[clangd] Fix an inlay-hint crash on a broken designator.

Differential Revision: https://reviews.llvm.org/D131696

clang-tools-extra/clangd/InlayHints.cpp

@@ -141,8 +141,10 @@ void collectDesignators(const InitListExpr *Sem,
       Fields.next();       // Always advance to the next subobject name.
       Prefix.resize(Size); // Erase any designator we appended.
     });
-    if (llvm::isa<ImplicitValueInitExpr>(Init))
-      continue; // a "hole" for a subobject that was not explicitly initialized
+    // Skip for a broken initializer or if it is a "hole" in a subobject that
+    // was not explicitly initialized.
+    if (!Init || llvm::isa<ImplicitValueInitExpr>(Init))
+      continue;
 
     const auto *BraceElidedSubobject = llvm::dyn_cast<InitListExpr>(Init);
     if (BraceElidedSubobject &&

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

@@ -1417,6 +1417,17 @@ TEST(DesignatorHints, OnlyAggregateInit) {
   )cpp" /*no designator hints expected (but param hints!)*/);
 }
 
+TEST(DesignatorHints, NoCrash) {
+  assertDesignatorHints(R"cpp(
+    /*error-ok*/
+    struct A {};
+    struct Foo {int a; int b;};
+    void test() {
+      Foo f{A(), $b[[1]]};
+    }
+  )cpp", ExpectedHint{".b=", "b"});
+}
+
 TEST(InlayHints, RestrictRange) {
   Annotations Code(R"cpp(
     auto a = false;