[PATCH] D71644: [clangd] Heuristically resolve dependent call through smart pointer type

[Nathan Ridge via Phabricator via cfe-commits]

nridge created this revision.
nridge added a reviewer: sammccall.
Herald added subscribers: cfe-commits, usaxena95, kadircet, arphaman, jkorous, MaskRay, ilya-biryukov.
Herald added a project: clang.

Fixes https://github.com/clangd/clangd/issues/227


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D71644

Files:
  clang-tools-extra/clangd/FindTarget.cpp
  clang-tools-extra/clangd/unittests/XRefsTests.cpp


Index: clang-tools-extra/clangd/unittests/XRefsTests.cpp
===================================================================
--- clang-tools-extra/clangd/unittests/XRefsTests.cpp
+++ clang-tools-extra/clangd/unittests/XRefsTests.cpp
@@ -502,7 +502,7 @@
 
       R"cpp(// FIXME: Heuristic resolution of dependent method
             // invoked via smart pointer
-        template <typename> struct S { void foo(); };
+        template <typename> struct S { void [[foo]]() {} };
         template <typename T> struct unique_ptr {
           T* operator->();
         };
Index: clang-tools-extra/clangd/FindTarget.cpp
===================================================================
--- clang-tools-extra/clangd/FindTarget.cpp
+++ clang-tools-extra/clangd/FindTarget.cpp
@@ -27,6 +27,7 @@
 #include "clang/AST/TypeLoc.h"
 #include "clang/AST/TypeLocVisitor.h"
 #include "clang/Basic/LangOptions.h"
+#include "clang/Basic/OperatorKinds.h"
 #include "clang/Basic/SourceLocation.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
@@ -86,6 +87,58 @@
   });
 }
 
+ASTContext *hackyFindASTContext(const Type *T) {
+  auto *TST = T->getAs<TemplateSpecializationType>();
+  if (!TST)
+    return nullptr;
+  const ClassTemplateDecl *TD = dyn_cast_or_null<ClassTemplateDecl>(
+      TST->getTemplateName().getAsTemplateDecl());
+  if (!TD)
+    return nullptr;
+  return &TD->getASTContext();
+}
+
+// Given the type T of a dependent expression that appears of the LHS of a "->",
+// heuristically find a corresponding pointee type in whose scope we could look
+// up the name appearing on the RHS.
+const Type *getPointeeType(const Type *T) {
+  if (!T)
+    return nullptr;
+
+  if (T->isPointerType()) {
+    return T->getAs<PointerType>()->getPointeeType().getTypePtrOrNull();
+  }
+
+  // Try to handle smart pointer types.
+
+  // Look up operator-> in the primary template. If we find one, it's probably a
+  // smart pointer type.
+  ASTContext *Ctx = hackyFindASTContext(T);
+  if (!Ctx)
+    return nullptr;
+  auto ArrowOps = getMembersReferencedViaDependentName(
+      T, Ctx->DeclarationNames.getCXXOperatorName(OO_Arrow),
+      /*IsNonStaticMember=*/true);
+  if (ArrowOps.empty())
+    return nullptr;
+
+  // Getting the return type of the found operator-> method decl isn't useful,
+  // because we discarded template arguments to perform lookup in the primary
+  // template scope, so the return type would just have the form U* where U is a
+  // template parameter type.
+  // Instead, just handle the common case where the smart pointer type has the
+  // form of SmartPtr<X, ...>, and assume X is the pointee type.
+  auto *TST = T->getAs<TemplateSpecializationType>();
+  if (!TST)
+    return nullptr;
+  if (TST->getNumArgs() == 0)
+    return nullptr;
+  const TemplateArgument &FirstArg = TST->getArg(0);
+  if (FirstArg.getKind() != TemplateArgument::Type)
+    return nullptr;
+  return FirstArg.getAsType().getTypePtrOrNull();
+}
+
 // TargetFinder locates the entities that an AST node refers to.
 //
 // Typically this is (possibly) one declaration and (possibly) one type, but
@@ -250,14 +303,7 @@
       VisitCXXDependentScopeMemberExpr(const CXXDependentScopeMemberExpr *E) {
         const Type *BaseType = E->getBaseType().getTypePtrOrNull();
         if (E->isArrow()) {
-          // FIXME: Handle smart pointer types by looking up operator->
-          // in the primary template.
-          if (!BaseType || !BaseType->isPointerType()) {
-            return;
-          }
-          BaseType = BaseType->getAs<PointerType>()
-                         ->getPointeeType()
-                         .getTypePtrOrNull();
+          BaseType = getPointeeType(BaseType);
         }
         for (const NamedDecl *D :
              getMembersReferencedViaDependentName(BaseType, E->getMember(),


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