[clangd] Avoid crash when summarizing pointer-to-member expr for block-end hint

[HighCommander4]

Fixes clangd/clangd#1873

[llvmbot]

@llvm/pr-subscribers-clangd

Author: Nathan Ridge (HighCommander4)

Changes

Fixes clangd/clangd#1873

---

Full diff: https://github.com/llvm/llvm-project/pull/76492.diff

2 Files Affected:

• (modified) clang-tools-extra/clangd/InlayHints.cpp (+1-1)
• (modified) clang-tools-extra/clangd/unittests/InlayHintTests.cpp (+13)

diff --git a/clang-tools-extra/clangd/InlayHints.cpp b/clang-tools-extra/clangd/InlayHints.cpp
index 3da047f9542138..fd28b48b5a0b02 100644
--- a/clang-tools-extra/clangd/InlayHints.cpp
+++ b/clang-tools-extra/clangd/InlayHints.cpp
@@ -286,7 +286,7 @@ std::string summarizeExpr(const Expr *E) {
     // Step through implicit nodes that clang doesn't classify as such.
     std::string VisitCXXMemberCallExpr(const CXXMemberCallExpr *E) {
       // Call to operator bool() inside if (X): dispatch to X.
-      if (E->getNumArgs() == 0 &&
+      if (E->getNumArgs() == 0 && E->getMethodDecl() &&
           E->getMethodDecl()->getDeclName().getNameKind() ==
               DeclarationName::CXXConversionFunctionName &&
           E->getSourceRange() ==
diff --git a/clang-tools-extra/clangd/unittests/InlayHintTests.cpp b/clang-tools-extra/clangd/unittests/InlayHintTests.cpp
index 20c1cdd985dbc0..ea5ee18f1da65c 100644
--- a/clang-tools-extra/clangd/unittests/InlayHintTests.cpp
+++ b/clang-tools-extra/clangd/unittests/InlayHintTests.cpp
@@ -2172,6 +2172,19 @@ TEST(BlockEndHints, Macro) {
                       ExpectedHint{" // struct S1", "S1"});
 }
 
+TEST(BlockEndHints, PointerToMemberFunction) {
+  // Do not crash trying to summarize `a->*p`.
+  assertBlockEndHints(R"cpp(
+    class A {};
+    using Predicate = bool(A::*)();
+    void foo(A* a, Predicate p) {
+      if ((a->*p)()) {
+      $ptrmem[[}]]
+    } // suppress
+  )cpp",
+                      ExpectedHint{" // if", "ptrmem"});
+}
+
 // FIXME: Low-hanging fruit where we could omit a type hint:
 //  - auto x = TypeName(...);
 //  - auto x = (TypeName) (...);

[hokein]

Thanks. Can you add your analysis (clangd/clangd#1873 (comment)) to the commit description, I think it is useful to have it in the commit log.

btw, it looks like there is a FIXME (https://github.com/llvm/llvm-project/blob/main/clang/lib/AST/ExprCXX.cpp#L677) for supporting this particular case.

[HighCommander4]

btw, it looks like there is a FIXME (https://github.com/llvm/llvm-project/blob/main/clang/lib/AST/ExprCXX.cpp#L677) for supporting this particular case.

I saw it, but I'm not clear on what that would look like.

Which member function a member function pointer resolves to is a runtime property of the pointer variable. I don't think we can produce a CXXMethodDecl there unless perhaps the pointer is a constant expression, which seems like an edge case.