[Index] consider `delete X` a reference to ~X() if it can be resolved

[sammccall]

Summary

Fixes https://github.com/clangd/clangd/issues/1321

[ilya-biryukov]

Sorry for chiming in, left a comment on GitHub.
TLDR; destructors are easy to find and this is not the case for user-defined operator delete. Maybe this is a good reason to have operator delete references (either instead of in addition to destructors)?

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

const char *Tests[] = {
       )cpp",
       R"cpp(// Not touching any identifiers.
         struct Foo {
           $def[[~]]Foo() {};
         };
         void foo() {
           Foo f;
           f.[[^~]]Foo();
+          [[delete]] &f;
         }
       )cpp",
       R"cpp(// Lambda capture initializer
         void foo() {
           int $def[[w^aldo]] = 42;
           auto lambda = [x = [[waldo]]](){};
         }
       )cpp",

clang/lib/Index/IndexBody.cpp

public:
   bool VisitCXXConstructExpr(CXXConstructExpr *E) {
     SymbolRoleSet Roles{};
     SmallVector<SymbolRelation, 2> Relations;
     addCallRole(Roles, Relations);
     return IndexCtx.handleReference(E->getConstructor(), E->getLocation(),
                                     Parent, ParentDC, Roles, Relations, E);
   }
 
+  bool VisitCXXDeleteExpr(CXXDeleteExpr *E) {
+    CXXDestructorDecl *Destructor = nullptr;
+    if (const Type *T = E->getDestroyedType().getTypePtrOrNull()) {
+      if (const auto *CRD = T->getAsCXXRecordDecl())
+        Destructor = CRD->getDestructor();
+    }
+    if (Destructor) {
+      SymbolRoleSet Roles{};
+      SmallVector<SymbolRelation, 2> Relations;
+      addCallRole(Roles, Relations);
+      return IndexCtx.handleReference(Destructor, E->getBeginLoc(), Parent,
+                                      ParentDC, Roles, Relations, E);
+    }
+    return true;
+  }
+
   bool TraverseCXXOperatorCallExpr(CXXOperatorCallExpr *E,
                                    DataRecursionQueue *Q = nullptr) {
     if (E->getOperatorLoc().isInvalid())
       return true; // implicit.
     return base::TraverseCXXOperatorCallExpr(E, Q);
   }
 
   bool VisitDeclStmt(DeclStmt *S) {

clang/test/Index/index-refs.cpp

 };
 
 struct S {
   S& operator++();
   int operator*();
   S& operator=(int x);
   S& operator!=(int x);
   S& operator()(int x);
+  ~S();
 };
 
 void foo2(S &s) {
   (void)++s;
   (void)*s;
   s = 3;
   (void)(s != 3);
   s(3);
+  delete &s;
 }
 
 namespace NS {
   namespace Inn {}
   typedef int Foo;
 }
 
 using namespace NS;

 // CHECK-NEXT: [indexEntityReference]: kind: enumerator | name: EnumVal
 
 // CHECK:      [indexDeclaration]: kind: function | name: foo2
 // CHECK:      [indexEntityReference]: kind: c++-instance-method | name: operator++
 // CHECK-NEXT: [indexEntityReference]: kind: c++-instance-method | name: operator*
 // CHECK-NEXT: [indexEntityReference]: kind: c++-instance-method | name: operator=
 // CHECK-NEXT: [indexEntityReference]: kind: c++-instance-method | name: operator!=
 // CHECK-NEXT: [indexEntityReference]: kind: c++-instance-method | name: operator()
+// CHECK-NEXT: [indexEntityReference]: kind: destructor | name: ~S
 
-// CHECK:      [indexEntityReference]: kind: namespace | name: NS | {{.*}} | loc: 42:17
-// CHECK-NEXT: [indexEntityReference]: kind: namespace | name: NS | {{.*}} | loc: 43:17
-// CHECK-NEXT: [indexEntityReference]: kind: namespace | name: Inn | {{.*}} | loc: 43:21
-// CHECK-NEXT: [indexEntityReference]: kind: namespace | name: NS | {{.*}} | loc: 44:7
-// CHECK-NEXT: [indexEntityReference]: kind: typedef | name: Foo | {{.*}} | loc: 44:11
-
-// CHECK:      [indexDeclaration]: kind: c++-class-template | name: TS | {{.*}} | loc: 47:8
-// CHECK-NEXT: [indexDeclaration]: kind: struct-template-partial-spec | name: TS | USR: c:@SP>1#T@TS>#t0.0#I | {{.*}} | loc: 50:8
-// CHECK-NEXT: [indexDeclaration]: kind: typedef | name: MyInt | USR: c:index-refs.cpp@SP>1#T@TS>#t0.0#I@T@MyInt | {{.*}} | loc: 51:15 | semantic-container: [TS:50:8] | lexical-container: [TS:50:8]
-// CHECK-NEXT: [indexEntityReference]: kind: c++-class-template | name: TS | USR: c:@ST>2#T#T@TS | lang: C++ | cursor: TemplateRef=TS:47:8 | loc: 50:8 | <parent>:: <<NULL>> | container: [TU] | refkind: direct | role: ref
+// CHECK:      [indexEntityReference]: kind: namespace | name: NS | {{.*}} | loc: 44:17
+// CHECK-NEXT: [indexEntityReference]: kind: namespace | name: NS | {{.*}} | loc: 45:17
+// CHECK-NEXT: [indexEntityReference]: kind: namespace | name: Inn | {{.*}} | loc: 45:21
+// CHECK-NEXT: [indexEntityReference]: kind: namespace | name: NS | {{.*}} | loc: 46:7
+// CHECK-NEXT: [indexEntityReference]: kind: typedef | name: Foo | {{.*}} | loc: 46:11
+
+// CHECK:      [indexDeclaration]: kind: c++-class-template | name: TS | {{.*}} | loc: 49:8
+// CHECK-NEXT: [indexDeclaration]: kind: struct-template-partial-spec | name: TS | USR: c:@SP>1#T@TS>#t0.0#I | {{.*}} | loc: 52:8
+// CHECK-NEXT: [indexDeclaration]: kind: typedef | name: MyInt | USR: c:index-refs.cpp@SP>1#T@TS>#t0.0#I@T@MyInt | {{.*}} | loc: 53:15 | semantic-container: [TS:52:8] | lexical-container: [TS:52:8]
+// CHECK-NEXT: [indexEntityReference]: kind: c++-class-template | name: TS | USR: c:@ST>2#T#T@TS | lang: C++ | cursor: TemplateRef=TS:49:8 | loc: 52:8 | <parent>:: <<NULL>> | container: [TU] | refkind: direct | role: ref
 /* when indexing implicit instantiations
-  [indexDeclaration]: kind: struct-template-spec | name: TS | USR: c:@S@TS>#I | {{.*}} | loc: 50:8
-  [indexDeclaration]: kind: typedef | name: MyInt | USR: c:index-refs.cpp@593@S@TS>#I@T@MyInt | {{.*}} | loc: 51:15 | semantic-container: [TS:50:8] | lexical-container: [TS:50:8]
+  [indexDeclaration]: kind: struct-template-spec | name: TS | USR: c:@S@TS>#I | {{.*}} | loc: 52:8
+  [indexDeclaration]: kind: typedef | name: MyInt | USR: c:index-refs.cpp@593@S@TS>#I@T@MyInt | {{.*}} | loc: 53:15 | semantic-container: [TS:52:8] | lexical-container: [TS:52:8]
  */
 // CHECK-NEXT: [indexDeclaration]: kind: function | name: foo3
 /* when indexing implicit instantiations
-  [indexEntityReference]: kind: struct-template-spec | name: TS | USR: c:@S@TS>#I | {{.*}} | loc: 55:3
+  [indexEntityReference]: kind: struct-template-spec | name: TS | USR: c:@S@TS>#I | {{.*}} | loc: 57:3
 */
-// CHECK-NEXT: [indexEntityReference]: kind: struct-template-partial-spec | name: TS | USR: c:@SP>1#T@TS>#t0.0#I | {{.*}} | loc: 55:3
+// CHECK-NEXT: [indexEntityReference]: kind: struct-template-partial-spec | name: TS | USR: c:@SP>1#T@TS>#t0.0#I | {{.*}} | loc: 57:3
 
-// CHECK:      [indexEntityReference]: kind: variable | name: array_size | {{.*}} | loc: 59:22
-// CHECK:      [indexEntityReference]: kind: variable | name: default_param | {{.*}} | loc: 62:19 | {{.*}} | role: ref read
-// CHECK-NOT:  [indexEntityReference]: kind: variable | name: default_param | {{.*}} | loc: 62:19
-
-// CHECK:      [indexEntityReference]: kind: field | name: y | {{.*}} | loc: 69:20
-// CHECK-NEXT: [indexEntityReference]: kind: field | name: x | {{.*}} | loc: 69:28
-// CHECK-NOT:  [indexEntityReference]: kind: field | name: y | {{.*}} | loc: 69:20
-// CHECK-NOT:  [indexEntityReference]: kind: field | name: x | {{.*}} | loc: 69:28
-
-// CHECK:      [indexEntityReference]: kind: field | name: y | {{.*}} | loc: 70:5 | {{.*}} | role: ref write
-// CHECK:      [indexEntityReference]: kind: field | name: x | {{.*}} | loc: 70:11 | {{.*}} | role: ref read
-// CHECK:      [indexEntityReference]: kind: function | name: foo3 | {{.*}} | loc: 71:10 | {{.*}} | role: ref addr
-// CHECK:      [indexEntityReference]: kind: function | name: foo4 | {{.*}} | loc: 72:3 | {{.*}} | role: ref call
+// CHECK:      [indexEntityReference]: kind: variable | name: array_size | {{.*}} | loc: 61:22
+// CHECK:      [indexEntityReference]: kind: variable | name: default_param | {{.*}} | loc: 64:19 | {{.*}} | role: ref read
+// CHECK-NOT:  [indexEntityReference]: kind: variable | name: default_param | {{.*}} | loc: 64:19
+
+// CHECK:      [indexEntityReference]: kind: field | name: y | {{.*}} | loc: 71:20
+// CHECK-NEXT: [indexEntityReference]: kind: field | name: x | {{.*}} | loc: 71:28
+// CHECK-NOT:  [indexEntityReference]: kind: field | name: y | {{.*}} | loc: 71:20
+// CHECK-NOT:  [indexEntityReference]: kind: field | name: x | {{.*}} | loc: 71:28
+
+// CHECK:      [indexEntityReference]: kind: field | name: y | {{.*}} | loc: 72:5 | {{.*}} | role: ref write
+// CHECK:      [indexEntityReference]: kind: field | name: x | {{.*}} | loc: 72:11 | {{.*}} | role: ref read
+// CHECK:      [indexEntityReference]: kind: function | name: foo3 | {{.*}} | loc: 73:10 | {{.*}} | role: ref addr
+// CHECK:      [indexEntityReference]: kind: function | name: foo4 | {{.*}} | loc: 74:3 | {{.*}} | role: ref call
 
 // CHECK:      [indexDeclaration]: kind: variable | name: ginitlist |
-// CHECK:      [indexEntityReference]: kind: enumerator | name: EnumVal | {{.*}} | loc: 75:20
-// CHECK-NOT:  [indexEntityReference]: kind: enumerator | name: EnumVal | {{.*}} | loc: 75:20
+// CHECK:      [indexEntityReference]: kind: enumerator | name: EnumVal | {{.*}} | loc: 77:20
+// CHECK-NOT:  [indexEntityReference]: kind: enumerator | name: EnumVal | {{.*}} | loc: 77:20