[clang] [clang-tools-extra] [clang] Skip unqualified members in explicit member functions (PR #153760)

[Mythreya Kuricheti via cfe-commits]

https://github.com/MythreyaK created https://github.com/llvm/llvm-project/pull/153760

Fixes #141291

Skip suggesting members when not using `self.` in explicit object methods. 

[TODO: Need to add a semacodecomplete test too, will add it in a new commit]

>From 690ca3d679c2df1386a212533afecab3bc86995f Mon Sep 17 00:00:00 2001
From: Mythreya Kuricheti <git at mythreya.dev>
Date: Fri, 15 Aug 2025 00:52:37 -0700
Subject: [PATCH] [clang] Skip unqualified members in explicit-member functions

---
 .../clangd/unittests/CodeCompleteTests.cpp    | 39 +++++++++++++++++++
 clang/lib/Sema/SemaCodeComplete.cpp           | 10 +++++
 2 files changed, 49 insertions(+)

diff --git a/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp b/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
index 1a1c32c241602..360693a02a1f5 100644
--- a/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
+++ b/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
@@ -4473,6 +4473,45 @@ TEST(CompletionTest, SkipExplicitObjectParameter) {
                                   snippetSuffix(""))));
   }
 }
+
+TEST(CompletionTest, MemberAccessInExplicitObjMemfn) {
+  Annotations Code(R"cpp(
+    struct A {
+      int member {};
+
+      void foo(this A& self) {
+        // Should not offer `member` here, since it needs to be 
+        // referenced as `self.member`.
+        mem$c1^;
+        self.mem$c2^;
+      }
+    };
+  )cpp");
+
+  auto TU = TestTU::withCode(Code.code());
+  TU.ExtraArgs = {"-std=c++23"};
+
+  auto Preamble = TU.preamble();
+  ASSERT_TRUE(Preamble);
+
+  CodeCompleteOptions Opts{};
+
+  MockFS FS;
+  auto Inputs = TU.inputs(FS);
+
+  {
+    auto Result = codeComplete(testPath(TU.Filename), Code.point("c1"),
+                               Preamble.get(), Inputs, Opts);
+
+    EXPECT_THAT(Result.Completions, ElementsAre());
+  }
+  {
+    auto Result = codeComplete(testPath(TU.Filename), Code.point("c2"),
+                               Preamble.get(), Inputs, Opts);
+
+    EXPECT_THAT(Result.Completions, ElementsAre(named("member")));
+  }
+}
 } // namespace
 } // namespace clangd
 } // namespace clang
diff --git a/clang/lib/Sema/SemaCodeComplete.cpp b/clang/lib/Sema/SemaCodeComplete.cpp
index e4f276086af25..224d105c313e6 100644
--- a/clang/lib/Sema/SemaCodeComplete.cpp
+++ b/clang/lib/Sema/SemaCodeComplete.cpp
@@ -1428,6 +1428,16 @@ void ResultBuilder::AddResult(Result R, DeclContext *CurContext,
 
   AdjustResultPriorityForDecl(R);
 
+  if (isa<FieldDecl>(R.Declaration)) {
+    // If result is a member in the context of an explicit-object member
+    // function, drop it because it must be accessed through the object
+    // parameter
+    if (auto *MethodDecl = dyn_cast<CXXMethodDecl>(CurContext);
+        MethodDecl && MethodDecl->isExplicitObjectMemberFunction()) {
+      return;
+    }
+  }
+
   if (HasObjectTypeQualifiers)
     if (const auto *Method = dyn_cast<CXXMethodDecl>(R.Declaration))
       if (Method->isInstance()) {