[clangd] Fix hover crash on broken code

[hokein]

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

2447

IIUC, x refers to an undefined variable right? might be renamed it to undefine.

Instead of creating a new test, maybe add this no-crash test to TEST(Hover, NoHover) {, looks like a good fit there.

[kadircet]

• s/x/undefined

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

2447

IIUC, x refers to an undefined variable right? might be renamed it to undefine.

Done.

Instead of creating a new test, maybe add this no-crash test to TEST(Hover, NoHover) {, looks like a good fit there.

This produces a hover though. I think we should collect all the cases about crash-ness here, independent of whether they produce a hover or not.

clang-tools-extra/clangd/Hover.cpp

llvm::Optional<StringRef> setterVariableName(const CXXMethodDecl *CMD) {
   } else {
     return llvm::None;
   }
 
   // Detect the case when the item is moved into the field.
   if (auto *CE = llvm::dyn_cast<CallExpr>(RHS->IgnoreCasts())) {
     if (CE->getNumArgs() != 1)
       return llvm::None;
-    auto *ND = llvm::dyn_cast<NamedDecl>(CE->getCalleeDecl());
+    auto *ND = llvm::dyn_cast_or_null<NamedDecl>(CE->getCalleeDecl());
     if (!ND || !ND->getIdentifier() || ND->getName() != "move" ||
         !ND->isInStdNamespace())
       return llvm::None;
     RHS = CE->getArg(0);
   }
 
   auto *DRE = llvm::dyn_cast<DeclRefExpr>(RHS->IgnoreCasts());
   if (!DRE || DRE->getDecl() != Arg)

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

TEST(Hover, DocsFromAST) {
   auto AST = TU.build();
   for (const auto &P : T.points()) {
     auto H = getHover(AST, P, format::getLLVMStyle(), nullptr);
     ASSERT_TRUE(H);
     EXPECT_EQ(H->Documentation, "doc");
   }
 }
 
+TEST(Hover, NoCrash) {
+  Annotations T(R"cpp(
+    /* error-ok */
+    template<typename T> T foo(T);
+
+    // Setter variable heuristic might fail if the callexpr is broken.
+    struct X { int Y; void [[^setY]](float) { Y = foo(undefined); } };)cpp");
+
+  TestTU TU = TestTU::withCode(T.code());
+  auto AST = TU.build();
+  for (const auto &P : T.points())
+    getHover(AST, P, format::getLLVMStyle(), nullptr);
+}
+
 TEST(Hover, DocsFromMostSpecial) {
   Annotations T(R"cpp(
   // doc1
   template <typename T> class $doc1^X {};
   // doc2
   template <> class $doc2^X<int> {};
   // doc3
   template <typename T> class $doc3^X<T*> {};