[clangd] Add heuristic for dropping snippet when completing member function pointer

This implements the 1st heuristic mentioned in https://github.com/clangd/clangd/issues/968#issuecomment-1002242704:

When completing a function that names a non-static member of a class, and we are not inside that class's scope, assume the reference will not be a call (and thus don't add the snippetSuffix)

Reviewed By: nridge

Differential Revision: https://reviews.llvm.org/D137040

1 files changed, 27 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaCodeComplete.cpp b/clang/lib/Sema/SemaCodeComplete.cpp
index baf5676..2172692 100644
--- a/clang/lib/Sema/SemaCodeComplete.cpp
+++ b/clang/lib/Sema/SemaCodeComplete.cpp
@@ -1379,6 +1379,33 @@ void ResultBuilder::AddResult(Result R, DeclContext *CurContext,
         OverloadSet.Add(Method, Results.size());
       }
 
+  // When completing a non-static member function (and not via
+  // dot/arrow member access) and we're not inside that class' scope,
+  // it can't be a call.
+  if (CompletionContext.getKind() == clang::CodeCompletionContext::CCC_Symbol) {
+    const auto *Method = dyn_cast<CXXMethodDecl>(R.getDeclaration());
+    if (Method && !Method->isStatic()) {
+      // Find the class scope that we're currently in.
+      // We could e.g. be inside a lambda, so walk up the DeclContext until we
+      // find a CXXMethodDecl.
+      const auto *CurrentClassScope = [&]() -> const CXXRecordDecl * {
+        for (DeclContext *Ctx = SemaRef.CurContext; Ctx;
+             Ctx = Ctx->getParent()) {
+          const auto *CtxMethod = llvm::dyn_cast<CXXMethodDecl>(Ctx);
+          if (CtxMethod && !CtxMethod->getParent()->isLambda()) {
+            return CtxMethod->getParent();
+          }
+        }
+        return nullptr;
+      }();
+
+      R.FunctionCanBeCall =
+          CurrentClassScope &&
+          (CurrentClassScope == Method->getParent() ||
+           CurrentClassScope->isDerivedFrom(Method->getParent()));
+    }
+  }
+
   // Insert this result into the set of results.
   Results.push_back(R);