  /// Contains the byte-size of fields and types where it's interesting.
+  llvm::Optional<uint64_t> Size;
+  /// Contains the offset of fields within the enclosing class.
+  llvm::Optional<uint64_t> Offset;
 
   /// Produce a user-readable information.
   markup::Document present() const;
 };
 
 // Try to infer structure of a documentation comment (e.g. line breaks).
 void parseDocumentation(llvm::StringRef Input, markup::Document &Output);
 

clang-tools-extra/clangd/Hover.cpp

bool isHardLineBreakIndicator(llvm::StringRef Rest) {
   }
   return false;
 }
 
 bool isHardLineBreakAfter(llvm::StringRef Line, llvm::StringRef Rest) {
   return punctuationIndicatesLineBreak(Line) || isHardLineBreakIndicator(Rest);
 }
 
+void addLayoutInfo(const NamedDecl &ND, HoverInfo &HI) {
+  const auto &Ctx = ND.getASTContext();
+
+  if (auto *RD = llvm::dyn_cast<RecordDecl>(&ND)) {
+    if (auto Size = Ctx.getTypeSizeInCharsIfKnown(RD->getTypeForDecl()))
+      HI.Size = Size->getQuantity();
+    return;
+  }
+
+  if (const auto *FD = llvm::dyn_cast<FieldDecl>(&ND)) {
+    const auto *Record = FD->getParent()->getDefinition();
+    if (Record && !Record->isDependentType()) {
+      uint64_t OffsetBits = Ctx.getFieldOffset(FD);
+      if (auto Size = Ctx.getTypeSizeInCharsIfKnown(FD->getType())) {
+        HI.Size = Size->getQuantity();
+        HI.Offset = OffsetBits / 8;
+      }
+    }
+    return;
+  }
+}
+
 } // namespace
 
 llvm::Optional<HoverInfo> getHover(ParsedAST &AST, Position Pos,
                                    format::FormatStyle Style,
                                    const SymbolIndex *Index) {
   const SourceManager &SM = AST.getSourceManager();
   auto CurLoc = sourceLocationInMainFile(SM, Pos);
   if (!CurLoc) {
if (!HI) {
     SelectionTree ST =
         SelectionTree::createRight(AST.getASTContext(), TB, Offset, Offset);
     std::vector<const Decl *> Result;
     if (const SelectionTree::Node *N = ST.commonAncestor()) {
       // FIXME: Fill in HighlightRange with range coming from N->ASTNode.
       auto Decls = explicitReferenceTargets(N->ASTNode, DeclRelation::Alias);
       if (!Decls.empty()) {
         HI = getHoverContents(Decls.front(), Index);
+        // Layout info only shown when hovering on the field/class itself.
+        if (Decls.front() == N->ASTNode.get<Decl>())
+          addLayoutInfo(*Decls.front(), *HI);
         // Look for a close enclosing expression to show the value of.
         if (!HI->Value)
           HI->Value = printExprValue(N, AST.getASTContext());
       } else if (const Expr *E = N->ASTNode.get<Expr>()) {
         HI = getHoverContents(E, AST);
       }
       // FIXME: support hovers for other nodes?
       //  - built-in types
markup::Document HoverInfo::present() const {
   }
 
   if (Value) {
     markup::Paragraph &P = Output.addParagraph();
     P.appendText("Value =");
     P.appendCode(*Value);
   }
 
+  if (Offset)
+    Output.addParagraph().appendText(
+        llvm::formatv("Offset: {0} byte{1}", *Offset, *Offset == 1 ? "" : "s"));
+  if (Size)
+    Output.addParagraph().appendText(
+        llvm::formatv("Size: {0} byte{1}", *Size, *Size == 1 ? "" : "s"));
+
   if (!Documentation.empty())
     parseDocumentation(Documentation, Output);
 
   if (!Definition.empty()) {
     Output.addRuler();
     std::string ScopeComment;
     // Drop trailing "::".
     if (!LocalScope.empty()) {

clang-tools-extra/clangd/unittests/HoverTests.cpp

const std::function<void(HoverInfo &)> ExpectedBuilder;
          HI.ReturnType = "void";
          HI.Type = "void ()";
          HI.Parameters.emplace();
        }},
       // Field
       {R"cpp(
           namespace ns1 { namespace ns2 {
             struct Foo {
-              int [[b^ar]];
+              char [[b^ar]];
             };
           }}
           )cpp",
        [](HoverInfo &HI) {
          HI.NamespaceScope = "ns1::ns2::";
          HI.LocalScope = "Foo::";
          HI.Name = "bar";
          HI.Kind = index::SymbolKind::Field;
-         HI.Definition = "int bar";
-         HI.Type = "int";
+         HI.Definition = "char bar";
+         HI.Type = "char";
+         HI.Offset = 0;
+         HI.Size = 1;
        }},
       // Local to class method.
       {R"cpp(
           namespace ns1 { namespace ns2 {
             struct Foo {
               void foo() {
                 int [[b^ar]];
               }
             };
           }}
           )cpp",
        [](HoverInfo &HI) {
          HI.NamespaceScope = "ns1::ns2::";
          HI.LocalScope = "Foo::foo::";
          HI.Name = "bar";
          HI.Kind = index::SymbolKind::Variable;
          HI.Definition = "int bar";
          HI.Type = "int";
        }},
       // Anon namespace and local scope.
       {R"cpp(
           namespace ns1 { namespace {
             struct {
-              int [[b^ar]];
+              char [[b^ar]];
             } T;
           }}
           )cpp",
        [](HoverInfo &HI) {
          HI.NamespaceScope = "ns1::";
          HI.LocalScope = "(anonymous struct)::";
          HI.Name = "bar";
          HI.Kind = index::SymbolKind::Field;
-         HI.Definition = "int bar";
-         HI.Type = "int";
+         HI.Definition = "char bar";
+         HI.Type = "char";
+         HI.Offset = 0;
+         HI.Size = 1;
+       }},
+      // Struct definition shows size.
+      {R"cpp(
+          struct [[^X]]{};
+          )cpp",
+       [](HoverInfo &HI) {
+         HI.NamespaceScope = "";
+         HI.Name = "X";
+         HI.Kind = index::SymbolKind::Struct;
+         HI.Definition = "struct X {}";
+         HI.Size = 1;
        }},
       // Variable with template type
       {R"cpp(
           template <typename T, class... Ts> class Foo { public: Foo(int); };
           Foo<int, char, bool> [[fo^o]] = Foo<int, char, bool>(5);
           )cpp",
        [](HoverInfo &HI) {
          HI.NamespaceScope = "";
for (const auto &Case : Cases) {
     EXPECT_EQ(H->Documentation, Expected.Documentation);
     EXPECT_EQ(H->Definition, Expected.Definition);
     EXPECT_EQ(H->Type, Expected.Type);
     EXPECT_EQ(H->ReturnType, Expected.ReturnType);
     EXPECT_EQ(H->Parameters, Expected.Parameters);
     EXPECT_EQ(H->TemplateParameters, Expected.TemplateParameters);
     EXPECT_EQ(H->SymRange, Expected.SymRange);
     EXPECT_EQ(H->Value, Expected.Value);
+    EXPECT_EQ(H->Size, Expected.Size);
+    EXPECT_EQ(H->Offset, Expected.Offset);
   }
 }
 
 TEST(Hover, NoHover) {
   llvm::StringRef Tests[] = {
       "^int main() {}",
       "void foo() {^}",
       R"cpp(// structured binding. Not supported yet
llvm::StringRef ExpectedRender;
             HI.Kind = index::SymbolKind::NamespaceAlias;
             HI.Name = "foo";
           },
           R"(namespace-alias foo)",
       },
       {
           [](HoverInfo &HI) {
             HI.Kind = index::SymbolKind::Class;
+            HI.Size = 10;
             HI.TemplateParameters = {
                 {std::string("typename"), std::string("T"), llvm::None},
                 {std::string("typename"), std::string("C"),
                  std::string("bool")},
             };
             HI.Documentation = "documentation";
             HI.Definition =
                 "template <typename T, typename C = bool> class Foo {}";
             HI.Name = "foo";
             HI.NamespaceScope.emplace();
           },
           R"(class foo
 
+Size: 10 bytes
 documentation
 
 template <typename T, typename C = bool> class Foo {})",
       },
       {
           [](HoverInfo &HI) {
             HI.Kind = index::SymbolKind::Function;
             HI.Name = "foo";

 - type foo
 - type foo = default
 
 // In namespace ns
 ret_type foo(params) {})",
       },
       {
           [](HoverInfo &HI) {
-            HI.Kind = index::SymbolKind::Variable;
-            HI.LocalScope = "test::bar::";
+            HI.Kind = index::SymbolKind::Field;
+            HI.LocalScope = "test::Bar::";
             HI.Value = "value";
             HI.Name = "foo";
             HI.Type = "type";
             HI.Definition = "def";
+            HI.Size = 4;
+            HI.Offset = 12;
           },
-          R"(variable foo
+          R"(field foo
 
 Type: type
 Value = value
+Offset: 12 bytes
+Size: 4 bytes
 
-// In test::bar
+// In test::Bar
 def)",
       },
   };
 
   for (const auto &C : Cases) {
     HoverInfo HI;
     C.Builder(HI);
     EXPECT_EQ(HI.present().asPlainText(), C.ExpectedRender);