[clangd] Fix early selection for non-vardecl declarators

Summary:
Selection tree was performing an early claim only for VarDecls, but
there are other cases where we can have declarators, e.g. FieldDecls. This patch
extends the early claim logic to all types of declarators.

Fixes clangd/clangd#292

Reviewers: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75106

(cherry picked from commit e6b8181)

Modified the cherry-picked test as diagnostics differ on the branch.

Fixes clangd/clangd#421

clang-tools-extra/clangd/Selection.cpp

@@ -10,6 +10,7 @@
 #include "Logger.h"
 #include "SourceCode.h"
 #include "clang/AST/ASTTypeTraits.h"
+#include "clang/AST/Decl.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/Expr.h"
 #include "clang/AST/ExprCXX.h"
@@ -594,13 +595,23 @@ class SelectionVisitor : public RecursiveASTVisitor<SelectionVisitor> {
   // Usually empty, but sometimes children cover tokens but shouldn't own them.
   SourceRange earlySourceRange(const DynTypedNode &N) {
     if (const Decl *D = N.get<Decl>()) {
+      // We want constructor name to be claimed by TypeLoc not the constructor
+      // itself. Similar for deduction guides, we rather want to select the
+      // underlying TypeLoc.
+      // FIXME: Unfortunately this doesn't work, even though RecursiveASTVisitor
+      // traverses the underlying TypeLoc inside DeclarationName, it is null for
+      // constructors.
+      if (isa<CXXConstructorDecl>(D) || isa<CXXDeductionGuideDecl>(D))
+        return SourceRange();
+      // This will capture Field, Function, MSProperty, NonTypeTemplateParm and
+      // VarDecls. We want the name in the declarator to be claimed by the decl
+      // and not by any children. For example:
       // void [[foo]]();
-      if (auto *FD = llvm::dyn_cast<FunctionDecl>(D))
-        return FD->getNameInfo().getSourceRange();
       // int (*[[s]])();
-      else if (auto *VD = llvm::dyn_cast<VarDecl>(D))
-        return VD->getLocation();
-    } else if (const auto* CCI = N.get<CXXCtorInitializer>()) {
+      // struct X { int [[hash]] [32]; [[operator]] int();}
+      if (const auto *DD = llvm::dyn_cast<DeclaratorDecl>(D))
+        return DD->getLocation();
+    } else if (const auto *CCI = N.get<CXXCtorInitializer>()) {
       // : [[b_]](42)
       return CCI->getMemberLocation();
     }

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

@@ -339,7 +339,7 @@ class Foo {})cpp";
          HI.Definition = "~X()";
          HI.Parameters.emplace();
        }},
-      {"class X { operator [[in^t]](); };",
+      {"class X { [[op^erator]] int(); };",
        [](HoverInfo &HI) {
          HI.NamespaceScope = "";
          HI.Name = "operator int";
@@ -348,6 +348,13 @@ class Foo {})cpp";
          HI.Definition = "operator int()";
          HI.Parameters.emplace();
        }},
+      {"class X { operator [[^X]]*(); };",
+       [](HoverInfo &HI) {
+         HI.NamespaceScope = "";
+         HI.Name = "X";
+         HI.Kind = index::SymbolKind::Class;
+         HI.Definition = "class X {}";
+       }},
 
       // auto on lambda
       {R"cpp(

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

@@ -329,6 +329,12 @@ TEST(SelectionTest, CommonAncestor) {
         decltype([[^a]] + a) b;
         )cpp",
           "DeclRefExpr"},
+
+      {"struct foo { [[int has^h<:32:>]]; };", "FieldDecl"},
+      {"struct foo { [[op^erator int()]]; };", "CXXConversionDecl"},
+      {"struct foo { [[^~foo()]]; };", "CXXDestructorDecl"},
+      // FIXME: The following to should be class itself instead.
+      {"struct foo { [[fo^o(){}]] };", "CXXConstructorDecl"},
   };
   for (const Case &C : Cases) {
     Annotations Test(C.Code);